JP2000285974A - Photosensitized photovolatic power generation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent short circuit of an electric circuit between a charge transfer layer and a transparent electrode and separation between a transparent conductive film and an n-type semiconductor electrode and improve long-term reliability, by constituting the n-type semiconductor electrode with a dense portion with a specific thickness and a porous portion. SOLUTION: An n-type semiconductor electrode is constituted with a dense portion 8 and a porous portion 4, and thickness of the dense portion 8 is not less than 0.01 μm and not more than 0.6 μm. For forming the thickness of the dense portion 8 so thin, recesses and projections existing on this surface are preferably set not larger than 90 nm. As a result, a thin film with thickness less than 100 nm having no stress concentration is formed to provide a highly efficient cell with long-term reliability. Because microstructure may slightly vary depending on an employed raw material, preferably, relative density of the dense portion 8 is not less than 93% and not more than 100%. More preferably, pores in the dense portion 8 are closed. In addition, volume ratio of a polycrystalline phase contained in the dense portion 8 is preferably not less than 5% and not more than 70%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitized photovoltaic device having long-term reliability and high conversion efficiency.

[0002]

2. Description of the Related Art In general, there are photovoltaic elements using semiconductors such as Si and photo-sensitized photovoltaic elements as described in JP-A-1-220380. The structure of the photosensitized cell is such that substrates such as glass and polymer are used vertically and SnO ₂ doped with fluorine is used for each substrate.
Are formed as transparent electrodes. TiO with a porous structure of several tens of nanometers on one of the transparent electrodes
Compounds such as ₂ are used as n-type semiconductor electrodes. A complex dye having Ru or the like as a central metal is adsorbed on the n-type semiconductor electrode. An electrolyte (charge transport layer) containing redox ions such as iodine is used between the other substrate and an n-type semiconductor electrode such as TiO ₂ on which a dye is adsorbed. In this case, since the electrolytic solution is used, the device is a wet-sensitized solar power generation device.

[0003] First, sunlight hits a substrate used as a light receiving material of such a cell. Next, it passes through a transparent electrode. At this time, except for the very short wavelength side of the light, most of the light of other wavelengths hits an n-type semiconductor electrode such as TiO ₂ on which a complex dye for charge separation is adsorbed. Light excites electrons in the ground state of the dye. The excited electrons are n
Is injected into the conduction band of the type semiconductor electrode. Further, the electrons flow through the transparent electrode and go to an external load. The electrons that have reached the counter electrode reduce iodine by a reaction of I3 ⁻ + 2e ⁻ → 3I ⁻ . The reduced iodide ions pass electrons to the n-type semiconductor electrode and are Ru (III), but are reduced to Ru (I
I). And iodide ions are oxidized 3I ^- → I
3 ^- + 2e ^- to become. Power is generated as described above.

[0004] It has been proposed that the electrolyte portion of the photosensitized cell is formed of a hole conductive material of OMeTAD. In this case, TiO ₂ is used for the n-type semiconductor electrode, and a compact layer is provided so that the electrolyte portion and the transparent conductive film electrode are not electrically short-circuited. However, looking at the cross section of this film, a columnar crystal grows, and it is difficult to say that the column and the gap are dense and impervious to liquid at all, and there is a problem that a short circuit actually occurs.

[0005] Further, the stress caused by the coefficient of thermal expansion generated in the transparent conductive film and the n-type semiconductor electrode is reduced to the utmost, and peeling between the transparent conductive film and the n-type semiconductor electrode and peeling of the light-receiving side substrate and the transparent conductive film are prevented. There was a problem that it could not withstand long-term use with temperature changes.

[0006]

The conventional photovoltaic element has a microstructure in which an n-type semiconductor electrode is grown with columnar crystals, and the space between the columns is so dense that it is hard to say that liquid cannot pass at all. There was a problem that the electrolyte and the transparent conductive film electrode were electrically short-circuited. In addition, there is a problem that separation occurs between the transparent conductive film and the n-type semiconductor electrode due to stress caused by the coefficient of thermal expansion. The object of the present invention has been made in view of the above problems, and prevents short circuit of an electric circuit between a charge transport layer and a transparent electrode, and prevents peeling between a transparent conductive film and an n-type semiconductor electrode to provide a long-term reliability. An object of the present invention is to provide a photosensitized photovoltaic power generation element having improved performance.

[0007]

In order to solve the above-mentioned problems, the present invention specifically provides a first substrate having a light receiving surface and a surface of the first substrate facing the light receiving surface. A transparent conductive film formed on the transparent conductive film, an n-type semiconductor electrode formed on the surface of the transparent conductive film and adsorbing a dye, a charge transport layer formed adjacent to the n-type semiconductor electrode, A second substrate having a conductive film on the surface formed on the opposite side and with the charge transport layer interposed therebetween, wherein the n-type semiconductor electrode has a thickness of 0.01 μm or more.
The electrode is a completely new electrode comprising a dense part and a porous part of 0.6 μm or less, preferably 0.01 μm or more and 0.3 μm or less. The adhesion between the dense portion and the porous portion is extremely good, but when the transparent portion is in close contact with the transparent conductive film, the two layers work so as to absorb stress. Can be prevented. Furthermore, in addition to preventing the dense part from permeating the electrolyte, the boundary between the dense part and the porous part works to prevent the permeation of the electrolyte, resulting in the prevention of the permeation of the electrolyte and the transparency of the electrolyte. Short circuit of the conductive film electrode can be prevented.

The n-type semiconductor electrode has a grain size of several microns or less, and the electrode grains have a depletion layer. Due to the presence of the depletion layer, the n-type semiconductor electrode has an internal resistance. Therefore, the thickness of the n-type semiconductor electrode needs to be small in the direction in which electric charges are transmitted. In order to achieve a thin film, it is also effective that the unevenness on the surface of the dense portion of the n-type semiconductor electrode is small. In addition, a direct contact between the transparent electrode and the charge transport layer causes a short circuit in the electric circuit. Unless this is absolutely avoided, the characteristic of high efficiency cannot be obtained. For this purpose, it is conceivable that the charge transport layer is liquid or liquid even if it is solid, so that the relative density of the dense portion of the n-type semiconductor electrode is 90% or more and 100% or less, preferably 93%. It is preferable that the density is not less than 100% and that the pores in the dense portion of the n-type semiconductor electrode are closed pores and have a microstructure that does not allow liquid to pass through.

Further, the photosensitized cell includes a substrate for receiving light,
A cell is formed by using multiple layers of different materials such as a transparent electrode and an n-type semiconductor electrode. Depending on the manufacturing process of the n-type semiconductor electrode, heat treatment at a temperature of several hundred degrees is usually used for the formation, and the cell changes from the lowest temperature in midwinter to the highest temperature in direct sunlight in midsummer. It is necessary to reduce as much as possible the stress caused by the difference in the coefficient of thermal expansion that occurs under such severe temperature conditions, and the dense portion of the n-type semiconductor electrode contains the polycrystalline phase more reliably. Found to be relaxed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a high-efficiency photovoltaic power generation device having long-term reliability, and its embodiment will be described in detail. By making the structure and physical properties of the n-type semiconductor electrode unprecedented, the stress caused by the coefficient of thermal expansion generated in the transparent conductive film and the n-type semiconductor electrode is reduced to the utmost, and the distance between the transparent conductive film and the n-type semiconductor electrode is reduced. The peeling and the peeling of the transparent conductive film from the substrate on the light receiving side are prevented from long-term use with temperature change.

FIG. 1 is a sectional view of a specific photosensitized solar power generation device. Here, the photovoltaic power generation element of the present embodiment will be briefly described. Reference numeral 1 denotes a substrate having a light receiving surface for receiving sunlight (first substrate: upper and lower substrates in the figure) and a counter substrate (second substrate: lower substrate in the figure), 2 denotes an ion diffusion preventing film, Is a transparent conductive film, 4 is an n-type semiconductor electrode (porous portion), 5 is a complex dye adsorbed on the surface of the n-type semiconductor electrode, 6 is a charge transport layer serving as an electrolyte, 7 is a charge transport layer Is a sealing portion for sealing in a space formed by facing the substrate 1, and 8 is an n-type semiconductor electrode (dense portion).

As the substrate 1 used as a light receiving material, a glass or organic polymer substrate is used. In the case of glass, soda-lime glass (blue glass) is often used as a versatile substrate for the purpose of low cost. The coefficient of thermal expansion of soda lime glass is 8.5 to 9.0 × 10 ⁻⁶ / ° C. (around room temperature). 70 × 10 ^-6 / ℃ for acrylic resin (around room temperature)
It is. In the case of polycarbonate, it is 70 × 10 ⁻⁶ / ° C. (around room temperature). In addition, the transparent electrode has SnO
₂ (F), ITO, ZnO (Al) or the like is used. The thermal conductivity of the compound used for these transparent electrodes is SnO ₂ (F)
3.8 × 10 ⁻⁶ / ° C. (around room temperature), ZnO (A
In the case of 1), it is 2.1 to 4.0 × 10 ⁻⁶ / ° C. (around room temperature). In general, the thermal expansion coefficient of the compound used for the transparent electrode is very small with respect to the substrate 1. Furthermore, n
When the anatase phase of TiO ₂ is used for the type semiconductor electrode 8, it is 6.6 × 10 ⁻⁶ / ° C. to 10 × 10 ⁻⁶ / ° C. (around room temperature). 14 × 10 ⁻⁶ / ° C. for BaTiO ₃ (> 120
° C). 9.4 × 10 ⁻⁶ / ° C. for SrTiO ₃ (
(Around room temperature).

As described above, different materials have a multilayer structure. Materials with different coefficients of thermal expansion are subjected to stress due to heating and cooling during manufacturing, and thermal cycling from the lowest temperature in the middle of winter when using the cell to the highest temperature in direct sunlight in the middle of summer.
At present, peeling occurs, and high efficiency cannot be obtained with long-term reliability.

In order to prevent peeling or cracking due to stress, a photosensitized cell material was newly found to have a structure having a small film thickness and a material having a small Young's modulus.

In the present invention, the n-type semiconductor electrode is composed of the dense portion 8 and the porous portion 4, and the thickness of the dense portion is set to 0.1.
It was found that peeling and cracking did not occur when the thickness was set to 01 μm or more and 0.6 μm or less. Regarding this thickness,
The thinner one has a stress relaxation effect, preferably 0.01 μm
It was found that it was not less than 0.3 μm. More preferably, it is 0.01 μm or more and less than 0.1 μm. Further, the particle size forming the n-type semiconductor electrodes 4 and 8 is several microns or less, and a depletion layer exists in the particles of the electrodes. Exists. However, it was found that the thickness of the dense portions of the n-type semiconductor electrodes 4 and 8 of the present invention was extremely small, the internal resistance was extremely reduced, and high efficiency was obtained.

However, if the surface roughness of the film is too large even if a thin film is to be formed, a film thinner than the length of the surface cannot be formed. Does not become a film having a uniform thickness. Electrochim.Acta 40,643-
In the film described in 652 (1995), unevenness is 100 nm to 30 nm.
It is expected that a thin film having a thickness of 0 nm and having a thickness of less than 100 nm will be formed into an island structure and cannot be formed substantially. In the present invention, it has been newly proposed to form a thin film having a thickness of less than 100 nm without stress concentration by setting the unevenness existing on the surface of the dense portion 8 of the n-type semiconductor electrode to 90 nm or less to obtain a long-term reliable high-efficiency cell. did it.

The dense portion 8 has the effect of preventing a short circuit in the electric circuit between the charge transport layer and the transparent electrode 3 at all, and has the effect of eliminating electric loss. It was necessary not to allow it to do so (the effect was drastically reduced if a little was passed), and it was found that the dense portion 8 of the n-type semiconductor electrode was large. Since the microstructure may be slightly different depending on the raw material used, the relative density is preferably 93%.
It was also found that the effect was maximum when the percentage was not less than 100% and not more than 100%. More preferably, the pores of the dense portion 8 of the n-type semiconductor electrode are closed pores.

At the same time, it has been newly found that, if the Young's modulus of the n-type semiconductor electrode is reduced to reduce the stress caused by the thermal cycle, peeling and cracking will not occur. It has been found that the reduction in Young's modulus is achieved when the dense portion 8 of the n-type semiconductor electrode contains a polycrystalline phase (polycrystalline phase). In general, when there are many crystal phases, the electric conduction of the electrodes increases, and when there are many polycrystalline phases, the electric conduction of the electrodes decreases. The n-type semiconductor electrode is required to have high electric conductivity and low resistance, but it is also necessary to reduce the Young's modulus. The present invention provides a composition which solves both of these problems, as a dense portion 8 of an n-type semiconductor electrode.
A completely new material has been invented in which the volume fraction of the polycrystalline phase contained in the material is in the range of 5% to 70%. At this time, a highly reliable and highly efficient photosensitized cell free from peeling or cracking over a long period of time is achieved.

As described above, a completely new n
By making the structure and physical properties of the type semiconductor electrode and the crystal phase composition new, a high-efficiency photosensitized photovoltaic power generation device that solves the problem and has long-term reliability has been achieved completely new.

Embodiments of other parts constituting the cell of the present invention will be described in more detail. The high-efficiency photovoltaic power generation device with long-term reliability according to the present invention includes (1) a film 2 for preventing diffusion of ions on one surface of a light-receiving plate, such as glass or a polymer, which is transparent to almost all wavelength regions of sunlight. A light-receiving plate on which a light-receiving material is formed, where necessary, and on which a metal or a transparent conductive film is also formed, and (2) a thermal stress connected to the transparent conductive film on one side of the light-receiving material is relieved and short-circuited. An n-type semiconductor electrode 4 comprising a dense layer 8 having a function of preventing the occurrence of electrons and conducting electrons and a porous portion adsorbing the complex dye 5, (3) the dye 5 adsorbed on the n-type semiconductor electrode, and (4)
It is formed between the second substrate 1 on which the counter electrode 3 of the metal or the transparent conductive film 3 described in (1) is formed, and (5) the n-type semiconductor electrode 4 on which the dye 5 is adsorbed and the counter electrode 3. A charge transport layer 6 made of an ion-conductive or hole-conductive material;
(5) It is characterized by comprising a substrate on which an electrode electrically facing the electrode formed in (1) is formed.

The non-conductive substrate 1 on which the electrode group consisting of the anode and the cathode of (1) and (4) is formed may be of any type as long as it has good insulating properties. Specifically, for example, a glass substrate such as soda lime glass, an organic polymer substrate such as polycarbonate or acrylic resin,
A ceramic substrate such as alumina and aluminum nitride, a silicon substrate, and the like can be given. In addition, even if it is not a non-conductive material, the surface forming the electrode group may be coated with an insulating substance such as a polymer, glass, or ceramic, and a metal substrate such as stainless steel, aluminum, or titanium, or a carbon substrate can be used. . However, at least one of the substrates is required to be transparent to sunlight.

It is preferable that an ion diffusion preventing film 2 is provided between the light receiving side substrate and the transparent conductive film. As the ion diffusion preventing film 2, a silica film or the like can be used. Generally n
Materials used for the type semiconductor electrodes 4 and 8 are, in particular, titanium, zirconium, hafnium, strontium, zinc, indium, yttrium, lanthanum, vanadium, niobium,
Examples include oxides such as tantalum, chromium, molybdenum, and tungsten, and perovskites. Especially best is
It is an anatase phase of TiO ₂ . The porous portion 4 for adsorbing the complex dye 5 preferably has a large surface area per unit area, more preferably 100 or more. Preferably 500
And more preferably 1,000 or more. On the other hand, if the thickness of the porous portion 4 is small, the surface area on which the dye 5 is adsorbed becomes small, which is not preferable. On the other hand, if it is too thick, the internal resistance increases, leading to a decrease in conversion efficiency. Preferably 2μ
m to 15 μm, more preferably 5 μm to 10 μm.
μm. The pore size of the porous portion 4 is 100
nm or less and 1 μm or more are preferable. 100μm or more 1μ
Pores smaller than m are not preferred because they scatter light and lead to a reduction in conversion efficiency. The dense part 8 and the porous part of the n-type semiconductor electrode are preferably made of the same compound. However, electrons are injected from the complex dye 5 into the porous part 4 of the n-type semiconductor dye, In the case where the connection structure of the conduction band continuously injected into the n-type semiconductor electrodes is maintained, there is no problem in operation even if the n-type semiconductor electrodes 4 and 8 are composed of two different compounds.

The material forming the electrode group may be any conductive material. The materials constituting the anode and the cathode may be the same or different. When the charge transport layer 6 is an electrolyte layer, it is preferable to use a material that is electrochemically stable, and specifically, it is desirable to use platinum, gold, carbon, or the like. In addition, it is preferable that the conductive film be formed of an oxide-based conductive film such as SnO ₂ (fluorine-doped), ITO (In-Sn oxide), or ZnO (Al-doped). Even with other materials such as aluminum, copper, iron, stainless steel, titanium, silver, doped polyaniline, polypyrrole, polythiophene, and other conductive polymers, only the surface in contact with the electrolyte is coated with platinum, gold, carbon, etc. Then, the same stability can be obtained. Such a coating is performed by, for example, forming electrodes in a desired pattern (a full-surface electrode is also possible) and then coating platinum, gold, or the like by electrolytic or electroless plating. The surface of the electrode is preferably in a state where the surface area is increased by the fine structure. For example, it is preferable that platinum is in a platinum black state and that of carbon is in a porous state. It is desirable that the thickness of the electrode be small in order to alleviate the stress resulting from thermal cycling. It is preferably 1 μm or less, more preferably 0.7 μm or less. However, when the resistivity is large, the thickness should be such that the conversion efficiency does not decrease.

The dye 5 may be any dye as long as it has absorption in the visible light region and can inject electrons into the semiconductor layer by a photoexcitation reaction, and a transition metal complex or the like is used. Specific examples include metal complexes such as ruthenium, osmium, and iron. In particular, it is preferable that the ligand is a bidentate, tridentate or all-dentate polypyridyl compound and has a substituent such as a carboxyl group that can bind to a hydroxyl group on the surface of titanium dioxide.

The charge transport layer 6 is composed of an electrolyte solution containing a reversible redox couple such as iodide, bromide, or hydroquinone as an ion conductive material, or a matrix containing a crosslinked polyacryl resin derivative or a crosslinked polyacrylonitrile derivative as a matrix. , A polymer electrolyte in which an electrolyte is dissolved in a polyalkylene oxide, a silicone resin, or the like, and a molten salt electrolyte such as a polymer ammonium salt.

In the case of an electrolyte solution, an inorganic porous material such as porous silica, alumina and rutile phase titanium dioxide having a sufficient porosity, or a porous material of an organic substance such as poly (vinylidene fluoride) is impregnated. You may use it in the state made to be.

Examples of the hole conductive substance include amorphous materials such as triallylamines, polymeric hole transport materials such as polyvinyl carbazole, polyphenylene, and the like.
A conjugated polymer such as polyphenylenevinylene, polythiophene, polypyrrole, polyaniline, polysilole, or polysilane, or a derivative thereof is used.
The photosensitized photovoltaic device having long-term reliability and high conversion efficiency of the present invention is manufactured by, for example, the following method. First, a transparent conductive film 3 containing SnO ₂ , ITO, ZnO, or the like as a main component is formed on a glass or organic polymer substrate 1 having good light transmittance at a wavelength in the visible region by a sputtering method, a CVD method, a sol-gel method, or the like. Next, the dense portion 8 of the n-type semiconductor electrode is formed on the transparent conductive film 3 by various methods such as a sputtering method, a CVD method or a sol-gel method. If necessary, heat treatment or the like is performed to adjust the content ratio of the polycrystalline phase of the n-type semiconductor electrode to a desired ratio. Subsequently, the paste using the raw material compound powder is formed on the porous portion 4 of the n-type semiconductor portion by screen printing or squeegee printing. As another method, a sputtering method, a CVD method, a sol-gel method, or the like can be used. After that, depending on the process, heat treatment is performed if necessary. Performing etching or the like to increase the specific surface area is also permitted.

Subsequently, the glass substrate 1 on which the n-type oxide semiconductors 4 and 8 are formed is immersed in a solution in which the complex dye 5 is dissolved in an organic solvent such as alcohol, and held for a predetermined time. This step can also be achieved by placing the glass substrate 1 immersed in a solution in a reflux device and performing a reflux process. By performing the reflux treatment, a sufficient amount of the dye 5 can be adsorbed in a shorter time than when the dye 5 is simply immersed in the solution.

After the substrate with the n-type oxide semiconductor electrodes 4 and 8 on which the dye 5 has been sufficiently adsorbed is pulled out of the solution and dried, the substrate is placed so as to face the glass or organic substrate 1 with the counter electrode 3, and the surroundings are one-sided. Except for the portion, the package is sealed with an epoxy resin 7 or the like. In the case of sealing, it is also allowed to dispose glass or polymer beads for adjusting the space between the n-type oxide semiconductor electrodes 4 and 8 and the counter electrode.

Next, the charge transport layer 6 is impregnated between the two transparent conductive substrates 3. When a solution is used as the charge transport layer 6, an electrolytic solution is prepared in advance, put in a container, and placed in a container that can be degassed together with the transparent substrate 1 whose periphery is sealed, and then sufficiently degassed once. Is performed, and then the unsealed portion of the glass substrate 1 in the container is brought into contact with the electrolytic solution,
Subsequently, the vacuum in the degassing vessel is broken and the electrolyte 6 is transferred to the transparent substrate 1.
Inject in between. After the injection of the electrolyte 6 is sufficiently completed, the unsealed portion is sealed with an epoxy resin 7 to obtain a photovoltaic device.

When the charge transport layer 6 is a solid or pseudo solid, the transparent substrate 1 on which the n-type oxide semiconductors 4 and 8 are formed
Before sealing the transparent substrate 1 on which the counter electrode is formed, an appropriate amount of a powdery, granular or plate-like solid or quasi-solid electrolyte is disposed on the n-type oxide semiconductor electrodes 4 and 8, and further thereon. After the transparent substrate 1 on which the counter electrode 3 is formed is arranged, the charge transport layer 6 is melted while being heated in a degassing container, and the n-type oxide semiconductor electrodes 4 and 8 are impregnated with the charge transport layer 6 and then air. And cooled to complete the desired bonding. It should be noted that an appropriate load can be applied while the charge transport layer 6 is melted by heating in the degassing container. Finally, the periphery of the two transparent substrates 1 is sealed with an epoxy resin 7 or the like to obtain a target solar power generation element.

[0032]

The present invention can be better understood with reference to the following illustrative but non-limiting examples. (Example 1) A photosensitized solar power generation device having the structure shown in FIG. 1 was prepared by the following procedure. Titanium isopropoxide,
It was dissolved in dehydrated 2-propanol, and refluxed for 1 hour while heating using a reflux device, and mixed to form a uniform solution. Next, in a dry box, a 0.1 M nitric acid solution was dropped into the refluxed solution with vigorous stirring to prepare a transparent sol solution.

A borosilicate glass substrate on which an SiO ₂ ion diffusion preventing film and a 0.9 μm thick tin oxide are doped with fluorine in the obtained solution to form a transparent conductive film having a sheet resistance of 5Ω / □. 1 was immersed and pulled up at a speed of about 5 cm / min. This was heat-treated at a maximum temperature of 600 ° C. in air. The process from immersion in this solution to firing at 600 ° C. was performed a plurality of times to form a titanium oxide thin film having a thickness of 0.3 mm and a relative density of 98% and containing no polycrystalline phase. The unevenness on the surface of the dense portion 8 of the n-type semiconductor electrode was 50 nm. The phases were determined by measuring the constituent phases by the X-ray diffraction method. A peak corresponding to anatase was observed, the peak intensity of powder X-ray diffraction was compared with another sample heat-treated at a higher temperature, and the ratio of the polycrystalline phase remaining in the thin film was measured using chemical analysis in combination. , 0%.
The porosity was determined by observing the microstructure.
% (98% relative density).

Next, nitric acid was added to a high-purity titanium oxide (anatase) powder having an average primary particle diameter of 30 nm, kneaded with pure water, and a paste stabilized with a surfactant was prepared. This is printed by a screen printing method on the glass substrate 1 on the dense portion 8 of the n-type semiconductor electrode,
Heat treatment was performed at 0 ° C. to form n-type semiconductor electrodes 4 and 8 made of titanium oxide (anatase) having a thickness of 2 μm. This squeegee printing and heat treatment were repeated a plurality of times to finally form titanium oxide n-type semiconductor electrodes 4 and 8 having an anatase phase and having a thickness of 8 μm on the tin oxide conductive film. The roughness factor of the n-type semiconductor electrode 4 was 1500. The roughness factor was determined from the nitrogen adsorption amount with respect to the projected area of the substrate.

The glass substrate on which the titanium oxide thin film having the two-layer structure was formed was prepared using cis-bis (siocyanato) -N, N
-Bis (2,2'-dipyridyl-4,4'-dicarboxylic acid) -ruthenium (II) dihydrate complex dye was immersed in a 3.7 × 10 ^-4 M solution of ethanol, The dye 5 was sufficiently adsorbed on the titanium oxide thin film after being left for a while. The amount of the dye adsorbed was calculated from the calibration curve to be about 5.5 × 10 ⁻⁷ mol /
It was cm ^2. A glass substrate 1 on which an electrode coated thinly with platinum without being doped with fluorine as a counter electrode 3 was formed, and a titanium oxide n-type semiconductor electrode 4 having the above-mentioned two-layer structure was prepared using a spacer having a diameter of 20 μm. On board 1
And the periphery was fixed with an epoxy resin 7 except for an electrolyte injection port. An acetonitrile / ethylene carbonate mixed solvent electrolyte solution of tetrapropylammonium iodide 0.4M, potassium iodide 0.02M, and iodine 0.03M was injected from the injection hole. After the injection, the epoxy resin 7 was sealed to produce a photoelectric conversion element.

Immediately after fabrication, the solar cell was irradiated with simulated sunlight at an intensity of 15 mW / cm ² , and its conversion efficiency (initial) was measured. As a result, an energy conversion efficiency of 10.5% was obtained. Thereafter, a thermal cycle test (TCT) was performed. After leaving in an air atmosphere at 25 ° C. for 30 minutes, 100
The temperature was increased to 30 ° C. in 30 minutes. It was left at 100 ° C. for 30 minutes, then cooled to −10 ° C. in 40 minutes, and left at −10 ° C. for 30 minutes. Thereafter, the temperature was raised to 100 ° C. in 40 minutes and left for 30 minutes. Such a temperature cycle between −10 ° C. and 100 ° C. was performed 500 times. A solar cell is irradiated with simulated sunlight at an intensity of 15 mW / cm ² and its conversion efficiency (TC
After (T) was obtained, an energy conversion efficiency of 10.3% was obtained, and there was almost no decrease in efficiency. The cell was disassembled, and the vicinity of the interface of the ion diffusion preventing film 2 / the transparent conductive film 3 / the dense portion 8 of the n-type semiconductor electrode was observed with a scanning electron microscope and a transmission electron microscope. No peeling was observed. . The effects of the present embodiment can be summarized as follows: a high-efficiency photovoltaic power generation device having long-term reliability, in which the structure and physical properties of the n-type semiconductor electrode are unprecedented, and And the stress due to the coefficient of thermal expansion generated in the n-type semiconductor electrode 8 is reduced to the utmost, and the separation between the transparent conductive film 3 and the n-type semiconductor electrode 8 and the separation between the substrate 1 on the light receiving side and the transparent conductive film 3 are changed by a temperature change. Along with the armor from a certain long-term use, it prevents a short circuit of the electric circuit between the charge transport layer 6 and the transparent electrode 3 from occurring at all,
Electricity loss is extremely reduced, and furthermore, the n-type semiconductor electrode 4,
The electrical resistance in the inside 8 can be extremely reduced.

Example 2 A dense portion 8 of an n-type semiconductor electrode was formed by sputtering. Output 2k in an atmosphere of 0.1 Pa oxygen and 0.2 Pa argon using titanium as the target
Sputtering was performed with W. The constituent phase of the obtained thin film was powder X
When identified by a line diffraction method, the titanium oxide was found to be amorphous titanium oxide. Then, the glass substrate 1
Was subjected to a heat treatment at 500 ° C. for 4 hours to adjust the constituent phases. When the constituent phases of the obtained thin film were confirmed with a powder X-ray diffractometer, a peak corresponding to the anatase phase was confirmed. A comparison between the diffraction pattern and the peak intensity of a sample which was heat-treated at a high temperature and was completely crystallized showed that they were identical and did not contain a polycrystalline phase. Tables 1 and 2 show the conditions and evaluation results of Example 2. Parts not described in these tables are the same as those in the first embodiment.

[0038]

[Table 1]

[0039]

[Table 2]

(Embodiments 3 and 4) Embodiments 2 to 13
Table 1 and Table 2 also show the conditions up to and the evaluation results. The parts not described in these tables are the same as in the first or second embodiment.

(Examples 5 to 7) The dyes were the same as in Example 1 except that the dye having the structure shown in FIG. 2 was used. In the following embodiments, when the same parts and the same conditions as those of the first embodiment are used, the different parts will be described without particular description.

Example 8 When fabricating a dense portion 8 of an n-type semiconductor electrode, this glass substrate 1 was heat-treated at 450 ° C. for 3 hours.

(Example 9) When forming the dense portion 8 of the n-type semiconductor electrode, this glass substrate 1 was heat-treated at 430 ° C for 3 hours.

Example 10 When forming a dense portion of an n-type semiconductor electrode, this glass substrate was heat-treated at 410 ° C. for 3 hours.

(Example 11) When forming a dense portion of an n-type semiconductor electrode, this glass substrate was heat-treated at 400 ° C for 3 hours.

(Example 12) A solid material having a hole transporting property was used as a charge transporting material. A glass substrate on which a counter electrode is formed with an n-type semiconductor electrode on which a Ru complex is adsorbed, a solid carrier transporting material (solid charge transporting layer) as shown in FIG. 3, a spherical glass spacer having a diameter of 8 mm, and a sealing material inside the vacuum heating device. The carrier transport material was melted by heating to above the melting point of the solid carrier transport material while depressurizing, and pressed to achieve good bonding with the titanium oxide electrode, followed by cooling to produce a photovoltaic device. .

Example 13 A charge transporting material was a pseudo solid material having ion transportability. 1-methyl-liquid at room temperature
A cetylpyridinium salt having iodine ion (I-) as a counter anion was dissolved together with iodine in 3-ethylimidazolium triflate molten salt, and polyethylene glycol-diacrylate was further dissolved to form a charge transport layer. This charge transport layer is placed on the above-mentioned dye-adsorbed titanium oxide together with a polyethylene spacer having a diameter of 7 mm, a counter electrode and a glass substrate are stacked, and heated while deaerated in a vacuum vessel to lower the viscosity of the molten salt and oxidize it. The titanium electrode was impregnated. After impregnation, the molten salt was gelled by irradiating ultraviolet rays to obtain a photovoltaic device.

Table 1 shows conditions and evaluation results of Examples 2 to 11. Portions not described in the table are the same as in the first embodiment. (Comparative Examples 1 to 3) Tables 3 and 4 show conditions and evaluation results of Comparative Examples 1 to 3. Parts not described in the table are the same as in the example.

[0049]

[Table 3]

[0050]

[Table 4]

(Comparative Example 4) When forming a dense portion of an n-type semiconductor electrode, this glass substrate was heat-treated at 150 ° C for 3 hours. Tables 3 and 4 show the conditions and evaluation results up to Comparative Example 4. Parts not described in the table are the same as in the example.

[0052]

According to the above structure, a short circuit of the electric circuit between the charge transport layer and the transparent electrode is prevented, and separation between the transparent conductive film and the n-type semiconductor electrode is prevented to improve long-term reliability. A sensitive solar power generation element can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross section of a photoelectric conversion element of the present invention.

FIG. 2 is a structural diagram of a dye used in Examples 5, 6, and 7 of the present invention.

FIG. 3 is a diagram showing a solid charge transport layer used in Example 12 of the present invention.

[Explanation of symbols]

 1. Substrate 2. 2. Ion diffusion prevention film Transparent conductive film 4. 4. n-type semiconductor electrode (porous portion) Complex dye 6. Charge transport layer 7. Sealed part 8. n-type semiconductor electrode (dense part)

Continued on the front page (72) Inventor Maki Yonezu 1st address, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term (reference) 5F051 AA14 5H032 AA06 AS16 EE02 EE07 EE16 EE18 HH02 HH04

Claims (6)

[Claims] A first substrate having a light receiving surface;
A transparent conductive film formed on the surface of the substrate facing the light receiving surface, an n-type semiconductor electrode formed on the surface of the transparent conductive film and adsorbing a dye, and formed adjacent to the n-type semiconductor electrode. A photosensitized solar power generation device comprising: a charge transport layer; and a second substrate having a conductive film on a surface formed on the side facing the first substrate and with the charge transport layer interposed therebetween. n-type semiconductor electrode has a thickness of 0.01 μm or more and 0.6 μm
A photosensitized photovoltaic device having the following laminated structure of a dense portion and a porous portion. 2. The method according to claim 1, wherein a relative density of the dense portion is 90% or more.
2. The photosensitized solar power generation element according to claim 1, wherein the content is not more than 00%. 3. The photosensitized photovoltaic power generation device according to claim 1, wherein the pores in the dense portion are closed pores. 4. The photosensitized solar power generation device according to claim 1, further comprising an ion diffusion preventing film between the light receiving surface and the transparent conductive film. 5. The photosensitized solar power generation device according to claim 6, wherein said ion diffusion preventing film is a silica film. 6. The photosensitized solar power generation device according to claim 1, wherein the unevenness on the surface of the dense portion is 90 nm or less.