JP4938960B2 - Method for manufacturing photoelectric conversion device and photoelectric conversion device - Google Patents

Description

  The present invention relates to a method for manufacturing a photoelectric conversion device and a photoelectric conversion device.

As a photoelectric conversion device, a device using a photoelectric conversion element obtained by forming a silicon thin film or other thin film on a substrate is known.
Examples of the silicon thin film formed on the substrate include a crystalline silicon thin film, an amorphous silicon thin film, and a microcrystalline silicon thin film.
Among these silicon thin films, research on the quality evaluation of crystalline silicon thin films and amorphous silicon thin films is progressing, and the relationship between their physical properties and conversion efficiency is being clarified.
Therefore, for crystalline silicon thin films and amorphous silicon thin films, the conversion efficiency can be estimated based on the physical properties without actually incorporating them into the photoelectric conversion device. Selection from low-efficiency thin films can be performed.

  As a method for inspecting the performance based on the physical properties of the silicon thin film, for example, there is one described in Patent Document 1 described later. Patent Document 1 describes a technique for evaluating the quality of a crystalline silicon thin film based on information on physical properties obtained by an electron spin resonance method as a technique relating to quality inspection and selection of the crystalline silicon thin film.

JP 2002-141528 A (paragraphs [0019] to [0024])

On the other hand, a microcrystalline silicon thin film is obtained by generating crystal grains of several nm to several tens of nm called microcrystalline silicon (μc-Si) in an amorphous silicon network.
From such a structure, it is presumed that the relationship between the physical properties and the conversion efficiency in the microcrystalline silicon thin film is different from both the crystalline silicon thin film and the amorphous silicon thin film.
In addition, because the amorphous part has multiple types of structural defects due to its nature, even if the physical properties of the microcrystalline silicon thin film are measured, the influence of each structural defect in the amorphous part is detected in a superimposed manner. Defects may not be identified from the results.

As a method for evaluating the physical properties (optical characteristics) of microcrystalline silicon, there is an evaluation method based on measurement of a light absorption spectrum. However, the microcrystalline silicon thin film used for photoelectric conversion is too thin to transmit most of the light. Therefore, it is difficult to accurately measure the spectrum.
In addition, when the physical properties of the microcrystalline silicon thin film were actually inspected using the electron spin resonance method, the clearness between the high efficiency thin film and the low efficiency thin film as seen in the crystalline silicon thin film and amorphous silicon was observed. I could not find any difference in physical properties.

  In addition, even if physical properties are inspected by other methods, the correlation between the inspection result and conversion efficiency is unclear, or the contribution of other defects that are different from the defects to be inspected is large. Therefore, it has been difficult to properly evaluate the conversion efficiency based on the inspection result.

  Microcrystalline silicon thin film is a new technology compared to crystalline silicon thin film and amorphous silicon thin film, so it has not been studied as much as other silicon thin films, and the relationship between its physical properties and photoelectric conversion efficiency is sufficient. Not grasped.

For example, it is empirically known that a microcrystalline silicon thin film is easy to obtain a high-efficiency thin film when the film-forming speed is low, and a low-efficiency thin film is easy to obtain when the film-forming speed is high. However, a low-efficiency thin film may be formed even when the film forming speed is low, or a high-efficiency thin film may be formed even when the film forming speed is high.
From this, it is considered that other factors other than the film forming speed are greatly involved in the determination of the conversion efficiency of the microcrystalline silicon thin film, but until now it has not been possible to specify that factor.

The microcrystalline silicon thin film cannot improve the deposition rate for the above reasons, and the selection is based on the measured value obtained by actually measuring the conversion efficiency by providing an electrode on the thin film to be selected. There was nothing else to do.
Therefore, the microcrystalline silicon thin film has lower production efficiency and yield than other silicon thin films, and the photoelectric conversion device using the microcrystalline silicon thin film has a high manufacturing cost.

  The present invention has been made in view of such circumstances, and a photoelectric conversion device manufacturing method capable of easily manufacturing a high-efficiency photoelectric conversion device using a microcrystalline silicon thin film, and a high-efficiency An object is to provide a photoelectric conversion device.

In order to solve the above-described problems, the method for manufacturing a photoelectric conversion device of the present invention employs the following means.
That is, the method for manufacturing a photoelectric conversion device according to the present invention uses a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer, and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film. A method of manufacturing a thin film photoelectric conversion device, wherein the microcrystalline silicon thin film identified using piezoelectric element photothermal spectroscopy satisfies a first selection condition that a band gap is 1.0 eV or more and 1.5 eV or less , and a band tail. The photoelectric conversion element is selected so as to obtain a photoelectric conversion element satisfying the second selection condition that the start position on the high energy side of the band tail is 1.8 eV or less , and using the photoelectric conversion element, the thin film A type photoelectric conversion device is manufactured.

Here, in order to solve the above-mentioned problems, the present inventors have further studied the properties of the microcrystalline silicon thin film. In the course of this research, the present inventors have developed a piezoelectric element photothermal spectroscopy (Piezo-electric spectroscopy) for a microcrystalline silicon thin film.
Photo-Thermal Spectroscopy (hereinafter referred to as “PPTS”) was used to measure the optical characteristics with high accuracy by detecting non-radiative recombination.
As a result, it was discovered that there is a clear difference in the optical characteristics of the microcrystalline silicon thin film between the high-efficiency thin film with high conversion efficiency and the low-efficiency thin film with low conversion efficiency.

Specifically, in the microcrystalline silicon thin film, it was found that the high-efficiency thin film has a smaller band gap than the low-efficiency thin film. Furthermore, it has been found that among microcrystalline silicon thin films, those having a band gap value of 1.0 eV or more and 1.5 eV or less have excellent conversion efficiency.
The above-mentioned band gap difference and band gap value range are so small as to be buried within the range of measurement error in the method conventionally used for measuring the physical properties of the crystalline silicon thin film. In other words, the above-described knowledge has been overlooked in the measurement using the conventional measurement method, and is a completely new knowledge obtained for the first time by the highly accurate measurement performed by the present inventors.

In the method for manufacturing a photoelectric conversion device according to the present invention, the selection of the photoelectric conversion element having the microcrystalline silicon thin film is performed based on the first selection criterion and the second selection criterion obtained by the novel knowledge.
For this reason, selection of the photoelectric conversion element having a microcrystalline silicon thin film, which has been possible only by directly measuring the conversion efficiency after directly producing the photoelectric conversion element, can be performed at the stage of manufacturing the silicon thin film. .

Moreover, the method for manufacturing a photoelectric conversion device according to the present invention uses a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer, and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film. A method of manufacturing a thin film photoelectric conversion device , wherein the spectrum of the microcrystalline silicon thin film measured using piezoelectric element photothermal spectroscopy is up to the band gap of the microcrystalline silicon thin film identified by the piezoelectric element photothermal spectroscopy. The photoelectric conversion element is selected so as to obtain a photoelectric conversion element that satisfies the third selection condition that linearly decreases monotonically from the high energy side , and the thin film photoelectric conversion device is configured using the photoelectric conversion element. It is characterized by manufacturing.

Here, as a result of the above-described research, the present inventors obtained further new findings in addition to the above findings.
Specifically, in the microcrystalline silicon thin film, it was found that the high-efficiency thin film has no band tail on the energy side lower than the band gap.

  Such information on the presence / absence of band tails is also minute enough to be buried within the range of measurement error in the method conventionally used for measuring the physical properties of the crystalline silicon thin film. That is, the above knowledge is also a completely new knowledge that has been overlooked in the measurement using the conventional inspection method and obtained by the highly accurate measurement performed by the present inventors.

In the method for manufacturing a photoelectric conversion device according to the present invention, the selection of the photoelectric conversion element having the microcrystalline silicon thin film is performed based on the third selection criterion obtained by the above-described novel knowledge.
For this reason, selection of the photoelectric conversion element having a microcrystalline silicon thin film, which has been possible only by directly measuring the conversion efficiency in the past, can be performed at the stage of manufacturing the silicon thin film.

A method for producing a photoelectric conversion device according to the present invention comprises a thin film photoelectric device using a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer, and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film. A method of manufacturing a conversion device, wherein the photoelectric conversion elements are selected based on the first selection condition according to claim 1 and the third selection condition according to claim 2, and the photoelectric conversion obtained by the selection is performed. The thin film photoelectric conversion device is manufactured using an element.

In this method for manufacturing a thin film photoelectric conversion device, the photoelectric conversion element used in the thin film photoelectric conversion device is based on the first selection condition according to claim 1 and the third selection condition according to claim 2, Selection between a high-efficiency photoelectric conversion element and a low-efficiency photoelectric conversion element can be performed more reliably.
That is, in this thin film photoelectric conversion device manufacturing method, high efficiency photoelectric conversion elements can be more reliably selected at the photoelectric conversion element selection stage, and thus a high efficiency thin film photoelectric conversion device is easily manufactured. be able to.

A method of manufacturing a photoelectric conversion device according to the present invention includes a thin film photoelectric conversion using a photoelectric conversion element in which a photoelectric conversion layer formed of an amorphous silicon thin film and a photoelectric conversion layer formed of a microcrystalline silicon thin film are stacked. a method of manufacturing a device, the selection of the photoelectric conversion element, a second selection condition according to the first selection condition and claim 1 of claim 1, the third selection condition according to claim 2, wherein The thin-film photoelectric conversion device is manufactured using the photoelectric conversion element obtained by the selection based on either the first selection condition or the third selection condition.

In the method for manufacturing the thin film photoelectric conversion device, the thin film photoelectric conversion device is formed of an amorphous silicon thin film based on any one of the first selection condition, the second selection condition, the third selection condition, the first selection condition, and the third selection condition . As a photoelectric conversion element (tandem type photoelectric conversion element) in which a photoelectric conversion layer and a photoelectric conversion layer formed of a microcrystalline silicon thin film are stacked, a highly efficient photoelectric conversion element can be obtained, so a high efficiency tandem Type photoelectric conversion device can be easily manufactured.

A photoelectric conversion device according to a reference example of the present invention is a thin film type using a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer, and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film. In the photoelectric conversion device, the photoelectric conversion element is characterized in that a band gap of the microcrystalline silicon thin film identified by using a piezoelectric element photothermal spectroscopy is 1.0 eV or more and 1.5 eV or less.

In addition, the photoelectric conversion device according to the reference example of the present invention uses a photoelectric conversion element that has a single-layer or multiple-layer photoelectric conversion layer, and at least one of the photoelectric conversion layers is formed of a microcrystalline silicon thin film. A thin-film photoelectric conversion device, wherein the photoelectric conversion element has no band tail on a lower energy side than a band gap of the microcrystalline silicon thin film identified by using a piezoelectric element photothermal spectroscopy. To do.

  Since the photoelectric conversion device configured as described above uses a photoelectric conversion element having a microcrystalline silicon thin film with high conversion efficiency, the conversion efficiency is high.

According to the method for manufacturing a photoelectric conversion device according to the present invention, a highly efficient photoelectric conversion device can be reliably and easily manufactured.
Moreover, the photoelectric conversion apparatus according to the present invention has high conversion efficiency.

An embodiment of the present invention will be described below with reference to the drawings.
First, the configuration of the photoelectric conversion device will be described.
The photoelectric conversion device has a photoelectric conversion element that generates an electric charge by absorbing light, and generates light in an external circuit connected to the photoelectric conversion element by applying light to the photoelectric conversion element. Is.
The photoelectric conversion element is obtained by forming a plurality of thin films on a substrate such as a glass substrate by performing a film forming process such as plasma CVD using a silane gas diluted with hydrogen gas. A typical structure of such a photoelectric conversion element is shown in FIGS. Here, the substrate side light incident type having a pin structure is shown as the photoelectric conversion element, but a film surface side light incident type having a nip structure may be used.

In the photoelectric conversion element 1 shown in the longitudinal sectional view of FIG. 1, a first lower electrode layer 3 made of a metal material and a second lower electrode layer 4 made of a transparent electrode material are formed in this order on a substrate 2. ing.
On the second lower electrode layer 4, an n-type microcrystalline silicon layer 5 (first conductivity type semiconductor layer), an intrinsic microcrystalline silicon layer 6 serving as a photoelectric conversion layer (i layer), and a p-type microcrystalline silicon layer 7 (second conductivity type semiconductor layer) are formed in this order.
Further, on the p-type microcrystalline silicon layer 7, a transparent conductor layer 8 made of a transparent electrode material and a collecting electrode 9 made of a metal material are formed in this order.
Here, as the transparent electrode material constituting the second lower electrode layer 4 and the transparent conductor layer 8, zinc oxide (ZnO), stannic oxide (SnO ₂ ), ITO (Indium Tin Oxide), or the like is used. .

In the photoelectric conversion element 1, the n-type microcrystalline silicon layer 5, the intrinsic microcrystalline silicon layer 6 (i layer), and the p-type microcrystalline silicon layer 7 constitute a pin structure. That is, when photoelectric conversion element 1 receives light having energy greater than or equal to the band gap, such as sunlight, to intrinsic microcrystalline silicon layer 6, the photoelectric conversion element 1 absorbs the energy and forms a pair of electrons (e) and holes (h). Is generated.
In the photoelectric conversion element 1, the first lower electrode layer 3 and the collector electrode 9 are connected to an external load 10, respectively. Thus, a pair of electrons and holes is included in the pin structure. As a result, current flows through the external load 10.

The photoelectric conversion element 11 shown in the longitudinal sectional view of FIG. 2 is obtained by forming a pin structure made of an amorphous silicon layer between the pin structure made of a microcrystalline silicon layer and the transparent conductor layer 8 in the photoelectric conversion element 1. It is.
In the photoelectric conversion element 11, an n-type amorphous silicon layer 12, an amorphous silicon layer 13 to be an i layer, and a p-type amorphous silicon layer 14 are formed on the p-type microcrystalline silicon layer 7 in this order, and p-type A transparent conductor layer 8 and a collecting electrode 9 are formed in this order on the amorphous silicon layer 14.

This photoelectric conversion element 11 improves the overall conversion efficiency by utilizing the fact that the wavelength sensitivity is different between a pin structure made of a microcrystalline silicon layer and a pin structure made of an amorphous silicon layer.
That is, in the photoelectric conversion element 11, since incident light is absorbed by each pin structure and a pair of electrons and holes is generated in each pin structure, the total conversion compared to the photoelectric conversion element 1 is achieved. High efficiency.

The photoelectric conversion device 21 according to the present embodiment is configured to use any one of the photoelectric conversion elements 1 and 11 as a photoelectric conversion device, and is manufactured by the method for manufacturing a photoelectric conversion device according to the present invention. is there.
Specifically, the photoelectric conversion device 21 uses a first selection condition that the band gap of the microcrystalline silicon thin film identified using PPTS is 1.0 eV or more and 1.5 eV or less, and the microcrystalline silicon thin film identified using PPTS. The photoelectric conversion element is selected so as to obtain a photoelectric conversion element that satisfies at least one of the third selection conditions that no band tail is generated on the lower energy side than the band gap. It is manufactured using a photoelectric conversion element.

PPTS is a method that can measure non-radiative recombination of electrons in a semiconductor with high sensitivity, and measures a light absorption spectrum of a measurement sample.
Hereinafter, the principle of PPTS will be described.
When the measurement sample is irradiated with light of a certain intensity or more, a part of electrons and holes excited by the photon energy of the irradiation light taken into the measurement sample is converted into thermal energy by a non-radiative recombination process, It is transmitted to the medium (ambient atmosphere etc.) around the measurement sample. The magnitude of this thermal energy is proportional to the magnitude of photon energy absorbed by the measurement sample.
Here, if the measurement sample is irradiated with light in a pulsed manner, heat generation in the measurement sample is also intermittent, so that a dense wave is generated in the medium around the measurement sample. Then, if the measurement sample is irradiated with pulsed light with the piezoelectric element attached to the measurement sample, a dense wave is input to the piezoelectric element, and the piezoelectric element has the same cycle as the dense wave and the dense wave. An electrical signal having an intensity proportional to the intensity of

  PPTS is a technique for measuring the magnitude of the photon energy taken into the measurement sample based on the signal intensity by measuring the signal intensity of the electric signal generated by the piezoelectric element in this way. The light absorption spectrum of the measurement sample is measured by irradiating the monochromatic light in a shape and changing the wavelength of the irradiated light, and measuring the change in the signal intensity of the piezoelectric element with respect to the change in the wavelength.

  Since PPTS is an absolute measurement that measures the non-radiative recombination process after light absorption of the measurement sample as described above, the measurement sensitivity is good even for a microcrystalline silicon thin film that is a transparent material, and the scattered light. The influence of can also be eliminated.

Hereinafter, the configuration of the PPTS device 31 used for selecting the photoelectric conversion elements will be described.
The PPTS device 31 includes a light source 32 that continuously emits light, a chopper 33 that periodically blocks light emitted from the light source 32 and converts it into pulsed light, and splits the light that has passed through the chopper 33 to a desired wavelength. And a monochromator 34 for outputting only monochromatic light.
As the light source, for example, a halogen lamp, a mercury lamp, or the like is used, but any other light source can be used as long as it emits light with uniform and sufficient intensity in the wavelength range of the measurement range.

The measurement sample P is installed in the subsequent stage of the monochromator 34 with the substrate 2 side facing the monochromator 34, and pulsed monochromatic light that has passed through the monochromator 34 is applied to the measurement sample P on the substrate 2. It comes to be irradiated from the side.
A piezoelectric element 36 is attached to the film growth surface side of the measurement sample P with silicon grease. The measurement sample P detects a density wave generated by absorbing photon energy, and has the same period as the density wave. In addition, an electrical signal having an intensity proportional to the intensity of the dense wave is generated.
Here, in this PPTS apparatus 31, the measurement sample P is installed in the cryostat C, and the thermal noise generated in the measurement sample P can be reduced by cooling to a low temperature of about 173 K with, for example, liquid nitrogen. It can be done.

The PPTS device 31 is provided with a lock-in amplifier 37.
The lock-in amplifier 37 receives the output of the piezoelectric element 36 and the operation timing signal of the chopper 33 as a reference signal. In other words, the lock-in amplifier 37 detects only the output of the piezoelectric element 36 when the piezoelectric element 36 is irradiated with light.

The PPTS device 31 is provided with an arithmetic device 38. The computing device 38 has a CPU that performs various computations and a memory that holds computation results and other information.
The calculation device 38 receives the output signal of the lock-in amplifier 37 and the wavelength information of the monochromatic light output from the monochromator 34 as a signal.
The arithmetic unit 38 calculates the photon energy hν (eV) of the light irradiated to the measurement sample P from the information on the wavelength of the monochromatic light output from the monochromator 34, and the photon energy hν and the irradiation light are irradiated. Based on the strength PPTS of the output signal of the lock-in amplifier 37 at the time point, (hνPPTS) ^0.5 called Tauc plot used for calculating the band gap of the indirect transition semiconductor or amorphous silicon is recorded.

The arithmetic unit 38 also controls the operation of the monochromator 34. Then, the calculation device 38 records the photon energy hν (eV) of the light irradiated to the measurement sample P and the intensity PPTS of the output signal of the lock-in amplifier 37 (hνPPTS) ^0.5 , while recording monochrome. The wavelength of the monochromatic light output from the meter 34 is scanned from the long wavelength end side to the short wavelength end side within the wavelength range used for measurement, and the light absorption spectrum of the measurement sample P is obtained.

Here, the output signal of the piezoelectric element 36 irradiates the piezoelectric element 36 not only with the component derived from the dense wave generated by the measurement sample P absorbing the irradiation light but also the irradiation light that has passed through the measurement sample P. In this way, components derived from dense waves generated in the piezoelectric element 36 itself are also included.
In addition, since the intra-film interference of the irradiation light of the measurement sample P occurs, the measurement value of the piezoelectric element 36 includes the influence of the intra-film interference.

  The arithmetic unit 38 is configured to correct the background component derived from the piezoelectric element 36 and the in-film interference from the output signal of the lock-in amplifier 37 in order to increase the measurement accuracy.

Specifically, the arithmetic unit 38 inputs the background value of the output signal of the piezoelectric element 36 in advance, and subtracts this background value from the output of the lock-in amplifier 37 to derive from the measurement sample P. Only the signal strength is obtained.
The background of the output signal of the piezoelectric element 36 can be obtained from the signal intensity generated by the piezoelectric element 36 when the piezoelectric element 36 is directly irradiated with irradiation light without providing the measurement sample P.

  Further, the arithmetic unit 38 simulated the interference state of the irradiation light in the measurement sample P from information such as the refractive index and film thickness of the light of each thin film constituting the measurement sample P, and was obtained based on this simulation. The output signal of the piezoelectric element 36 is compared with the actual output signal, and the component from which the influence of the in-film interference is removed is extracted, thereby correcting the in-film interference.

From the information of the light absorption spectrum obtained by the measurement using this PPTS device 31, the band gap of the measurement sample P is obtained. Specifically, the horizontal axis represents the photon energy hν (eV) of the light irradiated on the measurement sample P, and the vertical axis represents the light absorption obtained by calculating from the intensity PPTS of the output signal of the lock-in amplifier 37 (hνPPTS) ^0.5. A horizontal axis intercept (photon energy value) of a straight line obtained by creating a graph representing a spectrum and extrapolating a substantially linear portion of the graph is the band gap of the measurement sample P.

Here, the measurement sample P is obtained by forming a microcrystalline silicon thin film on a glass substrate and is optically almost transparent. Therefore, the intensity (hνPPTS) of the output signal of the lock-in amplifier 37 is ^0.5 . It is proportional to the light absorption coefficient α of the material constituting the measurement sample P.
However, since the intensity (hνPPTS) ^0.5 of the output signal of the lock-in amplifier 37 varies depending on the measurement conditions (for example, how the piezoelectric element 36 is attached to the measurement sample P), the quality of the measurement sample P is evaluated. It cannot be used as an absolute indicator. What is important in the PPTS results is the shape of the graph of the light absorption spectrum.

The physical properties of the microcrystalline silicon thin film obtained by the PPTS device 31 (corresponding relationship between the light absorption spectrum and the conversion efficiency thereof will be described based on actual measurement results.
In this measurement, a high-efficiency thin film (generally obtained by low-speed film formation) and a low-efficiency thin film are formed as a single-layer microcrystalline silicon thin film formed on a glass substrate (substrate temperature at the time of film formation of about 200 ° C.) by plasma CVD. (Generally obtained by high-speed film formation) and a light absorption spectrum was obtained for each of these by PPTS.
Further, in this measurement, a halogen lamp is used as the light source 32, and the monochromatic light output from the monochromator 34 is scanned in the wavelength range of 400 to 1400 nm by the arithmetic unit 38, and the light of the measurement sample P in this wavelength region. Absorption spectrum was determined.
And it measured in the state which kept the measurement sample at normal temperature (297K).

In this measurement, a low-efficiency thin film formed at about three times the film-forming speed of a high-efficiency thin film was used. The photoelectric conversion device using the low-efficiency thin film had a conversion efficiency about half that of the photoelectric conversion device using the high-efficiency thin film.
In this measurement, for each of the high-efficiency thin film and the low-efficiency thin film, a measurement sample with a substrate thickness and a film thickness of 0.5 μm, a measurement sample with a substrate thickness and a film thickness of 1.0 μm, and a substrate thickness, respectively. A measurement sample having a thickness of 1.5 μm was prepared.
Here, two measurement samples (A group and B group) were prepared for each of the high-efficiency thin film and the low-efficiency thin film as the measurement sample having a film thickness of 1.0 μm.

Graphs of light absorption spectra of these measurement samples are shown in FIGS.
Here, FIG. 4 shows the light absorption spectrum of the high-efficiency thin film (film thickness 0.5 μm), and FIG. 5 shows the light absorption spectrum of the low-efficiency thin film (film thickness 0.5 μm).
FIG. 6 shows a light absorption spectrum of a highly efficient thin film (film thickness 1.0 μm, A group), and FIG. 7 shows a light absorption spectrum of a low efficiency thin film (film thickness 1.0 μm, A group).
FIG. 8 shows the light absorption spectrum of the high-efficiency thin film (film thickness 1.0 μm, B group), and FIG. 9 shows the light absorption spectrum of the low-efficiency thin film (film thickness 1.0 μm, B group).
FIG. 10 shows the light absorption spectrum of the high-efficiency thin film (film thickness 1.5 μm), and FIG. 11 shows the light absorption spectrum of the low-efficiency thin film (film thickness 1.5 μm).
Note that these graphs are plotted assuming that the optical transition of the microcrystalline silicon thin film is an indirect interband transition, and are called Tauc plots.

From these graphs, in any film thickness, high efficiency thin film (shifted to a lower energy side) the band gap E _g than low-efficiency thin film is small can be seen.
The reason why the band gap _Eg is different is that the high-efficiency thin film has a smaller proportion of the amorphous portion than the low-efficiency thin film, or the hydrogen content is increased and the dangling bonds are lower than the low-efficiency thin film. This is considered to be because the absorption of carriers (free electrons and holes) due to defects is less likely to occur.
Here, in the analysis by Raman spectroscopy, since there was no significant difference in the crystallization rate of the microcrystalline silicon thin film depending on the film forming speed, the difference in the band gap E _g is mainly due to the increase in the hydrogen content. Presumed to be the cause.

Furthermore, according to the tests conducted by the present inventors, among the microcrystalline silicon thin films, those having a band gap E _g value of 1.0 eV or more and 1.5 eV or less have better conversion efficiency. was gotten.

The above-mentioned band gap E _g difference and band gap E _g value range are minute differences that are buried within the range of measurement errors in the conventional method used for measuring the physical properties of a crystalline silicon thin film. . In other words, the above-described knowledge has been overlooked in the measurement using the conventional measurement method, and is a completely new knowledge obtained for the first time by the high-accuracy measurement using the PPTS.

Further, from the graphs of FIGS. 4 to 11, the high-efficiency thin film has a small band tail T located on the lower energy side than the band gap E _g , and in particular, a high-efficiency thin film having a film thickness of 1.0 μm (A group). Then, it turns out that the band tail T has not arisen.
On the other hand, in the low-efficiency thin film, a large band tail T is formed on the lower energy side than the band gap E _{g at} any film thickness.

The band tail T occurs because localized levels are formed in the band gap E _g due to structural disturbance in the thin film. In the high-efficiency thin film, the structural disturbance is small, and no localized level is generated in the band gap. Therefore, the band tail T is small or does not exist. It is considered that a large band tail T is generated since the localization order is formed.

  Such information on the presence / absence of the band tail T is also minute enough to be buried in the range of measurement errors in the method conventionally used for measuring the physical properties of the crystalline silicon thin film. That is, the above knowledge is also a completely new knowledge that has been overlooked in the measurement using the conventional inspection method and obtained by the above-described high-precision measurement using PPTS.

Any difference in physical properties between the high-efficiency thin film and the low-efficiency thin film causes a decrease in the conversion efficiency of the photoelectric conversion element. That is, the low-efficiency thin film reduces carriers generated by light absorption as the band gap E _g moves to the high energy side as compared with the high-efficiency thin film. Further, since the generated localized level works as a carrier trap, the output current is reduced. As a result, the conversion efficiency of the photoelectric conversion element using the low efficiency thin film is reduced.
Here, since it is not directly related to the deposition rate of the microcrystalline silicon thin film, it can be improved by adjusting the deposition conditions.

In the manufacturing method of the photoelectric conversion device according to the present embodiment, the selection of the photoelectric conversion element 1 or the photoelectric conversion element 11 having the microcrystalline silicon thin film is selected from the first selection standard and the third selection standard obtained by the above-described novel knowledge. Based on at least one of the above.

Specifically, when forming the photoelectric conversion element 1 (or 11) by forming various thin films on the substrate 2, the intrinsic microcrystalline silicon layer 6 is formed on the substrate 2, and then the entire substrate 2. Cut out the measurement sample.
And this measurement sample is analyzed by PPTS, and a photoelectric conversion apparatus is produced using only the photoelectric conversion element 1 or 11 which satisfy | fills the said selection conditions.

Thus, according to the manufacturing method of the photoelectric conversion device according to the present embodiment, the intrinsic microcrystalline silicon layer 6 that has been possible only by directly measuring the conversion efficiency after the production of the photoelectric conversion element is provided. The selection of the photoelectric conversion elements can be performed at the stage where the intrinsic microcrystalline silicon layer 6 is manufactured.
For this reason, according to the manufacturing method of the photoelectric conversion apparatus concerning this embodiment, a highly efficient photoelectric conversion apparatus can be manufactured reliably and easily.
In addition, the photoelectric conversion device according to the present invention has high conversion efficiency because a high-performance photoelectric conversion element is incorporated by the above manufacturing method.

  When a plurality of photoelectric conversion elements 1 (or 11) are created in one batch, one photoelectric conversion element 1 (or 11) is not cut out from all the photoelectric conversion elements 1 (or 11). ) May be extracted and the physical properties of the remaining photoelectric conversion element 1 (or 11) may be determined based on the physical properties of the measurement sample cut out from the photoelectric conversion element 1 (or 11).

  Here, when the intrinsic microcrystalline silicon layer 6 is a low-efficiency thin film, only a low-efficiency photoelectric conversion element can be obtained, and the subsequent film formation process is wasted. For this reason, it is preferable to cut out the measurement sample at a stage before finishing the film formation process of the intrinsic microcrystalline silicon layer 6 and moving to the next film formation process so that useless film formation process is not required. . When the intrinsic microcrystalline silicon layer 6 is a low-efficiency thin film as described above, the intrinsic microcrystalline silicon layer 6 becomes a high-efficiency thin film when newly producing the photoelectric conversion element 1 (or 11). As described above, the film forming conditions are adjusted.

  Further, the measurement sample may be cut out during the film formation of the intrinsic microcrystalline silicon layer 6. In this case, when the intrinsic microcrystalline silicon layer 6 in the middle of film formation is a low-efficiency thin film, the high-efficiency intrinsic microcrystalline silicon layer 6 is obtained by adjusting the film-forming conditions in the subsequent film-forming process. It is also possible to obtain.

Here, as the conditions of the film forming process to be adjusted in order to obtain a high-efficiency thin film, the hydrogen dilution concentration of silane gas, which is a plasma CVD process gas, the supply pressure of the process gas, and the like can be considered.
By appropriately setting these conditions, it is possible to improve the film quality and the film forming speed.

It is sectional drawing which shows an example of the typical structure of a photoelectric conversion element. It is sectional drawing which shows an example of the typical structure of a photoelectric conversion element. It is a block diagram which shows the structure of the measuring apparatus (PPTS apparatus) used for the manufacturing method of the photoelectric conversion apparatus of this invention. It is a graph which shows the result of PPTS of a highly efficient photoelectric conversion element (film thickness of 0.5 micrometer). It is a graph which shows the result of PPTS of a low efficiency photoelectric conversion element (film thickness of 0.5 micrometer). It is a graph which shows the result of PPTS of a highly efficient photoelectric conversion element (film thickness of 1.0 micrometer). It is a graph which shows the result of PPTS of a low efficiency photoelectric conversion element (film thickness of 1.0 micrometer). It is a graph which shows the result of PPTS of a highly efficient photoelectric conversion element (film thickness of 1.0 micrometer). It is a graph which shows the result of PPTS of a low efficiency photoelectric conversion element (film thickness of 1.0 micrometer). It is a graph which shows the result of PPTS of a highly efficient photoelectric conversion element (film thickness of 1.5 micrometers). It is a graph which shows the result of PPTS of a low efficiency photoelectric conversion element (film thickness of 1.5 micrometers).

Explanation of symbols

1,11 Photoelectric conversion element 6 Intrinsic microcrystalline silicon layer (photoelectric conversion layer)
13 Amorphous silicon layer (photoelectric conversion layer)
E _g Band gap T Band tail

Claims (4)

A method for producing a thin-film photoelectric conversion device using a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film,
The first selection condition that the band gap of the microcrystalline silicon thin film identified using the piezoelectric element photothermal spectroscopy is 1.0 eV or more and 1.5 eV or less, and
The photoelectric conversion element is selected so as to obtain a photoelectric conversion element satisfying the second selection condition that the band tail on the lower energy side than the band gap is small and the start position on the high energy side of the band tail is 1.8 eV or less,
A method of manufacturing a thin film photoelectric conversion device, wherein the thin film photoelectric conversion device is manufactured using the photoelectric conversion element. A method for producing a thin-film photoelectric conversion device using a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film,
The spectrum of the microcrystalline silicon thin film measured using the piezoelectric element photothermal spectroscopy decreases linearly and monotonically from the high energy side to the band gap of the microcrystalline silicon thin film identified by the piezoelectric element photothermal spectroscopy. The photoelectric conversion elements are selected so as to obtain photoelectric conversion elements that satisfy the third selection condition,
A method of manufacturing a thin film photoelectric conversion device, wherein the thin film photoelectric conversion device is manufactured using the photoelectric conversion element. A method for producing a thin-film photoelectric conversion device using a photoelectric conversion element having a single-layer or multiple-layer photoelectric conversion layer and at least one of the photoelectric conversion layers is composed of a microcrystalline silicon thin film,
The selection of the photoelectric conversion elements is performed based on the first selection condition according to claim 1 and the third selection condition according to claim 2,
A method of manufacturing a thin film photoelectric conversion device, wherein the thin film photoelectric conversion device is manufactured using a photoelectric conversion element obtained by the selection. A method for manufacturing a thin film photoelectric conversion device using a photoelectric conversion element in which a photoelectric conversion layer formed of an amorphous silicon thin film and a photoelectric conversion layer formed of a microcrystalline silicon thin film are stacked,
The selection of the photoelectric conversion elements is performed by selecting the first selection condition according to claim 1, the second selection condition according to claim 1, the third selection condition according to claim 2, the first selection condition and the third selection condition. Based on any of the sorting conditions,
A method of manufacturing a thin film photoelectric conversion device, wherein the thin film photoelectric conversion device is manufactured using a photoelectric conversion element obtained by the selection.

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