JP2002280084A - Photoelectric conversion device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transfer and move an electron and a hole smoothly. SOLUTION: This photoelectric conversion device has at least an electron receive type charge transportation layer 11, an electron providing type charge transportation layer 12, and a light absorption layer 16 provided between these charge transportation layers. The electron receive type charge transportation layer forms a needle crystal 17, and particlelike tin oxide 18 is formed on the needlelike crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device and a method of manufacturing the same, and more particularly, to an electron-accepting type charge transport layer.
The present invention relates to a photoelectric conversion device having at least an electron donating type charge transport layer and a light absorbing layer existing between these charge transport layers, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a method of converting light energy into electric energy, a solar cell using a semiconductor junction such as silicon or gallium-arsenic is generally used. Above all, a single-crystal silicon solar cell and a polycrystalline silicon solar cell using a pn junction of a semiconductor, and an amorphous silicon solar cell using a pin junction are well known, and their practical use is progressing. However, silicon solar cells are expensive to manufacture and consume a large amount of energy in the manufacturing itself. Therefore, long-term use is required to recover introduction costs and consumed energy. It is mainly at this cost that the bottleneck of the current spread is.

On the other hand, in recent years, research on practical use of CdTe, CuIn (Ga) Se, and the like as second-generation thin-film solar cells has been progressing, but these materials have raised environmental and resource problems. .

As a method other than the above-mentioned semiconductor bonding, a wet solar cell utilizing a photoelectrochemical reaction occurring at an interface between a semiconductor and an electrolyte solution has been reported. Metal oxide semiconductors such as titanium oxide and tin oxide used in this wet solar cell can be manufactured at low cost as compared with silicon and gallium-arsenic used in a dry solar cell. Since it is excellent in both photoelectric conversion characteristics and stability, it is expected as a future energy conversion material. However, a stable optical semiconductor such as titanium oxide has a wide band gap of 3 eV or more.
Only ultraviolet light, which is about 4% of sunlight, could be used, and the conversion efficiency was not sufficiently high.

Accordingly, a photochemical cell (dye-sensitized solar cell) in which a dye is adsorbed on the surface of the optical semiconductor has been studied. In the early days, semiconductor single-crystal electrodes were used. The electrodes include titanium oxide, zinc oxide, cadmium sulfide,
And tin oxide. However, single-crystal electrodes have a low efficiency because of a small amount of dye adsorbed and are expensive, and attempts have been made to make the semiconductor electrodes porous. Tsubomura et al. Reported that dyes were adsorbed on a semiconductor electrode composed of porous zinc oxide with sintered fine particles to improve efficiency (NATURE, 261 (1976))
p402).

Have reported that a dye and a semiconductor electrode have been further improved to obtain a performance comparable to that of a silicon solar cell (J. Am. Chem. Soc. 115 (1993) 638).
2, U.S. Pat. No. 5,350,644). Here, a ruthenium-based dye is used as the dye, and anatase-type porous titanium oxide (TiO ₂ ) is used as the semiconductor electrode.

FIG. 4 is a schematic sectional view showing a schematic structure of a photochemical battery (hereinafter referred to as a Graetzel type cell) using a Graetzel type dye-sensitized semiconductor electrode.

In FIG. 4, reference numerals 44a and 44b denote glass substrates; 45, a transparent electrode (anode) formed on the surface of the glass substrate 44a; 41, an anatase-type porous titanium oxide layer; It is made of a porous bonded body. Reference numeral 42 denotes a dye bonded to the surface of the titanium oxide fine particles, which functions as a light absorbing layer. 43 is an electrolytic solution, and 46 is a transparent electrode (cathode) formed on the surface of the glass substrate 44b.

Next, a method of manufacturing a Graetzel type cell will be described with reference to FIG.

First, a glass substrate 44 provided with a transparent electrode 45
A film of anatase type TiO ₂ fine particles 41 is formed on a.
Although there are various production methods, generally, a paste in which anatase-type TiO ₂ fine particles having a fine particle diameter of about 20 nm are dispersed is applied on an electrode, fired at 350 to 500 ° C., and baked at about 10 μm in thickness. Form a TiO ₂ fine particle film. At this time, the fine particles are appropriately bonded to each other, and the porosity is about 50% and the lathness factor (substantial surface area /
A film having a structure with an apparent surface area of about 1000 is obtained.

Next, a dye is adsorbed on the electrode with fine particles. Various substances have been studied for the dye, but generally a Ru complex or the like is used. When the electrode is immersed in a solution in which the dye is dissolved and dried, the light absorbing layer 42 is bonded to the surface of the TiO ₂ fine particles. In this solvent, ethanol or acetonitrile, which dissolves the dye well and does not inhibit the adsorption of the dye to the electrode and is electrochemically inactive even if it remains on the electrode surface, is used.

Next, a glass substrate 44b also having a transparent electrode 46 as a counter electrode is prepared, and an ultra-thin film such as platinum or graphite is formed on the surface. This thin film acts as a catalyst when transferring charges in redox (redox).

When the electrolyte 43 is held between the two electrodes and overlapped, a Graetzel type cell is completed. As a solvent for the electrolytic solution, acetonitrile, ethylene carbonate, or the like that is electrochemically inert and can dissolve a sufficient amount of the electrolyte is used. As the electrolyte, a stable ion redox pair such as I ⁻ / I ₃ ⁻ or Br ⁻ / Br ₃ ⁻ is used. For example, I ^- / I ₃ ^- mixing the ammonium salt and iodine iodine when making pairs.

Thereafter, it is preferable to seal the cells with an adhesive or the like in order to impart durability.

Next, the operating principle of the Graetzel type cell will be described. Light is incident on this Graetzel type cell from the left side of FIG. Then, the electrons in the dye constituting the light absorbing layer 42 are excited by the incident light, and move to the conduction band of titanium oxide. The dye that has lost electrons and is in an oxidized state quickly receives electrons from iodine ions in the electrolyte 43 and is reduced to return to the original state. The electrons injected into the titanium oxide layer 41 move between the titanium oxide fine particles by a mechanism such as hopping conduction and reach the anode 45. Further, iodine ions which have been converted to an oxidized state (I ₃ ⁻ ) by supplying electrons to the dye receive electrons from the cathode 46 and are reduced to return to the original state (I ⁻ ).

As can be inferred from the above operating principle, in order for electrons and holes generated by the dye to efficiently separate and move, the energy level of the electrons in the excited state of the dye is TiO.
_It must be higher than the conduction band of ₂ , and the energy level of the holes in the dye must be lower than the redox level.

In recent years, porous semiconductor electrodes in which the Graetzel type cell has been improved in various forms have been reported. For example, there is JP-A-9-237641 in which a Graetzel type cell is manufactured using niobium oxide fine particles. Furthermore, it has been reported by Tennakone et al. That a highly efficient cell was produced by mixing zinc oxide fine particles and tin oxide fine particles (J. Chem. Soc., Chem. Commun., 15 (1999)).

In order for such a Graetzel type cell to replace a silicon solar cell, higher energy conversion efficiency, higher short-circuit current, open-circuit voltage, shape factor, and durability are required.

[0019]

However, the above-described dye-sensitized semiconductor electrode of the prior art is obtained by applying a solution in which fine particles of titania are dispersed on a substrate having a transparent conductive film, followed by drying and sintering at a high temperature. Since the titanium oxide film was used, electron conduction tended to be scattered at the interface between the transparent electrode and the titania fine particles and at the interface between the titanium oxide fine particles. For this reason, the internal resistance generated at the interface between the transparent conductive film and the titanium oxide film and at the interface between the titanium oxide fine particles is increased, and as a result, the photoelectric conversion efficiency is reduced. The same problem occurred when fine particles other than titania were used.

In addition, since the dye-sensitized semiconductor electrode is made of a sintered body of fine particles, it takes time to adsorb the dye to the fine particles near the transparent electrode, and the diffusion of ions in the electrolyte is slow. There was a problem.

Accordingly, an object of the present invention is to provide a method for manufacturing a photoelectric conversion device in which the transfer of electrons is performed smoothly and the conversion efficiency is high.

Another object of the present invention is to provide a method for manufacturing a photoelectric conversion device having a semiconductor electrode in which a light-absorbing layer of a dye or the like or a charge transporting layer of an electrolyte or the like is quickly absorbed and moved.

Another object of the present invention is to provide a method for manufacturing a photoelectric conversion device having a large short-circuit current value.

[0024]

The above objects can be attained by the photoelectric conversion device of the present invention and its manufacturing method.

That is, a photoelectric conversion device having at least an electron-accepting type charge transporting layer, an electron-donating type charge-transporting layer, and a light-absorbing layer present between these charge-transporting layers. Provided is a photoelectric conversion device in which the charge transport layer is formed of acicular crystals having granular tin oxide formed on the surface.

Further, it is preferable that the needle-like crystal is zinc oxide.

The present invention also provides a method for manufacturing a photoelectric conversion device having at least an electron-accepting type charge transport layer, an electron-donating type charge transport layer, and a light absorbing layer existing between these charge transporting layers. There is provided a method for manufacturing a photoelectric conversion device, including a step of forming a crystal and a step of forming granular tin oxide on the needle-like crystal, wherein the method is used as the electron-accepting type charge transport layer.

Further, the tin oxide preferably includes a step of applying a colloidal solution of tin oxide and firing, or a step of applying and firing an alkoxide of tin and firing. Preferably, the crystal has a step of being generated by electrodeposition.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The main feature of the method of manufacturing a photoelectric conversion device according to the present invention is that a needle-like crystal is formed, and a tin oxide-adsorbed crystal in which granular tin oxide is formed on the needle-like crystal is electron-accepting. It is to be used for a type (n-type) charge transport layer. The acicular crystal is, for example, a so-called whisker, and is formed of an acicular single crystal having no defect or an acicular crystal containing a spiral transition or the like.

Further, as shown in FIGS. 7 (a), 7 (b) and 7 (c), the needle-like crystal has a larger number of needle-like crystals than one point including a tetrapod-like shape, or has a dendritic shape. Included are those that have been grown and those that have grown in a polygonal shape.

The needle-shaped crystal includes a cylinder, a cone, a cone having a flat tip, a column having a sharp tip, and a flat tip. In addition, triangular pyramids, square pyramids,
Hexagonal pyramids, other polygonal pyramids and those with flat tips, and triangular prisms, quadrangular prisms, hexagonal prisms, other polygonal prisms, or triangular prisms, tetragonal prisms, hexagonal prisms with sharpened tips,
Other polygonal columns and those having a flat tip are also included, and further, these broken line structures are also included.

The granular tin oxide includes all of tin oxide itself which is applied and bonded, and tin oxide which is formed by oxidizing tin and a compound containing tin on a needle crystal.

FIG. 5 is a diagram showing a specific example of the structure of the tin oxide adsorption crystal. Compared to the Graetzel type cell shown in FIG. 4, the influence of the grain boundary is almost eliminated, the movement of electrons and holes can be facilitated, and the influence of the grain boundary is small because the granular tin oxide 18 is adsorbed. The roughness factor can be improved as it is. Furthermore, irradiation light can reach a wide range regardless of which surface is irradiated with light. Therefore, many electrons can be transferred, and a cell of a photoelectric conversion device with high short-circuit current and high conversion efficiency can be manufactured. In order to explain the effect of this tin oxide adsorption electrode,
The present invention will be described by comparing the present invention with a conventional Graetzel type cell.

<Configuration of Photoelectric Conversion Device of the Present Invention>
First, the configuration of the present invention will be described.

In a dye-sensitized cell such as the above-described Graetzel type cell, the light absorption of one dye layer is not sufficient, so that the surface area is increased to increase the substantial light absorption. The present invention is not limited to dye sensitization but can be widely used in general for photoelectric conversion devices having a structure in which the surface area is increased due to insufficient light absorption. As a method for enlarging the surface, it is simple to disperse and join the fine particles as in the Graetzel type cell, but there is a problem that the transfer of electrons is not sufficiently efficient. For example, in the above Graetzel type cell, comparing the case where light is incident from the anode transparent electrode 45 side having the titanium oxide semiconductor layer 41 and the case where light is incident from the cathode transparent electrode 46 side, the former is more efficient in photoelectric conversion. Is often good. This is not only the difference in the amount of light absorbed by the dye, but also the electrons excited by the light absorption move through the titanium oxide semiconductor layer 41 to form the anode transparent electrode 45.
Implies that the probability of reaching the value decreases as the photoexcitation position moves away from the transparent electrode. That is, this suggests that a Graetzel type cell having many crystal grain boundaries has not achieved sufficiently efficient electron transfer.

FIGS. 1 (a), 1 (b) and 1 (c) are views showing a configuration example of the photoelectric conversion device of the present invention. FIG. 1A is a schematic configuration diagram, FIG. 1B is a diagram showing a needle crystal, and FIG.
(C) is a view showing a state in which granular tin oxide is formed on the needle-like crystals.

In FIG. 1, reference numeral 10 denotes a substrate with electrodes;
Denotes a semiconductor mixed crystal layer modified with an absorption layer, 12 denotes a charge transport layer, 1
3 is a substrate with electrodes. The substrate with electrodes 10 is composed of, for example, a glass substrate 14 on which a transparent electrode layer 15 is provided, and the absorption-layer-modified semiconductor mixed crystal layer 11 is formed on the surface of a granular tin oxide 18 adsorbed around a semiconductor needle crystal 17 and the surface thereof. Light absorbing layer 16. The granular tin oxide 18 adsorbed around the semiconductor needle crystal 17 becomes one charge transport layer,
A light absorbing layer 16 is provided between the charge transport layer and the charge transport layer 12.
Will be provided.

Comparing the tin oxide adsorption layer and the fine particle crystal layer according to the present invention, the tin oxide adsorption layer has a smaller probability that electrons or holes generated by photoexcitation are scattered by grain boundaries before moving to the collector. Become. That is, FIG.
In the case where one end of all tin oxide adsorbed crystals is joined to the electrode as shown in Fig. 7, the effect of grain boundaries on the movement of electrons or holes is almost smaller than that of the Graetzel type cell. Since the granular tin oxide 18 is adsorbed, the roughness factor can be increased while the influence of the grain boundary is small.

In the photoelectric conversion device according to the present invention, the tin oxide-adsorbed crystal is an n-type wide gap semiconductor. In the case of such a semiconductor, an electron donating type charge transporting layer 12 such as a p-type wide gap semiconductor, an electrolyte containing a redox pair, or a polymer conductor is sandwiched by a light absorbing layer 16 such as a dye.
is necessary.

The light irradiation surface is determined by which surface is to be used with the transparent electrode. The configuration shown in FIG. 2A is an example in which a transparent electrode is used on the semiconductor crystal layer side similarly to the Graetzel type cell. The configuration shown in FIG. 2B is the opposite configuration, and either configuration may be used as long as the absorption and reflection of irradiation light to the light absorption layer is small. Also, as shown in FIG.
There is also a configuration that can be used by light irradiation from either surface. These configurations depend on the method for producing the tin oxide-adsorbed crystal and the method and composition of the charge transport layer to be combined. For example, when a tin oxide-adsorbed crystal is formed on a Pt film, light cannot be irradiated from the tin oxide-adsorbed crystal surface. In addition, when a tin oxide-adsorbed crystal surface is prepared by a low-temperature process such as firing of tin oxide crystal powder and needle-shaped crystal powder, the transparent electrode layer can be prepared without deteriorating, so that either surface can be used as a light irradiation surface. it can.

Next, the tin oxide adsorption crystal according to the present invention will be described.

<Regarding tin oxide-adsorbed crystals>
In cells using a light-absorbing layer with low absorption efficiency per layer, such as a mold cell, the roughness factor is increased by using a fine-particle film having a large porosity in order to increase the surface area. Even if a crystal is used, the roughness factor can be increased if the aspect ratio of the needle-shaped crystal is large, and by adsorbing granular tin oxide on the needle-shaped crystal, efficient electron transfer with few crystal grain boundaries can be achieved. Can be.

The cross section of the needle-shaped crystal depends on the crystal.
Triangles, quadrangles, hexagons, and other polygons, some of which are almost circular. The sides do not necessarily have to be equal, and may have different lengths. As described above, the needle-shaped crystals include those having a sharp tip as well as those having a sharp tip.

Although it depends on the light absorptivity, the aspect ratio of at least the acicular crystal is preferably 5 or more, preferably 10 or more, and more preferably 100 or more. Further, the minimum length passing through the center of gravity of the transversely cut surface of the needle-shaped crystal is also 500 nm or less, preferably 100 nm or less, and more preferably 50 nm or less. Further, it is preferable to grow the needle-like crystal with c-axis orientation in order to enhance the crystallinity, in order to improve the electron transfer efficiency. Here, the aspect ratio refers to the ratio of the length to the diameter when the horizontal cut surface of the needle-shaped crystal is a circle or a shape close to a circle, and when the horizontal cut surface of the needle-shaped crystal is a square such as a hexagon. It refers to the ratio of the length to the minimum length passing through the center of gravity of the cut surface. When the needle-shaped crystal has a conical or pyramidal shape, the above-mentioned cross section indicates the bottom surface of the needle-shaped crystal having the largest cross-sectional area.

Further, the needle-shaped crystal preferably has a large energy gap, and more specifically, has a energy gap of 3 eV or more. Electron accepting type (n
Examples of the (type) crystal include TiO ₂ , ZnO ₂ and SnO ₂
And the like.

When such a tin oxide-adsorbed crystal is produced, the needle-like crystal is grown linearly from the substrate rather than overlapping with the substrate 14 as shown in FIG.
3 (b), or in a state where the ends of the needle-shaped crystals are bonded to the transparent electrode 15 and formed in the direction perpendicular to the substrate 14, as shown in FIG. preferable. Further, an angle 6 between the axial direction of the needle-shaped crystal and the main surface of the substrate.
It is preferably at least 0 °, more preferably at least 80 °. The form of the needle-like crystals is preferably linear.

Also, as shown in FIG. 1C and FIG.
In tin-adsorbed crystals, powdered tin oxide 18 is coated with granular tin oxide
Method of adsorbing and forming tin and tin on needle-shaped crystals
There is a method of producing the compound by oxidizing the compound. This
When the diameter of the powdery tin oxide 18 is 100 nm or less,
If so, fine particles of 20 nm or less are preferable. Also, powdery oxidation
The tin 18 is preferably present on the surface of the needle crystal. Sa
Furthermore, a colloidal solution of tin oxide was prepared and the colloid
The solution is applied and fired to produce tin oxide adsorbed crystals.
Is preferred. Also, the alkoxide of tin oxide is dissolved in a solvent.
Then, the solution is applied and baked to absorb tin oxide.
There is a method for producing a deposited crystal. In particular, C _Two~ C_FourLow tin
(IV) alkoxides of tetraethoxytin (IV),
Tora-i-propoxytin (IV), tetra-n-butoxy
It is preferable to use tin (IV) dissolved in an organic solvent.
No.

As a result, a tin oxide-adsorbed crystal having a large roughness factor can be produced even when the surface area of the needle-shaped crystal is insufficient, and a tin oxide-adsorbed crystal having a small influence of a grain boundary on the movement of electrons or holes. Can be produced.

<Regarding Preparation of Electrolytic and Electroless Needle-Shaped Crystal Films> The semiconductor needle-shaped crystal layer 17 may be manufactured by electrodeposition. Broadly speaking, there are two types of electrodeposition, one of which is a manufacturing method using an electrolytic electrodeposition method. The other is a manufacturing method by an electroless electrodeposition method. Each manufacturing method will be described.

FIG. 8 is an explanatory view of a manufacturing method when the semiconductor needle crystal layer shown in FIG. 1B is manufactured by the electrolytic electrodeposition method. As shown in FIG.
, A beaker 66 containing an electrolyte 67 is placed. When the counter electrode 82, the reference electrode 81, and the working electrode 83 are placed in the beaker 66 and electrolyzed, needle crystals are formed on the working electrode 83. At this time, for the working electrode 83, the substrate 10 with electrodes may be used directly, or an insulating part may be formed using a jig or the like, and needle crystals may be formed on the substrate 10 with electrodes only in a desired range.

As the electrolytic solution 67, an electrolytic solvent such as acetonitrile, IPA or water can be used. The type of solute of the electrolytic solution 67, the solute concentration, the concentration of active gas such as oxygen in the solution,
The temperature of the electrolytic solution, the presence or absence of a reaction accelerator such as dextrin, and the concentration,
Depending on the electrolysis potential value, electrolysis current value, electrolysis time, etc.
The shape of the needle crystal can be changed. Further, the needle-shaped crystals may be formed in, for example, a dark room, and the shape can be changed by causing convection by stirring the electrolytic solution 67 or the like.

Although it differs somewhat depending on the material of the substrate with electrodes 10 and the like, it is generally preferable to wash the transparent electrode layer 15 and the like in advance using IPA and acetone for surface cleaning. It is important to carry out anodic treatment for dissolving a very small amount.

FIG. 6 is an explanatory diagram of a manufacturing method when the semiconductor needle-like crystal 17 shown in FIG. 1 is manufactured by an electroless electrodeposition method. As shown in FIG. 6, the electrode-attached substrate 10 (sample 64) is immersed in an electrolytic solution 67, and a light source 63 irradiates the electrode-attached substrate 10 with light through a quartz tube 65, thereby forming a needle-like shape on the electrode-attached substrate 10. Form crystals. As in the case of the above-mentioned production by the electrolytic electrodeposition method, the shape of the needle crystal can be changed by changing various conditions at the time of forming the needle crystal. Further, it is effective to attach Pd or Ag as a catalyst to the transparent electrode layer 15 or the like during electroless.

<About the light absorbing layer> The photoelectric conversion device of the present invention
Various semiconductors and dyes can be used as the light absorbing layer
It is. As a semiconductor, an i-type light absorption coefficient is large.
Rufus semiconductors and direct transition semiconductors are preferred. With dye
A metal complex dye and / or a polymethine dye,
Perylene dye, Rose Bengal, Eosin Y, Mercu
Lochrome, Santalin dye, cyanine (Cy)
Anin) Organic dyes such as dyes and natural dyes are preferred. The color
Element has an appropriate bonding group to the surface of the semiconductor particles.
Is preferred. Preferred linking groups include COOH
Group, cyano group, PO_ThreeH_Two Group, or oxime, dioxy
, Hydroxyquinoline, salicylate and alpha ketoe
Chelating groups having π conductivity such as nolate
Can be Among them, COOH group, PO_ThreeH _TwoGroups are particularly preferred.
When the dye used in the present invention is a metal complex dye, ruthenium
Complex dye ｛Ru (dcbpy)_Two(SCN)_Two, (Dcbpy = 2,2-bipyridi
ne-4,4'-dicarboxylic acid), etc.
It is important that the compound / reductant is stable. Also, light absorption
The potential of the excited electrons in the absorption layer, that is, the
Charge (LUMO potential of the dye) and the conductive charge position in the semiconductor
Electron accepting potential of the accepting charge transport layer (conduction band of n-type semiconductor)
Potential) and generated by light excitation in the light absorbing layer
Hole potential is the electron donating charge of the electron donating charge transfer layer.
Potential (valence charge potential of p-type semiconductor, potential of redox couple)
(Such as the Char potential). Light absorbing layer
Low recombination probability of excited electron-hole in the vicinity
Is also important in increasing photoelectric conversion efficiency.
You.

<Regarding Electron Donating Type Charge Transfer Layer> When an n-type tin oxide adsorption crystal is used, it is necessary to form a hole transport layer with a light absorption layer interposed therebetween. For this hole transport layer, a redox system can be used as in a wet solar cell. Even when redox is used, not only a simple solution system but also a method of using carbon powder as a holding material or gelling an electrolyte is available. There is also a method using a molten salt or an ion conductive polymer. Further, as a method of transporting electrons (holes), there are electropolymerized organic polymers, CuI, CuSCN, Ni
A p-type semiconductor such as O can also be used.

Since the transport layer needs to penetrate between the powdery tin oxide crystals, a permeation method that can be used for a liquid or a polymer, an electrodeposition method that can be used for a solid transport layer, a CVD method, and the like are suitable. ing.

<Electrode> An electrode is provided so as to be adjacent to the tin oxide adsorption crystal layer and the electron donating type charge transporting layer. The electrodes may be provided on the outer front surface of these layers or may be provided partially. When the electron donating type charge transporting layer is not solid, it is better to provide an electrode on the front surface from the viewpoint of holding the electron donating type charge transporting layer. It is preferable to provide a catalyst such as Pt or C on the surface of the electrode adjacent to the electron donating type charge transport layer, for example, in order to efficiently reduce the redox couple.

As the electrode on the light incident side, a transparent electrode made of indium-tin composite oxide, tin oxide doped with fluorine or the like is preferably used. If the resistance of the layer (electron donating type charge transport layer or tin oxide adsorption crystal layer) in contact with the electrode on the light incident side is sufficiently low, a partial electrode such as a finger electrode is provided as the electrode on the light incident side. Is also possible.

The electrodes which are not on the light incident side are Cu, A
A metal electrode made of g, Al, or the like is preferably used.

<Regarding the Substrate> The material and thickness of the substrate can be appropriately designed according to the durability required for the photovoltaic device. As the substrate on the light incident side, a glass substrate, a plastic substrate, or the like is suitably used as long as it is translucent. As a substrate that does not become the light incident side, a metal substrate, a ceramic substrate, or the like can be used as appropriate. It is preferable to provide an anti-reflection film made of SiO ₂ or the like on the surface of the substrate on the light incident side.

It should be noted that the above-mentioned electrode may also serve as a substrate, so that a substrate separate from the electrode may not be provided.

<About Sealing> Although not shown, it is preferable that the photoelectric conversion device of the present invention seal at least a portion other than the substrate from the viewpoint of improving weather resistance. An adhesive or a resin can be used as the sealing material. When the light incident side is sealed, the sealing material is preferably light-transmitting.

[0063]

The present invention will be further described below with reference to examples.

(Example 1) This example is an example in which a semiconductor needle crystal is formed from a substrate electrode by electrolytic electrodeposition, and then a tin compound is applied and baked, and will be described with reference to FIG.

A conductive glass substrate (F-doped SnO ₂ , 1
0Ω / □), and use this substrate as a working electrode for 2 mm
l / L (mmol / L) zinc nitrate aqueous solution,
A potential of -1.2 V was applied for 5000 seconds. After the electrolysis, ZnO needle-like crystals 17 were placed on the substrate surface from
It grew as shown in (b). The diameter of the ZnO needle crystal was 40 to 50 nm, and the length was 20 to 30 times the length. Then, in order to adsorb tin oxide on the needle crystals, first, isopropoxide Sn (IV) was dissolved in an isopropanol solution, and the needle crystal electrodes were immersed in the solution. Thereafter, by baking at 550 ° C. for 1 hour while flowing oxygen at 1.67 × 10 ⁻³ L / s (liter / second), a tin oxide adsorption electrode as shown in FIG. 1C was produced. The dye is Ru, a Ru complex reported by Graetzel et al.
((dcbpy) (COOH) ₂ ) ₂ (SCN) ₂ was used. The dye was dissolved in distilled ethanol, and a ZnO electrode was immersed in the ethanol for 24 hours to allow the dye to be adsorbed on the electrode, and then taken out and dried at 80 ° C. In addition, conductive glass (F-doped SnO ₂ , 10Ω /
□) A counter electrode on which platinum was formed by sputtering to a thickness of 10 nm was used, and a redox pair of I ⁻ / I ₃ ⁻ was used. The solute is tetrapropylammonium iodide
iodide) (0.46mol / L) and iodine (0.06m
ol / L) and the solvent is ethylene carbonate (ethylene c
arbonate) (80 vol%) and acetonitrile (aceton)
Itrile) (20 vol%) was used. This mixed solution was dropped onto the tin oxide-adsorbed crystal, and was sandwiched between counter electrodes to form a cell.

As a comparative example, a cell was assembled in the same manner using a heat-treated ZnO powder having a particle size of 30 nm as a main component.

Then, a xenon lamp light of 500 W equipped with an ultraviolet cut filter was irradiated from the counter electrode side.
Then, the value of the photocurrent due to the photoelectric conversion reaction generated at this time was measured. As a result of the measurement, both the short-circuit current and the photoelectric conversion efficiency of the cell according to the present example were about 10%, which were higher than the comparative example. This is considered to be because the internal resistance of the electron-accepting charge transport layer was reduced by using the tin oxide adsorption electrode.

Example 2 In this example, a needle-like zinc oxide slurry was applied to an electrode and baked to produce a semiconductor needle-like crystal from a substrate, and then tin oxide was applied and baked. This will be described with reference to FIG.

A conductive glass substrate (F-doped SnO ₂ , 1
0 Ω / □), and using this substrate as a working electrode, 3 g of acicular zinc oxide crystals were mixed with 5 mL of water (milliliter), 0.2 mL of acetylacetone, and 0.2 mL of Triton-X (registered trademark: Union Carbide Co.). The mixed and slurried solution was applied on a substrate, and oxygen was added at 1.67 × 10 ⁻³ L.
Calcination was performed at 550 ° C. for 1 hour while flowing at a flow rate of / s. The substrate was immersed in a tin oxide colloid solution, and baked at 550 ° C. for 1 hour while flowing oxygen at 1.67 × 10 ⁻³ L / s. As shown in FIG. 1
No. 8 was produced. Commercially available mercurochrome was used as the dye. The dye was dissolved in distilled ethanol, and a ZnO electrode was immersed in the ethanol for 24 hours to allow the dye to be adsorbed on the electrode, and then taken out and dried at 80 ° C. Then, a counter electrode in which platinum was sputtered to a thickness of 10 nm on conductive glass (F-doped SnO ₂ , 10Ω / □) was used, and the redox pair was I ⁻ / I ₃ ^−.
Was used. The solutes were 0.05 mol / L I ₂ (iodine) and 0.1
mol / L LiI (lithium iodide) and 0.6 mol / L
DMPI (Im) (1,2-dimethyl-3-propylimidazolium iodide) and 0.5 mol / L TBP (4-tert-butylpyridine), and MAN (MeOAN) (methoxyacetonitrile) as a solvent. This mixed solution was dropped onto the tin oxide-adsorbed crystal, and was sandwiched between counter electrodes to form a cell.

Further, as a comparative example, a cell was similarly assembled using a heat-treated ZnO powder having a particle size of about 30 nm as a main component.

Then, in the same manner as in Example 1, a 500 W xenon lamp light equipped with an ultraviolet cut filter was irradiated from the counter electrode side. Then, the value of the photocurrent due to the photoelectric conversion reaction generated at this time was measured. As a result of the measurement, the short-circuit current and the photoelectric conversion efficiency of the cell of the present invention were about 6% larger than those of the comparative example. This is considered to be because the internal resistance of the electron-accepting charge transport layer was reduced by using the tin oxide adsorption electrode.

[0072]

As described above, according to the present invention, it is possible to provide a photoelectric conversion device in which transfer and movement of electrons and holes are performed smoothly, internal resistance and recombination probability are low, and conversion efficiency is high. it can.

Further, according to the present invention, it is possible to provide a photoelectric conversion device having a semiconductor electrode in which a light absorbing layer of a dye or the like or a charge transporting layer of an electrolyte or the like is quickly absorbed and moved.

Further, according to the present invention, a photoelectric conversion device having a large short-circuit current can be provided.

Further, according to the present invention, a method for manufacturing a photoelectric conversion device having the above characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a photoelectric conversion device of the present invention.

FIG. 2 is a cross-sectional view showing a configuration example of light irradiation, a transparent electrode, and a tin oxide adsorption crystal layer of the present invention.

FIG. 3 is a cross-sectional view showing a bonding state of a tin oxide adsorption crystal of the present invention.

FIG. 4 is a cross-sectional view showing a conventional Graetzel cell.

FIG. 5 is a sectional view showing a cell using a tin oxide adsorption crystal.

FIG. 6 is a diagram of an apparatus for electroless electrodeposition.

FIG. 7 is a view showing a structure of a needle-like crystal.

FIG. 8 is a diagram of an apparatus for electrolytic electrodeposition.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 Substrate with electrode 11 Absorbing layer-modified semiconductor acicular crystal layer 12 Charge transport layer 13 Substrate with electrode 14 Glass 15 Transparent electrode layer 16 Light absorbing layer 17 Semiconductor acicular crystal 18 Granular tin oxide crystal 41 Anatase TiO ₂ fine particles 42 Light absorption Layer 43 Electrolyte 44 Glass 45 Transparent electrode layer (Anode) 46 Transparent electrode layer (Cathode) 61 Mantle heater 62 Fixed base 63 Light source 64 Sample 65 Quartz tube 66 Beaker 67 Electrolyte 81 Reference pole 82 Counter pole 83 Sample (Reference pole)

Continued on the front page F term (reference) 5F051 AA14 FA02 FA03 FA08 GA03 GA06 5H032 AA06 AS16 BB02 BB05 CC11 CC16 EE02

Claims (6)

[Claims] 1. A photoelectric conversion device comprising at least an electron-accepting type charge transporting layer, an electron-donating type charge-transporting layer, and a light-absorbing layer existing between these charge-transporting layers, A photoelectric conversion device in which the charge transport layer is formed of needle-like crystals having granular tin oxide formed on the surface. 2. The photoelectric conversion device according to claim 1, wherein the needle-like crystal is zinc oxide. 3. A method for producing a photoelectric conversion device comprising at least an electron-accepting type charge transporting layer, an electron-donating type charge transporting layer, and a light absorbing layer existing between these charge transporting layers. Generating a crystal, comprising the step of forming granular tin oxide on the needle-like crystal, characterized in that the needle-like crystal formed the granular tin oxide is the electron-accepting type charge transport layer. Of manufacturing a photoelectric conversion device. 4. The method according to claim 3, wherein the particulate tin oxide is produced by applying a colloidal solution of tin oxide and baking it. 5. The method according to claim 3, wherein the particulate tin oxide is produced by applying and firing an alkoxide of tin. 6. The method according to claim 3, wherein the needle-like crystal is generated by electrodeposition.