JP2014017411A - Photovoltaic element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light utilization efficiency by improving photoelectric conversion efficiency.SOLUTION: A photovoltaic element 10 is constituted by sequentially laminating a transparent insulating substrate 1, a transparent electrode 2 (first electrode) serving as a surface electrode, an n-type semiconductor layer 3, a p-type semiconductor layer 4 (first p-type semiconductor layer), a p-type semiconductor layer 5 (second p-type semiconductor layer), and a back electrode layer 6 (second electrode). The first p-type semiconductor layer contains an electron-donating organic pigment and an organic metal compound having an electron-withdrawing functional group and a counter cation.

Description

  The present invention relates to a photovoltaic element such as a solar cell, a photosensor, and a photodiode, and a manufacturing method thereof, and more particularly, to a photovoltaic element using an internal electric field by a hetero pn junction and an improvement of the manufacturing method. .

  In recent years, solar cells (photovoltaic elements) have attracted attention as renewable energy, and active research and development has been performed. For solar cells, silicon-based solar cells using monocrystalline, polycrystalline or amorphous Si, compound semiconductor-based solar cells using GaAs, CdS, etc., organic-semiconductor-based solar cells using organic dyes or conductive polymers Or metal oxide (dye sensitized) solar cells.

  Among these, silicon solar cells and compound semiconductor solar cells are most popular. These solar cells are characterized by high photoelectric conversion efficiency, but have high life cycle costs, which are costs related to material procurement / manufacturing / use / disposal, which are important as renewable energy.

  On the other hand, photovoltaic devices using organic semiconductors are inexpensive and non-toxic, which are difficult to achieve with monocrystalline, polycrystalline or amorphous Si, and require large-scale equipment and a large amount of energy for production. It is not necessary and the life cycle cost can be expected to be reduced. However, photovoltaic devices using organic semiconductors have lower photoelectric conversion efficiency (energy conversion efficiency) than silicon-based solar cells and compound semiconductor-based solar cells, and research and development aimed at improving photoelectric conversion efficiency are being conducted. Yes.

  For example, in Patent Document 1, an electron-accepting organic material layer or an n-type inorganic semiconductor layer, a first electron-donating organic material layer, and a second electron-donating material different from the first electron-donating organic material layer A photovoltaic device having a three-layer structure composed of a conductive organic material layer has been proposed. Patent Document 2 proposes that the first electron-donating organic material layer be a mixed layer of an electron-accepting organic material and an electron-donating organic material. In Patent Document 3, various layer structures that can be laminated by coating are examined, and an electron-accepting inorganic n-type semiconductor layer and a p-type semiconductor layer are combined. It has been proposed to form a first p-type semiconductor layer and a second p-type semiconductor layer made of a conductive organic material, and to contain an electron-accepting compound in the first p-type semiconductor layer.

  The first and second layers made of the electron donating organic material described in Patent Document 1 and Patent Document 2 correspond to the first p-type semiconductor layer and the second p-type semiconductor layer of Patent Document 3, respectively. Here, the importance of the combination of the three-layer structure is that in the photovoltaic element, the first p-type semiconductor layer sandwiched between the n-type semiconductor layer and the second p-type semiconductor layer functions as a carrier generation layer. When the intermediate layer is a mixed layer of an electron-donating organic substance and an electron-accepting organic substance as in Patent Document 2 and Patent Document 3, when the intermediate layer is simply added to form a three-layer structure as in Patent Document 1 Higher photoelectric conversion efficiency can be obtained. This is presumably because the electron-accepting organic material contained in the mixed layer improved carrier mobility and contributed to conductivity.

JP-A-5-152594 JP-A-6-318725 JP 2009-81388 A

  However, with the aim of high photoelectric conversion efficiency such as silicon-based solar cells and compound semiconductor-based solar cells, photovoltaic devices using organic semiconductors are also more effective than the photovoltaic devices described in Patent Document 2 and Patent Document 3. However, there is a demand for a photovoltaic device that can achieve higher photoelectric conversion efficiency.

  The present invention has been made to address the above-described problems, and is a hetero pn-junction type photovoltaic device that is inexpensive and has further improved photoelectric conversion efficiency, and the photovoltaic device has high yield and high efficiency. An object of the present invention is to provide a manufacturing method that can be manufactured at a low cost, can reduce the life cycle cost, and can cope with a large area.

  The photovoltaic device of the present invention includes an n-type semiconductor layer, a p-type semiconductor layer, and a carrier generation layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer, and the carrier generation layer is provided with an electron donor. And an organometallic compound having an electron-withdrawing functional group and a counter cation.

  According to the above photovoltaic device, the hole that flows in the adjacent p-type semiconductor layer by containing the organometallic compound having the electron-withdrawing functional group and the counter cation in the carrier generation layer containing the electron-donating organic pigment. As a result, the hole density increases and the hole current increases, so that the photoelectric conversion efficiency can be dramatically improved.

  The photovoltaic device of the present invention includes an n-type semiconductor layer, a p-type semiconductor layer, and a carrier generation layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer, and the carrier generation layer is an electron. It contains a donating organic pigment, an organometallic compound having an electron donating functional group and a counter anion.

  According to the above photovoltaic element, the electron flowing into the adjacent n-type semiconductor layer is obtained by including the organometallic compound having the electron donating functional group and the counter anion in the carrier generation layer containing the electron donating organic pigment. As a result, the photoelectric conversion efficiency can be dramatically improved by increasing the electron density and increasing the current.

  The method for producing a photovoltaic device of the present invention comprises an n-type semiconductor coating solution obtained by adding a predetermined amount of a binder resin and a solvent to an electron-accepting inorganic pigment, an electron-donating organic pigment, an electron-withdrawing functional group, and a counter cation. A carrier generation layer coating solution obtained by adding a predetermined amount of a binder resin and a solvent to an organometallic compound having a p-type semiconductor coating solution obtained by adding a predetermined amount of a binder resin and a solvent to an electron donating organic pigment on an electrode substrate It is characterized by sequentially applying and laminating.

  According to the photovoltaic element manufacturing method of the present invention, the semiconductor layer can be formed only by coating. This eliminates the need for a conventional vacuum process, does not require large-scale equipment and a large amount of energy, and can greatly reduce the life cycle cost. Moreover, since a vacuum process is not used, a continuous production facility can be easily constructed, and it becomes easy to cope with an increase in the area of the photovoltaic device.

It is a schematic block diagram of the photovoltaic element which concerns on this embodiment. It is a figure which shows the manufacturing process of the photovoltaic element which concerns on this embodiment. It is a figure for demonstrating the effect of the organometallic compound in this embodiment. It is a figure for demonstrating the effect which the organometallic compound in this embodiment has on an exciton. It is a figure which shows the mechanism in which an electron attracts | sucks to the borobis (1, 1- diphenyl-1-oxo-acetyl) potassium salt in this embodiment. It is a figure which shows the optimal content of the borobis (1, 1- diphenyl- 1-oxo- acetyl) potassium salt in this embodiment. It is a figure which shows the optimal content of the alkyl salicylate chromium compound in this embodiment.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  When considering a photovoltaic device that is inexpensive, stable, and capable of dealing with a large area, each layer constituting the photovoltaic device such as an n-type semiconductor layer and a p-type semiconductor layer requires a vacuum process. If it can be formed by lamination by a coating method that does not, large-scale equipment and a large amount of energy are not required for production, and the life cycle cost can be significantly reduced. Hereinafter, an embodiment in which a three-layer semiconductor layer can be formed by stacking by a coating method will be described.

  FIG. 1 is a schematic configuration diagram of a photovoltaic element according to the present embodiment. As shown in FIG. 1, a photovoltaic device 10 according to the present embodiment includes a transparent insulating substrate 1, a transparent electrode 2 (first electrode) serving as a surface electrode, an n-type semiconductor layer 3, and a carrier generation layer. P-type semiconductor layer 4 (hereinafter also referred to as first p-type semiconductor layer 4), p-type semiconductor layer 5 (hereinafter also referred to as second p-type semiconductor layer 5), and back electrode layer 6 (second electrode). Are stacked in order. Note that illustrations of leads (electric wires) attached to the electrodes and protective resin for preventing moisture from entering the photovoltaic element 10 are omitted.

  The transparent insulating substrate 1 is preferably one that transmits a wide range of wavelengths in the visible light region. For example, a material such as glass or plastic film can be used in an appropriate form such as a sheet or plate.

  As with the transparent insulating substrate 1, the transparent electrode 2 preferably transmits a wide wavelength in the visible light region, and indium tin oxide (ITO), tin oxide (NESA), indium oxide, or the like is used.

  The n-type semiconductor layer 3 contains an electron-accepting inorganic pigment and a binder resin. Examples of the electron-accepting inorganic pigment used for the n-type semiconductor layer 3 include metal oxide semiconductors such as zinc oxide (ZnO) and titanium dioxide (TiO 2), and zinc oxide pigments are particularly preferably used. The zinc oxide pigment preferably has an average particle size of several nanometers to several hundreds of nanometers, and from the viewpoint of photoelectric conversion efficiency, it is desirable to use one having an average particle size of 80 to 120 nm. .

  The binder resin used for the n-type semiconductor layer 3 can be selected from a wide range of insulating resins such as polyvinyl butyral resin, polyvinyl formal resin, polystyrene resin, polyester resin, and cellulose resin. These binder resins may be used alone or in combination of two or more. In the present embodiment, polyvinyl butyral resin is used. Moreover, the preferable compounding ratio (weight) of an electron-accepting inorganic substance and binder resin is the range of 100: 1-100: 30, Preferably it is the range of 100: 5-100: 20.

  The first p-type semiconductor layer 4 contains an electron donating organic pigment, an organometallic compound, and a binder resin. Examples of the electron donating organic pigment that is the main component used in the first p-type semiconductor layer 4 include azo, phthalocyanine, anthraquinone, quinacridone, cyanine, merocyanine, fullerene, dioxazine, anthrapyrimidine, and anthrapyridone. Organic pigments such as those based on phenanthrene, anthanthrone, indanthrone, flavanthrone, perinone, thioindico, anthraquinone and polydiacetylene are used. Particularly preferably, the phthalocyanine pigment oxytitanium phthalocyanine (titanyl phthalocyanine) and a part of this ring substituted with an appropriate substituent are used. As titanyl phthalocyanine, it is desirable to use a powder having an average particle size of about 0.01 μm to several tens of μm.

  The organometallic compound used for the first p-type semiconductor layer 4 is an organometallic compound having an electron-withdrawing functional group and a counter cation. This organometallic compound has, for example, an alkyl group, a phenyl group, a hydroxy group, a carbonyl group, an amide group, an aryl group, a sulfuric acid group, a sulfo group, a halide, etc. as an electron-withdrawing functional group. have. A preferable blending ratio of the electron donating organic pigment and the organometallic compound is preferably in the range of 15 to 100 parts by weight of the organometallic compound with respect to 100 parts by weight of the electron donating organic substance. Furthermore, it is preferable to disperse molecules in a pigment dissolved and dispersed in a solution. As specific examples, preferably, borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt having boron as a central metal and having a phenyl group, or alkylsalicylic acid chromium compound having chromium as a central metal and an alkyl group, etc. Can be mentioned. In this embodiment, a borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt and a chromium alkylsalicylate compound are employed. These compounds are particularly well-known materials as charge control agents for toner and are easily available.

  The binder resin used for the first p-type semiconductor layer 4 is selected from a wide range of insulating resins such as polyvinyl butyral resin, polyvinyl formal resin, polystyrene resin, polyester resin, and cellulose resin, as in the example of the n-type semiconductor layer 3. be able to. These binder resins may be used alone or in combination of two or more. In the present embodiment, polyvinyl butyral resin is also used in the first p-type semiconductor layer 4. Moreover, the preferable compounding ratio (weight) of the electron donating organic pigment and the binder resin in the first p-type semiconductor layer 4 is in the range of 100: 10 to 100: 100, more preferably 100: 40 to 100: 60.

  The second p-type semiconductor layer 5 contains an electron donating organic pigment as a main component. Examples of the electron donating organic pigment used in the second p-type semiconductor layer 5 include azo, phthalocyanine, anthraquinone, quinacridone, cyanine, merocyanine, fullerene, dioxazine, anthrapyrimidine, anthrapyridone, anthane. Organic pigments such as throne, indanthrone, flavanthrone, perinone, thioindico, anthraquinone, polydiacetylene, etc. The material of the first p-type semiconductor layer 4 due to the energy band of the photovoltaic device It is desirable to use different materials. Among these, for example, when titanyl phthalocyanine is used for the first p-type semiconductor layer 4, a combination with a metal-free phthalocyanine of a phthalocyanine pigment and a part of this ring substituted with an appropriate substituent is preferable. As the metal-free phthalocyanine, it is desirable to use a powder having an average particle diameter of about 0.01 μm to several tens of μm.

  The second p-type semiconductor layer 5 also contains a binder resin. The binder resin used for the second p-type semiconductor layer 5 is selected from a wide range of insulating resins such as polyvinyl butyral resin, polyvinyl formal resin, polystyrene resin, polyester resin, and cellulose resin, as in the example of the n-type semiconductor layer 3. can do. These binder resins may be used alone or in combination of two or more. In the present embodiment, polyvinyl butyral resin is also used in the second p-type semiconductor layer 5. Moreover, the preferable compounding ratio (weight) of the electron donating organic pigment and the binder resin in the second p-type semiconductor layer 5 is in the range of 100: 10 to 100: 100, more preferably 100: 10 to 100: 30.

  The first p-type semiconductor layer 4 may contain an organometallic compound having an electron donating functional group and a counter anion. The organometallic compound has, for example, a hydroxyl group, a methoxy group, an alkoxy group, an amino group, a methylamino group, an alkylamino group, a dialkylamino group, a trialkylamino group, a methyl group, and the like as an electron-donating functional group. Anything that has a counter anion can be used.

  With the above configuration, the photovoltaic device in the present embodiment can improve the light utilization efficiency and the photoelectric conversion efficiency as compared with the conventional photovoltaic device.

  Next, a method for manufacturing the photovoltaic element in the present embodiment will be described with reference to FIG. FIG. 2 is a diagram showing a manufacturing process of the photovoltaic device according to the present embodiment. This photovoltaic device is composed of an n-type semiconductor coating solution in which a predetermined amount of a binder resin (polyvinyl butyral resin) and a solvent are added to an electron-accepting inorganic pigment (zinc oxide pigment), and an electron-donating organic pigment (titanyl phthalocyanine pigment). And a first compound in which a predetermined amount of a binder resin (polyvinyl butyral resin) and a solvent are added to an organometallic compound (borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt) having an electron-withdrawing functional group and a counter cation. P-type semiconductor coating solution (first p-type semiconductor coating solution), and a second p-type semiconductor coating obtained by adding a predetermined amount of a binder resin (polyvinyl butyral resin) and a solvent to an electron-donating organic pigment (metal-free phthalocyanine pigment) After sequentially applying and laminating a liquid (second p-type semiconductor coating liquid) on the transparent electrode 2, on these semiconductor layers, A conductive paste obtained by dispersing a conductive material in the fat coating, is formed by a method of forming a back electrode layer 6 facing the transparent electrode 2.

  The semiconductor coating liquid is produced by dispersing these predetermined raw materials with a solvent. Solvents include alcohols such as methanol, ethanol, n-propanol and i-propanol, ketones such as methyl ethyl ketone and cyclohexanone, cyclic or chain ethers such as tetrahydrofuran, dioxane, dioxolane and dimethyl cellosolve, benzene, toluene, Aromatic hydrocarbons such as xylene can be used alone or in admixture of two or more.

  Each semiconductor coating liquid is obtained by dispersing fine particles of an electron-accepting inorganic pigment or different types of electron-donating organic pigments in the coating liquid, so that the dispersion of the fine particles includes a homogenizer, an ultrasonic wave Conventionally known methods such as ball mill, sand mill, and attritor can be used.

  As shown in FIG. 2A, for example, the semiconductor layer is prepared by placing the transparent electrode 2 on the transparent insulating substrate 1 and then using, for example, the dip coating method or the air knife coating using the semiconductor coating solution described above. As shown in FIGS. 2 (b) to 2 (d), the n-type semiconductor layer 3 and the first p are formed by the method, the roller coating method, the wire bar coating method, the spin coating method, the ESD (electrospray deposition) method, and the like. A type semiconductor layer 4 and a second p-type semiconductor layer 5 were sequentially stacked. In general, the thickness is preferably about 0.01 to 3.0 μm, more preferably 0.05 to 0.4 μm.

  After the laminated semiconductor layers are sufficiently dried, the back electrode layer 6 is formed on the semiconductor layers as shown in FIG. As the conductive paste used to form the back electrode layer 6, a carbon paste in which conductive carbon black is dispersed in a resin, a metal paste in which metal fine particles are dispersed in a resin, or the like is used. The thickness of the back electrode layer 6 is preferably about 1 to 100 μm.

  By the above manufacturing method, the photovoltaic device 10 according to the present embodiment can be used without using a vacuum process such as vapor deposition or a high temperature process, or a gas or deoxygenated environment that has a safety problem, which is essential in the conventional manufacturing method. The semiconductor layer excluding the transparent insulating substrate 1 and the transparent electrode 2 and the back electrode layer 6 can be formed in a normal atmospheric pressure (normal temperature) environment. Moreover, this manufacturing method is not only a batch type production facility used in conventional photovoltaic elements, but also a continuous production facility capable of producing a long and large area photovoltaic element. It becomes easy.

  In addition, the structure of the back electrode in this invention is not restricted to the example in this embodiment, The other electroconductive film which can be joined to a semiconductor layer ohmic may be sufficient. For example, a film made of a metal having a high work function such as Au or Ag may be formed by vapor deposition or sputtering.

  Next, in order to confirm the effect of the photovoltaic element in the present embodiment, more specific examples 1 and 2 of the present invention will be described by actually measuring photoelectric conversion characteristics together with the comparative example 1. .

[Example 1]
The element manufactured as Example 1 of the present invention is a photovoltaic element having the hetero-pn junction type semiconductor layer having the three-layer structure described in the above-described embodiment. First, prior to the production of the photovoltaic element, the semiconductor coating solution was adjusted.

  The n-type semiconductor coating liquid is 8.5 parts by weight of polyvinyl butyral resin (Sekisui Chemical Co., Ltd.) as binder resin with respect to 100 parts by weight of zinc oxide powder (Sumitomo Osaka Cement Co., Ltd .: ZnO-410, average particle size 5 to 15 nm). Co., Ltd .: Esreck BM-1) and 560 parts by weight of 2-propanol as a solvent are mixed, put in a container with 0.5 mmφ zirconia beads, stirred for 60 minutes using a bead mill, and applied in a slurry n-type semiconductor. A liquid was prepared.

  In addition, the first p-type semiconductor coating solution is 65 parts by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd .: ESREC BM-1) with respect to 100 parts by weight of titanyl phthalocyanine pigment (Hodogaya Chemical Co., Ltd.). ), 65 parts by weight of a borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt (manufactured by Carlit Japan Ltd .: LR-147) as an organometallic compound having an electron-withdrawing functional group and a counter cation, As a solvent, 3000 parts by weight of 1,3-dioxolane was blended, placed in a container together with 0.5 mmφ glass beads, and stirred for 120 minutes using a bead mill to prepare a slurry-like first p-type semiconductor coating solution.

  Furthermore, the second p-type semiconductor coating solution contains 25 parts by weight of polyvinyl butyral resin (Sekisui Chemical Co., Ltd.) as a binder resin with respect to 100 parts by weight of a metal-free phthalocyanine pigment (manufactured by Sanyo Dye Co., Ltd., average particle size 2 to 10 μm). Co., Ltd .: ESREC BX-1) and 3000 parts by weight of 1,4-dioxane as a solvent are mixed, put in a container with 0.5 mmφ glass beads, stirred for 20 minutes using a bead mill, 2 p-type semiconductor coating solution was prepared.

  In the production of the photovoltaic device in Example 1, first, ITO glass provided with a transparent electrode made of an oxide of indium tin was placed horizontally on a transparent insulating substrate 1 made of glass. The n-type semiconductor coating solution described above was applied by a bar coating method to form an n-type semiconductor layer 3 having a thickness of 150 nm. After the n-type semiconductor layer 3 is sufficiently dried at room temperature, the above-described first p-type semiconductor coating solution is applied onto the n-type semiconductor layer 3 by the same bar coating method to obtain a film thickness of 300 nm. The first p-type semiconductor layer 4 was formed. After the first p-type semiconductor layer 4 is sufficiently dried at room temperature, the above-described second p-type semiconductor coating solution is similarly applied onto the first p-type semiconductor layer 4 by the bar coating method. A second p-type semiconductor layer 5 having a thickness of 200 nm was formed.

  After the obtained hetero pn junction semiconductor layer having a three-layer structure is sufficiently dried, a conductive carbon paste (manufactured by Kuretake Co., Ltd.) is applied on the semiconductor layer by a screen printing method, and a back electrode layer having a film thickness of 50 μm. Thus, the photovoltaic element of Example 1 was produced.

[Example 2]
The photovoltaic element of Example 2 uses an alkylsalicylic acid chromium compound (manufactured by Orient Chemical Co., Ltd.) as an organometallic compound having an electron-withdrawing functional group and a counter cation contained in the first p-type semiconductor layer 4, and a titanyl phthalocyanine pigment ( (Hodogaya Chemical Co., Ltd.) was added in an amount of 35 parts by weight with respect to 100 parts by weight, and the others were prepared in the same manner as in Example 1 above.

[Comparative Example 1]
As a comparative example in Examples 1 and 2, the first p-type semiconductor layer 4 containing 10 parts by weight of the electron-accepting compound (TBDQ) described in Patent Document 3 was used. A photovoltaic device of Comparative Example 1 was produced in the same manner. In Comparative Example 1, the performance is improved by changing the blending ratio and part of the material in the same manner as in Examples 1 and 2 compared to Patent Document 3.

The photoelectric conversion characteristics of each of the produced photovoltaic elements were measured by current-voltage (IV) measurement in the dark state and under irradiation with pseudo light AM1.5-100 mWcm- ² . The measurement was performed at room temperature and in the air. Table 1 below shows the photoelectric conversion characteristics of the photovoltaic elements obtained by the measurement.

  From this table, as in Example 1 and Example 2, when the first p-type semiconductor layer 4 contains an organometallic compound having an electron-withdrawing functional group and a counter cation, the short-circuit current density (Jsc) increases, Compared with the conventional photovoltaic element (Comparative Example 1), the conversion efficiency η could be remarkably increased.

  FIG. 6 shows the relationship between the photoelectric conversion efficiency in Example 1 and the content of the organometallic compound with respect to 100 parts by weight of the electron-donating organic substance. FIG. 7 shows the relationship between the photoelectric conversion efficiency in Example 2 and the content of the organometallic compound relative to 100 parts by weight of the electron donating organic substance. As can be seen from FIGS. 6 and 7, in Examples 1 and 2, the content of the organometallic compound relative to 100 parts by weight of the electron donating organic material is preferably in the range of 15 to 100 parts by weight.

  As described above, in the present invention, the photoelectric conversion efficiency is improved by including an organometallic compound having an electron-withdrawing functional group and a counter cation in the first p-type semiconductor layer 4, a so-called carrier generation layer. As is clear from Comparative Example 1, the short-circuit current density is increased and the photoelectric conversion efficiency is greatly improved. This is considered that the short circuit current density increased due to two factors.

  Here, with reference to FIG.3 and FIG.4, the mechanism of the electric current generation of a photovoltaic element is demonstrated. Note that the organometallic compound having an electron-withdrawing functional group and a counter cation is molecularly bonded to the electron-donating organic pigment in the carrier generation layer, and acts as an acceptor to contribute to carrier mobility.

  First, as shown in FIGS. 3A and 4A, excitons (a state in which electrons and holes are combined by Coulomb force) are generated in the carrier generation layer by light irradiation. The generated excitons move to the interfaces of the n-type semiconductor layer, the first p-type semiconductor layer (carrier generation layer), and the first p-type semiconductor layer (carrier generation layer) / second p-type semiconductor layer by diffusion. Thereafter, as shown in FIG. 4B, at the interface, excitons are dissociated into electrons and holes due to the difference in energy levels, and become carriers. At this time, as shown in FIG. 3B, some holes and electrons are recombined and deactivated.

  However, in the photovoltaic device of the present embodiment, the first p-type is formed as shown in FIG. 3C by containing an organometallic compound having an electron-withdrawing functional group and a counter cation in the carrier generation layer. At the interface between the semiconductor layer (carrier generation layer) and the second p-type semiconductor layer, electrons are captured by counter cations and the recombination probability of holes and electrons is reduced, so that the hole lifetime is extended. This increases the hole density, increases the hole current, and increases the short-circuit current density.

  At this time, as shown in FIG. 4C, electrons other than the vicinity of the interface are extracted by the counter cation and separated by carriers, and the hole density increases, the hole current increases, and the short circuit current density. Will increase. As described above, in the photovoltaic device of this embodiment, the organometallic compound having the electron-withdrawing functional group and the counter cation is included in the carrier generation layer, so that the organometallic compound has not only the carrier movement but also the current density. This is thought to have contributed to the increase. On the other hand, it is presumed that the electron-accepting compound contained in Comparative Example 1 contributes only to carrier mobility.

  As shown in FIG. 6 and FIG. 7, when the content of the organometallic compound is increased, the photoelectric conversion efficiency η is saturated and decreases. This photoelectric conversion efficiency η is expressed by the following formula (1).

Here, V _{OC is an} open circuit voltage, J _{SC is a} short circuit current density, FF is a fill factor, and P _{inc is} incident light energy. The conversion efficiency η as can be seen from equation (1) is proportional to the short-circuit current density J _SC.

The short-circuit current density _JSC is expressed by the following equation (2) when n: carrier density (separated hole / electron density), μ: mobility, q: elementary charge amount, and E: electric field.

From equation (2), short-circuit current density J _SC, it seen that proportion increasing photoelectric conversion efficiency and the carrier density n increased content increases organometallic compounds η increases. However, the carrier mobility μ in the formula (2) is expressed by the following formula (3), where τ _C is an average relaxation time, and _{mn is} an effective mass of electrons. Note that the average relaxation time τ _C is the time for the carrier to move in the mean free path, which is the distance that the carrier collides with the impurity atom or other scatterer and moves.

At this time, when the content of the organometallic compound (impurities) is increased as shown in FIGS. 6 and 7, the total amount of ionized impurities increases, and the carriers pass through the ionized impurities (donor and acceptor ions) side. Impurity scattering caused by Coulomb force increases and the number of collisions between impurities and carriers increases. 1 / τ _C, which is the reciprocal of the average carrier relaxation time τ _C , represents the number of collisions that occur during a unit time. The number of collisions 1 / τ _C is the number of collisions 1 / τ _C due to lattice vibration, the number of collisions 1 / τ _{C due to lattice} and impurity scattering _, and the sum of _impurities as shown in the following formula (4).

When the organometallic compound is increased from this formula (4) and the impurity scattering is increased, the average relaxation time τ _C is shortened and the carrier mobility μ is lowered. From these facts, as the content of the organometallic compound is increased, the carrier density n increases and the photoelectric conversion efficiency η increases. However, if the content is excessive, the impurity scattering increases and the average relaxation time τ _C decreases. , Mobility μ decreases, short circuit current density _JSC decreases, and photoelectric conversion efficiency η decreases. For this reason, as shown in FIGS. 6 and 7, it is considered that when the content of the organometallic compound is increased, the photoelectric conversion efficiency η is saturated and decreases. (Reference: "Semiconductor Device" by SM GE)

  The mechanism by which an organometallic compound having an electron-withdrawing functional group and a counter cation withdraws electrons is specifically described in borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt as shown in FIG. This is probably because the potassium ion of a certain counter cation attracts electrons constituting carriers or excitons, and this electron further propagates to the π electron system of the phenyl group. The same applies to the alkyl salicylate chromium compound of Example 2, and it is considered that the π electron system of the benzene ring of salicylic acid is charged from a cationic counter ion.

In the above examples, borobis (1,1-diphenyl-1-oxo-acetyl) potassium salt and a chromium alkylsalicylate compound were used, but the present invention is not limited thereto, and other electron-withdrawing functional groups and counter cations are used. The same applies to the organometallic compound possessed.
Moreover, although tital phthalocyanine was used as a pigment in the first p-type semiconductor layer 4 in Examples, azo, phthalocyanine, anthraquinone, quinacridone, cyanine, merocyanine, fullerene, dioxazine, anthrapyrimidine, The same applies to carrier generating materials for organic pigments such as anthrapyridone, ansanthrone, indanthrone, flavanthrone, perinone, thioindico, anthraquinone, and polydiacetylene compounds.

  In the present embodiment, the carrier generation layer of the first p-type semiconductor layer containing the electron donating organic pigment as a main component has been described as containing an organometallic compound having an electron-withdrawing functional group and a counter cation. The same effect can be obtained by containing an organometallic compound having an electron donating functional group and a counter anion. In this case, the organometallic compound acts as a donor in the carrier generation layer and contributes to improvement of the carrier mobility of electrons and holes, and the generated carrier holes are attracted to the electron donating functional group through the counter anion. As a result, the probability of recombination of electrons and holes of carriers is decreased, the number of electrons flowing in the adjacent n-type semiconductor layer is increased, and the current is increased. Except for the vicinity of the interface, exciton holes are extracted by the counter anion of the organometallic compound to separate carriers, increasing electron density, increasing current, and increasing short-circuit current density, thereby improving energy conversion efficiency. .

  In the above-described embodiment, the carrier generation layer of the first p-type semiconductor layer contains one type of organometallic compound having an electron-withdrawing functional group and a counter cation, or has an electron-donating functional group and a counter anion. Although one kind of organometallic compound is contained, two or more kinds of organometallic compounds may be contained.

  In the present embodiment, the main component of the n-type semiconductor layer 3 is the electron-accepting inorganic pigment, but an electron-accepting organic material may be used. In the case of using an electron-accepting inorganic pigment, there are no problems such as an electron-accepting organic material that is unstable in the air and changes its properties when combined with oxygen or has low charge mobility. It is useful in.

DESCRIPTION OF SYMBOLS 1 Transparent insulating substrate 2 Transparent electrode 3 N-type semiconductor layer 4 1st p-type semiconductor layer (carrier generation layer)
5 Second p-type semiconductor layer 6 Back electrode layer

Claims (5)

an n-type semiconductor layer;
a p-type semiconductor layer;
A carrier generation layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer,
The photovoltaic device, wherein the carrier generation layer contains an electron donating organic pigment, an organometallic compound having an electron withdrawing functional group and a counter cation. an n-type semiconductor layer;
a p-type semiconductor layer;
A carrier generation layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer,
The photovoltaic element, wherein the carrier generation layer contains an electron donating organic pigment, an organometallic compound having an electron donating functional group and a counter anion.   In the carrier generation layer, the electron-withdrawing functional group and the organometallic compound having a counter cation are contained in an amount of 15 to 100 parts by weight with respect to 100 parts by weight of the electron-donating organic pigment. Item 2. The photovoltaic device according to Item 1. The p-type semiconductor layer contains an electron-donating organic pigment;
The electron-donating organic pigment of the p-type semiconductor layer and the electron-donating organic pigment of the carrier generation layer are made of phthalocyanine pigments different from each other. The photovoltaic element as described.   An n-type semiconductor coating solution obtained by adding a predetermined amount of a binder resin and a solvent to an electron-accepting inorganic pigment, an electron-donating organic pigment, and a predetermined amount of a binder resin and an organic metal compound having an electron-withdrawing functional group and a counter cation; A carrier generation layer coating solution to which a solvent is added and a p-type semiconductor coating solution to which an electron-donating organic pigment is added with a predetermined amount of a binder resin and a solvent are sequentially applied and laminated on an electrode substrate. Photovoltaic element manufacturing method.