JP2017045767A - Photoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a decrease in conversion efficiency.SOLUTION: A crystal semiconductor region 110 of a photoelectric conversion element 101 includes a first surface 112 and a second surface 111. Hydrogenated amorphous semiconductor films 120 and 130 are arranged so as to come into contact with the second surface 111. A first work function film 150 is arranged so as to come into contact with the film 120, and formed of a material including a first work function. A second work function film 160 is separated from the film 150, is arranged so as to come into contact with the film 130, and is formed of a material including a second work function. A hydrogenated amorphous semiconductor film 140 is arranged so as to come into contact with the second surface 111 between the films 150 and 160. An electric charge holding insulation film 190 is arranged between the films 150 and 160 so as to come into contact with the film 140. When the crystal semiconductor region is an N type, the electric charge holding insulation film holds electric charge with a positive polarity. When the crystal semiconductor region is a p type, the electric charge holding insulation film holds electric charge with a negative polarity.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a photoelectric conversion element that converts light into electricity and a method for manufacturing the photoelectric conversion element.

  The photoelectric conversion element includes a photo-resistor whose element resistance changes as a result of changes in intensity, wavelength, etc. of the irradiation light, a photodiode whose element current or voltage changes, a phototransistor whose element current is amplified and changed by the photodiode, There are solar cells whose output current, voltage and power change. Known electronic structures constituting photodiodes and solar cells include pn junctions and MIS structures.

  The pn junction further includes a homojunction in which a p-type semiconductor and an n-type semiconductor are made of the same semiconductor material to form a pn junction, and a heterojunction in which a p-type semiconductor and an n-type semiconductor are made of a pn junction. is there. This heterojunction has been used as a means for realizing a photodiode having a short wavelength sensitivity and a high-efficiency solar cell with a compound semiconductor.

  On the other hand, when a photodiode or phototransistor is realized with a silicon semiconductor, a homojunction is often used. However, a heterojunction solar cell using a pn junction of hydrogenated amorphous silicon and crystalline silicon has been developed for high efficiency. An “i” layer (i-type hydrogenated amorphous silicon) in which no valence-control impurity is intentionally added between the p-type hydrogenated amorphous silicon and the n-type crystalline silicon at the heterojunction of hydrogenated amorphous silicon and crystalline silicon, A technique for improving the open-circuit voltage Voc by interposing a so-called hydrogenated amorphous silicon has been developed since the 1990s (see, for example, Non-Patent Document 1). Furthermore, high efficiency has been promoted by providing n-type and i-type hydrogenated amorphous silicon on the back side of a crystalline silicon substrate provided with p-type and i-type hydrogenated amorphous silicon. Hereinafter, these two layers of p-type and i-type hydrogenated amorphous silicon may be referred to as p / i layers, and these two layers of n-type and i-type hydrogenated amorphous silicon may be referred to as n / i layers.

  On the other hand, in recent years, the development of back contact type solar cells has been promoted with the aim of improving the conversion efficiency. In the back contact type, the positive and negative current / voltage extraction electrodes, which were conventionally provided separately on both sides (front and back) of the solar cell, are collected and arranged on the back side of the solar cell (opposite the light receiving surface). The output current is improved so as not to block. Also in the above heterojunction solar cell, a back contact type structure as shown in FIG. 13 has been developed (see, for example, Non-Patent Document 2).

  FIG. 13 is a cross-sectional view in which reference numerals are added to the components of the photoelectric conversion element in “FIG. 3” of Non-Patent Document 2. In FIG. 13, 510 is an n-type crystal Si substrate having a first surface 511 and a second surface (back surface) 512, and 520 is an i-type hydrogenated amorphous silicon layer provided in contact with the back surface 512 of the n-type crystal Si substrate 510. Reference numeral 530 denotes a high impurity concentration n-type hydrogenated amorphous silicon layer provided in contact with the i-type hydrogenated amorphous silicon layer 520, and forms an n / i layer.

540 is an i-type hydrogenated amorphous silicon layer provided in contact with the back surface 512 of the n-type crystalline Si substrate 510, and 550 is a high impurity concentration p-type hydrogenated amorphous silicon provided in contact with the i-type hydrogenated amorphous silicon layer 540. A p / i layer. Reference numeral 560 denotes an i-type hydrogenated amorphous silicon layer provided in contact with the surface 511 of the n-type crystal Si substrate 510, and reference numeral 570 denotes a passivation layer provided in contact with the i-type hydrogenated amorphous silicon layer 560, which has a high impurity concentration. It is made of n-type hydrogenated amorphous silicon. Reference numeral 580 denotes an antireflection film made of titanium oxide (TiO ₂ ) provided in contact with the passivation layer 570.

  Here, paying attention to the positional relationship between the p / i layer and the n / i layer on the back surface, the n / i layer is superimposed on the p / i layer at a portion 551. When the p layer 550 and the n layer 530 come into contact with each other, a short circuit of the output voltage occurs, and therefore the p layer 550 and the n layer 530 must be separated from each other. However, when the p layer 550 and the n layer 530 are separated along the back surface 512, current and voltage are lost at the gap. For this reason, the n layer 530 is superimposed on the p / i layer via the i layer 520 at the portion 551. The length of the overlapped portion 551 is determined by the pattern creation accuracy of the manufacturing technique and the alignment accuracy of the p / i layer and the n / i layer, but for example, a size of about 100 μm is required.

  The dimensions of the portion 531 where the n-layer conductive electrode 590 related to the pattern creation accuracy and the alignment accuracy cannot cover the n-layer 530 and the size of the portion 552 where the p-layer conductive electrode 600 cannot cover the p-layer 550 are similar. It becomes.

M. Taguchi, M. Tanaka, T. Matsuyama, T. Matsuoka, S. Tsuda, S. Nakano, Y. Kishi and Y. Kuwano, “Improvement of the conversion efficiency of coated silicon thin film solar cell”, Technical Digest of the International PVSEC-5, paper number C-IIIa-1, p. 689, Kyoto, Japan, 1990. K. Saito, H. Noge, A. Sato, T. Kaneko, and M. Kondo, “Fabrication of interdigitated back contact silicon heterojunction solar cells by inkjet patterning”, 29th European Photovoltaic Solar Energy Conference and Exhibition, EUPVSEC2014, Lecture number 2BV .8.47, Amsterdam, Netherland, September, 2014.

  The idea of overlapping the n / i layer on the p / i layer to minimize the separation distance between the p layer and the n layer can be evaluated, but the recombination level density at the interface between the back surface 512 and the i layer 540 is large. It is reported in Non-Patent Document 2 that when the overlapping distance of the 551 portion is 100 μm, the conversion efficiency decreases to 0.85 or less when the overlapping distance is 0. This decrease rate is shown to be about twice the decrease rate when the dimension of the portion 531 where the p-layer conductive electrode 590 cannot cover the p-layer 550 is the same value. These aspects are shown in “FIGURE 4” of Non-Patent Document 2. Even if the folding angle and the distance between the p layer and the n layer are reduced to the minimum, the effect is small. Even if the distance between the p layer and the n layer is large, it is desired to provide a photoelectric conversion element with little reduction in conversion efficiency.

  The present invention has been made in view of these problems, and an object thereof is to provide a technique for suppressing a decrease in conversion efficiency.

  The photoelectric conversion element of the first invention made to achieve the above object includes a crystalline semiconductor region, a first hydrogenated amorphous semiconductor film, a first work function film, a second hydrogenated amorphous semiconductor film, and a second A work function film, a third hydrogenated amorphous semiconductor film, and a first charge retention insulating film are provided.

  The crystalline semiconductor region is formed of a polycrystalline or single crystal semiconductor, has a first conductivity type, and has a first surface and a second surface that face each other. This crystalline semiconductor region can be any shape such as layer, sheet, substrate, cube separated in or on the substrate, multiple shapes integrated in or on the substrate, cylindrical, etc., depending on the purpose and raw materials Can take the shape of The first conductivity type may be p-type or n-type.

The first hydrogenated amorphous semiconductor film is disposed so as to be in contact with the second surface of the crystalline semiconductor region, is formed of an amorphous semiconductor, and is hydrogenated.
The first work function film is disposed in contact with the first hydrogenated amorphous semiconductor film and is formed of a material having the first work function.

The second hydrogenated amorphous semiconductor film is disposed in contact with the second surface, is formed of an amorphous semiconductor, and is hydrogenated.
The second work function film is disposed away from the first work function film and in contact with the second hydrogenated amorphous semiconductor film, and is formed of a material having a second work function.

  The third hydrogenated amorphous semiconductor film is disposed between the first work function film and the second work function film so as to be in contact with the second surface, is formed of an amorphous semiconductor, and is hydrogenated.

  The first charge retaining insulating film is an insulating film that is disposed between the first work function film and the second work function film so as to be in contact with the third hydrogenated amorphous semiconductor film and retains charges on the surface and / or inside thereof. .

  In the photoelectric conversion element of the first invention, the polarity of the first retained charge, which is the charge retained on the surface and / or inside the first charge retaining insulating film, is the case where the first conductivity type of the crystalline semiconductor region is n-type Is positive, and negative when the first conductivity type of the crystalline semiconductor region is p-type. The electric charge held by the first charge holding insulating film and the second charge holding insulating film described later functions both on the surface and inside of the insulating film.

  In the photoelectric conversion element of the first invention configured as described above, the light generation current generated inside the photoelectric conversion element by the incidence of light from the first surface side of the crystal semiconductor region is applied to the second surface of the crystal semiconductor region. They can be taken out between a first work function film and a second work function film provided through the first hydrogenated amorphous semiconductor film and the second hydrogenated amorphous semiconductor film, respectively.

  When the energy level of the first work function is on the Fermi level side of the crystalline semiconductor region with respect to the energy level of the midgap of the crystalline semiconductor region, the photogenerated current having the same sign as the majority carrier is expressed as (second surface side of the crystalline semiconductor region) Can be extracted from the first work function film. Further, when the energy level of the first work function is opposite to the Fermi level of the crystal semiconductor region with respect to the energy level of the mid gap of the crystal semiconductor region, a photocurrent having the same sign as the minority carrier is taken out from the first work function film. be able to.

  In the photoelectric conversion element according to the first aspect of the present invention, when light is incident from the first surface side of the crystal semiconductor region, the energy level of the second work function is about the Fermi of the crystal semiconductor region with respect to the energy level of the midgap of the crystal semiconductor region. When it is on the level side, a photo-generated current having the same sign as the majority carrier can be taken out from the second work function film. When the energy level of the second work function is opposite to the Fermi level of the crystal semiconductor region with respect to the energy level of the mid gap of the crystal semiconductor region, a photocurrent having the same sign as the minority carrier is taken out from the second work function film. be able to.

  When the energy level of the first work function and the energy level of the second work function are on the same side with respect to the midgap energy level of the crystalline semiconductor region, the photoelectric conversion element of the first invention functions as a photoresistor and a light-current conversion element To do.

  When the energy level of the first work function and the energy level of the second work function are opposite to each other (up and down) with respect to the midgap energy level of the crystalline semiconductor region, between the first work function film and the second work function film In addition, the photovoltage and the photocurrent generated inside the photoelectric conversion element can be taken out. In this case, the photoelectric conversion element of the first invention functions as a photodiode and a solar cell.

  Of the materials desirable for use as the first work function film and the second work function film, a crystalline semiconductor region is crystalline silicon, and an example of a combination of materials desirable for taking out a photovoltaic voltage in combination with crystalline silicon will be given. A material having a work function energy level on the conductive band side of the crystalline silicon from the mid gap energy of the crystalline silicon is set as one of the first work function film and the second work function film. A combination of a material having a work function energy level on the silicon valence band side as the other material of the first work function film and the second work function film, that is, the first work function energy level and the second work function film. This is a combination when the energy level of the function is in the opposite direction (up and down) with respect to the midgap energy level of the energy band of the crystalline semiconductor region.

  Materials whose work function energy level is closer to the conduction band side of crystalline silicon than the mid gap energy of crystalline semi-silicon are aluminum and magnesium (need to be coated with a chemically stable material) n-type zinc oxide (Ti-doped ZnO) Etc.). Furthermore, the conversion efficiency can be increased more than when a material having an energy level work function exceeding the conduction band of crystalline silicon in a direction close to the vacuum energy level is selected.

  Examples of the material having a work function energy level closer to the valence band side of crystalline silicon than the mid gap energy of crystalline half silicon include nickel, platinum, and tungsten oxide. Furthermore, the conversion efficiency can be increased by selecting a material such as molybdenum oxide having a work function with an energy level exceeding the valence band of crystalline silicon in a direction far from the vacuum energy level.

  The mid gap indicates the energy level at the center of the forbidden band of the crystalline semiconductor region. The work function energy level is an energy level lower than the vacuum energy level (vacuum level) by the value of the work function.

  And the photoelectric conversion element of 1st invention is equipped with the 1st electric charge retention insulating film between the 1st work function film and the 2nd work function film in the 2nd surface side of a crystalline semiconductor region, A portion of the second surface facing the first charge retaining insulating film is in an accumulation state, that is, a state where more majority carriers are collected than in an equilibrium state. This portion of the electric field becomes a polar electric field that repels minority carriers from the second surface, thus preventing the opportunity for light-generated minority carriers to be recombined and lost on the second surface. Therefore, the photoelectric conversion element of the first invention can improve the photocurrent output and can also improve the output voltage. Further, since the majority carriers are collected on the second surface of the crystalline semiconductor region more than the equilibrium state, the surface resistance of the second surface of the crystalline semiconductor region between the first work function film and the second work function film is reduced. The photoelectric conversion element of the first invention can also improve the fill factor. For this reason, the photoelectric conversion element of 1st invention can suppress the fall of conversion efficiency, even if the space | interval of a 1st work function film | membrane and a 2nd work function film | membrane becomes large.

  At this time, since the first charge retention insulating film is an insulating film even if it overlaps with the first work function film and the second work function film, the first work function film and the second work function film are electrically connected. Is not short-circuited. Therefore, since the alignment accuracy of the first work function film, the second work function film, and the charge holding insulating film is not strictly required, this structure is easy to make from the viewpoint of manufacturing technology.

  A silicon nitride film is known as an insulating film having a positive charge, and an aluminum oxide film is known as an insulating film having a negative charge. An aluminum oxide film can be deposited at a low temperature of 250 ° C. or less by atomic layer deposition (ALD), and a silicon nitride film can be deposited at a low temperature plasma CVD at about 100 ° C. or a low temperature catalytic CVD including room temperature ( catCVD).

In the photoelectric conversion element of the first invention, the charge density of the first held charge may be 4 × 10 ¹¹ [q / cm ² ] or more, where q is an elementary charge amount. Note that q = 1.6 × 10 ⁻¹⁹ coulombs.

  In addition, when the current value taken out from the first work function film is large and the voltage drop due to the resistance of the first work function film when taking out through the first work function film is large, the low resistance is in contact with the first work function film. The first conductive electrode is provided.

  When the current value taken out from the second work function film is large and the voltage drop due to the resistance of the second work function film when taking out through the second work function film is large, the resistance is low in contact with the second work function film. The first conductive electrode is provided. Here, the first conductive electrode and the second conductive electrode are separated from each other.

  The first and second conductive electrodes are composed of a metal thin film, a metal printed film (metal paste coated, dried or baked), nanocarbon such as graphene. Further, in order to ensure light reflection or to prevent reaction between the first and second conductive electrode metals and the first and second work function films, the transparent conductive film is made of a metal thin film, metal printed film, nano In some cases, a two-layer structure provided between the carbon and the first and second work function films is employed. In addition, as transparent conductive film, indium oxide (InOx), hydrogenated indium oxide (InOx: H), indium tin oxide (ITO), zinc oxide (ZnOx) and its aluminum (Al) additive or boron (B) additive , Etc. are used. Silver (Ag), aluminum (Al), etc. are used as a metal of a metal thin film and a metal printing film.

  On the other hand, the photoelectric conversion element of the second invention includes a crystalline semiconductor region, a first hydrogenated amorphous semiconductor film, a first semiconductor film, a second hydrogenated amorphous semiconductor film, a second semiconductor film, and a fourth hydrogenated film. An amorphous semiconductor film, a second charge retaining insulating film, and a first conductive electrode and a second conductive electrode, if necessary.

The crystalline semiconductor region is formed of a polycrystalline or single crystal semiconductor, has a first conductivity type, and has a first surface and a second surface that face each other.
The first hydrogenated amorphous semiconductor film is disposed in contact with the second surface of the crystalline semiconductor region. The second hydrogenated amorphous semiconductor film is disposed in contact with the second surface of the crystalline semiconductor region.

The first semiconductor film is disposed in contact with the first hydrogenated amorphous semiconductor film and is formed of a semiconductor having the first conductivity type.
The second semiconductor film is disposed so as to be separated from the first semiconductor film and in contact with the second hydrogenated amorphous semiconductor film, and is formed of a semiconductor having a second conductivity type opposite to the first conductivity type. ing.

The fourth hydrogenated amorphous semiconductor film is disposed between the first semiconductor film and the second semiconductor film so as to be in contact with the second surface, is formed of an amorphous semiconductor, and is hydrogenated.
The second charge retaining insulating film is an insulating film that is disposed between the first semiconductor film and the second semiconductor film so as to be in contact with the fourth hydrogenated amorphous semiconductor film and retains charges on the surface and / or inside thereof.

  In the photoelectric conversion element of the second invention, the polarity of the second retained charge, which is the charge retained on the surface and / or inside the second charge retaining insulating film, is the case where the first conductivity type of the crystalline semiconductor region is n-type Is positive, and negative when the first conductivity type of the crystalline semiconductor region is p-type.

  The photoelectric conversion element according to the second aspect of the present invention configured as described above generates a photo-generated current having the same sign as the majority carrier generated inside the photoelectric conversion element when light is incident from the first surface side of the crystal semiconductor region. It can be drawn from the first semiconductor film provided on the second surface side of the semiconductor region. Further, the photoelectric conversion element of the second invention is a photovoltage generated when light is incident from the first surface side of the crystalline semiconductor region, and a photogenerated current having the same sign as the minority carrier generated inside the photoelectric conversion element. Can be extracted from the second semiconductor film provided on the second surface side of the crystalline semiconductor region.

  The photoelectric conversion element according to the second aspect of the present invention includes the second charge retention insulating film between the first semiconductor film and the second semiconductor film on the second surface side of the crystal semiconductor region, so that the second in the crystal semiconductor region. A portion of the surface facing the second charge retaining insulating film is in an accumulation state. This portion of the electric field becomes a polar electric field that repels minority carriers from the second surface, thus preventing the opportunity for light-generated minority carriers to be recombined and lost on the second surface. Therefore, the photoelectric conversion element of the second invention can improve the photocurrent output and can also improve the output voltage. In the portion of the second surface of the crystalline semiconductor region facing the second charge retaining insulating film, the majority carriers are collected on the second surface of the crystalline semiconductor region more than the equilibrium state. The surface resistance of the second surface of the crystalline semiconductor region between the semiconductor film and the semiconductor film is reduced, and the photoelectric conversion element of the second invention can also improve the fill factor. For this reason, the photoelectric conversion element of 2nd invention can suppress the fall of conversion efficiency, even if the space | interval of a 1st semiconductor film and a 2nd semiconductor film becomes large.

  At this time, even if the second charge retaining insulating film overlaps with the first semiconductor film and the second semiconductor film, the first work function film and the second work function film are not electrically short-circuited. Therefore, since the alignment accuracy of the first semiconductor film, the second semiconductor film and the charge retaining insulating film is not strictly required, this structure is easy to make from the viewpoint of manufacturing technology.

  A silicon nitride film is known as an insulating film having a positive charge, and an aluminum oxide film is known as an insulating film having a negative charge. An aluminum oxide film can be deposited at a low temperature of 250 ° C. or less by atomic layer deposition (ALD), and a silicon nitride film can be deposited at a low temperature plasma CVD at about 100 ° C. or a low temperature catalytic CVD including room temperature ( catCVD).

In the photoelectric conversion element of the second invention, the charge density of the second held charge may be 4 × 10 ¹¹ [q / cm ² ] or more, where q is the elementary charge.
In the photoelectric conversion element of the second invention, the first semiconductor film and the second semiconductor film are hydrogenated amorphous silicon formed of amorphous silicon and hydrogenated, and 10 ¹⁸ [atoms / cm. ³ ] It is preferable to add the above valence electron control impurities.

In the photoelectric conversion element of the second invention, the first semiconductor film and the second semiconductor film are hydrogenated microcrystalline silicon formed and hydrogenated with microcrystalline silicon, and 10 ¹⁸ [atoms / cm 2]. ³ ] It is preferable to add the above valence electron control impurities. The microcrystal has a structure in which a nanometer to submicron size crystal is embedded in an amorphous structure, and has a lower resistivity than an amorphous structure.

On the other hand, the first, second, third and fourth hydrogenated amorphous semiconductor films are required to have few electron defects. For this reason, even if valence electron control impurities such as boron, neighbor, arsenic, etc. are not intentionally added, or even if they are added for adjusting the resistivity, Fermi level, etc., 10 ¹⁸ [ It is desirable to keep the addition at a lower concentration than atoms / cc.

  In the photoelectric conversion elements of the first and second inventions, the first, second, third, and fourth hydrogenated amorphous semiconductor films (hereinafter simply referred to as hydrogenated amorphous semiconductor films) are the first of the crystalline semiconductor regions. The interface between the surface and the surface including the second surface can be passivated by hydrogen bonding. Therefore, the interface state density can be kept low. In particular, the effect is great when the crystalline semiconductor region is formed of silicon, silicon-germanium, or germanium.

  In the photoelectric conversion elements of the first and second inventions, the hydrogenated amorphous semiconductor is hydrogenated amorphous silicon (aSi: H), hydrogenated amorphous silicon carbide (aSixCy: H), hydrogenated amorphous silicon containing oxygen (aSixOy: H), hydrogenated amorphous silicon containing nitrogen (aSixNy: H), hydrogenated amorphous silicon germanium (aSixGey: H), etc., these amorphous semiconductors can be formed by low-temperature plasma CVD at about 100 ° C. In the case of CVD (catCVD), film formation at room temperature is also possible.

  In the photoelectric conversion elements of the first and second inventions, radical hydrogen is formed by plasma, photoexcitation, catalyst (heated tungsten, heated palladium, etc.) excitation, etc. before depositing the hydrogenated amorphous semiconductor film on the surface of the crystalline semiconductor region, The second surface of the crystalline semiconductor region can be cleaned and hydrogenated. In addition, impurities that can be hydrogenated and vaporized among the impurities attached to the second surface of the crystalline semiconductor region can be removed.

  When the crystalline semiconductor region is silicon, silicon germanium, or germanium, SF6 or the like can be excited in the same manner to etch and clean the second surface of the crystalline semiconductor region. In such a state, the interface between the hydrogenated amorphous semiconductor film and the crystalline semiconductor region with a lower interface state can be obtained by transporting to the deposition chamber of the hydrogenated amorphous semiconductor film without breaking the vacuum.

In the photoelectric conversion elements of the first and second inventions, the hydrogenated amorphous semiconductor film has a current of several tens of mA / cm ^{2 in} the thickness direction compared to the ultrathin insulating film used in the MIS type photoelectric conversion element. There is little deterioration even if it flows.

  In the photoelectric conversion element of the second invention, when the current value taken out from the first semiconductor film is large and the voltage drop due to the resistance of the first semiconductor when taking out through the first semiconductor film is large, the first semiconductor film A low-resistance first conductive electrode is provided in contact therewith.

  In the photoelectric conversion element of the second invention, when the current value taken out from the second semiconductor film is large and the voltage drop due to the resistance of the second semiconductor film when taken out through the second semiconductor film is large, the second semiconductor film A low-resistance first conductive electrode is provided in contact with the electrode. Here, the first conductive electrode and the second conductive electrode are separated from each other.

The materials and combinations of materials used for the first conductive electrode and the second conductive electrode of the photoelectric conversion element of the second invention are the same as those of the above-described photoelectric conversion element of the first invention.
In the photoelectric conversion element of the first invention, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film are formed using the same semiconductor as a material. It may be. Thereby, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the first invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  In the photoelectric conversion element of the second invention, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are formed using the same semiconductor as a material. It may be. As a result, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the second invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  In the photoelectric conversion element of the first invention, the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film may be one continuous film. As a result, the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the first invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region uniformly and low. .

  In the photoelectric conversion element of the second invention, the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film may be one continuous film. Thereby, the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the second invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  In the photoelectric conversion element of the first invention, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film may have the same film thickness. . Thereby, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the first invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  In the photoelectric conversion element of the second invention, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film may have the same film thickness. . As a result, at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film can be deposited simultaneously. For this reason, the photoelectric conversion element of the second invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  A third invention is a method for manufacturing a photoelectric conversion element according to the first invention, wherein at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film are formed. , Simultaneously deposited on the second surface. Thereby, the manufacturing method of the third invention can reduce the frequency with which the second surface of the crystalline semiconductor region is exposed to processing, and can keep the interface state density on the second surface of the crystalline semiconductor region low.

  The fourth invention is a method for manufacturing a photoelectric conversion element according to the second invention, wherein at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are formed. , Simultaneously deposited on the backside. Thereby, the manufacturing method of the 4th invention can reduce the frequency which the back surface of a crystalline semiconductor layer is exposed to a process, and can suppress the interface state density in the back surface of a crystalline semiconductor layer low.

1 is a cross-sectional view illustrating a configuration of a photoelectric conversion element 1. 3 is a first cross-sectional view showing a manufacturing process of the photoelectric conversion element 1. FIG. 5 is a second cross-sectional view showing the manufacturing process of the photoelectric conversion element 1. FIG. FIG. 5 is a third cross-sectional view showing the manufacturing process of the photoelectric conversion element 1. 6 is a fourth cross-sectional view showing the manufacturing process of the photoelectric conversion element 1. FIG. It is a graph which shows the dependence with respect to the electric charge Qf of solar cell efficiency. 2 is a cross-sectional view illustrating a configuration of a photoelectric conversion element 101. FIG. 11 is a first cross-sectional view showing the manufacturing process of Modification 1. FIG. 11 is a second cross-sectional view showing the manufacturing process of Modification 1. FIG. 11 is a third cross-sectional view showing the manufacturing process of Modification 1. FIG. 11 is a fourth cross-sectional view showing the manufacturing process of Modification 1. FIG. 10 is a fifth cross-sectional view showing the manufacturing process of Modification 1. FIG. It is sectional drawing which shows the structure of the photoelectric conversion element of a nonpatent literature 2.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
[Configuration of Photoelectric Conversion Element 1]
As shown in FIG. 1, the photoelectric conversion element 1 of this embodiment includes a crystalline semiconductor region 10, a hydrogenated amorphous semiconductor film 20, first and second semiconductor films 30 and 40, and first and second conductive electrodes. 50, 60, a second charge retaining insulating film 70, a passivation film 80, and an antireflection film 90.

The crystalline semiconductor region 10 is a region formed of a polycrystalline or single crystal semiconductor. In the present embodiment, the crystalline semiconductor region 10 is a substrate made of silicon and having a thickness of 150 μm. In the present embodiment, the crystalline semiconductor region 10 is doped with n-type impurities at a concentration of 1.9 × 10 ¹⁵ [/ cm ³ ]. The crystal semiconductor region 10 may be p-type.

The hydrogenated amorphous semiconductor film 20 is a film formed of an amorphous semiconductor and hydrogenated.
The hydrogenated amorphous semiconductor film 20 is disposed in contact with the second surface 11 of the crystalline semiconductor region 10. In the present embodiment, the hydrogenated amorphous semiconductor film 20 is hydrogenated amorphous silicon having a thickness of 5 nm. Further, in this embodiment, the hydrogenated amorphous semiconductor film 20 is not intentionally doped with impurities, or even if doped, n-type impurities are doped at a concentration of 2.2 × 10 ¹⁵ [/ cm ³ ]. It is a grade that has been done. Further, the hydrogenated amorphous semiconductor film 20 can passivate the interface between the crystalline semiconductor region 10 and the second surface 11 by hydrogen bonding. For this reason, the interface state density can be kept low. In particular, the effect is great when the crystalline semiconductor region 10 is formed of silicon, silicon-germanium, or germanium.

The hydrogenated amorphous semiconductor film 20 is less deteriorated even when a current of the order of several tens [mA / cm ² ] is passed, compared to the ultrathin insulating film used in the MIS type photoelectric conversion element. Valence control impurities (for example, boron, phosphorus, arsenic, etc.) can be added to adjust the resistivity and Fermi level, but the addition of valence electron control impurities is accompanied by an increase in electronic defects in the film. The concentration of electron control impurities (boron, phosphorus, etc.) is preferably less than 10 ¹⁸ [/ cm ³ ].

  The first and second semiconductor films 30 and 40 are disposed in contact with the second surface 21 of the hydrogenated amorphous semiconductor film 20. In the present embodiment, the first semiconductor film 30 and the second semiconductor film 40 are formed of a hydrogenated amorphous silicon film and have a thickness of 20 nm.

  The first semiconductor film 30 and the second semiconductor film 40 are alternately arranged in contact with the second surface 21 of the hydrogenated amorphous semiconductor film 20. In FIG. 1, one each of the first and second semiconductor films 30 and 40 is shown. The first semiconductor film 30 and the second semiconductor film 40 juxtaposed with each other are spaced apart so as not to be electrically connected to each other.

In the present embodiment, the first semiconductor film 30 is doped with an n-type impurity (phosphorus) at a concentration of 1.5 × 10 ¹⁹ [/ cm ³ ], and the second semiconductor film 40 is formed of a p-type impurity (boron). ) Is doped at a concentration of 2.05 × 10 ¹⁹ [/ cm ³ ]. Note that at least 10 ¹⁸ [atoms / cm ³ ] or more of valence electron control impurities (phosphorus, arsenic, boron, or the like) are added to the first semiconductor film 30 and the second semiconductor film 40.

The conductive electrode 50 is formed of nanocarbon such as silver (Ag), aluminum (Al), or graphene, and is disposed on the first semiconductor film 30.
The conductive electrode 60 is made of nanocarbon such as silver (Ag), aluminum (Al), or graphene, and is disposed on the second semiconductor film 40.

  Further, in order to ensure light reflection or to prevent a reaction between the first and second conductive electrode metals and the first and second semiconductor films, the transparent conductive film is made of a metal thin film, a metal printed film, graphene, etc. In some cases, a two-layer structure provided between the nanocarbon and the first and second semiconductor films is employed. In addition, as transparent conductive film, indium oxide (InOx), hydrogenated indium oxide (InOx: H), indium tin oxide (ITO), zinc oxide (ZnOx) and its aluminum (Al) additive or boron (B) additive , Etc. are used. Silver (Ag), aluminum (Al), etc. are used as a metal of a metal thin film and a metal printing film.

The charge retaining insulating film 70 is an insulating film formed so as to retain charges on the surface and / or inside thereof, and is in contact with the second surface 21 of the hydrogenated amorphous semiconductor film 20, and includes the first semiconductor film 30 and the second semiconductor film 30. It arrange | positions so that it may be located between the semiconductor films 40. In the present embodiment, the charge holding insulating film 70 is a silicon nitride film, and holds positive charges with a charge density of 1 × 10 ¹³ [q / cm ² ], for example. In addition, q in [q / cm ² ] is an elementary charge (a charge of one electron) and is 1.6 × 10 ⁻¹⁹ coulomb.

When the crystalline semiconductor region 10 is n-type, the charge density of the charge retaining insulating film 70 for creating a state in which the second surface 11 is accumulated and minority carriers are repelled is about 1 to 10 Ωcm in the crystalline semiconductor region 10. In the case where a valence control impurity is not intentionally added to a portion of the hydrogenated amorphous semiconductor film 20 that is in contact with the charge retention insulating film 70, it is 8 × 10 ¹¹ [q / cm ² ] or more.

  When the crystalline semiconductor region 10 is p-type, an insulating film having a positive charge, such as alumina, is used as the charge holding insulating film 70 for creating a state in which the second surface 11 is accumulated and minority carriers are repelled.

  The passivation film 80 is disposed so as to be in contact with the first surface 12 of the crystalline semiconductor region 10 in order to suppress recombination of minority carriers generated when light enters the photoelectric conversion element 1. In the present embodiment, the passivation film 80 is hydrogenated amorphous silicon formed of amorphous silicon and hydrogenated, and has a thickness of 5 nm. The passivation film 80 can improve conversion efficiency.

  The antireflection film 90 is disposed so as to contact the first surface 81 of the passivation film 80. In the present embodiment, the antireflection film 90 is a silicon nitride film and has a thickness of 75 nm. This antireflection film 90 can further improve the conversion efficiency.

[Manufacturing Process of Photoelectric Conversion Element 1]
Next, an example of the manufacturing process of the photoelectric conversion element 1 will be described.
As shown in FIG. 2, in a state where the passivation film 80 and the antireflection film 90 are stacked on the first surface 12 of the crystalline semiconductor region 10, first, cleaning and hydrogen are performed on the second surface 11 of the crystalline semiconductor region 10. After the termination treatment, a hydrogenated amorphous semiconductor film 20 is deposited on the second surface 11 of the crystalline semiconductor region 10 by low temperature plasma CVD (Chemical Vapor Deposition) or low temperature catalytic CVD.

Hydrogenated amorphous semiconductor film 20 is hydrogenated amorphous silicon (aSi: H), hydrogenated amorphous silicon carbide (aSi _x C _y : H), hydrogenated amorphous silicon containing oxygen (aSi _x O _y : H), hydrogenated In the case of amorphous silicon / germanium (aSi _x Ge _y : H), these hydrogenated amorphous semiconductors can be formed by low-temperature plasma CVD at about 100 ° C., and in the case of catalytic CVD, film formation at room temperature is also possible. is there.

  Before depositing the hydrogenated amorphous semiconductor film on the second surface of the crystalline semiconductor region 10, radical hydrogen is formed by plasma, photoexcitation, or catalyst (heated tungsten, heated palladium, etc.) excitation to clean the second surface of the crystalline semiconductor region 10. Can be hydrogenated. Further, impurities that can be hydrogenated and vaporized among the impurities attached to the second surface of the crystalline semiconductor region 10 can be removed.

  In the case where the crystalline semiconductor region 10 is silicon, silicon germanium, or germanium, SF 6 or the like can be excited in the same manner to etch and clean the second surface of the crystalline semiconductor region 10. In this state, the interface between the hydrogenated amorphous semiconductor film and the crystalline semiconductor region 10 with fewer interface states can be obtained by transporting it to the hydrogenated amorphous semiconductor film deposition chamber without breaking the vacuum.

  Next, as shown in FIG. 3, the second semiconductor is deposited by depositing a hydrogenated amorphous silicon film to which a valence electron control impurity is added on a part of the hydrogenated amorphous semiconductor film 20 by low temperature plasma CVD or low temperature catalytic CVD. A film 40 is formed. In order to set the position where the second semiconductor film 40 is disposed and the shape of the second semiconductor film 40, a deposition mask in which an opening corresponding to the shape of the second semiconductor film 40 is formed is used. it can.

  Next, as shown in FIG. 4, the first semiconductor film is deposited on the hydrogenated amorphous semiconductor film 20 so as to be separated from the second semiconductor film 40 by low temperature plasma CVD or low temperature catalytic CVD. A film 30 is formed. In order to set the position where the first semiconductor film 30 is disposed and the shape of the first semiconductor film 30, a deposition mask in which an opening corresponding to the shape of the first semiconductor film 30 is formed is used. it can.

  Next, as shown in FIG. 5, a vapor deposition mask having openings corresponding to the shape of the conductive electrodes 50 and 60 is used to set the positions and shapes of the conductive electrodes 50 and 60 by vacuum vapor deposition or sputtering. Then, an electrode material (for example, silver or aluminum) is deposited on the first semiconductor film 30 and the second semiconductor film 40 to form the conductive electrodes 50 and 60. The conductive electrodes 50 and 60 have a length along the alignment direction DA so that the electrode material does not adhere to regions other than the first and second semiconductor films 30 and 40 by vacuum deposition or sputtering. 30, formed to be shorter than the second semiconductor film 40. Therefore, regions 33 and 43 that are not covered with the conductive electrodes 50 and 60 exist on the second surfaces 31 and 41 of the first semiconductor film 30 and the second semiconductor film 40. The widths of the regions 33 and 43 are set such that an interval Wg between the first semiconductor film 30 and the second semiconductor film 40 is obtained by using a self-alignment process as shown in FIG. 10 (see FIG. 1). It can be adjusted smaller.

  Next, silicon nitride is used by low temperature plasma CVD or low temperature catalytic CVD, using a deposition mask in which an opening corresponding to the shape of the charge holding insulating film 70 is formed in order to set the position and shape of the charge holding insulating film 70. By depositing the film, the charge retaining insulating film 70 is formed. The silicon nitride film can be deposited by low-temperature plasma CVD at about 100 ° C. or low-temperature low-temperature catalytic CVD including room temperature.

  As shown in FIG. 1, the charge retention insulating film 70 is in contact with the hydrogenated amorphous semiconductor film 20 between the first semiconductor film 30 and the second semiconductor film 40, and on the regions 33 and 43, the first semiconductor film 30. , Formed in contact with the second semiconductor film 40.

[Solar cell efficiency of photoelectric conversion element 1]
Next, in order to quantitatively confirm the effect of the charge retention insulating film 70, the photovoltaic cell efficiency (open voltage Voc) for the charge retained in the charge retention insulating film 70 (hereinafter referred to as retained charge) for the photoelectric conversion element 1. Changes in [mV], short circuit current density Jsc [mA / cm ² ], fill factor FF [%], power conversion efficiency η [%]) were examined. For evaluation of the conversion efficiency, a simulated light source of Air Mass 1.5 is used. For example, when a silicon nitride film is used as the charge retention insulating film, the retained charge changes by changing the ratio of silicon and nitrogen in the silicon nitride or from the electrode provided on the charge retention insulating film. This can be realized by injecting.

Further, the width of the first semiconductor film 30 is 500 μm, the width of the second semiconductor film 40 is 1200 μm, and the interval Wg (see FIG. 1) between the first semiconductor film 30 and the second semiconductor film 40 is 50 μm, 100 μm, 150 μm. And the density Qf of the retained charge was changed from 10 ¹¹ to 10 ¹³ [q / cm ² ]. Note that the interface state density of the second surface 11 of the crystalline semiconductor region 10 is 10 ¹² [/ cm ² ]. The dimensions of the regions 33 and 43 were made small enough to be ignored by the self-alignment process.

The interface state density (= 10 ¹² [/ cm ² ]) of the second surface 11 of the crystalline semiconductor region 10 is much larger than the interface state density (= 10 ¹⁰ [/ cm ² ]) of the clean interface, Although it is a level that can be realized without maintaining ultra-cleanness, as shown in FIG. 6, the density Qf of the retained charge increases from 1 × 10 ¹¹ to 8 × 10 ¹¹ , and when it exceeds that, all solar cells The parameter approaches the maximum value rapidly. The power conversion efficiency approaches 0.95 times the maximum value of about 21%. This tendency does not change greatly even if the interval Wg changes between 50 and 150 μm.

As described above, in the photoelectric conversion element 1, even if the interface state density of the second surface 11 of the crystalline semiconductor region 10 is as large as 10 ¹² [/ cm ² ], the distance between the first semiconductor film 30 and the second semiconductor film 40. Wg can be increased, and even if the interval Wg varies, the conversion efficiency close to the maximum efficiency can be obtained by increasing the density Qf of the retained charge.

Further, when 8 × 10 ¹⁷ atoms / cm ³ of valence electron control impurities (phosphorus when the semiconductor region 10 is n-type) is added to the amorphous semiconductor film 20 at the portion where the charge retention insulating film 70 is in contact, the retained charge density Qf is 4 × 10 ¹¹ [ / Cm ² ] and above, all solar cell parameters approach 0.95 times the maximum value.

As described above, the photoelectric conversion element 1 includes the crystalline semiconductor region 10, the hydrogenated amorphous semiconductor film 20, the first semiconductor film 30, the second semiconductor film 40, and the charge retention insulating film 70.
The crystalline semiconductor region 10 is formed of polycrystalline or single crystal silicon and has an n-type.

The hydrogenated amorphous semiconductor film 20 is disposed so as to be in contact with the second surface 11 of the crystalline semiconductor region 10 and is formed of amorphous silicon and hydrogenated.
The first semiconductor film 30 is disposed so as to be in contact with the hydrogenated amorphous semiconductor film 20, and is formed of 20 nm thick hydrogenated amorphous silicon to which a donor (phosphorus) is added at 1.5 × 10 ¹⁹ atoms / cm ³ .

The second semiconductor film 40 is separated from the first semiconductor film 30, is disposed so as to be in contact with the hydrogenated amorphous semiconductor film 20, and is 20 nm thick hydrogenated with acceptor (boron) added at 2.05 × 10 ¹⁹ atoms / cm ³ . It is made of amorphous silicon.

  The charge retaining insulating film 70 is an insulating film that is disposed between the first semiconductor film 30 and the second semiconductor film 40 so as to be in contact with the hydrogenated amorphous semiconductor film 20 and retains charges on the surface and / or inside thereof.

In the photoelectric conversion element 1, the polarity of the charge held on the surface and / or inside the charge holding insulating film 70 is positive when the crystalline semiconductor region 10 is n-type.
The photoelectric conversion element 1 configured as described above generates a photogenerated current having the same sign as the majority carriers generated inside the photoelectric conversion element 1 when light enters from the first surface 12 side of the crystal semiconductor region 10. The semiconductor region 10 can be extracted from the first semiconductor film 30 provided on the second surface 11 side. In addition, the photoelectric conversion element 1 includes a photovoltage generated when light enters from the first surface 12 side of the crystal semiconductor region 10, and a photogenerated current having the same sign as the minority carrier generated inside the photoelectric conversion element 1. Can be extracted from the second semiconductor film 40 provided on the second surface 11 side of the crystalline semiconductor region 10.

  The photoelectric conversion element 1 includes the charge retaining insulating film 70 between the first semiconductor film 30 and the second semiconductor film 40 on the second surface 11 side of the crystal semiconductor region 10, thereby providing the second in the crystal semiconductor region 10. A portion of the surface 11 facing the charge retaining insulating film 70 is in an accumulated state. This portion of the electric field becomes an electric field having a polarity for repelling minority carriers from the second surface 11, and thus prevents the chance that the light-generated minority carriers are recombined on the second surface 11 and lost. Therefore, the photoelectric conversion element 1 can improve the photocurrent output and can also improve the output voltage. In addition, since the majority carriers are collected on the second surface 11 of the crystalline semiconductor region 10 more than the equilibrium state, the surface of the second surface 11 of the crystalline semiconductor region 10 between the first semiconductor film 30 and the second semiconductor film 40. Resistance becomes small and the photoelectric conversion element 1 can also improve a fill factor. For this reason, even if the space | interval of the 1st semiconductor film 30 and the 2nd semiconductor film 40 becomes large, the photoelectric conversion element 1 can suppress the fall of conversion efficiency.

  In addition, since the charge retaining insulating film 70 is an insulating film, even if the charge retaining insulating film 70 overlaps the first semiconductor film 30 and the second semiconductor film 40, the charge retaining insulating film 70 is between the first semiconductor film 30 and the second semiconductor film 40. Is not electrically shorted. Therefore, alignment between the first semiconductor film 30 and the second semiconductor film 40 and the charge retaining insulating film 70 does not require high accuracy, and the structure is easy to manufacture from the viewpoint of manufacturing technology. That is, the photoelectric conversion element 1 and further the photoelectric conversion element of the present invention can be manufactured with a margin in processing dimensions.

  In the photoelectric conversion element 1, the hydrogenated amorphous semiconductor film 20 in contact with the first semiconductor film 30, the second semiconductor film 40, and the charge retention insulating film 70 is a continuous film. That is, the hydrogenated amorphous semiconductor films that are in contact with the first semiconductor film 30, the second semiconductor film 40, and the charge retention insulating film 70 are formed using the same semiconductor as the material and have the same film thickness. Thereby, the hydrogenated amorphous semiconductor film 20 in contact with the first semiconductor film 30, the second semiconductor film 40 and the charge retention insulating film 70 can be deposited simultaneously. For this reason, the photoelectric conversion element 1 can reduce the frequency with which the second surface 11 of the crystalline semiconductor region 10 is exposed to processing, and can keep the interface state density at the second surface 11 of the crystalline semiconductor region 10 low.

  In the embodiment described above, the crystalline semiconductor region 10 is the crystalline semiconductor region in the present invention, and the hydrogenated amorphous semiconductor film 20 is the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor in the present invention. The semiconductor film, the first semiconductor film 30 is the first semiconductor film in the present invention, the second semiconductor film 40 is the second semiconductor film in the present invention, and the charge retaining insulating film 70 is the second charge retaining insulating film in the present invention.

(Second Embodiment)
A second embodiment of the present invention will be described below with reference to the drawings.
[Configuration of Photoelectric Conversion Element 101]
As shown in FIG. 7, the photoelectric conversion element 101 of this embodiment has a first conductive electrode 170, a first work function film 150, and a region 33 and 34 shown in FIG. The planar shape of the first hydrogenated amorphous film 120 is automatically aligned (self-aligned), and the planar shapes of the second conductive electrode 180, the second work function film 160, and the second hydrogenated amorphous film 130 are automatically aligned ( The self-aligned structure is stacked on the second surface 111 of the crystalline semiconductor region 110. FIG. A charge retaining insulating film 190 and a fourth hydrogenated amorphous semiconductor film are stacked on the second surface 111 of the crystalline semiconductor region 110 in a portion where the first work function film 150 and the second work function film 160 are separated by Wg. . In addition, FIGS. 8-12 of the Example of another photoelectric conversion element shows an example of the manufacturing method to perform the said automatic alignment.

  As shown in FIG. 7, the photoelectric conversion element 101 of the present embodiment includes a crystalline semiconductor region 110, hydrogenated amorphous semiconductor films 120, 130, and 140, work function films 150 and 160, conductive electrodes 170 and 180, A charge retaining insulating film 190, a passivation film 200, and an antireflection film 210 are provided.

The crystalline semiconductor region 110 is a substrate formed of a polycrystalline or single crystal semiconductor. In the present embodiment, the crystalline semiconductor region 110 is formed of silicon whose conductivity type is n-type. P-type silicon may be used. The thickness is selected to be smaller than the minority carrier diffusion length. In the present embodiment, the crystalline semiconductor region 110 is doped with n-type impurities at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁶ [/ cm ³ ].

The hydrogenated amorphous semiconductor films 120, 130, and 140 are formed of an amorphous semiconductor and hydrogenated, and are disposed so as to be in contact with the second surface 111 of the crystalline semiconductor region 110. In this embodiment, the hydrogenated amorphous semiconductor films 120 and 130 are hydrogenated amorphous silicon having a thickness of 5 nm. In this embodiment, the hydrogenated amorphous semiconductor films 120 and 130 are not intentionally doped with impurities. The hydrogenated amorphous semiconductor film 140 is hydrogenated amorphous silicon having a thickness of 7 nm, and the n-type impurity is variable at a concentration from 2.2 × 10 ¹⁵ [/ cm ³ ] to 8 × 10 ¹⁷ [/ cm ³ ]. Further, the hydrogenated amorphous semiconductor films 120, 130, and 140 can passivate the interface with the second surface 111 of the crystalline semiconductor region 110 by hydrogen bonding. For this reason, the interface state density can be kept low. In particular, the effect is large when the crystalline semiconductor region 110 is formed of silicon, silicon-germanium, or germanium.

  The hydrogenated amorphous semiconductor films 120 and 130 are provided in contact with the second surface 111 of the crystalline semiconductor region 110 and are alternately arranged along a preset arrangement direction DA. In FIG. 7, one hydrogenated amorphous semiconductor film 120 and 130 is shown. The hydrogenated amorphous semiconductor film 120 and the hydrogenated amorphous semiconductor film 130 that are juxtaposed with each other are arranged apart from each other. The hydrogenated amorphous semiconductor films 120 and 130 may be the same thickness or different from each other.

  The hydrogenated amorphous semiconductor film 140 is disposed so as to be positioned between the hydrogenated amorphous semiconductor film 120 and the hydrogenated amorphous semiconductor film 130. The hydrogenated amorphous semiconductor film 140 may have a thickness different from that of the hydrogenated amorphous semiconductor films 120 and 130.

  The work function film 150 is formed of a material having a work function having an energy level on the Fermi level side of the crystal semiconductor region 110 when viewed from the energy level of the mid-gap of the energy band of the crystal semiconductor region 110. Arranged on the amorphous semiconductor film 120. Note that the mid gap indicates an energy level at the center of the forbidden band of the crystalline semiconductor region 110. The work function energy level is an energy level lower than the vacuum energy level (vacuum level) by the value of the work function. In this embodiment, the work function film 150 is made of n-type zinc oxide, aluminum, or the like, and is deposited on the hydrogenated amorphous semiconductor film 120 by vacuum deposition or sputtering.

  The work function film 160 is formed of a material having a work function having an energy level opposite to the Fermi level of the crystal semiconductor region 110 when viewed from the energy level of the mid gap of the crystal semiconductor region 110, and on the hydrogenated amorphous semiconductor film 130. Placed in. In the present embodiment, the work function film 160 is made of molybdenum oxide (MoOx), tungsten oxide (WOx), or the like, and is deposited on the hydrogenated amorphous semiconductor film 130 by vacuum deposition or sputtering.

  The conductive electrode 170 is made of silver (Ag), aluminum (Al), or the like, and is disposed on the work function film 150. The conductive electrode 180 is made of silver (Ag), aluminum (Al), or the like, and is disposed on the work function film 160. In order to prevent the case where the first and second work function films and the metal film are combined at the interface between the first and second work function films and the metal film when the metal films are used as the conductive electrodes 170 and 180. In order to secure a high reflectance of light at the interface, a transparent conductive film such as indium oxide, indium tin oxide, or zinc oxide may be inserted between the metal film and the first and second work function films. .

  The charge retaining insulating film 190 is an insulating film formed so as to retain charges on the surface and / or inside thereof, and is disposed on the hydrogenated amorphous semiconductor film 140. In the present embodiment, the charge retention insulating film 190 is a silicon nitride film when the crystalline semiconductor region 110 is n-type, and an aluminum oxide film when the crystalline semiconductor region 110 is p-type.

  The passivation film 200 is disposed in contact with the first surface 112 of the crystalline semiconductor region 110 in order to suppress recombination of minority carriers generated when light enters the photoelectric conversion element 101. The antireflection film 210 is disposed so as to contact the first surface 201 of the passivation film 200.

  Thus, the photoelectric conversion element 101 includes the crystalline semiconductor region 110, the hydrogenated amorphous semiconductor films 120, 130, and 140, the work function films 150 and 160, and the charge retention insulating film 190.

The crystalline semiconductor region 110 is formed of polycrystalline or single crystal silicon and has an n-type.
The hydrogenated amorphous semiconductor film 120 is disposed so as to be in contact with the second surface 111 of the crystalline semiconductor region 110, is formed of amorphous silicon, and is hydrogenated.

  The work function film 150 is disposed so as to be in contact with the hydrogenated amorphous semiconductor film 120, and has a work function having an energy level on the Fermi level side of the crystalline semiconductor region 110 as viewed from the energy level of the mid gap of the energy band of the crystalline semiconductor region 110. It is formed with the material which has.

The hydrogenated amorphous semiconductor film 130 is disposed so as to be in contact with the second surface 111 of the crystalline semiconductor region 110, is formed of amorphous silicon, and is hydrogenated.
The work function film 160 is disposed so as to be separated from the work function film 150 and in contact with the hydrogenated amorphous semiconductor film 130, and is opposite to the Fermi level of the crystalline semiconductor region 110 when viewed from the energy level of the mid gap of the crystalline semiconductor region 110. It is made of a material having a work function with an energy level on the (opposite side).

  The hydrogenated amorphous semiconductor film 140 is disposed between the work function film 150 and the work function film 160 so as to be in contact with the second surface 111 of the crystalline semiconductor region 110, is formed of amorphous silicon, and is hydrogenated. ing.

  The charge retaining insulating film 190 is an insulating film that is disposed between the work function film 150 and the work function film 160 so as to be in contact with the hydrogenated amorphous semiconductor film 140 and retains charges on the surface and / or inside thereof.

  In the photoelectric conversion element 101, the polarity of the retained charge held on the surface and / or inside the charge retaining insulating film 190 is positive when the conductivity of the crystalline semiconductor region is n-type, and the conductivity of the crystalline semiconductor region is p-type. The case is negative.

  The photoelectric conversion element 101 configured as described above generates a photo-generated current having the same sign as the majority carrier generated inside the photoelectric conversion element 101 when light enters from the first surface 112 side of the crystalline semiconductor region 110. It can be extracted from the work function film 150 provided on the second surface 111 side of the semiconductor region 110. In addition, the photoelectric conversion element 101 includes a photovoltage generated when light enters from the first surface 112 side of the crystalline semiconductor region 110, and a photogenerated current having the same sign as the minority carrier generated in the photoelectric conversion element 101. Can be extracted from the work function film 160 provided on the second surface 111 side of the crystalline semiconductor region 110.

  The photoelectric conversion element 101 includes the charge retaining insulating film 190 between the work function film 150 and the work function film 160 on the second surface 111 side of the crystal semiconductor region 110, whereby the second surface 111 of the crystal semiconductor region 110. The portion facing the charge retaining insulating film 190 is in the accumulation state. This portion of the electric field becomes an electric field having a polarity for repelling minority carriers from the second surface 111, so that the opportunity for light-generated minority carriers to be recombined on the second surface 111 and lost is prevented. Therefore, the photoelectric conversion element 101 can improve the photocurrent output and can also improve the output voltage. In addition, since more carriers are collected on the second surface 111 of the crystalline semiconductor region 110 than in the equilibrium state, the first surface of the second surface 111 of the crystalline semiconductor region 110 between the work function film 150 and the work function film 160. The resistance is reduced, and the photoelectric conversion element 101 can also improve the fill factor. For this reason, even if the space | interval of the work function film | membrane 150 and the work function film | membrane 160 becomes large, the photoelectric conversion element 101 can suppress the fall of conversion efficiency.

  In addition, since the charge retaining insulating film 190 is an insulating film, the work function film 150 and the work function film 160 are not electrically short-circuited even if the charge retaining insulating film 190 is superimposed on the work function films 150 and 160. Therefore, the alignment between the work function films 150 and 160 and the charge retaining insulating film 190 does not require high accuracy, and the structure is easy to manufacture from the viewpoint of manufacturing technology. That is, the photoelectric conversion element 101 can be manufactured with a margin in processing dimensions.

  In the photoelectric conversion element 101, the hydrogenated amorphous semiconductor films 120 and 130 are formed using the same semiconductor as a material and can have the same film thickness. Thereby, the hydrogenated amorphous semiconductor films 120 and 130 can be deposited simultaneously. Therefore, the photoelectric conversion element 101 can reduce the frequency with which the second surface 111 of the crystalline semiconductor region 110 is exposed to processing, and can suppress the interface state density on the second surface 111 of the crystalline semiconductor region 110 to be low.

  In the embodiment described above, the crystalline semiconductor region 110 is the crystalline semiconductor region in the present invention, the hydrogenated amorphous semiconductor film 120 is the first hydrogenated amorphous semiconductor film in the present invention, and the work function film 150 is the first work function film in the present invention. The hydrogenated amorphous semiconductor film 130 is the second hydrogenated amorphous semiconductor film in the present invention, the work function film 160 is the second work function film in the present invention, and the hydrogenated amorphous semiconductor film 140 is the third hydrogenated amorphous semiconductor film in the present invention. The charge retaining insulating film 190 is the first charge retaining insulating film in the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
(Modification 1)
For example, in the first embodiment, the manufacturing process in which the regions 33 and 43 not covered with the conductive electrodes 50 and 60 exist on the second surfaces 31 and 41 of the first and second semiconductor films 30 and 40 is shown (FIG. 5). However, in order to avoid the formation of the regions 33 and 43, the following manufacturing process may be employed.

  First, as shown in FIG. 8, the widths of the first and second semiconductor films 30 and 40 and the conductive electrodes 50 and 60 (that is, the length along the arrangement direction DA) are made larger than those in the first embodiment. First, second semiconductor films 30 and 40 and conductive electrodes 50 and 60 are formed. Then, as shown in FIG. 9, etching resists 56 and 66 are printed with a width smaller than the width of the first and second semiconductor films 30 and 40 and the conductive electrodes 50 and 60 formed in the step shown in FIG. Further, as shown in FIG. 10, the conductive electrode 50, the first semiconductor film 30, the conductive electrode 60, and the second semiconductor film 40 are etched using the etching resist 56 and the etching resist 66 as a mask, respectively. Thereby, formation of the regions 33 and 43 can be avoided.

  Next, as shown in FIG. 11, the hydrogenated amorphous semiconductor film 25 and the charge retaining insulating film 70 are deposited using a deposition mask with the etching resists 56 and 66 adhered to the conductive electrodes 50 and 60. After that, when the etching resists 56 and 66 are melted or vapor-phase etched with a solvent or ozone or the like, a charge is held between the first semiconductor film 30 and the second semiconductor film 40 as shown in FIG. The insulating film 70 remains. In this case, the hydrogenated amorphous semiconductor film 25 is interposed between the charge retaining insulating film 70 and the first and second semiconductor films 30 and 40. However, while the thickness of the hydrogenated amorphous semiconductor film 25 is usually around 10 nm, the interval Wg is on the order of several tens to one hundred μm. For this reason, the influence of the hydrogenated amorphous semiconductor film 25 can be ignored.

  Further, in order to avoid the hydrogenated amorphous semiconductor film 25 being interposed between the charge retaining insulating film 70 and the first and second semiconductor films 30 and 40, the conductive electrode 50 using the etching resists 56 and 66 as a mask. , 60 and the first and second semiconductor films 30 and 40 are preferably not etched until the hydrogenated amorphous semiconductor film 20 is etched. This is because it is not necessary to deposit the hydrogenated amorphous semiconductor film 25.

(Modification 2)
In the first embodiment, the crystalline semiconductor region 10 has an n-type conductivity. However, the conductivity type of the crystalline semiconductor region 10 may be p-type. In this case, it is necessary that the conductivity type of the first semiconductor film 30 is p-type, the conductivity type of the second semiconductor film 40 is n-type, and the polarity of the charge held by the charge holding insulating film 70 is negative. An example of the insulating film having a negative charge is aluminum oxide. The aluminum oxide film can be deposited at a low temperature of 250 ° C. or lower by an atomic layer deposition (ALD) method.

(Modification 3)
In the first embodiment, the first and second semiconductor films 30 and 40 are used. However, hydrogenated microcrystalline silicon may be used instead of the first and second semiconductor films 30 and 40. The microcrystal has a structure in which a nanometer to submicron size crystal is embedded in an amorphous structure, and has a lower resistivity than an amorphous structure.

(Modification 4)
In the first embodiment, the antireflection film 90 is a silicon nitride film. However, the antireflection film 90 may be made of titanium oxide. Alternatively, a material that serves as both a passivation film and an antireflection film may be selected. An example of such a material is a silicon nitride film when the crystalline semiconductor region 10 is n-type silicon.

(Modification 5)
In the first and second embodiments, the hydrogenated amorphous semiconductor film is hydrogenated amorphous silicon (aSi: H). However, as a hydrogenated amorphous semiconductor film, hydrogenated amorphous silicon (aSi: H), hydrogenated amorphous silicon carbide (aSi _x C _y : H), hydrogenated amorphous silicon containing oxygen (aSi _x O _y : H), Hydrogenated amorphous silicon germanium (aSi _x Ge _y : H) or the like may be used.

In the first and second embodiments, the conductive electrode is a metal thin film. However, the conductive electrode may be a metal printed film (metal paste coated, dried or baked), or nanocarbon such as graphene. Further, in order to ensure light reflection, or to prevent the reaction between the metal and the first and second semiconductor films or the first and second work function films, a transparent conductive film is formed between the conductive electrodes 50 and 60 and the first and second conductive films. It may be provided between the two semiconductor films 30 and 40 and between the conductive electrodes 170 and 180 and the work function films 150 and 160. As the transparent conductive film, for example, indium oxide (InO _x ), hydrogenated indium oxide (InO _x : H), indium tin oxide (ITO), zinc oxide (ZnO _x ) and its aluminum (Al) additive or boron ( B) An additive etc. are mentioned.

(Modification 6)
In the first embodiment, after depositing the hydrogenated amorphous semiconductor film 20 so as to be in contact with the crystalline semiconductor region 10, the first and second semiconductor films 30, 40 and the charge retention are brought into contact with the hydrogenated amorphous semiconductor film 20. What forms the insulating film 70 is shown. However, the hydrogenated amorphous semiconductor film formed so as to be in contact with the crystalline semiconductor region 10 has a portion in contact with the first semiconductor film 30, a portion in contact with the second semiconductor film 40, and a portion in contact with the charge retention insulating film 70. Each may be deposited separately.

In the first embodiment, the portion of the hydrogenated amorphous semiconductor film 20 in contact with the first and second semiconductor films 30 and 40 is not intentionally doped with impurities, or the n-type impurity concentration even if it has been intentionally doped. Is 2.2 × 10 ¹⁵ [/ cm ³ ], and the n-type impurity concentration of the portion in contact with the charge retaining insulating film 70 in the hydrogenated amorphous semiconductor film 20 is 8 × 10 ¹⁷ [/ cm ³ ]. The retained charge density Qf that causes a rapid increase in conversion efficiency is 4 × 10 ¹¹ [q / cm ² ]. That is, if Qf ≧ 4 × 10 ¹¹ [q / cm ² ], the conversion efficiency increases.

The charge retention insulating film 70 for creating a state in which the second surface 11 of the crystalline semiconductor region 10 is in an accumulated state and minority carriers are repelled is crystalline silicon in which the crystalline semiconductor region 10 is about 1 to 10 Ωcm, When about 8 × 10 ¹⁷ [/ cm ³ ] of the valence electron control impurity is added to the portion of the amorphous semiconductor film 20 in contact with the charge retention insulating film 70, the value is 4 × 10 ¹¹ [q / cm ² ] or more.

  The hydrogenated amorphous semiconductor film formed so as to be in contact with the crystalline semiconductor region 10 includes at least a portion in contact with the first semiconductor film 30, a portion in contact with the second semiconductor film 40, and a portion in contact with the charge retention insulating film 70. Two may be deposited simultaneously. As a result, the frequency with which the second surface 11 of the crystalline semiconductor region 10 is exposed to processing can be reduced, and the interface state density on the second surface 11 of the crystalline semiconductor region 10 can be kept low.

(Modification 7)
In the second embodiment, the crystalline semiconductor region 110 has an n-type conductivity. However, the conductivity type of the crystalline semiconductor region 10 may be p-type. In this case, the work function film 150 is formed of a material having a work function whose energy level is closer to the valence band side than the mid gap energy level of the energy band of the crystalline semiconductor region 110, and the work function film 160 has the energy level. Is formed of a material having a work function located on the conduction band side of the midgap energy level of the energy band of the crystalline semiconductor region 110.

(Modification 8)
In the second embodiment, the work function film 150 is formed of n-type zinc oxide, aluminum, or the like. However, the work function film 150 is a material having a work function that is an energy level close to the conduction band from the midgap energy level of the energy band of crystalline silicon, or an energy level closer to the vacuum energy level than the conduction band of crystalline silicon. For example, magnesium (a coating with a chemically stable material is necessary) can be used.

  In the second embodiment, the work function film 160 is made of molybdenum oxide (MoOx) or tungsten oxide (WOx). However, the work function film 160 has a work function that is close to the valence band from the midgap energy level of the crystalline silicon energy band, or is further away from the vacuum energy level than the valence band of crystalline silicon. Any material can be used.

Note that when the conductivity type of the crystalline semiconductor region 110 is p-type, the material selection groups for the work function film 150 and the work function film 160 are reversed.
(Modification 9)
In the second embodiment, the work function film 150 is formed of a material having a work function having an energy level on the Fermi level side of the crystalline semiconductor region 110 when viewed from the energy level of the mid gap of the energy band of the crystalline semiconductor region 110. Showed what has been. However, when the crystalline semiconductor region 110 is n-type, the work function film 150 is formed of a material having a work function whose energy level is closer to the conduction band than the Fermi level of the crystalline semiconductor region 110. Is desirable. When the conductivity type of the crystalline semiconductor region 110 is p-type, the work function film 150 has a valence band when the energy level is viewed from the energy level of the mid gap of the energy band of the crystalline semiconductor region 110. It is preferably formed of a material having a work function on the side. By this combination, an energy band is bent on the second surface 111 of the crystalline semiconductor region 110 to form an accumulation layer. For this reason, the photogenerated current having the same sign as the majority carriers in the crystalline semiconductor region 110 can be easily drawn, and the photogenerated minority carriers having the opposite sign can be extracted from the second under the work function film 150 by the electric field formed by the accumulation layer. It is repelled from the surface 111 and extracted at the second surface 111 under the work function film 160, and the efficiency of photocurrent is also increased.

(Modification 10)
In the second embodiment, when the crystalline semiconductor region 110 is n-type, the work function film 160 is on the valence band side when viewed from the energy level of the mid gap of the energy band of the crystalline semiconductor region 110. It is desirable to form with the material which has. When the conductivity type of the crystalline semiconductor region 110 is p-type, the work function film 160 has a work function whose energy level is on the conduction band side when viewed from the energy level of the mid gap of the energy band of the crystalline semiconductor region 110. It is desirable to form with the material which has. By this combination, an energy band is bent on the second surface 111 of the crystalline semiconductor region 110, and a depletion layer or an inversion layer is formed. Therefore, a photovoltaic voltage and a photogenerated current having the same sign as the minority carrier in the crystalline semiconductor region 110 can be extracted from the photoelectric conversion element 101.

(Modification 11)
Moreover, in the said 1st Embodiment, what was provided with the conductive electrodes 50 and 60 was shown. However, when the resistances of the first and second semiconductor films 30 and 40 are large enough to draw current from the first and second semiconductor films 30 and 40, the conductive electrodes 50 and 60 are omitted. May be. Similarly, in the said 2nd Embodiment, what was provided with the conductive electrodes 170 and 180 was shown. However, when the resistances of the work function films 150 and 160 are large enough to draw current from the work function films 150 and 160, the conductive electrodes 170 and 180 may be omitted.

(Modification 12)
In the first embodiment, after depositing the hydrogenated amorphous semiconductor film 20 so as to be in contact with the crystalline semiconductor region 10, the first and second semiconductor films 30, 40 and the charge retention are brought into contact with the hydrogenated amorphous semiconductor film 20. What forms the insulating film 70 is shown. That is, the hydrogenated amorphous semiconductor film formed so as to be in contact with the crystalline semiconductor region 10 includes a portion in contact with the first semiconductor film 30, a portion in contact with the second semiconductor film 40, and a portion in contact with the charge holding insulating film 70. The film thickness was equal. However, the portion in contact with the first semiconductor film 30, the portion in contact with the second semiconductor film 40, and the portion in contact with the charge retention insulating film 70 may have different thicknesses.

  Alternatively, the hydrogenated amorphous semiconductor film formed so as to be in contact with the crystalline semiconductor region 10 includes at least a portion in contact with the first semiconductor film 30, a portion in contact with the second semiconductor film 40, and a portion in contact with the charge retention insulating film 70. The two may have the same film thickness. As a result, the frequency with which the second surface 11 of the crystalline semiconductor region 10 is exposed to processing can be reduced, and the interface state density on the second surface 11 of the crystalline semiconductor region 10 can be kept low.

  In the second embodiment, the hydrogenated amorphous semiconductor film 140 has a thickness different from that of the hydrogenated amorphous semiconductor films 120 and 130. However, the hydrogenated amorphous semiconductor films 120, 130, and 140 may have different thicknesses.

  Alternatively, the hydrogenated amorphous semiconductor films 120, 130, and 140 may have the same thickness. Thereby, the hydrogenated amorphous semiconductor films 120, 130, and 140 can be deposited simultaneously. Therefore, the photoelectric conversion element 101 can reduce the frequency with which the second surface 111 of the crystalline semiconductor region 110 is exposed to processing, and can suppress the interface state density on the second surface 111 of the crystalline semiconductor region 110 to be low.

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric conversion element, 10 ... Crystal semiconductor region, 20, 25, 30, 40 ... Hydrogenated amorphous semiconductor film, 70 ... Charge holding insulating film, 101 ... Photoelectric conversion element, 110 ... Crystal semiconductor region, 120, 130, 140 ... Hydrogenated amorphous semiconductor film, 30, 40 --- Semiconductor film, 150, 160 ... Work function film, 190 ... Charge retention insulating film

Claims (19)

A crystalline semiconductor region formed of a polycrystalline or single crystal semiconductor and having a first conductivity type;
The crystalline semiconductor region has two opposing surfaces, one surface being a first surface and the other surface being a second surface, and a first hydrogenated amorphous semiconductor film disposed in contact with the second surface; ,
A first work function film disposed in contact with the first hydrogenated amorphous semiconductor film and formed of a material having a first work function;
A second hydrogenated amorphous semiconductor film disposed in contact with the second surface;
A second work function film formed of a material having a second work function, disposed away from the first work function film and in contact with the second hydrogenated amorphous semiconductor film;
A third hydrogenated amorphous semiconductor film disposed between and in contact with the second surface between the first work function film and the second work function film;
A first charge retaining insulation which is an insulating film which is disposed between the first work function film and the second work function film so as to be in contact with the third hydrogenated amorphous semiconductor film and retains charges on the surface and / or inside thereof. With a membrane,
The polarity of the first retained charge, which is the charge retained on the surface and / or inside the first charge retaining insulating film, is positive when the first conductivity type of the crystalline semiconductor region is n-type, and the crystal When the first conductivity type of the semiconductor region is p-type, the photoelectric conversion element is negative. ^{2. The} photoelectric conversion element according to claim 1, wherein the charge density of the first held electric charge is 4 × 10 ¹¹ [q / cm ² ] or more, where q is an elementary charge amount.   The energy level of the first work function of the first work function film and the energy level of the second work function of the second work function film are opposite to each other with respect to the energy level of the mid gap of the energy band of the crystalline semiconductor region. The photoelectric conversion element according to claim 1.   The photoelectric conversion element according to claim 1, wherein a first conductive electrode is provided in contact with the first work function film.   The photoelectric conversion element according to claim 1, wherein a second conductive electrode is provided in contact with the second work function film. A crystalline semiconductor region formed of a polycrystalline or single crystal semiconductor and having a first conductivity type;
The crystalline semiconductor region has two opposing surfaces, one surface being a first surface and the other surface being a second surface, and a first hydrogenated amorphous semiconductor film disposed in contact with the second surface; ,
A first semiconductor film disposed in contact with the first hydrogenated amorphous semiconductor film and formed of a semiconductor having the first conductivity type;
A second hydrogenated amorphous semiconductor film disposed in contact with the second surface;
The second semiconductor layer is formed of a semiconductor having a second conductivity type that is spaced apart from the first semiconductor film and is in contact with the second hydrogenated amorphous semiconductor film and having a conductivity type opposite to the first conductivity type. A semiconductor film;
A fourth hydrogenated amorphous semiconductor film disposed between and in contact with the second surface between the first semiconductor film and the second semiconductor film;
A second charge retaining insulating film which is disposed between the first semiconductor film and the second semiconductor film so as to be in contact with the fourth hydrogenated amorphous semiconductor film and is an insulating film which retains charges on the surface and / or inside thereof; With
The polarity of the second held charge, which is the charge held on the surface and / or inside the second charge holding insulating film, is positive when the first conductivity type of the crystalline semiconductor region is n-type, and the crystal When the first conductivity type of the semiconductor region is p-type, the photoelectric conversion element is negative. 7. The photoelectric conversion element according to claim 6, wherein a charge density of the second retained charge is 4 × 10 ¹¹ [q / cm ² ] or more, where q is an elementary charge amount. Providing a first conductive electrode in contact with the first semiconductor film;
The photoelectric conversion element according to claim 6, wherein a second conductive electrode is provided in contact with the second semiconductor film and apart from the first conductive electrode. The first semiconductor film and the second semiconductor film are hydrogenated amorphous silicon, and a valence electron control impurity of 10 ¹⁸ [atoms / cm ³ ] or more is added thereto. The photoelectric conversion element according to any one of 8. The first semiconductor film and the second semiconductor film are hydrogenated microcrystalline silicon which is formed of microcrystalline silicon and is hydrogenated, and is added with a valence electron control impurity of 10 ¹⁸ [atoms / cm ³ ] or more. The photoelectric conversion element according to any one of claims 6 to 8, wherein the photoelectric conversion element is provided. The at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film are formed using the same semiconductor as a material. The photoelectric conversion element of any one of Claim 3. The at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are formed using the same semiconductor as a material. The photoelectric conversion element according to claim 10. The first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, the third hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are not added or added with a valence control impurity. However, the density | concentration is less than 10 ^<18 > [atom / cm < ³ >], The photoelectric conversion element of any one of Claims 1-3 and Claims 6-10 characterized by the above-mentioned. The first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film are one continuous film. The photoelectric conversion element of a term. The first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are one continuous film. The photoelectric conversion element of a term. The film thickness of at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film is the same. The photoelectric conversion element of any one. The film thickness of at least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film is the same. The photoelectric conversion element of any one. It is a manufacturing method of the photoelectric conversion element given in any 1 paragraph of Claims 1-3,
At least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the third hydrogenated amorphous semiconductor film are simultaneously deposited on the second surface. Manufacturing method. It is a manufacturing method of the photoelectric conversion element given in any 1 paragraph of Claims 6-10,
At least two of the first hydrogenated amorphous semiconductor film, the second hydrogenated amorphous semiconductor film, and the fourth hydrogenated amorphous semiconductor film are simultaneously deposited on the second surface. Manufacturing method.