JP2010103335A - Method for manufacturing photoelectric conversion device, method for manufacturing electronic apparatus, photoelectric conversion device and electronic apparatus - Google Patents

Abstract

A method for manufacturing a photoelectric conversion device with favorable characteristics is provided.
A coating film is formed by applying a liquid containing polysilazane in which nanocrystal grains made of a semiconductor are dispersed above a substrate, and the coating film is subjected to a heat treatment to form the nanocrystal grains ( A silicon oxynitride film (8z) containing d) is formed. The heat treatment is performed in a nitrogen atmosphere containing oxygen or an oxygen compound, and the composition ratio of oxygen and nitrogen in the silicon oxynitride film is adjusted by adjusting the oxygen concentration in the atmosphere. According to this method, nanocrystal grains can be confined in the silicon oxynitride film by a simple method. In addition, since the silicon oxynitride film has a smaller band gap than the silicon oxide film (SiO ₂ ), the depth of the quantum well can be reduced. Furthermore, by adjusting the composition ratio of oxygen and nitrogen, the band gap of the silicon oxynitride film can be adjusted between 9 eV which is the band gap of SiO ₂ and 5 eV which is the band gap of Si ₃ N ₄ .
[Selection] Figure 1

Description

  The present invention relates to a photoelectric conversion device, in particular, a photoelectric conversion device using nanocrystal grains, a manufacturing method thereof, and the like.

  BACKGROUND ART Solar cells (photoelectric conversion devices) are actively developed as energy sources that are energy-saving and resource-saving and clean. A solar cell is a power device that uses the photovoltaic effect to directly convert light energy into electric power. Various structures such as organic thin-film solar cells, dye-sensitized solar cells, and multi-junction structure solar cells have been studied for the configuration. Among them, a solar cell using quantum dots (nanocrystal grains) has attracted attention as a next-generation solar cell that theoretically enables conversion efficiency of 60% or more.

For example, Patent Document 1 below discloses a solar cell having a plurality of crystalline semiconductor material quantum dots separated by a thin dielectric material layer.
Special Table 2007-535806

  However, in the configuration in which silicon is used as the quantum dot and the silicon oxide is used as the dielectric material thin layer, which is studied in detail in Patent Document 1, the quantum well is deep and charges (electrons) cannot be extracted efficiently. In addition, since a manufacturing method is adopted in which silicon is deposited as quantum dots by heat-treating a silicon-rich dielectric material layer, it is difficult to easily disperse quantum dots with good controllability.

  Therefore, a specific aspect of the present invention aims to provide a photoelectric conversion device with good characteristics and a method for manufacturing the photoelectric conversion device.

  The method for manufacturing a photoelectric conversion device according to the present invention includes a step of forming a coating film by applying a liquid containing polysilazane in which nanocrystal grains made of a semiconductor are dispersed above a substrate; And a step of forming a silicon oxynitride film containing the nanocrystal grains by performing a heat treatment.

According to such a method, the nanocrystal grains can be confined in the silicon oxynitride film by a simple method by dispersing the nanocrystal grains in the liquid containing polysilazane, performing heat treatment, and forming the film. In addition, since the silicon oxynitride film has a smaller band gap than the silicon oxide film (SiO ₂ ), the depth of the quantum well can be reduced.

  For example, the semiconductor is silicon or a silicon compound. For example, the band gap of the nanocrystal grain is 2 eV or less. Thus, silicon or silicon compound nanocrystal grains may be used. Alternatively, nanocrystal grains having a band gap of 2 eV or less may be used to facilitate carrier transition.

The heat treatment is performed in a nitrogen atmosphere containing oxygen or an oxygen compound, and the composition ratio of oxygen and nitrogen in the silicon oxynitride film is adjusted by adjusting the oxygen concentration in the atmosphere. Thus, by adjusting the composition ratio of oxygen and nitrogen, the band gap of the silicon oxynitride film can be adjusted between 9 eV which is the band gap of SiO ₂ and 5 eV which is the band gap of Si ₃ N _4. And the depth of the quantum well can be adjusted.

  A step of forming a first conductivity type semiconductor layer above the substrate; a step of forming a silicon oxynitride film containing the nanocrystal grains on the first conductivity type semiconductor layer; and Forming a second conductivity type semiconductor layer which is a reverse conductivity type of the first conductivity type on the contained silicon oxynitride film. As described above, the first and second conductive semiconductor layers are formed, and the silicon oxynitride film containing the nanocrystal grains is provided between the first conductive semiconductor layer and the second conductive semiconductor layer. Also good.

  The manufacturing method of the photoelectric conversion device according to the present invention includes a first step of forming a first coating film by applying a liquid containing polysilazane in which nanocrystal grains made of a semiconductor are dispersed above a substrate; A second step of forming a second coating film by applying a liquid containing polysilazane not containing nanocrystal grains, and the first coating film and the second coating by repeating the first and second steps. A third step of forming a laminated film in which the films are repeatedly laminated, a silicon oxynitride film containing the nanocrystal grains, and a silicon oxynitride film not containing the nanocrystal grains by performing a heat treatment on the laminated film, Forming a layer in which is repeatedly laminated.

  According to such a method, by alternately stacking silicon oxynitride films containing nanocrystal grains and silicon oxynitride films not containing nanocrystal grains, the arrangement of nanocrystal grains in the layer can be periodic, A device with high photoelectric conversion efficiency can be formed.

  In the method for manufacturing a photoelectric conversion device according to the present invention, a liquid containing polysilazane in which nanocrystal grains having a first grain size made of a semiconductor are dispersed is applied above a substrate, and heat treatment is performed. A step of forming a silicon oxynitride film containing nanocrystal grains having a grain size and a silicon oxynitride film containing nanocrystal grains having a first grain size, which are different from the first grain size made of the semiconductor. Applying a liquid containing polysilazane in which nanocrystal grains having a second grain size are dispersed, and performing heat treatment to form a silicon oxynitride film containing nanocrystal grains having the second grain size. Have.

  According to this method, a silicon oxynitride film containing nanocrystal grains having different particle diameters can be formed, and a device with high photoelectric conversion efficiency can be formed.

  In the method for manufacturing a photoelectric conversion device according to the present invention, a liquid containing polysilazane, in which first nanocrystal grains made of a first semiconductor are dispersed, is applied above a substrate and subjected to a heat treatment, to thereby perform the first nanocrystal. A step of forming a silicon oxynitride film containing crystal grains, and second nanocrystal grains made of a second semiconductor other than the first semiconductor are dispersed above the silicon oxynitride film containing the first nanocrystal grains And applying a liquid containing polysilazane and performing a heat treatment to form a silicon oxynitride film containing the second nanocrystal grains.

  According to such a method, a silicon oxynitride film containing nanocrystal grains having different grain types can be formed, and a device with high photoelectric conversion efficiency can be formed.

  For example, the silicon oxynitride film is represented by SiOxNy, and y is 0. Thus, the nitrogen component of the silicon oxynitride film may be set to 0 to form a silicon oxide film.

  The manufacturing method of the electronic device which concerns on this invention has the manufacturing method of the said photoelectric conversion apparatus.

  According to this method, the characteristics of the electronic device can be improved. In addition, the productivity of such electronic devices can be improved.

  The photoelectric conversion device according to the present invention has a silicon oxynitride film containing nanocrystal grains made of a semiconductor, the band gap of the nanocrystal grains is 2 eV or less, and the silicon oxynitride film has its band gap Is a film in which the composition ratio of oxygen and nitrogen is adjusted so as to be 2 to 3 times the band gap of the nanocrystal grains.

According to this configuration, quantum wells resulting from the band gap difference between the nanocrystal grains and the silicon oxynitride film are formed, and a photoelectric conversion device with high photoelectric conversion efficiency is obtained. In particular, by adjusting the composition ratio of oxygen and nitrogen, the band gap of the silicon oxynitride film is adjusted between 9 eV that is the band gap of SiO ₂ and 5 eV that is the band gap of Si ₃ N _4. The depth of the well can be adjusted, and the photoelectric conversion efficiency can be improved.

  The electronic device according to the present invention includes the photoelectric conversion device. According to such a configuration, the characteristics of the electronic device can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same or related code | symbol is attached | subjected to what has the same function, and the repeated description is abbreviate | omitted.

<Structure of photoelectric conversion device>
1 and 2 are cross-sectional views illustrating the configuration of the quantum dot photoelectric conversion device (photoelectric conversion element, solar cell) of the present embodiment.

  The photoelectric conversion device illustrated in FIG. 1 is a device having a so-called pin structure, and has a configuration in which a p layer, an i layer, and an n layer are sequentially stacked. Specifically, as shown in the figure, a transparent electrode 3, a p-type (first conductivity type) amorphous silicon layer 5, an i layer 8, and an n-type (second conductivity type) amorphous silicon layer 9 are formed on a substrate 1. And the upper electrode 11 is laminated | stacked sequentially. The i layer 8 is made of a silicon oxynitride film (SiNxOy) 8z containing quantum dots (QD, nanocrystal grains) d in a dispersed state. Here, “quantum dots (nanocrystal grains)” mean fine crystal particles made of a semiconductor (including a compound semiconductor), and are a collection of hundreds to tens of thousands of atoms. The particle diameter is about the de Broglie wavelength of electrons (several tens to several nanometers). In particular, in this specification, a particle having a particle size of 1 nm or more and 20 nm or less is referred to as a “quantum dot”, and the crystal includes a single crystal and a polycrystalline state.

  As the substrate 1, for example, a light transmissive quartz glass substrate is used. In addition, another glass substrate such as a soda glass substrate, a resin substrate using a resin such as polycarbonate, polyethylene terephthalate, or a ceramic substrate may be used.

As the transparent electrode 3, for example, indium tin oxide (ITO) added with indium is used. In addition, other conductive metal oxides such as fluorine-doped tin oxide (FTO), indium oxide (IO), and tin oxide (SnO ₂ ) may be used. By using such a transparent electrode, the light transmittance from the back surface side (lower side in the figure) of the substrate 1 can be improved.

  The first and second conductivity types are p-type or n-type. In the case of p-type, p-type impurities such as boron and in the case of n-type have n-type impurities such as phosphorus. Note that i-type (intrinsic) usually means a layer in which no impurity is implanted and has a lower impurity concentration than a p-type or n-type layer, but here, no impurity is contained. Alternatively, it refers to a silicon oxynitride film containing quantum dots having a low impurity concentration in a dispersed state.

  As the material of the metal electrode 11, for example, Al (aluminum) is used. Other metals such as nickel (Ni), cobalt (Co), platinum (Pt), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), titanium (Ti), and tantalum (Ta) Materials can be used. Moreover, you may use these alloys. Alternatively, the above conductive metal oxide may be used.

  In the photoelectric conversion device shown in FIG. 2, the i layer 8 includes a silicon oxynitride film (thin film) 8A containing quantum dots (QD, nanocrystal grains) d and a silicon oxynitride film (thin film) not containing quantum dots d. 8B is repeatedly laminated.

  Thus, in this Embodiment, since the quantum dot d is contained in the i layer 8, the photoelectric conversion efficiency can be improved. The reason why the photoelectric conversion efficiency is improved is considered to be due to (1) quantum size effect, (2) multiple exciton generation effect, and (3) miniband formation effect. Hereinafter, these will be described in detail with reference to FIGS. FIG. 3 is an energy band diagram for explaining the quantum size effect. FIG. 4 is an energy band diagram for explaining the effect of multiple exciton generation in the case of bulk and the case of quantum dots. FIG. 5 is a cross-sectional perspective view schematically showing a superlattice structure, FIGS. 6 and 7 are energy band diagrams when a miniband is formed, and FIG. 8 is a case where a miniband is not formed. FIG. In the band diagram, black circles indicate electrons (e) and white circles indicate holes (h).

(1) Quantum size effect As shown in Fig. 3, HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) for one semiconductor atom are molecules, clusters. As the number of aggregates of nanocrystal grains, bulk, and atoms increases, in the bulk, each orbital continues and becomes a conduction band and a valence band. Conversely, when a bulk semiconductor mass is reduced to the atomic level through the particle level, the band gap (Band gap, forbidden band) Eg increases. In FIG. 3, the vertical axis represents energy, and the relationship between “particle size (nm) and number of atoms” of atoms, molecules, clusters, nanocrystal grains, and bulk is, for example, “0.1 nm or less and one atom number”, respectively. ", 0.2 nm or less, 2 atoms", "less than 1 nm, 10 atoms or less", "1 nm or more and 20 nm or less, 10 ² or more atoms and 10 ⁴ or less", "1000 nm or more, 10 atoms. More than ²³ ".

  Here, in photoelectric conversion, electrons (carriers) that have absorbed light energy transit between the valence band and the conduction band across the band gap Eg, and are extracted as electric energy (electric power).

  Therefore, the band gap can be adjusted by changing the grain size of the nanocrystal grains, and thus, for example, in the solar spectrum, the ultraviolet light region, the visible light region, the infrared light region, etc. having a large energy can be specified. The band gap can be adjusted according to the wavelength (for example, 400 nm to 800 nm). As a result, light can be efficiently converted into electrical energy. In addition, by stacking photoelectric conversion units having different band gaps, it is possible to efficiently convert light of various wavelengths in the solar spectrum into electric energy, not limited to the visible light region and the infrared light region.

(2) Multiple Exciton Generation (MEG)
As shown in FIG. 4A, in a bulk semiconductor, carriers (electrons) are light energy (E = hν = hc / λ, h: Planck constant, ν: frequency, c: speed of light, λ: wavelength), transitions to the valence band, and is extracted as electrical energy. Here, when the optical energy hν is more than twice as large as the band gap Eg (hν> 2Eg), the carrier transitions to the upper part of the valence band, but the excess energy exceeding Eg quickly moves to the lattice system as heat. Then, it moves to the lower part of the more stable valence band. That is, energy exceeding Eg is lost as heat. Therefore, only one carrier can be generated by one photon. Since holes remain for the excited electrons, these pairs are called excitons.

  On the other hand, as shown in FIG. 4B, when the quantum dot d is used, the band gap Eg of the quantum dot d and a layer surrounding the periphery (hereinafter, this layer may be referred to as “matrix layer”). ) With the band gap Egs (Egs> Eg), a quantum well is formed.

  This quantum well restricts the direction of electron movement three-dimensionally. Also, the electron orbit formed in this quantum well is not continuous. Therefore, when the light energy hν is more than twice as large as the band gap Eg (hν> 2Eg), when the electrons excited to the upper orbit fall to the upper end of the band gap, energy is given to the lattice system as heat. The process of relaxation is very slow. As a result, the probability of impact ionization that excites other electrons in the same quantum well to Eg or higher is increased, and when the light energy hν is larger than 2 Eg, further electrons (exciton) are generated. Therefore, a plurality of carriers (for example, electrons) can be generated from one photon. Therefore, photoelectric conversion efficiency can be improved by taking out these as currents.

(3) Miniband formation effect For example, as shown in FIG. 5, quantum dots (quantum wells) can be formed by regularly arranging quantum dots d through a thin film (having a three-dimensional periodicity). ) To form a miniband. That is, as shown in FIG. 6, a miniband is generated between the quantum wells by the tunnel effect, and excited carriers can be taken out to the outside through the miniband at high speed. Therefore, loss due to carrier recombination can be reduced and photoelectric conversion efficiency can be improved. Further, as shown in FIG. 7, transition electrons generated by the above-described multiple exciton generation effect, transition electrons between minibands, and the like can be efficiently extracted via the minibands. As shown in FIG. 7, not only electrons but also holes remaining in the lower quantum well can be taken out. A structure in which quantum dots are given a three-dimensional periodicity in this way is called a superlattice (SL) or multi-quantum well (MQW) structure.

  On the other hand, when the quantum dots d are randomly dispersed three-dimensionally (see, for example, FIG. 1), there are places where the tunnel effect between the quantum wells hardly occurs as shown in FIG. In this case, no miniband is formed between the quantum wells. However, in this case as well, as shown in the figure, the excited electrons can pass through the quantum well by thermal excitation or the like and escape out of the quantum well. Therefore, even if it is not a superlattice, although the probability is low, electrons can be taken out of the quantum well. Also, as shown in FIG. 6, a structure in which quantum dots d are regularly arranged vertically and horizontally and vertically is ideal, but it is not easy to arrange quantum dots d in this way. Therefore, in FIG. 2, in each film (8A), the quantum dots d are arranged randomly in a plane and alternately arranged with the film (8B) not including the quantum dots d, thereby providing the periodicity of the arrangement. It is Such a configuration can also improve the formation rate of the miniband and improve the photoelectric conversion efficiency. In FIG. 2, the quantum dots d are arranged one atom at a time in the film 8A. However, in the atomic arrangement in the film, about two or three atoms may be arranged in the vertical direction. . In short, it is important to provide periodicity of the arrangement by alternately laminating thin films (8A, 8B).

  As described in detail through (1) to (3) above, the photoelectric conversion efficiency can be improved by including the quantum dots d.

Further, in this embodiment, since a silicon oxynitride film is used as the i layer 8, carriers can be easily taken out, and the photoelectric conversion efficiency is improved. Hereinafter, the effect will be described with reference to FIGS. 9 and 10. FIG. 9 is an energy band diagram of the i layer of the photoelectric conversion device when the matrix layer is made of silicon oxide (SiO ₂ ) (comparative example), and FIG. 10 shows the i layer of the photoelectric conversion device of the present embodiment. It is an energy band figure.

That is, as shown in FIG. 9, when quantum dots made of silicon are contained in silicon oxide (SiO ₂ ), the band gap difference becomes 7.9 (= 9−1.1) eV, and the quantum well Is deep.

On the other hand, as shown in FIG. 10, the band gap of the silicon oxynitride film (SiNxOy) varies depending on the composition ratio of oxygen and nitrogen, but from 9 eV which is the band gap of SiO _{2 to} the band gap of Si ₃ N _4. It is between some 5eV. Therefore, the depth of the quantum well can be reduced.

  Further, by changing the composition ratio of oxygen and nitrogen in the silicon oxynitride film (SiNxOy), the depth of the quantum well can be adjusted with respect to the band gap of the quantum dots to be used. Therefore, the device can be designed so as to match the characteristics of the target photoelectric conversion device.

  Since the value of Eg (Si) is in a bulk state, in the case of a quantum dot, it is slightly larger than 1.1 eV due to the (1) quantum size effect. For example, there is a report that the band gap changes to about 1.65 to 1.2 eV when the particle size of the quantum dots is changed about 3 to 8 nm. Therefore, the band gap difference (quantum well depth) can be further adjusted by controlling the particle size and grain type of the quantum dots in a range where the band gap is smaller than that of the matrix layer.

  For example, by setting the band gap of the quantum dots to 2 eV or less and the band gap of the matrix layer to 2 times or more and 3 times or less of the band gap Eg of the quantum dots, it is easy to excite carriers, the quantum effect occurs efficiently, The depth of the quantum well can be made relatively shallow, and the photoelectric conversion efficiency can be improved.

  FIG. 11 is a cross-sectional view illustrating another configuration of the photoelectric conversion device of this embodiment. Here, a so-called tandem photoelectric conversion device will be described.

  The photoelectric conversion device shown in FIG. 11 has a structure in which three pin structures are stacked, and a p-type amorphous silicon layer 5, quantum dots (nanocrystal grains) d 1 and a metal electrode 11 on the substrate 1 and the upper part thereof. An i-layer 8a made of a silicon oxynitride film (SiNxOy) 8z and a first pin structure part (pin1) made of an n-type amorphous silicon layer 9 are arranged, and further, a p-type is formed above this via a transparent electrode 3. The amorphous silicon layer 5, the i layer 8 b made of the quantum dots d 2 and the silicon oxynitride film (SiNxOy) 8 z, and the second pin structure part (pin 2) made of the n-type amorphous silicon layer 9 are arranged, and further on this The p-type amorphous silicon layer 5, the quantum dots d3, and the silicon oxynitride film (SiNxOy) 8z are formed through the transparent electrode 3. The 3pin structure portion made of amorphous silicon layer 9 layers 8c and n-type (pin3) is arranged. The transparent electrode 3 is disposed on the third pin structure portion (pin 3). In this case, the main light incident side is the upper part (transparent electrode side) in the figure.

  As described above, by stacking the pin structure portion in order of increasing band gap of the quantum dots from the light incident side, that is, in ascending order of the particle diameter, a photoelectric effect can be generated for a wide range of wavelengths.

  For example, in the third pin structure portion (pin 3), electrons are excited by light having a short wavelength that is high energy. At this time, light having a longer wavelength and having lower energy than that used in the third pin structure (pin 3) reaches the second pin structure (pin 2) and excites electrons. Further, low-energy long-wavelength light not used in the second pin structure part (pin2) reaches the third pin structure part (pin3) and excites electrons.

  On the other hand, for example, as shown in FIG. 12, only the second pin structure portion (pin2) can efficiently use only moderate energy light (see (b) in the figure). It cannot be used and cannot excite electrons (see (a) in the figure). On the other hand, high-energy short-wavelength light can be used, but part of it is emitted as heat and cannot be used efficiently (see (c) in the figure). FIG. 12 is a diagram showing the relationship between the wavelength of light and the excitation of electrons.

  As described above, the tandem structure can generate a photoelectric effect with respect to a wide range of wavelengths and improve the photoelectric conversion efficiency.

<Method for Manufacturing Photoelectric Conversion Device>
Next, the method for manufacturing the photoelectric conversion device described in Embodiment 1 will be described, and the configuration thereof will be clarified. FIG. 13, FIG. 15 and FIG. 16 are cross-sectional views showing the manufacturing process of the photoelectric conversion device of this embodiment. FIG. 14 is a diagram showing a general formula of a main skeleton of polysilazane.

  As shown in FIG. 13A, for example, a quartz glass substrate is prepared as the substrate 1, and an ITO film, for example, is deposited on the substrate 1 by a sputtering method, and then the transparent electrode 3 is formed by patterning as necessary. Form.

Next, a p-type amorphous silicon layer 5 is formed on the transparent electrode 3. For example, it is formed using an impurity-added precursor liquid obtained by adding a p-type impurity such as boron to a silicon precursor liquid (liquid silicon material). The “precursor liquid” refers to a substance in a previous stage for obtaining a specific substance, and here, it refers to a liquid silicon material for obtaining a silicon layer. As the silicon precursor liquid, for example, a liquid in which cyclopentasilane (Si ₅ H ₁₀ ) is dispersed in an organic solvent is used and polymerized by irradiating with ultraviolet rays to obtain a polysilane solution. This impurity-added precursor liquid is applied onto the transparent electrode 3 by spin coating. Next, heat treatment is performed to make it amorphous (solidify and fire). As heat treatment conditions, for example, treatment is performed at 250 ° C. to 350 ° C. for 10 minutes to 1 hour in a nitrogen atmosphere. In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used.

  Next, the polysilazane liquid L8 in which the quantum dots d are dispersed is prepared and applied on the p-type amorphous silicon layer 5. Silazane refers to a compound having a Si—N bond, and polysilazane is obtained by polymerizing the compound and has a main skeleton represented by the general formula shown in FIG. R1 to R3 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the group directly bonded to silicon is carbon, an alkylsilyl group, an alkylamino group, Represents an alkoxy group or a metal atom. However, at least one of R1, R2, and R3 is a hydrogen atom. Here, perhydropolysilazane (hereinafter referred to as “PHPS”) in which R1 to R3 are all H in the above general formula is used.

This PHPS reacts with oxygen (O ₂ ) and water (H ₂ O) to form a silicon oxide film (SiO ₂ ) according to the following reaction formula [1].
-[SiH ₂ NH] -m + mO ₂ → mSiO ₂ + mNH ₃ ... [1]
On the other hand, in an atmosphere in which oxygen and water are scarce, N remains and becomes a silicon oxynitride film (SiNxOy).

  Therefore, the composition ratio of oxygen and nitrogen in the silicon oxynitride film (SiNxOy) can be changed by adjusting the content of oxygen and water (oxygen compound) in the reaction atmosphere.

  The polysilazane (here, PHPS) is dissolved in an organic solvent, and the quantum dots d are dispersed. Examples of the organic solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbon hydrocarbon solvents, halogenated hydrocarbons such as halogenated methane, halogenated ethane, and halogenated benzene, aliphatic ethers, and fatty acids. Ethers such as cyclic ethers can be used.

  Preferred solvents include halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane, tetrachloroethane, ethyl ether, isopropyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane, Ethers such as dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, pentanehexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, ethylbenzene, etc. And the like. Particularly preferred solvents include xylene or dibutyl ether.

  As the quantum dots d, for example, silicon nanocrystals are used. Such quantum dots of various semiconductor materials can be manufactured using, for example, molecular beam epitaxy, chemical vapor deposition, colloidal wet chemical method, etc. For example, various semiconductor materials can be manufactured by Quantum Dot and Evident Technology. Quantum dots with different particle sizes are manufactured and sold.

  Such quantum dots d are manufactured or obtained and dispersed in the PHPS liquid (an organic solvent liquid of PHPS) L8. Next, the quantum dot d-containing PHPS liquid L8 is applied onto the p-type amorphous silicon layer 5 by a spin coating method (FIG. 13A). Next, heat treatment is performed and baking (film formation) is performed. As the heat treatment conditions, for example, the treatment is performed at 300 ° C. for about 1 hour in a nitrogen atmosphere containing oxygen at a volume concentration of 3 to 5%. Thereby, the i layer 8 made of the silicon oxynitride film 8z containing the quantum dots (nanocrystal grains) d made of silicon in a dispersed state is formed (FIG. 13B). In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used.

Next, as shown in FIG. 13C, an n-type amorphous silicon layer 9 is formed on the i layer 8. For example, it is formed using a silicon precursor solution (for example, the aforementioned polysilane solution) to which an n-type impurity such as yellow phosphorus (P ₄ ) is added. This precursor liquid is applied onto the i layer 8 by spin coating. Next, for example, heat treatment is performed at 250 ° C. to 350 ° C. for about 10 minutes to 1 hour to make it amorphous.

  Moreover, in the heat treatment at the time of forming each amorphous layer (5, 9), heat treatment is performed in an atmosphere containing hydrogen gas in an inert atmosphere such as nitrogen or argon so that hydrogen is included in the amorphous layer. Good. The hydrogen gas concentration in the atmosphere is, for example, 1% or more and 3% or less. Further, hydrogen may be contained by performing heat treatment in a steam atmosphere or performing hydrogen plasma treatment. Thus, by including hydrogen atoms in the layer, dangling bonds in the layer are terminated by hydrogen atoms, and carrier trapping can be prevented.

  Next, an Al film is formed as a metal electrode 11 on the n-type amorphous silicon layer 9. For example, Al is deposited on the n-type amorphous silicon layer 9 by a sputtering method, and the metal electrode 11 is formed by patterning as necessary. Through the above steps, the photoelectric conversion device of this embodiment is formed (FIG. 13C).

  When the i layer 8 is composed of a plurality of thin films (8A, 8B) (see FIG. 2), as shown in FIG. 15 (A), the transparent electrode 3 is formed on the substrate 1 as described above. After the p-type amorphous silicon layer 5 is formed, the quantum dot d-containing PHPS liquid L8A is applied onto the amorphous silicon layer 5 by a spin coating method and dried to form a thin dry coating film D8A. Next, as shown in FIG. 15B, a thin dry coating film D8B is formed by applying and drying a PHPS liquid L8B that does not contain quantum dots d on the dry coating film D8A. Thereafter, the formation of the dried coating films D8A and D8B is repeated to form a laminated film of the dried coated film (FIG. 15C), and then the laminated film is subjected to heat treatment to be amorphous (solidified and fired). As the heat treatment conditions, for example, the treatment is performed at 300 ° C. for about 1 hour in a nitrogen atmosphere containing oxygen at a volume concentration of 3 to 5%. Thereby, the i layer 8 in which the thin film 8A containing the quantum dot d made of silicon and the thin film 8B containing no quantum dot d made of silicon are alternately stacked is formed (FIG. 15D).

  FIG. 15 schematically shows a state in which one quantum dot d1 is randomly arranged in a plane on the thin film 8A. However, the present invention is not limited to this, and a plurality of atoms are stacked vertically in the thin film 8A. It is good also as a film thickness of the grade to do. That is, as described above, it is important to increase the number of locations where the minibands are formed by alternately laminating thin films so as to provide the periodicity of the arrangement of quantum dots d. 2 and 15, the thin film 8A containing the quantum dots d is the lowest layer, but the thin film 8B not containing the quantum dots d made of silicon may be the lowest layer, and the number of stacked layers is an even number. But it may be an odd number.

  When forming the tandem photoelectric conversion device described with reference to FIG. 11, PHPS solutions each containing three types of quantum dots (d1 to d3) with different particle sizes are prepared, applied, and fired. Thus, the i layers 8a to 8c may be formed.

  As described above, according to this embodiment, since the i layer is formed using the polysilazane liquid in which the quantum dots are dispersed, the photoelectric conversion device can be easily formed with good controllability. In addition, production at low cost is possible.

  The p-type and n-type amorphous silicon layers (5, 9) may be formed using a CVD (Chemical Vapor Deposition) method. Further, impurities may be implanted by an ion implantation method. Alternatively, a p-type amorphous silicon layer may be formed by dispersing quantum dots containing p-type impurities in a silicon precursor solution. Similarly, an n-type amorphous silicon layer may be formed by dispersing quantum dots containing n-type impurities in a silicon precursor solution.

  Further, as shown in FIG. 16, a silicon oxynitride film 8z containing p-type quantum dots dp is formed using a PHPS solution in which quantum dots dp containing p-type impurities are dispersed, and p layer 5P is formed. It is good. Alternatively, the silicon oxynitride film 8z containing the n-type quantum dots dn may be formed using the PHPS liquid in which the quantum dots dn containing the n-type impurities are dispersed to form the n layer 9N. Also, the p-type and n-type amorphous silicon layers (5, 9) in FIGS. 1 and 13 may be used as the quantum dot-containing films (5P, 9N), respectively.

  In this embodiment, the quantum dots d made of silicon are used as the quantum dots, but various materials shown in FIG. 17 such as silicon germanium and germanium may be used as the quantum dot materials. FIG. 17 is a table showing usable quantum dot materials and matrix layer materials. In addition, the core-shell structure in the figure means particles in which a core material is coated with a shell material. For example, CdS / ZnSe refers to particles in which a core made of CdS is coated with a ZnSe material.

  As described above, by changing the composition ratio of oxygen and nitrogen in the silicon oxynitride film (SiNxOy) serving as the matrix layer in accordance with various materials, the target photoelectric conversion device such as the band gap and the quantum well depth can be obtained. The device can be designed to meet the characteristics of

  In addition, as shown in FIG. 18, the photoelectric effect can be generated with respect to a wide range of wavelengths by making the apparatus a tandem type. FIG. 18 is a cross-sectional view illustrating another structure of the photoelectric conversion device of this embodiment.

  In this case, as shown in FIG. 18, the particle types of the quantum dots da to dc in the i layers 8 in the three pin structure portions (pins 1 to 3) are different. Other configurations are the same as those in FIG.

  In this case, by arranging the pin structure portion in the descending order of the band gap of the quantum dots (Eg (dc)> Eg (db)> Eg (da)) from the light incident side, FIG. As in the case, the photoelectric effect can be generated for a wide range of wavelengths. As the quantum dot, for example, silicon, silicon germanium, germanium, or the like can be used. In addition to compound semiconductors such as CdTe (1.52 eV), GaA (1.43 eV), InP (1.35 eV), and GaP (2.3 eV), the materials shown in FIG. 17 may be used in appropriate combinations. Good. The band gap indicates the band gap. In each pin structure portion of FIG. 18, the composition ratio of oxygen and nitrogen of the silicon oxynitride film (SiNxOy) of each i layer 8 constituting the matrix layer may be changed.

  As described above, by appropriately selecting and adjusting the composition ratio of oxygen and nitrogen in the quantum dots and the silicon oxynitride film (SiNxOy) of the i layer 8, a photoelectric conversion device with favorable characteristics can be obtained.

  Moreover, in the manufacturing process described in Patent Document 1 described above, a high temperature treatment of 1100 ° C. or higher is necessary, and the substrate and electrode material that can be used are limited. On the other hand, according to the solution process of the above embodiment, a low-temperature process is possible, and a substrate having low heat resistance can be used. Therefore, it is possible to manufacture a device with high productivity at low cost. In addition, according to the above embodiment, the process of the conventional semiconductor integrated circuit and the conventional photoelectric conversion device is good, and these circuits and devices are mixedly mounted on the same substrate to form a multifunctional system. You can also.

In the above embodiment, the silicon oxynitride film (SiNxOy) is formed as the matrix layer. However, the composition ratio y of nitrogen in the film may be set to 0 to form a silicon oxide film. In this case, although the depth of the quantum well may be deepened by 9 eV which is the band gap of SiO ₂ , the merit (low temperature process, low cost, high productivity, etc.) of the solution process using polysilazane can be achieved. . Moreover, the depth of a quantum well can also be made shallow by combining with a quantum dot with a large band gap.

<Electronic equipment>
The photoelectric conversion device can be incorporated into various electronic devices. There is no limitation on applicable electronic devices, but an example thereof will be described.

  FIG. 19 is a plan view showing a calculator to which the solar cell (photoelectric conversion device) of the present invention is applied, and FIG. 20 is a perspective view showing a cellular phone (including PHS) to which the solar cell (photoelectric conversion device) of the present invention is applied. FIG.

  A calculator 100 illustrated in FIG. 19 includes a main body unit 101, a display unit 102 provided on the upper surface (front surface) of the main body unit 101, a plurality of operation buttons 103, and a photoelectric conversion element installation unit 104.

  In the configuration shown in FIG. 19, five photoelectric conversion elements 1 d are arranged in series in the photoelectric conversion element installation unit 104. The photoelectric conversion device can be incorporated as the photoelectric conversion element 1d.

  A cellular phone 200 illustrated in FIG. 20 includes a main body portion 201, a display portion 202 provided on the front surface of the main body portion 201, a plurality of operation buttons 203, an earpiece 204, a mouthpiece 205, and a photoelectric conversion element installation portion 206. I have.

  In the configuration illustrated in FIG. 20, the photoelectric conversion element installation unit 206 is provided so as to surround the display unit 202, and a plurality of photoelectric conversion elements 1 d are arranged in series. The photoelectric conversion device can be incorporated as the photoelectric conversion element 1d.

  In addition to the calculator shown in FIG. 19 and the cellular phone shown in FIG. 20, the electronic device of the present invention can be applied to, for example, an optical sensor, an optical switch, an electronic notebook, an electronic dictionary, a wristwatch, a clock, and the like.

  FIG. 21 is a perspective view illustrating a wrist watch that is an example of an electronic apparatus. The wristwatch 1100 includes a display unit 1101. For example, the photoelectric conversion device can be incorporated in the outer periphery of the display unit 1101.

  The photoelectric conversion device is suitable for cost reduction and mass production, and is also suitable for use in a solar power generation system for home use or business use.

  It should be noted that the examples and application examples described through the above embodiment can be used in appropriate combination according to the application, or can be used with modifications or improvements, and the present invention is limited to the description of the above embodiment. Is not to be done.

It is sectional drawing which shows the structure of the quantum dot type photoelectric conversion apparatus of this Embodiment. It is sectional drawing which shows the structure of the quantum dot type photoelectric conversion apparatus of this Embodiment. It is an energy band figure for demonstrating a quantum size effect. It is an energy band figure for demonstrating the multiple exciton production | generation effect in the case of a bulk and the case of a quantum dot. It is the cross-sectional perspective view which showed the superlattice structure typically. It is an energy band figure in case a miniband is formed. It is an energy band figure in case a miniband is formed. It is an energy band figure in case a miniband is not formed. The matrix layer is an energy band diagram of the i layer of the photoelectric conversion device of the silicon oxide when the (SiO ₂₎ (Comparative Example). It is an energy band figure of i layer of the photoelectric conversion apparatus of this Embodiment. It is sectional drawing which shows the other structure of the photoelectric conversion apparatus of this Embodiment. It is a figure which shows the relationship between the wavelength of light, and excitation of an electron. It is sectional drawing which shows the manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is a figure which shows the general formula of the main frame | skeleton of polysilazane. It is sectional drawing which shows the manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is sectional drawing which shows the manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is a table | surface which shows the material of the quantum dot which can be used, and the material of a matrix layer. It is sectional drawing which shows the other structure of the photoelectric conversion apparatus of this Embodiment. It is a top view which shows the calculator to which the solar cell (photoelectric conversion apparatus) is applied. It is a perspective view which shows the mobile telephone to which the solar cell (photoelectric conversion apparatus) is applied. It is a perspective view which shows the wristwatch which is an example of an electronic device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 1d ... Photoelectric conversion element, 3 ... Transparent electrode, 5 ... p-type amorphous silicon layer, 8 ... i layer, 8z ... Silicon oxynitride film, 9 ... n-type amorphous silicon layer, 11 ... Upper electrode, 8A ... Silicon oxynitride film containing quantum dots d, 8B ... Silicon oxynitride film not containing quantum dots d, 8a, 8b, 8c ... i layer, 100 ... Calculator, 101 ... Main unit, 102 ... Display unit, 103 DESCRIPTION OF SYMBOLS ... Operation button, 104 ... Photoelectric conversion element installation part, 200 ... Mobile phone, 201 ... Main body part, 202 ... Display part, 203 ... Operation button, 204 ... Earpiece, 205 ... Mouthpiece, 206 ... Photoelectric conversion element installation part DESCRIPTION OF SYMBOLS 1100 ... Wristwatch 1101 ... Display part, d, d1-d3, da-dc ... Quantum dot, D8A ... Dry coating film, D8B ... Dry coating film, L8 ... Polysilazane liquid, L8A ... Quantum dot d included PHPS solution, L8b ... PHPS solution containing no quantum dot d, pin1 ... first 1pin structure, pin2 ... first 2pin structure, pin3 ... first 3pin structure

Claims (12)

A step of forming a coating film by applying a liquid containing polysilazane in which nanocrystal grains made of a semiconductor are dispersed above a substrate;
Forming a silicon oxynitride film containing the nanocrystal grains by performing a heat treatment on the coating film;
A process for producing a photoelectric conversion device, comprising:   The method for manufacturing a photoelectric conversion device according to claim 1, wherein the semiconductor is silicon or a silicon compound.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein a band gap of the nanocrystal grains is 2 eV or less.   The heat treatment is performed in a nitrogen atmosphere containing oxygen or an oxygen compound, and a composition ratio of oxygen and nitrogen in the silicon oxynitride film is adjusted by adjusting an oxygen concentration in the atmosphere. The manufacturing method of the photoelectric conversion apparatus as described in any one of claim | item 1 thru | or 3. Forming a first conductivity type semiconductor layer above the substrate;
Forming a silicon oxynitride film containing the nanocrystal grains on the first conductivity type semiconductor layer;
Forming a second conductivity type semiconductor layer that is a reverse conductivity type of the first conductivity type on the silicon oxynitride film containing the nanocrystal grains;
The manufacturing method of the photoelectric conversion apparatus as described in any one of Claims 1 thru | or 4 which has these. A first step of forming a first coating film by applying a liquid containing polysilazane in which nanocrystal grains made of a semiconductor are dispersed above a substrate;
A second step of forming a second coating film by applying a liquid containing polysilazane not containing the nanocrystal grains;
A third step of forming a laminated film in which the first coating film and the second coating film are repeatedly laminated by repeating the first and second steps;
A fourth step of forming a layer in which the silicon oxynitride film containing the nanocrystal grains and the silicon oxynitride film not containing the nanocrystal grains are repeatedly laminated by performing a heat treatment on the laminated film;
A process for producing a photoelectric conversion device, comprising: A silicon oxynitride containing nanocrystal grains having the first grain size is applied by applying a liquid containing polysilazane in which nanocrystal grains having a first grain size made of a semiconductor are dispersed above the substrate and performing a heat treatment. Forming a film;
A liquid containing polysilazane in which nanocrystal grains having a second grain size different from the first grain size made of the semiconductor are dispersed above the silicon oxynitride film containing the nanocrystal grains having the first grain size. Applying and heat treating to form a silicon oxynitride film containing nanocrystal grains of the second grain size;
A process for producing a photoelectric conversion device, comprising: A silicon oxynitride film containing the first nanocrystal grains is formed by applying a liquid containing polysilazane in which the first nanocrystal grains made of the first semiconductor are dispersed over the substrate and performing a heat treatment. Process,
A liquid containing polysilazane in which second nanocrystal grains made of a second semiconductor other than the first semiconductor are dispersed is applied above the silicon oxynitride film containing the first nanocrystal grains and subjected to heat treatment. A step of forming a silicon oxynitride film containing the second nanocrystal grains,
A process for producing a photoelectric conversion device, comprising:   9. The method of manufacturing a photoelectric conversion device according to claim 1, wherein the silicon oxynitride film is represented by SiOxNy, and the y is 0.   A method for manufacturing an electronic apparatus, comprising the method for manufacturing a photoelectric conversion device according to claim 1. It has a silicon oxynitride film containing nanocrystal grains made of a semiconductor,
The band gap of the nanocrystal grains is 2 eV or less,
The photoelectric conversion device, wherein the silicon oxynitride film is a film in which a composition ratio of oxygen and nitrogen is adjusted so that a band gap thereof is not less than 2 times and not more than 3 times a band gap of the nanocrystal grains.   An electronic apparatus comprising the photoelectric conversion device according to claim 11.

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