JP5125169B2 - Photovoltaic device - Google Patents

Description

  The present invention relates to a photovoltaic device.

Traditional photovoltaic devices are based on the joining of two semiconductor layers. One is p-type (main carriers are holes), and the other is n-type (main carriers are electrons). The most widely used photovoltaic device is made of Si (silicon). This is a homojunction by two Si layers, one of the two layers is doped with an impurity so as to be n-type, and the other layer is doped with an impurity so as to be p-type. is there. Other known photovoltaic devices are heterojunctions in which the two layers are made of different semiconductor materials. For example, this corresponds to a photovoltaic device including a layer of CdTe / CdS or CuInSe ₂ / CdS. A feature common to these photovoltaic devices is that the semiconductor is manufactured by stacking flat layers. In addition to the two semiconductor layers, the photovoltaic device as the final product may be provided with other additional layers such as a contact layer for a front contact and a counter electrode, a buffer layer, and the like. However, a form based on a flat stack is always maintained. The operation principle of this photovoltaic device is as follows. That is, when solar radiation enters the junction, photons are absorbed by both semiconductor layers and turned into electron / hole pairs. That is, the charge is separated, and the electrons move to the n-type semiconductor side electrode and the holes move to the p-type semiconductor side electrode.
One of the problems of this photovoltaic device is that a high-purity semiconductor is required and a material having an impurity doping amount that is accurately controlled in the high-purity semiconductor must be used. This is to avoid performance degradation of the photovoltaic device due to charge recombination. Carriers of different charges (electrons and holes) move along the same material and recombine without being converted to electricity if there are recombination centers such as impurities, lattice defects, crystal grains or crystal grain boundaries, etc. End up. This recombination phenomenon is an important loss factor that affects the performance of photovoltaic devices. Processes relating to high purity and precise impurity doping require complex and sophisticated manufacturing techniques and greatly increase manufacturing costs. Cost is a very important constraint when designing this type of photovoltaic device for use in large-area panels used on residential roofs as residential solar cells. The typical nominal output of such a device is on the order of 1-5 kilowatts (at the maximum power point), which corresponds to a panel area of the order of 10-30 m ² for a typical nominal conversion efficiency of the order of 10%.

  Another problem with photovoltaic devices consisting of pn heterojunctions is the use of toxic compounds. A toxic compound is a compound containing elements, such as Cd, Se, and Te, for example. Another problem is that elements such as In have a small reserve.

An interstitial cell using quantum dots (fine particles of a few nm size) made of antimony sulfide (especially) is disclosed in, for example, the document “Vogel et al., J. Phys. Chem. 93, 3183 (1994)”. ing. However, this has the disadvantage of using an unstable liquid electrolyte. US Patent Application No. 2002/017656 discloses another example using quantum dots. Among them, a composition composed of PbS (lead sulfide) and a possible composition such as Sb ₂ S ₃ (antimony sulfide) are claimed. However, these photovoltaic devices are unstable due to the drawback of using a hole conductor material made of organic molecules and filling the holes. In any case, sufficient photoelectric conversion efficiency is not obtained.

  As shown in Non-Patent Document 1 and Non-Patent Document 2, as another technique for converting light into electricity, a new type of photovoltaic device that has an advantage of low manufacturing cost has been proposed. It is mainly based on three kinds of solid inorganic materials arranged in an intrusive form and is different from the form of a flat stack layer. This photovoltaic device uses a light-transmitting n-type semiconductor. This semiconductor is in the form of a porous film, and the surface of the pores of this film is coated with a thin film of a semiconductor material of a light absorber. Filled with semiconductor.

  The operation principle of this photovoltaic device is as follows. Sunlight (photons) is absorbed only by the light absorber material to generate electron / hole pairs. Next, this is a mechanism in which electrons move toward a light-transmitting n-type semiconductor, while holes move toward a p-type semiconductor. According to this principle, the transport of charge carriers with opposite signs takes place in separate materials. This theoretically greatly reduces the loss of photovoltaic cell performance due to charge recombination. The reason for using the porous nanocrystalline film or microcrystalline film of the semiconductor is to provide a sufficient internal area so that a sufficient amount of light absorber material is included in the film with respect to the incident area.

  The basic advantages of this type of penetration configuration for photovoltaic devices consisting of flat stacked layers are: First, because inexpensive materials that do not have to be highly pure are used, photovoltaic devices can be manufactured at low manufacturing costs (especially high vacuum technology as opposed to technology used in the manufacture of silicon-based devices). No need to use). This type of penetration configuration has the following other advantages over other types of photovoltaic cell devices. First, the well-known dye-sensitized solar cell disclosed in the molecule (document “Desilvestro et al., J. Amer. Chem. Soc. 107, 2988 (1985)” and US Pat. No. 5,084,365. To obtain a larger photocurrent and photoelectric conversion efficiency by using a thin layer of light absorber material rather than a molecule) or by using quantum dots (fine particles of a few nm size) (Recombination at the interface due to the fact that a larger amount of light absorber material can be used and because there is no direct contact between the two semiconductors, n-type and p-type) Because there is no). Second, the fact that a solid inorganic material is used makes it possible to obtain long-term stability. Other technologies use liquid electrolytes or use organic hole conductor materials, even in the solid state, where these electrolytes and conductor materials have high temperatures and strong solar irradiance ( And typical conditions of outdoor and rooftop installation) and thereby deteriorate.

However, photovoltaic devices that have all been made of solid inorganic materials and have been made using an intrusion form have only achieved very low photoelectric conversion efficiency. Examples based on this concept have been introduced in several literatures (literature "Tennakone et al., J. Phys. D Appl. Phys. 31, 2326 (1998)") and literature "Kaiser, Koenenkamp et al., Solar Energy Materials & Solar Cells 67, 89 (2001)). In these cases, a porous film of TiO _{2 made} of crystals or crystal grains is made, and then electrodeposition or ILGAR, respectively (impregnated with Cu and In precursors and then treated with high temperature H ₂ S gas) The light absorber made of Se or CuInS ₂ deposited by the above is coated, and further filled or covered with a light-transmitting p-type semiconductor made of CuSCN. Spectral sensitivity characteristics or light absorption efficiency were revealed, but the short circuit photocurrent is very low (less than 10 ⁻³ or 10 ⁻⁴ mA / cm ² ) or the fill factor of the current voltage curve is very low (0. (Below 1), the photoelectric conversion efficiency was extremely low. However, the photovoltaic device should exhibit a current-voltage curve of at least an acceptable form (ie, a fill factor close to 1) in the absence of large photocurrent. This is a good sign of good rectifier diode behavior for photovoltaic devices, low resistance to internal charge transport.

Similar types of photovoltaic devices have been reported (literature "Levy-Clement et al., 205th Electrochemical Society Meeting, San Antonio, USA (2004) Abstract 402; Adv Mater. 17, 1512 (2005)"). It is made from a ZnO / CdSe / CuSCN material. In this case, the porous n-type semiconductor ZnO is made of a prism-shaped crystal having a width larger than 100 nm and a length of 1 to 2 μm. The reporters describe that the photoelectric conversion efficiency was about 2% at an illuminance of 360 W / m ² . The reason for this improvement can be attributed to the use of a porous layer having a very coarse (and large) pore size. However, this structure has a problem that the roughness coefficient (roughness coefficient is a ratio between the internal surface area and the incident area of the porous layer) is small and lower than 10. This limits the maximum photocurrent that can be obtained (since the maximum photocurrent is directly related to the amount of photoabsorber present in the layer) and thus the maximum photoelectric conversion efficiency that can be obtained. Restrict. In order to solve this problem, it is necessary to increase the thickness of the light absorber layer to 25 to 30 nm or more. However, if the thickness of the light absorber layer becomes too thick, impurity doping is not sufficiently managed, and the recombination of charges generated inside the light absorber layer degrades the photovoltaic device performance.

  Other photovoltaic devices made of antimony sulfide, such as solar cells, Schottky junctions and photoelectrochemical cells, have been disclosed, but all have two main elements.

In the document “Deshmukh et al. J. Electrochem. Soc. 141, 1779 (1994)”, a solar cell using a semiconductor / electrolyte junction composed of a layer of Sb ₂ S ₃ and a liquid electrolyte is reported. This has the disadvantage that the photoelectric conversion efficiency is very low.

In the literature “Savadogo et al. J. Phys. D Appl. Phys. 27, 1070 (1994)” and literature “Savadogo et al. Appl. Phys. Lett. 63, 228 (1993)”, Sb ₂ S ₃ (n Type) and a solar cell based on a pn heterojunction composed of a pure single crystal such as Si (p-type) or Ge (p-type) has been reported. This solar cell has a very thick p-type layer (500 μm) and functions as a light absorber. As a result, when applying to a large area type, there exists a problem which becomes an expensive solar cell.

In the document “Savadogo et al. J. Electrochem. Soc. 141, 2871 (1994)”, a semiconductor / metal junction (known as a Schottky junction) using an n-type semiconductor layer composed of Sb ₂ S ₃ is reported. Has been. Here, the n-type semiconductor layer may or may not contain WO ₃ . A layer of a high purity noble metal such as platinum or gold is deposited on the layer. The conversion efficiency of the pure Sb ₂ S ₃ composition was less than 0.7% and the conversion efficiency of the mixture of Sb ₂ S ₃ and WO ₃ was about 5%. In any case, a platinum layer is used, which is a photovoltaic device having a very low active surface area (less than 0.1 cm ² ). This type of photovoltaic device can be applied to electronics applications, but not large area solar cells. Since it is necessary to use a noble metal layer for bonding, the photovoltaic device itself is expensive.

Finally, the document “Rodriguez-Lazcano et al. J. Electrochem. Soc. 152, G635 (2005)” reports a flat solar cell having an Sb ₂ S ₃ layer. However, the Sb ₂ S ₃ layer does not function as a light absorber. It is realized by layers of different composition. Moreover, the result of very low photoelectric conversion efficiency is shown (less than 0.01%).

In summary, these photovoltaic devices consisting of a flat layer of Sb ₂ S ₃ do not show high efficiency and use liquid electrolytes (unstable) or very expensive materials (germanium single crystal, silicon Since a single crystal, platinum, and gold) layer is required, it cannot be used for a large area solar cell.
Siebentritt, Koenenkamp et al., 14th European Photovoltaic Solar Energy Conference & Exhibition Proceedings, p. 1823, Barcelona 1997 Rost, Koenenkamp et al., 2nd World Conference & Exhibition Photovoltaic Solar Energy Conversion Proceedings, p 212, Vienna 1998

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a photovoltaic device having low cost and high photoelectric conversion efficiency.

In order to solve the above-described problems, the photovoltaic device of the present invention includes a TiO ₂ layer having porous vacancies as an n-type semiconductor, and a layer formed on the inner surface of the vacancies and in contact with the TiO ₂ layer , A light absorber containing antimony sulfide, and a Cu (I) -based compound as a p-type semiconductor that penetrates into the pores and contacts the light absorber, and the roughness coefficient of the TiO ₂ layer is 100 Larger configuration. Here, the roughness factor of the TiO ₂ layer, to the projected area of the light incident on the light absorber in contact with the TiO ₂ layer, indicating the ratio of internal surface area of the TiO ₂ layer. According to this configuration, it is possible to provide a photovoltaic device that has an advantage of being manufactured at low cost and is excellent in photoelectric conversion efficiency.

  The light absorber is preferably subjected to thermal annealing. Photoelectric conversion efficiency can be improved by thermal annealing.

  A three-layer structure consisting of an n-type semiconductor, a light absorber, and a p-type semiconductor. Since the light absorber contains antimony sulfide, it has an advantage that it can be manufactured at a low cost, and a photovoltaic device that has excellent photoelectric conversion efficiency. Can be provided.

  The best photovoltaic device of the present invention has three components: an n-type semiconductor, a light absorber, and a p-type semiconductor. All three components are solid inorganic components. The light absorber is in contact with the n-type semiconductor, and the p-type semiconductor is in contact with the light absorber. That is, a light absorber is interposed between the n-type semiconductor and the p-type semiconductor, and the n-type semiconductor and the p-type semiconductor are in a non-contact state. The light absorber contains antimony sulfide. The n-type semiconductor is preferably light-transmitting. The p-type semiconductor is preferably translucent. That is, it is desirable that both the n-type semiconductor and the p-type semiconductor are light-transmitting materials.

In the chemical formula, antimony sulfide (Sb ₂ S ₃ ) has a stoichiometric ratio of Sb (antimony) and S (sulfur) of 2 to 3, but in the present invention, one of the elements of Sb or S is a certain ratio. Those that contain excess or those that contain oxygen ions and / or hydroxide ions substituted for sulfide ions in a certain ratio are also called antimony sulfide (Sb ₂ S ₃ ).

  Translucency means that it does not absorb light significantly. That is, it is desirable that the average light absorptance at a wavelength of 400 to 1200 nm is less than 35%. It is more desirable that the light absorption rate is less than 10%.

  The light absorber only needs to have a light absorption function, but a higher light absorption rate is desirable. It is desirable that the light absorption rate at a wavelength of 400 nm is 50% or more. In addition, the absorption edge (long wavelength side) of the light absorber is preferably between 600 and 1200 nm.

  The light absorber is preferably subjected to thermal annealing. The thermal annealing is desirably performed after contacting the n-type semiconductor or the p-type semiconductor. When thermal annealing is performed, it is desirable to perform heat treatment at about 300 ° C. in a nitrogen gas atmosphere.

  The photovoltaic device of the present invention comprising three solid components (n-type semiconductor, p-type semiconductor and light absorber) has the advantage of low manufacturing cost even in an example where the photoelectric conversion efficiency is excellent.

The n-type semiconductor is preferably a metal oxide such as TiO ₂ , ZnO, or SnO ₂ , and more preferably TiO ₂ . The p-type semiconductor is preferably a Cu (I) -based compound such as CuSCN, CuI, or CuAlO ₂ or a metal oxide such as nickel oxide. Of these, nickel oxide is more preferable as the metal compound.

  In the first embodiment of the present invention, the n-type semiconductor or p-type semiconductor (semiconductor having the first conductivity type) is a porous layer (semiconductor porous layer) having pores with a size of 10 to 100 nm. The internal surface area of the pores is completely coated with a thin film made of a light absorber and a continuous absorber layer (the semiconductor porous layer and the light absorber are in contact). The void is formed by a filling layer (semiconductor layer) made of a solid translucent semiconductor of a p-type semiconductor or an n-type semiconductor (conductivity type opposite to the porous layer: semiconductor having the second conductivity type). At least 10%, preferably at least 15% of the total volume is filled (the light absorber and the packed layer are in contact). This type of photovoltaic device has a penetration form or a penetration structure. Here, the size of the hole means not the size of the hole diameter, that is, the length or depth in the thickness direction of the light absorber, but the average dimension in the cross section of the hole.

  Preferably, the photovoltaic device according to the first embodiment of the present invention has the following characteristics. The roughness coefficient of the porous layer before being coated with the light absorber is greater than 50, preferably greater than 100. The roughness coefficient is the ratio between the internal surface area of the porous layer (corresponding to the internal surface area of the pores existing in the porous layer) and the incident area (projected area) of the light absorber on the porous layer. means. This porous layer can be realized by forming a film of a light absorber with aggregates of particles or crystals. It can also be realized by forming pores directly in a monolithic material without crystal grain boundaries as a porous layer having pores. In the former case, when particles or crystal aggregates are formed, pores are formed by gap spaces left between the particles or between the crystals. The roughness factor can be approximately estimated (for vacancies close to a sphere with a pore size greater than 2 nm) by measuring the porosity (and the pore size distribution). For the measurement, a nitrogen adsorption / desorption method is used with a BET specific surface area measuring device.

  When the porous layer is made of particles or crystals, it means that the internal surface area of the pores consists of the surfaces of the particles or crystals. In the first embodiment, the average size of the particles or crystals is 30 to 50 nm, and the average pore size is 20 to 50 nm.

In the first embodiment, the porous layer is preferably made of an n-type semiconductor metal oxide porous film (semiconductor porous film), and the filling layer is preferably made of a p-type semiconductor. The n-type semiconductor metal oxide is preferably made of a TiO ₂ layer having an average particle size of 30 to 50 nm and an average pore size of 20 to 50 nm. For TiO _2, particle size, when expressed in a BET specific surface area before the porous layer is coated with light absorbing material, larger than ^{25 m} 2 / g, is the size of preferably 25~50m ² / g .

  In the first embodiment, the filling layer preferably forms a coating layer having a thickness of at least 10 nm. This covering layer is on one surface of the porous layer, in particular, on the surface of the porous layer having no contact with the conductive substrate described later. In the first embodiment, the filling layer is preferably made of CuSCN or nickel oxide.

  In the first embodiment of the present invention, the photovoltaic device has a light-transmitting semiconductor non-porous first dense layer. The first dense layer is interposed between the semiconductor porous layer and the conductive substrate acting as a transparent electrode (front contact). The first dense layer is formed as a very thin layer. The thickness of the first dense layer is preferably 10 nm or less. The first dense layer is formed of a semiconductor material having the same conductivity type as the semiconductor porous layer. The first dense layer is called a shielding layer and can prevent an electrical short circuit between the semiconductor filling the holes and the transparent electrode. The transparent electrode can be made from a commercially available transparent conductive glass.

  In the first embodiment of the present invention, the second dense layer is provided between the semiconductor porous layer and the conductive substrate layer that acts as the counter electrode (the filling layer is very thin). The second dense layer is formed as a very thin layer. The thickness of the second dense layer is preferably 10 nm or less. The second dense layer is made of a semiconductor material having the same conductivity type as the semiconductor porous layer or the filling layer. The second dense layer can prevent an electrical short circuit between the semiconductor porous layer and the counter electrode. The counter electrode can be made of a conductive material such as carbon or metal.

  More specifically, the photovoltaic device according to the first embodiment of the present invention has the following features.

A transparent and conductive transparent electrode such as conductive glass is covered with a dense and non-porous light-transmitting shielding layer. The shielding layer is preferably made of an n-type semiconductor metal oxide. A semiconductor porous layer is formed on the shielding layer formed on the transparent electrode. One surface of the semiconductor porous layer is in contact with the shielding layer.

The semiconductor porous layer constitutes a thin film having a thickness exceeding 1 μm, preferably 2 to 10 μm. The light absorber layer has a thickness of 1 to 25 nm, preferably 2 to 10 nm. The packing layer is filled with at least 10% of the pore volume, preferably more than 15% of the pore volume;
-The other surface of the semiconductor porous layer is covered with a counter electrode.-The filling layer is preferably provided between the semiconductor porous layer and the counter electrode. The filling layer constitutes a coating layer having a thickness of at least 10 nm. The semiconductor porous layer, the light absorber layer and the filling layer are confined between two conductive substrates acting as a transparent electrode and a counter electrode. ing. The second conductive substrate acting as a counter electrode may or may not be transparent and is made in particular of metal or carbon.

The porous membrane of nanocrystals of a semiconductor metal oxide such as TiO ₂ consists of a doctor blade method using a colloidal dispersion of a metal oxide such as TiO ₂ (or tape molding method) or TiO ₂ metal oxide It can be produced using low-cost manufacturing techniques such as screen printing using paste.

  The light absorber layer can be produced using a low-cost manufacturing technique such as chemical bath deposition or electrochemical deposition. The filling of the vacancies with the semiconductor forming the filling layer is performed by impregnating the solution of the dissolved material and then evaporating the solvent, or by impregnating the precursor solution of the semiconductor using the spin coating method. Alternatively, it can be performed by using a low-cost manufacturing technique such as electrochemical deposition.

  The photovoltaic device of the present invention uses low-cost manufacturing technology (especially not using high-vacuum techniques such as those used in silicon-based equipment) and materials that do not need to be high-purity, so the manufacturing cost is low It is in the point that high photoelectric conversion efficiency can be obtained while maintaining the advantage.

The photovoltaic device having the penetration configuration according to the first embodiment of the present invention exhibits a photovoltaic cell performance superior to that of a conventional photovoltaic device using the same concept. In particular, a larger short-circuit photocurrent and photoelectric conversion efficiency can be obtained. More specifically, according to the present invention, when the roughness coefficient of the semiconductor porous layer is greater than 50, preferably greater than 100, the short-circuit light of 10 mA / cm ² or more in the case of 1000 W / m ² illuminance. It becomes possible to obtain a current, an open-circuit voltage Voc greater than 0.60 V (when current I = 0) and a photoelectric conversion efficiency greater than 3%.

  The three components of the first embodiment of the present invention satisfy the matching conditions of the respective energy bands. The conduction band of the light absorber shows a smaller energy level than that of the n-type semiconductor (in most conventional types used, the energy level is negative when the vacuum level is zero). The valence band of the light absorber is preferably a negative value larger than the valence band of the p-type semiconductor. All this is to allow the injection of electrons and holes respectively.

  The three components are solid inorganic materials that can provide longer durability for outdoor applications, particularly for installation on the roof of a house.

  The present invention also provides a semiconductor porous layer useful for photovoltaic devices. In the first embodiment, the semiconductor porous layer is made of an n-type or p-type translucent semiconductor, and preferably a thin light absorber layer of a light absorber whose pores have an internal surface area made of antimony sulfide. It is comprised from the n-type semiconductor metal oxide coat | covered with. The pore size is 10 to 100 nm, the roughness coefficient of the semiconductor porous layer is larger than 50, preferably larger than 100, and the light absorber layer has a compound made of antimony sulfide.

  The semiconductor porous layer of the present invention exhibits an absorption property of greater than 70% at a wavelength greater than 400 nm and an absorption edge of at least 700 nm. This relates to thin films having a roughness coefficient greater than 50, preferably greater than 100. The expression “absorption edge” refers to the wavelength value at the end on the long wavelength side where the material can absorb light remarkably.

  This type of semiconductor porous layer can also be applied to other devices based on photoexcited charge separation in the light absorber layer and in which the pores are filled with a fluid (liquid or gas). Since the pores are filled with fluid, compounds in the fluid can be transformed properly by light-induced redox reactions such as photocatalytic devices (chemical reactions) and photo-electrolytic devices (electrochemical reactions). .

  In a second embodiment of the invention, the photovoltaic device has a structure consisting of three flat stacked layers, each made from three inorganic solid materials. The three layers are two dense layers of an n-type and p-type translucent semiconductor and a light absorber layer, and the n-type and p-type translucent semiconductor layer is an optical absorber layer. Separated by layers. The n-type semiconductor is in contact with the light absorber. The light absorber is in contact with the p-type semiconductor.

  The thickness of each layer of this photovoltaic device is as follows. The thickness of the n-type semiconductor layer is larger than 10 nm, preferably smaller than 1 μm. The thickness of the light absorber layer is larger than 50 nm, preferably larger than 100 nm and smaller than 3 μm. The thickness of the p-type semiconductor layer is larger than 10 nm, preferably smaller than 1 μm.

  The expression dense layer is a monolithic layer that does not have crystal grain boundaries and therefore does not include voids, or an aggregate of particles or crystals, and a layer in which no gap space remains between particles or crystals, or between particles or crystals. By a gap is meant a layer having pores with a diameter smaller than 5 nm, preferably smaller than 2 nm. The light absorber layer does not necessarily have to be dense, but even when the light absorber layer exhibits a certain porosity, the two semiconductor layers are not in contact with each other.

  In the second embodiment of the present invention, one surface of one of the light-transmitting semiconductor layers of the n-type semiconductor layer and the p-type semiconductor layer is formed on a transparent and conductive transparent electrode such as conductive glass. The other surface of the other light-transmitting semiconductor layer is covered with a counter electrode (conductive substrate). That is, the n-type semiconductor layer, the p-type semiconductor layer, and the light absorber layer are confined between the transparent electrode that acts as a front contact and the counter electrode.

  In the second embodiment, a solid-state photovoltaic device in a flat layer shape made of three components (a light-transmitting n-type semiconductor, a light-transmitting p-type semiconductor, and a light absorber) is provided. The photovoltaic device has a composition resembling an intrusion configuration. These different layers are manufactured in a procedure similar to that used for the intrusive layer, but do not have a porous semiconductor film. This flat layer shape not only has the advantage that it can be manufactured at a lower cost than the penetration mode (less manufacturing process), but also has a remarkable photoelectric conversion of about 0.7% at a short-circuit photocurrent of about 3 mA / cm 2. Shows efficiency. This configuration also has the advantage of being manufactured at a lower cost compared to conventional photovoltaic devices having a flat layer configuration made from a flat layer of antimony sulfide. Conventional photovoltaic devices use expensive materials for bonding antimony sulfide layers, such as high-purity precious metals and high-purity, well-controlled dopants (impurities) such as silicon and germanium single crystals There is a need to.

The composition of the flat light absorber layer is mainly antimony sulfide (Sb ₂ S ₃ ). In the chemical formula, antimony sulfide (Sb ₂ S ₃ ) has a stoichiometric ratio of Sb (antimony) and S (sulfur) of 2 to 3, but in the present invention, one of the elements of Sb or S is a certain ratio. Those that contain excess or those that contain oxygen ions and / or hydroxide ions substituted for sulfide ions in a certain ratio are also called antimony sulfide (Sb ₂ S ₃ ). The composition of the light absorber layer is preferably only antimony sulfide.

  The features and advantages of the present invention will be described with reference to FIGS. 1-5 based on the following several embodiments.

  FIG. 1 is a schematic diagram of a photovoltaic device according to a first embodiment of the present invention having the following components assembled according to the following procedure.

The transparent electrode 4 is a commercially available conductive substrate in which a transparent conductive oxide thin film such as ITO is formed on one surface of a transparent substrate such as glass. The transparent electrode 4 is light transmissive. The surface of the transparent electrode 4 on which the transparent conductive oxide thin film is formed is coated with a thin (several tens of nm) dense non-porous shielding layer 5 formed of TiO ₂ . An n-type semiconductor layer 1, which is a porous nanocrystalline thin film made of a light-transmitting n-type semiconductor such as TiO ₂ , is formed on the shielding layer 5. Here, it does not matter whether the porous layer of TiO ₂ (n-type semiconductor layer 1) is white or translucent. Even if the compound is transparent, it appears to be white or translucent depending on the light scattering properties unrelated to the light absorption properties.

The light absorber layer 2 made of a light absorber material having a thickness of 1 nm or more is deposited on the surface of the TiO ₂ nanocrystal 12 of the n-type semiconductor layer 1. A filler 3 made of a translucent p-type semiconductor such as CuSCN or nickel oxide is formed so as to coat the light absorber layer 2 in the n-type semiconductor layer 1. Filling treatment is preferably performed so that at least 10%, preferably 15% or more (100% is ideal) of the volume of the pores 11 is filled with the filler 3. Filling treatment is preferably performed so that a thin coating layer having a thickness of more than 10 nm remains on the upper portion of the n-type semiconductor layer 1 (opposite the transparent electrode 4 side).

  A layer made of a conductive material such as carbon or metal is formed on the filler 3. This layer acts as a counter electrode 6 that collects charges from the filler 3 made of a p-type semiconductor. The final product is sealed with a sealing material 7 so as to be protected from deterioration due to moisture and air pollutants.

Formation of the light absorber layer 2 that coats the porous TiO ₂ thin film (n-type semiconductor layer 1) is performed using a conventionally known chemical bath deposition method for producing a flat layer on a flat substrate. Can be done. As reported in the literature “Nair et al. J. Electrochem. Soc. 145, 2113 (1998)”, a method of depositing a flat layer made of antimony sulfide uses a light absorber coated inside the porous film. It has been improved to be able to. That is, by making a thin coating that does not fill or block the pores, the inner surface area of the porous TiO ₂ thin film is improved so that the light absorber can sufficiently coat. Regarding other deposition methods of the flat layer made of antimony sulfide disclosed in this document, it was sufficient as an absorbent, but it did not lead to the formation of a coating with TiO ₂ that could be coated uniformly.

Furthermore, in the method of Example 1 shown below, a current technique called chemical bath deposition is used in which a substrate is impregnated with a solution having an antimony and sulfide precursor at a predetermined temperature for a predetermined time. In the present invention, a film of the light absorber layer 2 having a uniform film thickness along all directions of a porous TiO ₂ thin film made of TiO ₂ having a thickness of less than 6 μm could be obtained. This is an estimation of the distribution state of the light absorber by measuring the distribution shape of atoms in the cross section of the film using SEM (scanning electron microscope) and EDX (energy dispersive X-ray spectroscopy). . The total amount of the light absorber in the film was estimated by measuring the atomic ratio of Sb / Ti by EDX over the entire cross section. As a result, it was about 2 to 20%, and on average about 10%. The thickness of the light absorber layer was estimated by TEM (transmission electron microscope), and was about 1 to 5 nm.

  The composition of the light absorber layer 2 was estimated by EDX (Sb / S ratio measurement) and X-ray diffraction (XRD). This estimation is based on the low density occupied by the light absorber in the porous film and the accuracy of EDX. And is somewhat approximate. The Sb / S atomic ratio measured by EDX and the peak value obtained by XRD probably indicate the presence of oxygen as antimony oxide in addition to antimony sulfide, which accounts for the majority. As a result, the composition of the present light absorber was recognized as antimony sulfide.

The advantage of this light absorber film 2 is that it has a large light absorption rate that the maximum light absorption rate is larger than 70% in a wide wavelength range between 400 nm and 700 nm (absorption edge). Moreover, all this is achieved while maintaining the large porosity of the final membrane (the pores are not blocked or filled). These absorption characteristics of such a film are shown in FIG. 3 (characteristic line a). Absorption spectra in the visible and near infrared were measured with a commercial spectrophotometer equipped with an integrating sphere for measuring diffuse light. A porous film based on nanocrystalline TiO ₂ coated with the light absorber layer 2 exhibits good absorption characteristics and retains a large porosity. This is not limited to applications where these two characteristics are required simultaneously, ie, for example, photovoltaic device applications, but also optical devices, photocatalytic devices, or photoelectrolytic generators such as those that generate hydrogen from water. This is also an advantage for possible applications.

By filling the pores with the porous TiO ₂ film (n-type semiconductor layer 1), the light absorber layer 2 and more preferably a CuSCN-based translucent p-type semiconductor filler 3. A photovoltaic device was made. The procedure for producing the CuSCN filler is described in known techniques (literature "Kumara et al., Solar Energy Materials Solar Cells 69, 195 (2001)" and literature "O'Regan et al. Chem. Mater. 14, 5023 (2002)". ), And a method of impregnating the substrate with a CuSCN solution and performing solvent evaporation. This procedure is described later in Example 1. The counter electrode of the photovoltaic device of the present invention was prepared by depositing a gold or carbon layer. The active surface area of these photovoltaic devices was 0.54 cm ² .

The evaluation of the photovoltaic device was performed by the two most widely used methods. One is quantum efficiency (QE) (also known as spectral sensitivity characteristics or IPCE (photoelectric conversion efficiency)) as a function of wavelength λ in nm. This is the rate at which incident photons (radiation) are converted to electrons (electricity), with the following formula:
QE (λ) = (short-circuit electron flow) / (incident photon flow)
= (Short-circuit photocurrent) / (Output of incident radiation) × (1240 / λ)
It is expressed by

  The ideal quantum efficiency spectrum should be the same as the spectrum modified by absorption of inert components (eg, conductive glass substrate).

Another method is a measure of the photoelectric conversion efficiency η calculated from the current-voltage (IV) curve of the photovoltaic device under light irradiation. This is the ratio of the electrical output generated by the photovoltaic device at the maximum output point to the output of the incident light.
η = (Electrical output at maximum output point) / (Output of incident radiation)
It is expressed by

This efficiency was measured with a bench test apparatus consisting of a solar simulator and other equipment. The response of the photovoltaic device was evaluated under an illuminance of 1000 W / m ² corresponding to the reference sunlight AM1.5G. The bench test apparatus was calibrated according to standard procedures for photovoltaic devices commonly used in each authorized public authority. This efficiency can also be expressed as the product of three factors that can better interpret the performance of the photovoltaic device. That is,
η [%] = I _sc × V _oc × ff (with reference illuminance of 1000 W / m ² )
It is. Where I _sc is the short circuit photocurrent (ie current at voltage V = 0) in units of mA / cm ² , V _oc is the open circuit voltage (ie voltage at current I = 0) and the unit is V (volts). ) And ff is a fill factor (no unit), which represents how close the curve is to the ideal rectangular shape (ff = 1) and is the electrical output at the maximum output point of the current-voltage curve. And the theoretical maximum output is calculated (same as I _sc × V _oc ).

The results obtained using an antimony sulfide light absorber layer (see Example 2 below) reliably show that this type of photovoltaic device has an excellent potential to exhibit high photovoltaic performance. Yes. That is, the quantum efficiency reached the maximum value (considering 20% loss due to absorption of the conductive glass substrate), and a large short-circuit photocurrent of 10 mA / cm ² was achieved (between 400 and 700 nm (reference sunlight AM1 · When the maximum theoretical current value at corresponding to 5G) is considered to be a 20 mA / cm ^2, for the use of a conductive glass substrate having a light transmittance of 80% in the visible ray and near infrared, 20 mA / cm ² That should have fallen to 16 mA / cm ² ), achieving a photoelectric conversion efficiency greater than 3%, good filter factor ff, high open circuit voltage V _oc and good photocurrent I _sc Is shown.

  Further, further improvement in the photoelectric conversion efficiency of the photovoltaic device of the present invention can still be achieved by optimizing the preparation conditions of the light absorber coating, improving the interlayer contact, and good filling of the p-type semiconductor. The three factors used in this equation will increase.

  As shown in FIG. 2 and Example 5, the second embodiment of the present invention has a composition similar to that of the penetrating form and includes three components (a light-transmitting n-type semiconductor and a light-transmitting p). Other solid-state photovoltaic devices that use flat layers of type semiconductors and light absorbers are provided.

  The semiconductor layer and the light absorber layer can be formed by spray pyrolysis, chemical bath deposition, impregnation using a solution of dissolved material, solvent evaporation, spin coating using a precursor solution, or electric It can be performed using low-cost manufacturing techniques such as chemical precipitation.

  FIG. 2 shows a schematic diagram of the photovoltaic device of the second embodiment, which has the following components and procedures. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description will be simplified.

The surface of the transparent electrode 4 on which the conductive oxide is formed is coated with a flat non-porous n-type semiconductor layer 10 (dense layer). The n-type semiconductor layer 10 is thicker than 10 nm and is made of a transparent n-type semiconductor such as TiO ² . The light absorber layer 20 has a thickness of 50 nm or more and is formed on the n-type semiconductor layer 10. The light absorber layer 20 is made of antimony sulfide. For example, the translucent p-type semiconductor layer 30 made of CuSCN or metal oxide has a thickness of more than 10 nm and is formed on the light absorber layer 2. On the p-type semiconductor layer 30, a counter electrode 60 made of a conductive material such as carbon or metal is formed. The counter electrode 60 has a function of collecting charges from the p-type semiconductor layer 30 (dense layer). The photovoltaic device is finally sealed with a sealing material 7 in order to be protected from any possibility of deterioration due to moisture and air pollutants.

  The n-type semiconductor layer 10, which is a dense layer, acts as a current collector for electrons (negative charges) so as to prevent a short circuit of positive charges (holes) moving from the light absorber layer 20 to the transparent electrode 4. Works. The p-type semiconductor layer 30, which is a dense layer, acts as a collector for positive holes (positive charges) and prevents short-circuiting of electrons (negative charges) moving from the light absorber layer to the conductive substrate counter electrode. Works. The light absorber layer 20 acts as a light absorber, converts photons into electrons and holes (negative and positive charges, respectively), and transports the charges to the n-type semiconductor layer 10 side and the p-type semiconductor layer 30 side, respectively. . In order to avoid loss due to charge recombination that may occur before the charge reaches the n-type semiconductor layer 10 side or the interface with the p-type semiconductor layer 30, the light absorber layer 20 has as few recombination centers as possible. It is desirable to do. Therefore, it is desirable that the material constituting the light absorber layer 20 has a higher purity. This characteristic is not necessary for the case of the light absorber layer 2 existing in the penetration form of the first embodiment. However, the second embodiment of this flat layer has the advantage that it can be manufactured at a lower cost than the penetrating form because it can be manufactured with fewer steps than necessary for manufacturing the penetrating form. This cost advantage is also evident for other photovoltaic devices manufactured by expensive technologies such as those used for silicon-based devices, such as high vacuum technology.

  The three components of the first embodiment of the present invention satisfy the matching conditions of the respective energy bands. The conduction band of the light absorber shows a smaller energy level than that of the n-type semiconductor (in most conventional types used, the energy level is negative when the vacuum level is zero). The valence band of the light absorber must be negative and larger than the valence band of the p-type semiconductor. All this is to allow the injection of electrons and holes respectively.

The three components are inorganic materials, which offer the potential advantage of providing long durability for outdoor applications, particularly for installations on house roofs. The three components do not contain toxic substances such as cadmium (Cd) and selenium (Se) and elements with low natural abundance (content and reserves) such as indium (In). Compared to other photovoltaic devices based on heterojunctions such as CdTe and CdS / CuInSe ₂ , it has the advantage that it can be used for large areas, especially for roofs of houses.

Therefore, this form currently shows a low photoelectric conversion efficiency of about 0.7% due to a short circuit photocurrent of about 3 mA / cm ² and a low V _oc and fill factor, but compared to the penetration form. It has the advantage that it can be manufactured at low cost (the number of manufacturing steps is small). Nevertheless, if an inexpensive manufacturing method capable of manufacturing a flat light absorber layer having excellent semiconductor characteristics is found, this efficiency can be improved while having the advantage of lower cost. In addition, the second embodiment has an advantage that it can be manufactured at a lower cost than other photovoltaic cell devices having a flat layer form using a flat layer made of antimony sulfide. In other photovoltaic devices, expensive materials for making junctions with antimony sulfide layers, such as silicon and germanium single crystals with very high purity noble metals, high purity and very well controlled dopants (impurities) Had to be used.

Hereinafter, an example will be described. In Examples 1 to 3 and Example 5, the composition of the light absorber layer is mainly antimony sulfide (Sb ₂ S ₃ ), but may contain an element (Sb or S) in a certain ratio in excess of the stoichiometric ratio. And / or oxygen ions and / or hydroxide ions substituted for S in a certain ratio. They are generally referred to as antimony sulfide.

Example 1: Porous Nanocrystalline TiO ₂ film (average particle size 40 nm) orange antimony sulfide layer in, and produced by the filler made of the film and CuSCN, preparation of the solid type photovoltaic device having a penetration form.

A commercially available transparent conductive glass (for example, with a fluorine-doped SnO ₂ layer) is cut into 2.5 cm square pieces and wiped with ethanol and distilled water. A dense (non-porous) TiO ₂ layer having a thickness of about 50 nm is deposited on this substrate (SnO ₂ layer side) by spray pyrolysis. That is, a solution in which 10% by volume of titanium (IV) bis (acetylacetonato) diisopropoxide was dissolved in ethanol was sprayed on the surface of a glass substrate held at a high temperature of about 450 ° C. for 10 minutes. A shielding layer was formed according to the method described in Kavan et al. Electrochim. Acta 40, 643 (1995). This shielding layer acts as a shield that prevents migration of holes or positive charges towards the contacts that collect the electrons. After depositing the shielding layer, a porous nanocrystalline TiO ₂ film is formed using a colloidal dispersion of TiO _{2 with} an average particle size of about 40 nm, prepared according to the description of “European Patent Application No. 1271580”. Precipitation was performed by the doctor blade method (or tape molding method). Then, it heated and sintered at 450 degreeC for 30 minutes. This removes organics from the porous nanocrystalline TiO ₂ film, ensuring good contact not only between the nanocrystals but also between the nanocrystals and the substrate. The thickness of the porous nanocrystalline TiO ₂ film was about 3 μm.

The antimony sulfide light absorber layer was deposited using chemical bath deposition. One container containing 35 ml (milliliter) of precursor solution was used. This solution was mixed with acetone / water (20:80 by volume) containing 0.025 M (molar) SbCl ₃ and 0.25 M sodium thiosulfate (Na ₂ S ₂ O ₃ ). It consists of an aqueous solution. The substrate was immersed in this solution and the container containing the substrate was placed in a 10 ° C. cooler and left in that state for 2 hours. Thereafter, the substrate was pulled out, washed with distilled water, and finally dried with dry nitrogen. The porous nanocrystalline TiO ₂ film on the substrate turned orange. The light absorber film was then finished and the properties were measured. The absorption spectrum of the light absorber layer is shown by the characteristic line b in FIG.

CuSCN was used as the filler. The precipitation of CuSCN is performed by the method described in the literature “Kumara et al., Solar Energy Materials Solar Cells 69, 195 (2001)” and the literature “O'Regan et al. Chem. Mater. 14, 5023 (2002)”. A similar method was used. A solution containing CuSCN at a concentration of 15 mg / ml in dipropyl sulfide (S (CH ₂ CH ₂ CH ₃ ) ₂ ) (CuSCN solution) is placed on the hot plate at 80 ° C. Used for impregnation. The total amount of CuSCN solution poured onto the sample was 100 μl. After the precipitation was complete, the sample was heated for an additional 3 minutes at the same temperature in order to completely evaporate all excess solvent. A thin layer of gold having a thickness of about 25 nm was then deposited on the top surface of the sample using a metal deposition apparatus (eg Edwards 306 type). In another example (a cheaper alternative than gold), a carbon layer was applied over the sample using a commercially available conductive ink made of carbon. The upper surface of the sample here is the side on which the porous nanocrystalline TiO ₂ film of conductive glass is formed.

  Photocell performance was evaluated by measuring quantum efficiency and current-voltage curves as described above. The quantum efficiency (characteristic line d in FIG. 4) and the current-voltage curve showed extremely low values.

Example 2: Porous Nanocrystalline TiO ₂ film (average particle size 40 nm) dark brown antimony sulfide layer in, and produced by the filler made of the film and CuSCN, preparation of the solid type photovoltaic device having a penetration form.

  The production of a light absorber layer made from antimony sulfide was carried out in the same procedure as in Example 1. However, once the coating was complete and the thin film was cleaned and dried, the film was heat annealed at 300 ° C. for 30 minutes under a nitrogen gas atmosphere. The membrane turned from orange to dark brown. The light absorber film was then finished and the properties were measured. The absorption spectrum of the light absorber layer is shown by the characteristic line a in FIG. As is clear from FIG. 3, the absorption spectrum of the thin film subjected to the thermal annealing treatment is wider than that of the thin film not subjected to the thermal annealing treatment.

  Regarding the production of the solid-state photovoltaic device, in particular, the filler and the contact layer made of CuSCN semiconductor (the thin gold layer and the carbon layer in Example 1) were performed in the same manner as in Example 1.

Photovoltaic cell performance was evaluated as described above. The quantum efficiency (characteristic line a in FIG. 4) shows a value of 80%. In particular, the maximum value can be achieved in the wavelength range of 400 to 700 nm (considering loss due to light absorption by the conductive glass substrate). The current-voltage curve (characteristic line a in FIG. 5) shows a photocurrent I _sc of 10 mA / cm ² and an open circuit voltage V _{oc of} 0.63 V under an illuminance of 1000 W / m ² corresponding to the reference sunlight AM1.5G. It showed 3.4% photoelectric conversion efficiency.

Example 3: Porous Nanocrystalline TiO ₂ film (average particle size 40 nm) thicker antimony sulfide layer is coated with a dark brown in and produced by the filler consisting of the membrane and CuSCN, solid-type photovoltaic cell having a penetration form Device manufacturing.

  The production of the light absorber layer made from antimony sulfide was carried out in a procedure similar to that in Example 1, except that the chemical bath deposition method was repeated three times in succession using a new solution having the same composition for each deposition. Different. The third deposition is complete, the thin film is washed and dried, and then the film annealed by heating at 300 ° C. for 30 minutes under a nitrogen gas atmosphere in a manner similar to Example 2 turns dark brown. It was. According to EDX, the amount of light absorber was about three times that of the thin films of Examples 1 and 2. According to SEM, the vacancies on the upper side of the thin film (opposite side of the conductive glass substrate side) were almost closed.

  Regarding the production of the solid-state photovoltaic device, in particular, the filler and the contact layer made of CuSCN semiconductor (the thin gold layer and the carbon layer in Example 1) were performed in the same manner as in Example 1.

  Regarding the manufacture of the solid-state photovoltaic device, in particular, the filler and the contact layer made of CuSCN semiconductor were performed in the same manner as in Examples 1 and 2.

  Photovoltaic cell performance was evaluated as described above. The quantum efficiency and current-voltage curves showed very low values. This is due to coatings with light absorbers that are too thick (increasing losses due to recombination) or vacancy closure (especially on the top side of the film), which can lead to poor filling of the vacancies with CuSCN.

Example 4: Porous Nanocrystalline TiO ₂ film (average particle size 40 nm) bismuth sulfide layer in, and produced by the filler made of the film and CuSCN, preparation of the solid type photovoltaic device having a penetration form.

The substrate and porous nanocrystalline TiO ₂ thin film are the same as in Example 1. The light absorber layer formed of bismuth sulfide was deposited using a chemical bath deposition method. One container containing 50 ml of precursor solution was used. The solution has 0.025M concentration of Bi (NO ₃ ) ₃ , 0.12M concentration of triethanolamine (OHCH ₂ CH ₂ ) ₃ N), and 0.04M concentration of thioacetamide (CH ₃ CSNH ₂ ). It consists of an aqueous solution. The sample was immersed in this solution and the container containing the sample was placed in a thermostat bath at 35 ° C. and left in that state for 30 seconds. Thereafter, the sample was drawn out, washed with distilled water, and finally dried with dry air. The light absorber layer was thermally annealed by heating at 300 ° C. for 30 minutes under a nitrogen gas atmosphere.

The same method as in Example 1 was used for the production of the solid photovoltaic device having this layer. Photovoltaic cell performance was evaluated as described above. The quantum efficiency is a slanted shape in the wavelength range of 400 to 600 nm and has a maximum value of 30% (characteristic line c in FIG. 4). The current-voltage curve (characteristic line c in FIG. 5) shows a photocurrent I _sc of 0.9 mA / cm ² and 0.3% under an irradiance of 1000 W / m ² corresponding to the reference sunlight AM1.5G. The photoelectric conversion efficiency was shown.

Example 5: flat consists TiO ₂ dense layer, planarization layer made of dark brown antimony sulfide, and preparation of the solid type photovoltaic device having a flat layer forms made from a flat layer consisting of CuSCN.

A flat dense layer of TiO ₂ was deposited on a conductive crow substrate according to a method similar to that described in Example 1. The thickness of the layer was about 50 nm (measured with SEM).

A flat layer made of antimony sulfide was deposited on a flat dense layer made of TiO ₂ according to a procedure similar to Example 1 using chemical bath deposition. The light absorber layer was orange. Thereafter, the flat layer made of antimony sulfide was heated at 300 ° C. for 30 minutes in a nitrogen gas atmosphere and subjected to thermal annealing. The thin film became dark brown. The flat layer made of antimony sulfide was dense and flat with a thickness of about 150 nm (measured in cross section using SEM).

  A flat layer made of CuSCN was deposited on the upper side of the flat layer made of antimony sulfide using an evaporation method. The procedure was similar to Example 1, but 50 μl of CuSCN solution was used. When precipitation was complete, the sample was heated for an additional 3 minutes at the same temperature to completely evaporate excess solvent. The thickness of the CuSNC layer (measured in cross section using SEM) was about 500 nm.

  Next, using a metal evaporator (for example, Edwards 306 type), a gold layer having a thickness of about 25 nm was deposited on the upper side of the CuSCN layer. In another example (a cheaper alternative than gold), a carbon layer was applied over the sample using a commercially available conductive ink made of carbon.

Photocell performance was evaluated as described above. The quantum efficiency (characteristic line b in FIG. 4) shows a maximum value of 25% smaller than that of the device having the penetrating form, but shows a similar shape with a large wavelength width (400 to 700 nm). The current-voltage curve (characteristic line b in FIG. 5) shows a photocurrent I _sc of 2.9 mA / cm ² and an open circuit voltage of 0.54 V under an illuminance of 1000 W / m ² corresponding to the reference sunlight AM1.5G. V _oc showed 0.7% photoelectric conversion efficiency.

As described above, the present invention uses a three-layer structure of an n-type semiconductor, a light absorber, and a p-type semiconductor, and has an advantage that it can be manufactured at low cost because the light absorber contains antimony sulfide. A photovoltaic device excellent in photoelectric conversion efficiency can be provided. The photovoltaic device of the present invention is preferably improved, and in particular obtains a short circuit photocurrent greater than ² mA / cm ² , preferably greater than 5 mA / cm ² when illuminated with 1000 W / cm ² solar radiation. This makes it possible to obtain a photoelectric conversion efficiency greater than 0.5%, in particular greater than 1%. In addition, the photovoltaic device of the present invention is not highly toxic, has no negative impact on the environment, and can be manufactured using an inexpensive and stable material.

  The following technical idea can be recognized in the above description.

(1) A transparent electrode having transparency and conductivity, a first semiconductor layer having a first conductivity type provided in electrical contact with the transparent electrode, and light provided on the surface of the first semiconductor layer An absorber layer, a second semiconductor layer provided in electrical contact with the light absorber layer and having a second conductivity type different from the first semiconductor layer, and electrical contact with the second semiconductor layer And a counter electrode provided in step (b), and the light absorber layer contains antimony sulfide. It is possible to provide a photovoltaic device that has the advantage of being manufactured at low cost and is excellent in photoelectric conversion efficiency.

(2) a transparent electrode having transparency and conductivity; a dense first semiconductor dense layer (first shielding layer) having a first conductivity type provided in electrical contact with the transparent electrode; A porous first semiconductor porous layer having a first conductivity type provided in electrical contact with a semiconductor dense layer, a light absorber layer provided on a surface of the first semiconductor porous layer, A porous second semiconductor layer having a second conductivity type different from that of the first semiconductor layer, provided in electrical contact with the light absorber layer, and provided in electrical contact with the second semiconductor. And a counter electrode, and the light absorber layer contains antimony sulfide. It is possible to provide a photovoltaic device that has the advantage of being manufactured at low cost and is excellent in photoelectric conversion efficiency.

(3) The photovoltaic device according to (1), wherein at least one of the first semiconductor layer and the second semiconductor layer is non-porous.

(4) a first step of forming a first semiconductor layer having a first conductivity type on a transparent electrode having transparency and conductivity;
A second step of forming a light absorber layer containing antimony sulfide on the surface of the first semiconductor layer;
And a third step of forming a second semiconductor layer provided on the surface of the light absorber layer and having a second conductivity type different from that of the first semiconductor layer. Production method.

  It is possible to provide a photovoltaic device that has the advantage of being manufactured at low cost and is excellent in photoelectric conversion efficiency.

(5) a first step of forming a porous first semiconductor layer having a first conductivity type on a transparent electrode having transparency and conductivity;
A second step of forming a light absorber layer containing antimony sulfide on the surface of the first semiconductor layer including the inner surface of vacancies;
And a third step of filling a second semiconductor layer having a second conductivity type different from that of the first semiconductor layer into the voids of the first semiconductor layer. Method.

  It is possible to provide a photovoltaic device that has the advantage of being manufactured at low cost and is excellent in photoelectric conversion efficiency.

(6) In (5), a shielding layer for preventing an electrical short circuit between the transparent electrode and the second semiconductor layer is provided between the transparent electrode and the first semiconductor layer. A method of manufacturing a photovoltaic device characterized by the above.

1 is a schematic diagram of a solid-state photovoltaic cell device comprising three main components with an intrusive nanocrystal structure according to the present invention. FIG. 1 is a schematic diagram of a solid state photovoltaic device in the form of a flat stacked layer of three main components according to the present invention. The absorption spectrum of the light absorber layer of Examples 1 and 2 is shown (absorption corresponding to conductive glass is subtracted). Characteristic line a shows the absorption spectrum of Example 2, and characteristic line b shows the absorption spectrum of Example 1. The wavelength-quantum efficiency (%) curve of the photovoltaic device of Examples 1, 2, 4, and 5 is shown. The characteristic line a is Example 2, the characteristic line b is Example 5, the characteristic line c is Example 4, and the characteristic line d is Example 1. The current-voltage curve of Example 2, 4, 5 is shown. Characteristic line a shows Example 2, characteristic line b shows Example 5, and characteristic line c shows Example 4.

Explanation of symbols

1 ... n-type semiconductor (porous nanocrystal thin film made from transparent n-type semiconductor)
2 ... light absorber 3 ... p-type semiconductor (hole filling material made of transparent p-type semiconductor)
4 ... Transparent electrode (transparent conductive substrate acting as a front contact)
5 ... Shielding layer (thin and dense shielding layer made from n-type semiconductor)
6 ... Counter electrode (conductive substrate collecting charges from p-type semiconductor)
7: Sealing material 10: n-type semiconductor layer (dense layer)
11 ... hole 12 ... TiO ₂ nanocrystal (crystal or particle of transparent n-type semiconductor)
20 ... light absorber layer 30 ... p-type semiconductor layer (dense layer)

Claims (2)

a TiO ₂ layer having porous pores as an n-type semiconductor;
A light absorber comprising antimony sulfide formed as a layer on the inner surface of the pores and in contact with the TiO ₂ layer;
A Cu (I) -based compound as a p-type semiconductor that penetrates into the pores and contacts the light absorber;
A photovoltaic device, wherein the TiO ₂ layer has a roughness coefficient greater than 100.
Here, the roughness factor of the TiO ₂ layer, to the projected area of the light incident on the light absorber in contact with the TiO ₂ layer, indicating the ratio of internal surface area of the TiO ₂ layer. In claim 1,
A photovoltaic device, wherein the light absorber is subjected to a thermal annealing treatment.

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