JP2003282164A - Photoelectric converter and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a photoelectric converter manufacturable at low cost and having high transfer efficiency, in particular, being suitable for a solar battery and to improve transmission efficiency and recombination loss of a semiconductor minute particle layer in a Glotzl type solar battery. <P>SOLUTION: In the photoelectric converter having an n-type charge transport layer, a light absorption layer 16, and a p-type charge transport layer 12 between a pair of substrates, the n-type charge transport layer is composed of zinc oxide comblike crystals composed of at least a trunk part 41 and a plurality of branch parts 42 derived from the trunk part. Preferably, a diameter of the branch part is 200 nm or less. Moreover, the n-type charge transport layer is formed by heating zinc or zinc oxide or a mixture of zinc and zinc oxide to gasify it and make the zinc oxide comblike crystals grow. <P>COPYRIGHT: (C)2004,JPO

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 at least an electron-accepting charge transport layer, an electron-donating charge transport layer, and a light absorption layer existing between these charge transport layers. The present invention relates to a photoelectric conversion device and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as a method for converting light energy into electric energy, a solar cell using a semiconductor junction such as silicon or gallium-arsenide has been generally used. Among them, single crystal silicon solar cells and polycrystalline silicon solar cells using pn junctions of semiconductors, and amorphous silicon solar cells using pin junctions are well known and are being put to practical use. However, since the silicon solar cell has a high manufacturing cost and consumes a large amount of energy in the manufacturing itself, it is necessary to use it for a long period of time to recover the introduction cost and the consumed energy. It is this cost that is the main bottleneck of current diffusion.

On the other hand, recently, as a second-generation thin film solar cell,
Although researches for practical use of CdTe and CuIn (Ga) Se are progressing, environmental problems and resource problems have been raised in these material systems.

As a method other than the above-mentioned semiconductor bonding, a wet solar cell utilizing a photoelectrochemical reaction occurring at the 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 type solar cell can be manufactured at a low cost compared with silicon, gallium-arsenic and the like used in dry type solar cells, and in particular, they can be oxidized. Since titanium is excellent in both photoelectric conversion characteristics and stability, it is expected as a future energy conversion material.

However, since stable optical semiconductors such as titanium oxide have a wide band gap of 3 eV or more, only ultraviolet light, which is about 4% of sunlight, can be used, and it cannot be said that the conversion efficiency is sufficiently high. .

Therefore, photochemical cells (dye-sensitized solar cells) in which a dye is adsorbed on the surface of an optical semiconductor have been studied. In the early days, a semiconductor single crystal electrode was used, and examples of this electrode include titanium oxide, zinc oxide, cadmium sulfide, and tin oxide. However, since the single crystal electrode has a small amount of adsorbed dye, the efficiency is low and the cost is high, and attempts have been made to make the semiconductor electrode porous.

For example, Tsubomura et al. Reported that a dye was adsorbed on a semiconductor electrode made of porous zinc oxide obtained by sintering fine particles to improve the efficiency (NATURE, 261 (1976) p402).
In addition, Graetzel et al. Reported that the dye and the semiconductor electrode were further improved to obtain the performance comparable to that of a silicon solar cell (J. Am. Chem. Soc. 115 (1993) 6382, US Pat. No. 5).
350644). Here, a ruthenium-based dye is used as the dye, and anatase-type porous titanium oxide (TiO ₂ ) is used as the semiconductor electrode.

Further, in recent years, porous semiconductor electrodes in which the Graetzel type cell is improved in various forms have been reported. For example, it was reported by Tennakone et al. That a highly efficient cell was prepared by mixing zinc oxide fine particles and tin oxide fine particles (J. Chem. Soc., Chem. Commun., 15 (1999)).

FIG. 7 is a schematic cross-sectional view showing a schematic structure of a photochemical cell using a Graetzel type dye-sensitized semiconductor electrode (hereinafter referred to as Graetzel type cell in the present specification). In the figure, 64 is a glass substrate, and 65 is a transparent electrode formed on the surface thereof. Further, reference numeral 61 is an anatase type porous titanium oxide layer, which is formed from a porous bonded body in which titanium oxide fine particles are bonded to each other. Reference numeral 62 denotes a pigment bonded to the surface of the titanium oxide fine particles, which acts as a light absorbing layer.

Explain the operating principle of this Graetzel cell
Reveal When light shines from the left side of Fig. 7,
Electrons in the dye that constitutes the absorption layer 62 are excited to cause oxidation of titanium oxide.
Move to Tan's conduction band. Loses electrons and is in oxidation state
The dye rapidly receives an electron from the iodine ion of the electrolytic solution 63.
It is taken back and returned to its original state. Pour into the titanium oxide layer 61
The injected electrons travel through hopping between titanium oxide particles.
It moves by a mechanism such as a guide and reaches the anode 65. Well
In addition, by supplying electrons to the dye, the oxidation state (I₃ ^-) Became yo
Arsenic ions receive electrons from the cathode 66 and are reduced.
The original state (I ^-) Return to.

As can be inferred from the above operating principle, in order for electrons and holes generated in the dye to be efficiently separated and moved, the energy level of electrons in the excited state of the dye needs to be higher than the conduction band of TiO _2. Yes, the energy level of the hole of the dye needs to be lower than the redox level. Like this
In order for Graetzel-type cells to replace silicon solar cells, higher energy conversion efficiency, higher short-circuit current, open circuit voltage, form factor, and durability will be required.

Further, generally, as a means for producing a zinc oxide film, various methods such as a sputtering method, a vapor deposition method, a CVD method and an electrodeposition method can be currently produced. For example, a method capable of uniformly producing film-shaped zinc oxide on a large-area conductive substrate is disclosed in JP-A-8-217443 and JP-A-8-260.
No. 175.

As a means for producing acicular zinc oxide crystals, “J. Crystal Growth, 102, 965, (1990)”, a tetrapod acicular zinc oxide crystal is formed by vapor phase oxidation of metallic Zn. It is reported that it was manufactured at 920 degrees.

Furthermore, "Jpn.J.Appl.Phys., Vol.38 (1999) p.
p.L586 "with a diameter of 1.5 μm using the open-air CVD method
Have reported that needle-shaped crystals of zinc oxide having a length of 100 μm can be produced. Also, "Science, 291, 1947
(2001) ", it is reported that a belt-shaped zinc oxide having orientation is produced by heating zinc oxide as a raw material at 300 torr and 1400 ° C.

Also, Iwanaga et al., "Japan J.Appl.Phys.,"
11 (1972) 121 "and" Metal, 2 (1991) 89 ", using the reaction of ZnS vapor and steam, the manufacturing method in which the trunk grows in the [01-10] direction and the reaction of ZnS vapor and oxygen It has been reported that, using the method, a branch grows in the [0001] direction, a trunk grows in a direction shifted by about 10 ° C from the [1-210] direction, and a branch grows in the [0001] direction.

[0016]

However, the above-mentioned dye-sensitized semiconductor electrode of the prior art is obtained by applying a solution in which fine titania particles are dispersed onto a substrate having a transparent conductive film, followed by drying and high-temperature sintering. Further, 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 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 the interface between the titanium oxide fine particles becomes large, and as a result, the photoelectric conversion efficiency is reduced. This was the same when fine particles other than titania were used.

Further, since the dye-sensitized semiconductor electrode is composed of a sintered body of fine particles, it takes time to adsorb the dye to the fine particles in the vicinity of the transparent electrode, and the diffusion of ions in the electrolytic solution is slow. There were problems such as.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a photoelectric conversion device which can smoothly transfer electrons and has high conversion efficiency, and a method for manufacturing the photoelectric conversion device. is there.

Another object of the present invention is to provide a photoelectric conversion device having a semiconductor electrode in which a light absorption layer of a dye or the like and a charge transport layer of an electrolyte or the like penetrate or move quickly, and a manufacturing method thereof. is there.

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

[0021]

In order to achieve the above-mentioned object, the present invention provides a photoelectric conversion device having an n-type charge transport layer, a light absorption layer, and a p-type charge transport layer between a pair of substrates, The n-type charge transport layer includes a zinc oxide comb crystal having at least a trunk portion and a plurality of branch portions connected to the trunk portion.

The present invention also provides a method for manufacturing a photoelectric conversion device having an n-type charge transport layer, a light absorption layer, and a p-type charge transport layer between a pair of substrates, wherein the n-type charge transport layer is It is characterized in that zinc, zinc oxide, or a mixture of zinc and zinc oxide is heated and vaporized to grow a zinc oxide comb crystal.

Further, according to the present invention, a step of heating a raw material containing at least zinc and evaporating the raw material to form a zinc oxide comb crystal film on the crystal collecting substrate, the zinc oxide on the crystal collecting substrate. A step of scraping off the comb-shaped crystal film and mixing with a predetermined solution, a step of applying the mixture on a cell substrate and baking the cell substrate, and a light absorption layer on the zinc oxide comb-shaped crystal film on the cell substrate. Forming step, forming a p-type charge transport layer on the zinc oxide comb-shaped crystal on which the light absorption layer is formed, and forming the zinc oxide comb-shaped crystal on which the p-type charge transport layer is formed on the other side cell The method is characterized by including a step of manufacturing a photoelectric conversion cell by sandwiching the substrate.

The present invention also provides a step of preparing a pair of cell substrates, a step of heating a raw material containing at least zinc and evaporating the raw material to form a zinc oxide comb crystal film on one of the cell substrates. Forming a light absorption layer on the zinc oxide comb crystal film on the cell substrate, forming a p-type charge transport layer on the zinc oxide comb crystal on which the light absorption layer is formed,
The method is characterized by including a step of manufacturing a photoelectric conversion cell by sandwiching the zinc oxide comb-shaped crystal on which the p-type charge transport layer is formed with the other cell substrate.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The main feature of the photoelectric conversion device according to the present invention is to provide an electron transfer type charge transport layer in which electrons and holes are transferred and transferred smoothly, and which has low internal resistance and recombination probability and high conversion efficiency.
This photoelectric conversion device and its manufacturing method will be described in detail below.

First, the configuration of the photoelectric conversion device of this embodiment will be described. In the dye-sensitized cell such as the above-mentioned Graetzel cell, since the light absorption rate of the dye 1 layer is not sufficient, the surface area is increased to substantially increase the light absorption amount. The photoelectric conversion device according to the present embodiment is not limited to dye sensitization, and can be widely used for general photoelectric conversion devices having a structure in which the surface area is increased because the light absorptivity is not sufficient. As a method for increasing the surface, a method of dispersing and bonding fine particles like the above-mentioned Graetzel type cell is simple, but there is a problem that the movement of electrons is not sufficiently efficient.

For example, comparing the case where light is incident from the anode transparent electrode 65 side having the titanium oxide semiconductor layer 61 and the case where light is incident from the cathode transparent electrode 66 side in the above Graetzel type cell, the former case is However, the photoelectric conversion efficiency is often good. This is not only the difference in the amount of light absorption due to the dye, but the electrons excited by light absorption move through the titanium oxide semiconductor layer 61 and the anode transparent electrode 6
It is suggested that the probability of reaching 5 decreases as the photoexcitation position moves away from the transparent electrode. That is, it is suggested that the Graetzel type cell having many grain boundaries does not achieve sufficiently efficient electron transfer.

FIG. 1A is a sectional view showing the configuration of an embodiment of the photoelectric conversion device according to the present invention, and FIG. 1B is FIG.
It is sectional drawing which shows in detail the part except the glass 13 with an electrode of (a). In FIG. 1, 10 is a substrate with an electrode, 11
Is an absorption layer modified semiconductor crystal layer, 12 is a charge transport layer, and 13 is a substrate with an electrode.

As shown in FIG. 1B, the electrode-equipped substrate 10 comprises, for example, a glass substrate 14 provided with a transparent electrode layer 15. The electrode-equipped substrate 13 similarly includes an electrode layer and a substrate, but when the light incident side is on the right side in the drawing, the substrate and the electrode layer need to be translucent. This is not the case unless it is on the light incident side.

The absorption layer modified semiconductor crystal layer 11 is shown in FIG.
As shown in (b), it comprises a zinc oxide comb crystal 17 and a light absorption layer 16 formed on the surface thereof. The zinc oxide comb crystal layer 17 is one charge transport layer (n type), and the light absorption layer 16 is provided between the charge transport layer and the charge transport layer (p type) 12.

Here, comparing the zinc oxide comb crystal layer 17 and the fine grain crystal layer by the photoelectric conversion device of this embodiment,
In the zinc oxide comb-shaped crystal layer 17, the probability that electrons or holes generated by photoexcitation are scattered by the grain boundaries before moving to the collecting electrode is reduced. In particular, as shown in FIG. 1B, one end of all zinc oxide comb crystals 17 has a transparent electrode layer 1
In the case of being bonded to No. 5, the influence of grain boundaries can be almost eliminated in the movement of electrons or holes as compared with the Graetzel type cell.

In the photoelectric conversion device according to this embodiment, since the zinc oxide comb crystal 17 is an n-type wide gap semiconductor, a p-type wide gap semiconductor or a redox pair is sandwiched between the light absorption layers 16 such as dyes. An electron donating type charge transport layer 12 such as an electrolytic solution containing a polymer conductor is required.

Here, the light irradiation surface is determined by which surface the transparent electrode (glass substrate 14 and transparent electrode layer 15) is used for. The configuration shown in FIG. 2A is an example of the case where a transparent electrode is used on the semiconductor crystal layer side as in the Graetzel type cell, and light is emitted from the left side of the drawing. The configuration shown in FIG. 2B is the opposite of that, and is an example in which a transparent electrode is provided on the charge transport layer side and light is incident from the right side of the drawing. If there is little absorption and reflection of the irradiation light to the light absorption layer,
Either configuration of (a) and FIG. 2 (b) may be used.

Further, as shown in FIG. 2 (c), the structure may be such that light irradiation from either surface can be used. That is, the transparent electrodes may be provided on both the semiconductor crystal layer side and the charge transport layer side. These configurations depend on the method for producing the zinc oxide comb-like crystal and the method and composition for forming the charge transport layer to be combined. For example, in the case of producing a zinc oxide comb crystal by electrodeposition on a Pt film, light irradiation cannot be performed from the zinc oxide comb crystal surface. When the zinc oxide comb crystal face is produced by a low temperature process such as firing of zinc oxide comb crystal powder, it can be produced without degrading the transparent electrode layer, so that either face can be the light irradiation surface.

Next, the zinc oxide comb crystal 17 which is the n-layer will be described. A zinc oxide comb crystal has a stem part and a branch part, and the branch part is one or more crystals grown in a certain direction, forming a comb-like structure. is there. FIG. 3A is a diagram showing this zinc oxide comb crystal. The portion of the trunk portion 41 extends in a certain direction, and the branch portion 42 grows from the trunk portion 41.

The branch portion 42 is preferably a c-axis oriented crystal, and the diameter of the branch portion 42 is 200 nm or less and may have many long branches in order to improve the roughness factor when used in a photoelectric conversion device. Preferably, further, the branch portion 4
The diameter of 2 is preferably 50 nm or less. The length of the branch portion 42 is 1 μm or more, preferably 10 μm.
That is all.

The growth direction of the trunk portion 41 is [0
The 1-10] direction is preferable, and the growth direction of the branch portion 42 is preferably the [0001] direction. The diameter of the trunk portion 41 is 1 μm or less, preferably 100 nm or less. The length of the trunk portion 41 is 10 μm or more, preferably 100 μm
m or more is good.

Here, the branch portion 42 includes all of a cylinder and a cone, a cone having a flat tip, a cylinder having a sharp tip, a flat tip, and the like. Furthermore, a triangular pyramid,
Square pyramids, hexagonal pyramids, other polygonal pyramids and those with flat tips, or triangular prisms, quadrangular prisms, hexagonal prisms, other polygonal prisms, or triangular prisms with a sharp tip, quadrangular prisms,
Hexagonal prisms, other polygonal prisms and those with a flat tip are also included, and further, these polygonal line-like structures are also included.
The shape of the cross section of the branch portion 42 tends to be hexagonal.

Further, as shown in FIG. 3B, the shape in which the branch portion 42 is joined also from the side opposite to the main branch portion 42,
Included in zinc oxide comb crystals. Further, it also includes a case where a metal such as Sn, Sb, Al, or Ga, or a compound of metal, or S, Cl, N, or the like, which is an impurity, is mixed in the zinc oxide comb crystal.

As a method for producing a zinc oxide comb crystal, there is a method of heating zinc or an inorganic compound having zinc as a constituent element to vaporize the zinc oxide comb crystal to grow the zinc oxide comb crystal. Here, as the heating method, simple resistance heating can be used, and the metal raw material itself can be used as the resistor. Furthermore, when trying to grow on a substrate, it is preferable to form irregularities that generate crystal nuclei on the surface of the substrate or to form a seed crystal.

Further, since the electron transfer efficiency is improved with the growth on the substrate, as compared with the manufacturing method in which the zinc oxide comb crystal 17 is formed and then applied and baked as shown in FIG. 4A.
It is preferable to form it on the substrate as shown in FIG. Here, a zinc oxide comb-shaped crystal layer mixed with granular zinc oxide crystals or another n-type semiconductor is also effective as the n layer of the photoelectric conversion device.

Next, the zinc oxide comb crystal 17 corresponding to the n-layer.
The manufacturing method will be specifically described. In the present embodiment, it is described that the manufacturing is performed by the heating method as described above. However, as the heating method, in addition to the resistance heating method, a method such as a laser heating method or a high frequency induction heating method can be mentioned. An example using the resistance heating mechanism will be specifically described.

FIG. 5 is a view showing an apparatus for producing a zinc oxide comb crystal film having a crucible type resistance heating mechanism. In the apparatus shown in FIG. 5, the electrode 10 arranged in the reaction vessel 107
When a crucible 105, which is a resistance heating body, is connected to 6 and the crucible 105 is heated by applying an electric current, the raw material 104 in the crucible 105 is vaporized and designed so that it can be attached to the substrate 101 attached to the facing substrate holder 102. is there. Also,
The gas is introduced through a gas introduction line 108 below the reaction container 107 and rises in the reaction container 107 so that the reaction container 10
The gas is exhausted from the gas exhaust line 109 at the upper part of 7. Board 1
01 is a substrate holder 10 so that it can be maintained at an appropriate temperature.
Substrate heater 103 is provided on the back side of 2.

In order to grow a zinc oxide comb crystal on the substrate 101, first, a carrier gas and an oxidizing gas are introduced from the gas introduction line 108 to keep the reaction vessel 101 at an appropriate pressure. At this time, the carrier gas is preferably an inert gas such as He, Ar or nitrogen, and the oxidizing gas is preferably oxygen. In some cases air or water may also be used. The pressure in the reaction vessel 101 is usually 100 to 10
Although about 10,000 Pa is used, it is not limited to this.

Next, the substrate heater 103 is used to set the substrate temperature to a temperature convenient for zinc oxide comb crystals. Therefore, although not shown, it is preferable to install a thermocouple near the substrate 101. Although the substrate temperature depends on the oxide to be grown and the pressure, it is generally several 100 to 1000 ° C. Then, a current is passed from the electrode 106,
The crucible 105 containing the raw material 104 is heated. For this crucible 105, a tungsten wire bonded with an alumina crucible can be used, but other ones can of course be used.

It is preferable to install a thermocouple near the crucible 105 so that the temperature of the crucible 105 can also be controlled. When the crucible 105 is heated and the raw material 104 starts to evaporate, the vapor rides on an ascending air current, moves toward the substrate 101, and adheres to the substrate 101. Generally, oxidation of the raw material progresses in the process from evaporation to adhesion, but at which point the oxidation progresses depends on pressure, oxygen concentration, temperature and the like.

When the pressure and the evaporation amount are particularly high, the substrate 1
In some cases, ultrafine particles of zinc oxide and the like grow before reaching 01. In addition, zinc oxide ultrafine particles may grow on the substrate 101 depending on the oxygen concentration, the pressure, and the substrate temperature. The manufacturing apparatus in FIG. 5 is used when manufacturing the photoelectric conversion device in FIG.

FIG. 6 is a view showing an apparatus for producing a zinc oxide comb crystal film by heating a crucible in an annular furnace. In this manufacturing apparatus, a crucible 105 is installed inside a quartz tube 110, and a heater 112 is provided around the quartz tube 110. Also, the substrate holder 102 is installed on the gas exhaust line 109 side of the quartz tube 110,
The other side of 0 is the gas introduction line 108. Figure 6
The manufacturing apparatus of is used when manufacturing the photoelectric conversion device of FIG.

Next, the light absorption layer 16 will be described. Various semiconductors and dyes can be used as the light absorption layer of the photoelectric conversion device according to the present embodiment. As a semiconductor, i
An amorphous semiconductor or a direct transition type semiconductor having a large light absorption coefficient of type is preferable. As the dye, a metal complex dye and /
Or polymethine dye, perylene dye, rose bengal, eosin Y, mercury chrome, santaline (Sant
Organic dyes such as alin dye and cyanine dye and natural dyes are preferable.

The dye preferably has an appropriate bonding group for the surface of the semiconductor fine particles. Preferred linking groups include COOH groups, cyano groups, PO3H2 groups or chelating groups having π conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. Among them, COOH group, PO
The 3H2 group is particularly preferred.

When the dye used in this embodiment is a metal complex dye, a ruthenium complex dye {Ru (dcbpy) 2 (SCN) 2, (dc
bpy = 2,2-bipyridine-4,4'-dicarboxylic acid) etc. can be used, but it is important that the oxidized / reduced form is stable. In addition, the potential of excited electrons in the light absorption layer, that is, the potential of the photoexcited dye (LUMO potential of the dye) and the conduction charge potential in the semiconductor are determined by the electron accepting potential (n
Hole potential generated by photoexcitation in the light absorption layer, which is higher than the conduction charge potential of the p-type semiconductor, and the electron-donation potential of the electron-donation charge transfer layer (valence electron charge potential of the p-type semiconductor, potential potential of the redox pair). Etc.) is required. Reducing the recombination probability of excited electron-holes in the vicinity of the light absorption layer is also important for increasing the photoelectric conversion efficiency.

Next, the charge transport layer 12 will be described.
When an n-type semiconductor crystal is used, it is necessary to form a hole transport layer with a light absorption layer sandwiched therebetween. A redox system can be used for this hole transport layer as in the case of wet solar cells.
Even when using redox, not only a simple solution system,
There are methods of using carbon powder as a holding material and gelling the electrolyte. There is also a method of using a molten salt or an ion conductive polymer. Further, as a method for transporting electrons (holes), an electropolymerized organic polymer or a p-type semiconductor such as CuI, CuSCN or NiO can be used.

Since the transport layer needs to be inserted between the zinc oxide comb crystals, the permeation method that can be used for liquids and polymers, the electrodeposition and the CVD method that can be used for solid transport layers, etc. are suitable for the production. ing.

Next, the electrode layer will be described. An electrode layer is provided so as to be adjacent to the charge transport layer and the zinc oxide comb crystal layer. The electrode layer may be provided on the entire outer surface of these layers or on a part thereof. When the charge transport layer is not solid, it is better to provide the electrode layer on the entire surface from the viewpoint of holding the charge transport layer. For example, a catalyst such as Pt or C is preferably provided on the surface of the electrode layer adjacent to the charge transport layer in order to efficiently reduce the redox couple.

The electrode layer on the light incident side is formed of indium-
A transparent electrode made of tin composite oxide, tin oxide doped with fluorine, or the like can be preferably used. If the resistance of the layer in contact with the light incident side electrode (charge transport layer or zinc oxide comb crystal layer) is sufficiently low, a partial electrode such as a finger electrode can be provided as the light incident side electrode. Is. The electrodes not on the light incident side are Cu,
A metal electrode made of Ag, Al or the like can be preferably used.

Next, the substrate 14 will be described. The material and thickness of the substrate can be appropriately designed according to the durability required for the photovoltaic device. As the light incident side substrate, a glass substrate, a plastic substrate, or the like can be preferably used as long as it is translucent. A metal substrate, a ceramic substrate, or the like can be appropriately used as the substrate that does not become the light incident side. An antireflection film made of SiO ₂ or the like is preferably provided on the surface of the substrate on the light incident side.

The electrode layer 15 described above may also serve as the substrate 14 so that a substrate which is a member separate from the electrode may not be provided.

Next, the sealing will be described. Although not shown, it is preferable to use a wet type photoelectric conversion device in which at least a portion other than the substrate is sealed from the viewpoint of improving weather resistance. An adhesive or resin can be used as the sealing material. When the light incident side is sealed, the sealing material is preferably translucent.

[0059]

EXAMPLES Next, examples of the present invention will be described. The inventor of the present application produced the photoelectric conversion device described in the above embodiment and tried an evaluation experiment. Hereinafter, this is described in Examples 1 and 2.
As described below.

Example 1 In Example 1, a zinc oxide comb crystal was manufactured using the zinc oxide comb film manufacturing apparatus of FIG.
A photoelectric conversion device was produced using this zinc oxide comb crystal. In addition, Example 1 corresponds to the photoelectric conversion device of FIG.

First, the surface-oxidized Zn powder in the alumina crucible 105 attached to the W wire is used as the raw material 104.
And was connected to the electrode 106. An alumina substrate having a thickness of 0.5 mm is used as the substrate 101, and 450 to 550 ° C.
Set to. Next, 100 sccm of argon gas mixed with 3% oxygen is flown into the reaction vessel 107 to obtain 30,000.
It was kept at Pa. Set the temperature of the crucible 105 to 650 to 750.
The Zn was gradually evaporated by heating to 0 ° C. for about 30 minutes.

Next, when the produced sample was observed using an FE-SEM (electric field scanning electron microscope), the substrate 1
A large number of zinc oxide comb crystal films having orientation were formed on 01, and the crystal axis corresponding to the stem portion was connected to the substrate to grow. The stem part is several tens of nm near the crystal root,
The tip was thinner. Moreover, the length of the trunk portion was several to several tens of μm, and the stem portion was grown in the [01-10] direction. On the other hand, in the branch portion, the vicinity of the crystal root was several tens nm, the length of the branch portion was several to several tens of μm, and the growth was in the [0001] direction.

Next, the zinc oxide comb crystals formed on the alumina substrate were scraped off, and 3 g of the scraped crystals were washed with 5 mL of water, 0.2 mL of acetylacetone, and Triton-X (registered trademark: Union.
Carbite Co., Ltd.) to prepare a slurry. This slurry was applied on a conductive glass (F-doped SnO ₂ , 10 Ω / □) with a spacer to a thickness of about 50 μm and a 1 cm square. Then, while flowing oxygen gas at 100 sccm, 55
Firing was performed at 0 ° C. for 1 hour. The film thickness of the zinc oxide comb crystal layer 17 after firing was about 10 μm. Conductive glass,
It corresponds to one substrate of the photoelectric conversion cell, and corresponds to, for example, the electrode-attached substrate 10 in FIG. 1.

Commercially available Mercurochrome was used as the dye. This dye was dissolved in distilled ethanol, and the zinc oxide comb-shaped crystal electrode coated with the zinc oxide comb-shaped crystal film on the conductive glass as described above was immersed in the electrode for 24 hours to adsorb the dye onto the electrode. It was taken out later and dried at 80 ° C. Further, a counter electrode (corresponding to the other side substrate of the photoelectric conversion cell, which is formed by sputtering platinum with a thickness of 10 nm on conductive glass (F-doped SnO ₂ , 10Ω / □), for example, corresponds to the electrode-attached substrate 13 in FIG. 1. to) using the redox couple I ^- / I ₃ ^-
Was used.

The solute is 0.05 mol / L I2 (iodine) and 0.1 mol / L
LiI (lithium iodide) and 0.6 mol / LDMPI (Im) (1,2-dimethyl-3-propylimidazolium iodide) and 0.
5mol / L TBP (4-tert-butylpyridine), solvent is MAN (Me
OAN) (methoxyacetonitrile) was used. This mixed liquid (corresponding to the charge transport layer 12) was dropped on the zinc oxide comb crystal and sandwiched between the substrates on the other side to prepare a photoelectric conversion cell.

Further, as a comparative example, a cell was similarly assembled by using zinc oxide fine particles having a particle diameter of about 100 nm as a main component, which had been heat-treated. Then, 500 W of xenon lamp light with an ultraviolet cut filter attached was irradiated from the counter electrode side. The value of the photocurrent generated by the photoelectric conversion reaction at this time was measured. The measurement results are those of Example 1 as compared with Comparative Example.
The short-circuit current and the photoelectric conversion efficiency of the cell No. 2 were about 5% higher. It is considered that this is because the internal resistance of the electron-accepting charge transport layer was reduced by using the zinc oxide comb-shaped crystal electrode.

Example 2 In Example 2, zinc oxide comb crystals were manufactured using the zinc oxide comb film manufacturing apparatus shown in FIG.
A photoelectric conversion device was produced using this zinc oxide comb crystal. The second embodiment corresponds to the photoelectric conversion device shown in FIG.

First, the surface-oxidized Zn powder was put into the alumina crucible 105 as the raw material 104 and set in the apparatus. A conductive glass (F-doped SnO ₂ , 10 Ω / □) having a thickness of 10 mm was used as the substrate 101, and the temperature was set to 450 to 550 ° C. Then, 100 sccm of argon gas mixed with 2% oxygen was flowed in the reactor 111 to 100,000 Pa.
Held in. In addition, the temperature of the crucible 105 is set to 650 to 75.
The Zn was gradually evaporated by heating to 0 ° C. for about 180 minutes.
The conductive glass corresponds to one substrate of the photoelectric conversion cell, for example, the electrode-attached substrate 10 of FIG. 1.

When the produced film was observed with an FE-SEM (electric field scanning electron microscope), a large number of zinc oxide comb crystal films 17 having orientation were formed on the substrate 101, and the crystal axis corresponding to the trunk region was found. It was connected to the substrate and was growing. The stem portion was several tens of nm near the crystal root, and became thinner toward the tip. Also, the length of the trunk part is several to several tens of μm,
It was growing in the [01-10] direction. The branch portion is several tens of nm near the crystal root, and the length of the branch portion is several to several tens μ.
At m, it was growing in the [0001] direction.

As a dye, Ru ((dcbpy) (COO
H) ₂ ) ₂ (SCN) ₂ was used. The dye was dissolved in distilled ethanol, and a zinc oxide comb-shaped crystal electrode was formed by applying and firing the zinc oxide comb-shaped crystal film on the conductive glass as described above.
After soaking for a while to adsorb the dye on the electrode, take it out, and remove it at 80 ° C.
Dried.

Conductive glass (F-doped SnO ₂ , 10 Ω
/ □) using a counter electrode formed by sputtering platinum to a thickness of 10 nm (corresponding to the other side substrate of the photoelectric conversion cell, for example, the substrate 13 with electrodes in FIG. 1), and the redox pair is I ⁻ /
I ₃ ⁻ was used. The solute is tetrapropylammonium iodide (0.46mol / L) and iodine (0.06mol / L), and the solvent is ethylene carbonate (e
thylene carbonate) (80vol%) and acetonitrile (20vol
%) Mixed solution was used. This mixed liquid (corresponding to the p-type charge transport layer 12) was dropped on the zinc oxide comb crystal and sandwiched between the substrates on the other side to prepare a photoelectric conversion cell.

As a comparative example, a cell was similarly assembled by using zinc oxide fine particles having a particle diameter of about 100 nm as a main component, which had been heat-treated. Then, 500 W of xenon lamp light with an ultraviolet cut filter attached was irradiated from the counter electrode side. The value of the photocurrent generated by the photoelectric conversion reaction at this time was measured. The measurement results are those of Example 2 as compared with Comparative Example.
The short-circuit current and the photoelectric conversion efficiency of the cell No. 2 were about 10% higher. It is considered that this is because the internal resistance of the electron-accepting charge transport layer was decreased by using the zinc oxide comb crystal electrode.

[0073]

As described above, according to the present invention, n
Since zinc oxide comb crystals are used as the charge transport layer of the mold, electrons can be transferred smoothly, and a photoelectric conversion device with high conversion efficiency can be realized. Further, it is possible to realize a photoelectric conversion device having a semiconductor electrode in which a light absorbing layer such as a dye or a charge transporting layer such as an electrolytic solution penetrates or moves quickly, and a photoelectric conversion device having a large short-circuit current value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a photoelectric conversion device of the present invention.

FIG. 2 is a cross-sectional view for explaining the relationship between the light irradiation direction and the transparent electrode of the photoelectric conversion device according to the present invention.

FIG. 3 is an enlarged view showing a zinc oxide comb crystal according to the embodiment of FIG.

FIG. 4 is a cross-sectional view showing a state of a zinc oxide comb crystal according to a difference in manufacturing method of the photoelectric conversion device of the present invention.

FIG. 5 is a view showing an apparatus for manufacturing a zinc oxide comb crystal film having a crucible type resistance heating mechanism.

FIG. 6 is a diagram showing a manufacturing apparatus for manufacturing a zinc oxide comb crystal film by heating a crucible in an annular furnace.

FIG. 7 is a cross-sectional view showing a conventional Graetzel cell.

[Explanation of symbols]

10 Substrate with Electrode 11 Absorption Layer Modified Semiconductor Crystal Layer 12 Charge Transport Layer 13 Substrate with Electrode 14 Glass Substrate 15 Transparent Electrode Layer 16 Light Absorption Layer 17 Zinc Oxide Comb Crystal (Zinc Oxide Comb Crystal Layer) 41 Stem 42 Branch 101 Substrate 102 Substrate holder 103 Substrate heater 104 Raw material 105 Crucible 106 Electrode 107 Reaction vessel 108 Gas introduction line 109 Gas exhaust line 110 Quartz tube 111 Reactor 112 Heater 61 Anatase type TiO ₂ fine particles 62 Light absorption layer 63 Electrolyte 64 Glass 65 Transparent electrode Layer (anode) 66 Transparent electrode layer (cathode)

Continued front page    F term (reference) 5F051 AA14 AA20 CB13 CB24 FA02                       FA06 GA02                 5H032 AA06 AS06 AS16 BB02 BB05                       BB06 EE02 HH04

Claims (6)

[Claims] 1. In a photoelectric conversion device having an n-type charge transport layer, a light absorption layer, and a p-type charge transport layer between a pair of substrates, the n-type charge transport layer includes at least a trunk portion and the trunk portion. A photoelectric conversion device comprising a zinc oxide comb crystal composed of a plurality of branch portions connected to each other. 2. The photoelectric conversion device according to claim 1, wherein the branch portion has a diameter of 200 nm or less. 3. The zinc oxide comb crystal is [01-1
The photoelectric conversion device according to claim 1 or 2, wherein the trunk portion grows in the [0] direction and the branch portion grows in the [0001] direction. 4. In a method for manufacturing a photoelectric conversion device having an n-type charge transport layer, a light absorption layer, and a p-type charge transport layer between a pair of substrates, the n-type charge transport layer is zinc or oxide. A method for manufacturing a photoelectric conversion device, which comprises forming zinc oxide comb-shaped crystals by evaporating them by heating zinc or a mixture of zinc and zinc oxide. 5. A step of heating a raw material containing at least zinc and evaporating the raw material to form a zinc oxide comb crystal film on the crystal collection substrate, a zinc oxide comb crystal film on the crystal collection substrate. Scraping off and mixing with a predetermined solution,
Applying the mixture onto a cell substrate and baking the cell substrate; forming a light absorbing layer on the zinc oxide comb crystal film on the cell substrate; and forming a zinc oxide comb on which the light absorbing layer is formed. And a step of forming a p-type charge transport layer on the crystal, and sandwiching the zinc oxide comb crystal having the p-type charge transport layer formed between the other side cell substrates to produce a photoelectric conversion cell. And a method for manufacturing a photoelectric conversion device. 6. A step of preparing a pair of cell substrates, a step of heating a raw material containing at least zinc and evaporating the raw material to form a zinc oxide comb crystal film on one of the cell substrates,
Forming a light absorption layer on the zinc oxide comb crystal film on the cell substrate; forming a p-type charge transport layer on the zinc oxide comb crystal on which the light absorption layer is formed; A method for manufacturing a photoelectric conversion device, comprising a step of manufacturing a photoelectric conversion cell by sandwiching a zinc oxide comb-shaped crystal on which a charge transport layer is formed with another cell substrate.