JP2014027224A - Organic thin-film solar cell and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic thin-film solar cell having a large open-circuit voltage.SOLUTION: An organic thin-film solar cell 100 includes a first electrode 102, a mixed layer 106 of an electron-donative semiconductor 104 and an electron-accepting semiconductor 105, and a second electrode 108; and a hole block layer 107 is provided between the second electrode 108 and the mixed layer 106. At least either of the electron-accepting semiconductor 105 included in the mixed layer 106 and the hole block layer 107 is composed of a group I-III-VI compound semiconductor.

Description

  The present invention relates to an organic thin film solar cell and a manufacturing method thereof, and more particularly to an organic thin film solar cell using a bulk heterojunction layer formed by mixing an electron donating substance and an electron accepting substance as a power generation layer and a manufacturing method thereof.

  Organic thin-film solar cells are expected to be more convenient solar cells because of their low manufacturing cost, light weight, and flexibility. In other words, unlike conventional solar cells, organic thin-film solar cells can be produced by printing such as roll-to-roll process, etc., and characteristics that cannot be achieved with conventional solar cells such as low cost, light weight, and flexibility. Is expected. Therefore, the organic thin film solar cell is expected to be used for a film solar cell, a photo sensor sheet, and the like.

  In addition, to increase the efficiency of organic thin-film solar cells, it has been reported that the conversion efficiency exceeds 10% due to the increase in light absorption intensity due to the development of narrow band gap conjugated polymer (see Patent Document 1), Future increases in conversion efficiency are expected.

  Since the principle of power generation of the organic thin-film solar cell is due to the function manifestation as a diode as in the case of the organic EL, it is important for improving the performance to ensure the rectification of holes and electrons. For example, a method of installing an electron blocking layer such as a nickel oxide thin film near the positive electrode in order to ensure the rectifying property of hole transport (see Patent Document 2), or a hole blocking layer in order to ensure the rectifying property of electron transport There are known methods (see Patent Documents 3 and 4).

  As described above, in order to improve the efficiency of the organic thin film solar cell, a method of extending the light absorption wavelength by controlling the band gap of the semiconductor, or a thin film that blocks one charge and extracts only the other charge is located near the electrode. There is a method to ensure rectification by installing.

JP2011-249757A JP20112333692A JP 2011-114004 A JP 2011-115849 A

  In order to increase the conversion efficiency of the organic thin film solar cell, it is important to improve the charge transport rectification. Therefore, in the present invention, in order to improve the rectification property of the organic thin film solar cell, the energy level in the organic thin film solar cell is optimized. In the conventional organic thin film solar cell, the point which such consideration was insufficient is improved. In addition, the hole blocking layer used so far has a large number of materials whose energy levels are around 4.0 eV, and there is a problem that applicable materials are limited.

  Therefore, the present invention aims at optimizing the energy level inside the organic thin film solar cell, and aims at selecting a constituent material therefor.

  In the organic thin film solar cell, in order to ensure the rectification of the diode, the absolute value of the electron affinity of the hole blocking layer is larger than the absolute value of the electron affinity of the electron accepting material constituting the mixed layer as the power generation layer, That is, it is desirable that the electron affinity has a stepped shape. In this way, the absolute value of the electron affinity of the hole blocking layer has a value larger than the absolute value of the electron affinity of the electron accepting material contained in the power generation mixed layer, that is, the electron affinity is provided in a step shape, and the rectifying property is improved. In order to increase it, it is important to obtain semiconductors having various electron affinities.

  As means for enabling this, it is possible to use a compound semiconductor material in which at least one of the electron-accepting semiconductor and the hole blocking layer is a group I-III-VI group. The compound semiconductor material of the I-III-VI group can easily control the electron affinity depending on the element composition, and various values can be obtained. By controlling the electron affinity in this way, it becomes possible to obtain an organic thin-film solar cell with improved rectification and increased photoelectric conversion efficiency.

That is, the organic thin film solar cell of the present invention is characterized by having the following configurations (1) to (4).
(1) A power generation layer (bulk heterojunction layer) composed of a mixed layer of an electron donating substance and an electron accepting substance is provided between the positive electrode and the negative electrode,
(2) A hole blocking layer is provided between the power generation layer and the negative electrode,
(3) At least one of the electron-accepting material and the hole blocking layer of the power generation layer is an I-III-VI group inorganic compound semiconductor,
(4) The absolute value of the electron affinity of the hole blocking layer is larger than the absolute value of the electron affinity of the electron accepting substance, and the electron negativity is large.

  In addition, various manufacturing methods can be adopted for the organic thin film solar cell of the present invention. In particular, in the present invention, a solution in which fine particles of a group I-III-VI group compound semiconductor are dispersed in a solvent is applied. By doing so, at least one of the electron-accepting semiconductor and the hole-blocking layer contained in the mixed layer is formed, and a method for producing an organic thin-film solar cell is provided.

  According to the present invention, compared with the conventional organic thin-film solar cell, the effect of optimization by the energy level step structure at the junction between the electron-accepting semiconductor of the mixed layer serving as the power generation layer and the hole blocking layer is achieved. Thus, the rectifying property is improved, and a highly efficient organic thin-film solar cell can be manufactured.

It is an example of the cross-sectional schematic diagram of the organic thin-film solar cell of the Example of this invention. It is an example of the schematic diagram which showed the relationship of the electron affinity of the constituent material of the organic thin-film solar cell of the Example of this invention. It is an example of the change of the electron affinity with respect to the composition change of the I-III-VI group compound semiconductor. It is an example of the cross-sectional schematic diagram of the organic thin-film solar cell of a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the Example described below is a representative example for explaining the embodiment, and the configuration of the present invention is not limited at all by these Examples.

  In Example 1, an organic thin film solar cell (OPV) in which a compound semiconductor composed of a group I-III-VI group is applied to an electron accepting material and a hole blocking layer will be described with reference to FIG.

  FIG. 1 is an example of a schematic cross-sectional view of an organic thin-film solar cell for easy understanding of an embodiment of the present invention, and is a schematic diagram conceptually illustrating a cross-sectional structure of an organic thin-film solar cell of an embodiment of the present invention. is there. In particular, the electron-accepting semiconductor material 105 of the power generation mixed layer 106 schematically shows a state in which fine particles are secondarily aggregated and connected.

  In FIG. 1, a first electrode which is a positive electrode is provided on a substrate 101, a hole transport layer 102 is provided thereon, and a bulk heterojunction is formed thereon by an electron donating semiconductor material and an electron donating semiconductor material. The generated power generation mixed layer 106 is provided. On the power generation mixed layer 106, a hole blocking layer 107 and a second electrode 108 which is a negative electrode are provided, and the organic thin film solar cell 100 is configured.

  Light incident from the substrate 101 side is absorbed by the power generation mixed layer, and a pair of holes and electrons is generated. If the work functions of the positive electrode 101 and the negative electrode 108 are made different depending on the internal electric field, for example, the potential difference between the positive electrode and the negative electrode causes electrons to be transported to the negative electrode through the electron-donating semiconductor material path, and holes to be transferred to the electron-donating semiconductor material. It reaches the positive electrode via the path and a photocurrent flows.

  The substrate 101 of the organic thin-film solar cell 100 is not particularly limited as long as light transmission is ensured if light is incident from the substrate 101 side, such as a glass substrate such as blue plate glass or white plate glass, polyethylene terephthalate, It may be a plastic substrate such as polyethylene naphthalate or a transparent resin film. Next, the transparent electrode 102 is placed in contact with the substrate 101. The transparent electrode 102 only needs to have a sheet resistance that ensures light transmission and OPV performance. For example, tin-doped indium oxide ITO can be installed by an existing method such as an ion plating method. At this time, the thickness is preferably in the range of 0.05 to 0.50 μm in order to realize a sheet resistance of 30Ω / □ or less, in which the internal resistance does not affect the performance of OPV.

  Of course, when light is incident from the second electrode (negative electrode) side, the substrate 101 and the first electrode (positive electrode) 102 are made of an opaque material such as metal, and the second electrode (negative electrode) is a transparent electrode. It may be said.

  A hole transport layer 103 is provided on the transparent electrode 102. The hole transport layer has a role of blocking only electrons by transporting only holes when power is generated by OPV. The hole transport layer is not particularly limited as long as it has conductivity and the maximum occupied molecular orbital (High Occupied Molecular Orbital, HOMO) corresponding to the Fermi level at a level lower than the work function of the transparent electrode 102. PEDOT-PSS (made by Aldrich) etc. can be used.

  The mixed layer 106 that is a power generation layer is a part that converts the energy of incident light into electrical energy, and mixes an electron-donating semiconductor (P-type semiconductor) material 104 and an electron-accepting semiconductor (N-type semiconductor) material 105. A layer in which a bulk heterojunction is formed.

  The electron-donating semiconductor 104 of the mixed layer 106 which is a power generation layer is a conjugated polymer, phthalocyanine, indigo, thioindigo pigment, quinacridone pigment, merocyanine compound, cyanine compound, squalium compound, polycyclic aromatic compound, or organic electrophotographic photosensitive material. A low molecular organic semiconductor such as a charge transfer agent or an electrically conductive organic charge transfer complex used for the body can be used without particular limitation. As the conjugated polymer, for example, Poly-3-Hexylthiophene (P3HT) or poly (2-methoxy-5- (3'7'-dimethyllocyloxy) 1,4-phenylene vinylene (MDMO-PPV) can be used.

  As the above-mentioned phthalocyanine-based low-molecular organic semiconductors, the central metal is divalent such as Cu, Zn, Co, Ni, Pb, Pt, Fe, Mg, metal-free phthalocyanine, aluminum chlorophthalocyanine, indium chlorophthalocyanine, gallium chloro Examples include, but are not limited to, trivalent metal phthalocyanines coordinated with halogen atoms such as phthalocyanine, and other phthalocyanines coordinated with oxygen such as baanadyl phthalocyanine and titanyl phthalocyanine.

  As the electron-accepting semiconductor 105, a I-III-VI group compound semiconductor is used. Copper, silver, aluminum or the like can be used as the group I element. Indium, gallium, or the like can be used as the group III element, and sulfur, selenium, tellurium, or the like can be used as the group VI element. As an example, a composition in which a group I element such as CuxInySz, AgxInySz, or AlxInySz (x, y, z is an arbitrary numerical value representing a composition) is changed, or CuxInyGa (1-y) Sz (x, y, z is a composition, respectively) Quaternary compounds such as any numerical value).

  The electron affinity of the I-III-VI group compound semiconductor can be changed depending on the elemental composition. By changing the composition ratio of the group I element and group III element (group I element / group III element) between 0.7 and 0.9, the optimum electron affinity as the electron-accepting semiconductor of the power generation layer can be obtained. As the ratio of group III elements increases, the absolute value of electron affinity increases. However, if the composition ratio (Group I element / Group III element) is larger than 0.9, the function as an electron-accepting semiconductor is impaired due to P-type, and if it is smaller than 0.7, phase separation may occur. Therefore, 0.7 or more and 0.9 or less are preferable.

  Various methods for producing an electron-accepting semiconductor 105 made of a compound semiconductor of the I-III-VI group are known, but it is desirable to synthesize them in a fine particle form so as to be mixed with the electron-donating semiconductor 104. There is no. By constituting in the form of fine particles, the light incident on the power generation mixed layer 106 is easily scattered, which can contribute to improvement of photoelectric conversion efficiency. In particular, since the fine particles of the electron-accepting semiconductor material are secondarily aggregated and in contact with each other inside the power generation mixed layer, the effect of internal scattering can be further obtained. On the other hand, since the electron-accepting semiconductor material must be in contact with or wrapped around the electron-donating semiconductor material in the power generation mixed layer to form a bulk heterojunction, the bulk heterojunction is formed in a wide area as the size of the fine particles. Therefore, 50 nm or less is desirable.

  As an example, a method of forming by reaction of sodium sulfide with a metal salt will be described. In the fine particle synthesis of the core portion, for example, indium (III) iodide and sodium sulfide are mixed in methanol, thereby forming the core fine particles by the reaction shown in the formula (1).

(Formula 1)
0.9 CuI + InI ₃ + 2Na ₂ S → Cu _0.9 In _1.0 S _2.0 + 2NaI

The produced Cu0.9In1.0S2.0 fine particles can be purified by washing with alcohol such as methanol and repeating fine particle precipitation by centrifugation. Other examples include a formation method using thermal decomposition of a dithiocarbamate derivative and a formation method using a solvothermal method, and any method can synthesize fine particles for carrying out the present invention. The electron-accepting semiconductor material 105 thus purified is dispersed in a solvent in which the electron-donating semiconductor material 104 is dissolved, and the dispersion can be applied by a method such as spin coating to produce the mixed film 106. The film thickness of the mixed film 106 is suitably in the range of 0.01 μm to 0.50 μm, and more preferably in the range of 0.05 μm to 0.30 μm, the performance of the solar cell can be appropriately exhibited.

  In the mixture of the electron-accepting semiconductor material 105 and the electron-donating semiconductor material 104 thus formed, it is desirable that the mixing ratio of the electron-accepting semiconductor material is 50% or more. As a result, the electron-accepting semiconductor material is wrapped in the electron-donating semiconductor material to form a suitable bulk heterojunction throughout the film, and the hole-blocking layer is formed by mutual contact or secondary aggregation of the electron-accepting semiconductor material. As a result, an electron transport route to the negative electrode is ensured, which can contribute to improvement of rectification.

  In Example 1, an I-III-VI group compound semiconductor is used as the hole blocking layer 107. FIG. 2 shows the relationship between the absolute values of the electron affinity Ea2 of the hole blocking layer 107, the electron affinity Ead of the electron-donating semiconductor 104, and the electron affinity Eaa of the electron-accepting semiconductor 105. In order to perform electron transport without loss, the absolute value of the electron affinity of the hole blocking layer 107 needs to be larger than the absolute value of the electron affinity of the electron-accepting semiconductor 105. In the I-III-VI group compound semiconductor, the electron affinity can be controlled by changing the elemental composition.

  As described above, the hole blocking layer for performing electron transport without loss by changing the composition ratio of the group I element and group III element (group I element / group III element) between 0.7 and 0.9. As a result, an optimum electron affinity can be obtained. As the ratio of group III elements increases, the absolute value of electron affinity increases. However, if it is larger than 0.9, it becomes P-type and the function as an electron-accepting semiconductor is impaired, and if it is smaller than 0.7, phase separation is likely to occur. Is preferred.

  Further, in a quaternary compound such as CuxInyGa (1-y) Sz (x, y, z is a numerical value representing the composition), the electron affinity can be controlled by compositional modulation of group III elements of In and Ga. An example of electron affinity control is shown in FIG.

  The hole blocking layer 107 can be formed by synthesizing fine particles in the same manner as the method for synthesizing the electron-accepting semiconductor 105 and applying a dispersion in which the electron-donating semiconductor 104 is dispersed in a solvent that does not dissolve. Examples of the solvent that does not dissolve the electron-donating semiconductor 104 include various alcohol solvents such as ethanol, methanol, and 2-propanol.

  By forming the inside of the hole blocking layer with a particulate substance, the light transmitted through the power generation mixed layer 106 is easily reflected by the hole blocking layer and returned to the power generation mixed layer, which can contribute to improvement in photoelectric conversion efficiency. In particular, since the fine particles in the hole blocking layer are secondarily aggregated and are in contact with each other, the effect of scattering reflection can be obtained. From this viewpoint, the size of the fine particles is preferably 200 nm or more and 500 nm or less in terms of effective scattering reflection. It should be noted that the size of the secondary aggregation of the fine particles may be 200 nm or more and 500 nm or less.

  The second electrode 108 which is a negative electrode is an electrode for efficiently collecting electrons generated in the mixed layer 106. As a material of the second electrode 108, a metal and an alloy having a small work function are used. It is preferable to use a material having a work function of 1.9 to 5 eV so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level does not become too large. Examples of the material of the second electrode 108 include alkali metals, alkaline earth metals, rare earths, and alloys of these with other metals such as sodium, sodium-potassium alloy, lithium, magnesium, magnesium- Examples thereof include a silver mixture, a magnesium-indium mixture, and an aluminum-lithium alloy. Aluminum can also be used. The negative electrode 108 described above may be formed by a vacuum evaporation method, a sputtering method, a coating method, or the like.

  Hereinafter, based on the form for carrying out the above, a method for producing an organic thin film solar cell using I-III-VI group compound semiconductor fine particles for the electron-accepting semiconductor and the hole blocking layer will be specifically described.

  A substrate was prepared by depositing 0.3 μm tin-doped indium oxide ITO on a non-alkali glass having a thickness of 0.7 mm by a sputtering method. The ITO surface was washed with acetone, ethanol, neutral detergent, and pure water in this order, and then treated with an ozone cleaner.

  PEDOT-PSS (manufactured by Aldrich) was formed into a film with a thickness of 40 nm on the cleaned substrate by spin coating.

A dichlorobenzene solution (concentration 2 wt%) in which fine particles of P3HT and Cu _0.9 In _1.0 S _2.0 were mixed at a weight ratio of 1: 4 on the formed PEDOT-PSS thin film was formed by spin coating. Filmed. The thickness of the mixed layer at this time was 250 nm.

On the mixed layer, an ethanol dispersion of Cu _0.9 In _0.2 Ga _0.8 S _2.0 fine particles (concentration 2 wt%) was applied by a spin coating method to form a 40 nm thick hole blocking layer. Provided. From the absolute value of electron affinity 3.4 eV of Cu _0.9 In _1.0 S _2.0 which is an electron-accepting semiconductor of the mixed layer, Cu _0.9 In _0.2 Ga _0. The electron affinity of ₈ S _2.0 is 3.8 eV, which satisfies the conditions of the present invention.

  Further, an organic thin film comprising aluminum as a second electrode having a thickness of 0.1 μm formed thereon by heating resistance vapor deposition, and comprising an electron-accepting semiconductor and a hole-blocking layer of I-III-VI group compound semiconductor fine particles A solar cell was produced.

The organic thin film solar cell 100 thus produced had a short-circuit current of 7.50 mA / cm ³ , an open-circuit voltage of 1.02 V, a fill factor (FF) of 0.54, and a photoelectric conversion efficiency of 4.13%. . The photoelectric conversion characteristics of the cell produced in Example 1 are summarized in Table 1 below.

  In this embodiment, an organic thin-film solar cell 100 using a fullerene derivative as the electron-accepting semiconductor 105 and a I-III-VI group compound semiconductor as the hole blocking layer 107 will be described with reference to FIG. In the second embodiment, the description of the portions that are not different from the first embodiment will be omitted as appropriate.

  In Example 2, a fullerene derivative is used as the electron-accepting semiconductor 205. As the fullerene derivatives, for example, 6,6′-Phenyl-C61-Butyric acid Methyl ester (C61-PCBM), 6,6′-Phenyl-C71-Butyric acid Methyl ester (C71-PCBM), 6,6′-Phenyl- C61-Hexanoic acid Methyl ester (C61-PCHM) or the like can be used, and these fullerene derivatives are excellent in solubility as compared with a fullerene single molecule.

  Hereinafter, the production method of the organic thin film solar cell of Example 2 will be specifically described. The substrate 101, the transparent electrode 102, and the hole transport layer 103 were produced in the same manner as in Example 1. A dichlorobenzene solution (concentration 2 wt%) in which P3HT as an electron-donating semiconductor 104 and C61-PCBM as an electron-accepting semiconductor 105 are mixed at a weight ratio of 1: 0.8 is spin-coated thereon, and a mixed layer 106 is formed. Obtained at a thickness of 250 nm.

An ethanol dispersion (concentration 2 wt%) of a compound semiconductor fine particle of I-III-VI group consisting of Cu _0.9 Ga _1.0 S _{2.0 is formed} on the mixed layer 106 by spin coating, and hole blocking is performed. Layer 107 was formed. The absolute value of the electron affinity of Cu _0.9 Ga _1.0 S _2.0 is 4.0 eV, which is larger than 3.8 eV which is the absolute value of the electron affinity of C61-PCBM, and satisfies the requirements of the present invention. Yes.

  On the hole blocking layer 106, aluminum was deposited as a second electrode by 0.1 μm resistance heating vapor deposition to obtain an organic thin film solar cell 100.

The organic thin film solar cell 200 thus fabricated had a short-circuit current of 8.90 mA / cm ³ , an open-circuit voltage of 0.65 V, a fill factor (FF) of 0.58, and a photoelectric conversion efficiency of 3.36%. . Table 1 summarizes the photoelectric conversion characteristics of the cell prepared in Example 2.

  In this embodiment, an organic thin film solar cell 100 using an I-III-VI group compound semiconductor as the electron-accepting semiconductor 105 and a fullerene derivative as the hole blocking layer 107 will be described with reference to FIG. In the third embodiment, the description of the portions that are not different from the first embodiment will be omitted as appropriate.

Hereinafter, the production method of the organic thin film solar cell of Example 3 will be specifically described. The substrate 101, the transparent electrode 102, and the hole transport layer 103 were produced in the same manner as in Example 1. A dichlorobenzene solution (concentration 2 wt%) in which P3HT as the electron-donating semiconductor 104 and Cu _0.9 In _0.6 Ga _0.4 S _2.0 as the electron-accepting semiconductor 105 are mixed at a weight ratio of 1: 3. ) Was spin-coated to obtain a mixed layer 106 with a thickness of 250 nm.

A dichlorobenzene solution of C61-PCBM (concentration: 3 wt%) was formed on the mixed layer 106 by spin coating to form a hole blocking layer 107. The absolute value of electron affinity of C61-PCBM constituting the hole blocking layer is 3.8 eV, and the absolute value of electron affinity of the electron accepting semiconductor Cu _0.9 In _0.6 Ga _0.4 S _2.0 is 3 It is greater than .5 eV and meets the requirements of the present invention.

  On the hole blocking layer 107, aluminum was deposited as a second electrode 108 by resistance heating vapor deposition of 0.1 μm, and the organic thin film solar cell 100 was obtained.

The organic thin film solar cell 100 thus fabricated had a short-circuit current of 7.60 mA / cm ³ , an open-circuit voltage of 0.85 V, a fill factor (FF) of 0.60, and a photoelectric conversion efficiency of 3.88%. . Table 1 summarizes the photoelectric conversion characteristics of the cell produced in Example 3.

Comparative Example 1

  In this comparative example, an organic thin film solar cell 100 using a fullerene derivative for both the electron-accepting semiconductor 105 and the hole blocking layer 107 will be described with reference to FIG. In addition, in the comparative example 1, description with respect to the part which is not different from Example 1 is abbreviate | omitted suitably.

  Hereinafter, the production method of the organic thin film solar cell of Comparative Example 1 will be specifically described. The substrate 101, the transparent electrode 102, and the hole transport layer 103 were produced in the same manner as in Example 1. A dichlorobenzene solution (concentration 2 wt%) in which P3HT as an electron-donating semiconductor 104 and C61-PCBM as an electron-accepting semiconductor 105 are mixed at a weight ratio of 1: 0.8 is spin-coated thereon, and a mixed layer 106 is formed. Obtained at a thickness of 250 nm.

  A dichlorobenzene solution of C61-PCBM (concentration: 3 wt%) was formed on the mixed layer 106 by spin coating to form a hole blocking layer 107. On the hole blocking layer 107, aluminum was deposited as a second electrode 108 by resistance heating vapor deposition of 0.1 μm, and the organic thin film solar cell 100 was obtained.

The organic thin film solar cell 100 thus fabricated had a short circuit current of 8.56 mA / cm ³ , an open circuit voltage of 0.65 V, a fill factor (FF) of 0.58, and a photoelectric conversion efficiency of 3.23%. . The photoelectric conversion characteristics of the cell produced in Comparative Example 1 are summarized in Table 1.

Comparative Example 2

  In this comparative example, an organic thin film solar cell 100 using a fullerene derivative as the electron-accepting semiconductor 105 and an amorphous titanium oxide thin film as the hole blocking layer 107 will be described with reference to FIG. It should be noted that in Comparative Example 2, the description of parts that do not differ from Example 1 will be omitted as appropriate.

  Hereinafter, the production method of the organic thin film solar cell of Comparative Example 2 will be specifically described. The substrate 101, the transparent electrode 102, and the hole transport layer 103 were produced in the same manner as in Example 1. A dichlorobenzene solution (concentration 2 wt%) in which P3HT as an electron-donating semiconductor 104 and C61-PCBM as an electron-accepting semiconductor 105 are mixed at a weight ratio of 1: 0.8 is spin-coated thereon, and a mixed layer 106 is formed. Obtained at a thickness of 250 nm.

  A hole blocking layer 107 was formed on the mixed layer 106 by spin-coating a solution obtained by diluting titanium tetraisopropoxide (manufactured by Wako Pure Chemical) 200 times with ethanol to a thickness of 10 nm. On the hole blocking layer 107, aluminum was deposited as a second electrode 108 by resistance heating vapor deposition of 0.1 μm, and the organic thin film solar cell 100 was obtained.

The organic thin film solar cell 100 thus produced had a short-circuit current of 8.16 mA / cm ³ , an open-circuit voltage of 0.67 V, a fill factor (FF) of 0.60, and a photoelectric conversion efficiency of 3.28%. . Table 1 summarizes the photoelectric conversion characteristics of the cell produced in Comparative Example 2.

Comparative Example 3

  In this comparative example, an organic thin film solar cell in which a fullerene derivative is used for the electron-accepting semiconductor 105 and the hole blocking layer 107 is not provided will be described with reference to FIG. It should be noted that in Comparative Example 3, the description of parts that are not different from Example 1 will be omitted as appropriate.

  Hereinafter, the production method of the organic thin film solar cell of Comparative Example 2 will be specifically described. The substrate 101, the transparent electrode 102, and the hole transport layer 103 were produced in the same manner as in Example 1. A dichlorobenzene solution (concentration 2 wt%) in which P3HT as an electron-donating semiconductor 104 and C61-PCBM as an electron-accepting semiconductor 105 are mixed at a weight ratio of 1: 0.8 is spin-coated thereon, and a mixed layer 106 is formed. Obtained at a thickness of 250 nm.

  Aluminum was deposited as a second electrode 108 on the mixed layer 106 by resistance heating vapor deposition of 0.1 μm, and an organic thin film solar cell 400 was obtained.

The organic thin film solar cell 100 thus fabricated had a short-circuit current of 6.50 mA / cm ³ , an open-circuit voltage of 0.60 V, a fill factor (FF) of 0.52, and a photoelectric conversion efficiency of 2.03%. . Table 1 summarizes the photoelectric conversion characteristics of the cell produced in Comparative Example 3.

100 Organic thin film solar cell 101 Substrate 102 Transparent electrode (first electrode)
103 hole transport layer 104 electron donating semiconductor 105 electron accepting semiconductor 106 mixed layer 107 hole blocking layer 108 second electrode

Claims (13)

  An organic thin-film solar cell having a first electrode, a second electrode, and a mixed layer of an electron-donating semiconductor and an electron-accepting semiconductor provided between the first electrode and the second electrode. In addition, a hole blocking layer is provided between the second electrode and the mixed layer, and at least one of the electron-accepting semiconductor and the hole blocking layer included in the mixed layer is I-III-VI An organic thin film solar cell comprising a group compound semiconductor, wherein an absolute value of an electron affinity of the hole blocking layer is larger than an absolute value of an electron affinity of an electron accepting semiconductor included in the mixed layer.   2. The organic thin film solar cell according to claim 1, wherein the electron-accepting semiconductor contained in the mixed layer is a fullerene derivative, and the hole blocking layer is made of a group I-III-VI compound semiconductor. Organic thin film solar cell.   3. The organic thin film solar cell according to claim 2, wherein the hole blocking layer is a thin film layer in which fine particles of a I-III-VI group compound semiconductor are dispersed in a film, and the I-III-VI group compound semiconductor is used. An organic thin film solar cell, wherein the size of the fine particles is 200 nm or more and 500 nm or less.   2. The organic thin film solar cell according to claim 1, wherein the electron-accepting semiconductor contained in the mixed layer is an I-III-VI group compound semiconductor, and the hole blocking layer is contained in the mixed layer. An organic thin film solar cell comprising an I-III-VI group compound semiconductor having a value larger than an absolute value of electron affinity of a semiconductor.   5. The organic thin film solar cell according to claim 4, wherein the mixed layer is a thin film layer in which fine particles of a compound semiconductor of the I-III-VI group are dispersed in a film, and the size of the fine particles is 50 nm or less. The hole blocking layer is a thin film layer in which fine particles of the I-III-VI group compound semiconductor are dispersed, and the size of the fine particles of the I-III-VI group compound semiconductor is 200 nm to 500 nm. An organic thin film solar cell characterized.   2. The organic thin film solar cell according to claim 1, wherein the electron-accepting semiconductor contained in the mixed layer is a group I-III-VI compound semiconductor, and the hole blocking layer is made of a fullerene derivative. Solar cell.   7. The organic thin film solar cell according to claim 6, wherein the mixed layer is a thin film layer in which fine particles of an I-III-VI group compound semiconductor material are dispersed in the film, An organic thin film solar cell having a fine particle size of 50 nm or less.   2. The organic thin film solar cell according to claim 1, wherein the group I element of the I-III-VI group compound semiconductor is copper.   2. The organic thin film solar cell according to claim 1, wherein the group III element of the I-III-VI group compound semiconductor includes at least one of indium, gallium, and aluminum.   2. The organic thin film solar cell according to claim 1, wherein the group VI element of the I-III-VI group compound semiconductor includes at least one of sulfur, selenium, and tellurium.   The organic thin-film solar cell of any one of Claims 1-10 WHEREIN: The composition ratio (I group element / III group element) of the group I element and group III element of the said I-III-VI group compound semiconductor is, It is 0.7 or more and 0.9 or less, The organic thin film solar cell characterized by the above-mentioned.   The organic thin film solar cell according to any one of claims 1 to 10, wherein a mixing ratio of the electron-accepting semiconductor material in the mixed layer is 50% or more.   A first electrode; a second electrode; and a mixed layer of an electron-donating semiconductor and an electron-accepting semiconductor provided between the first electrode and the second electrode, and the second electrode A hole blocking layer is provided between the electrode and the mixed layer, and at least one of the electron-accepting semiconductor and the hole blocking layer included in the mixed layer is made of a I-III-VI group compound semiconductor. A method for producing an organic thin film solar cell in which the absolute value of the electron affinity exhibited by the hole blocking layer is larger than the absolute value of the electron affinity of the electron-accepting semiconductor contained in the mixed layer, the group I-III-VI An organic thin film characterized in that at least one of an electron-accepting semiconductor and a hole-blocking layer contained in the mixed layer is formed by applying a solution in which fine particles of a compound semiconductor are dispersed in a solvent Solar cell Manufacturing method.

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