JPH07106617A - Transparent electrode, formation thereof and solar cell employing same - Google Patents

Abstract

PURPOSE:To provide a highly reliable transparent electrode excellent in transparency and conductivity and formation thereof, and to provide a highly reliable solar cell in which shunting is prevented while exhibiting good initial characteristics. CONSTITUTION:The transparent electrode comprises a substrate applied with a conductive paint containing a conductive filter and binder wherein the conductive filler has average particle size of 0.5Xm or less. The conductive tiller having average particle size of 0.1mum or less and a resin binder having a molecular weight low enough to prevent secondary aggregation are added to a solvent and dispersed therein thus producing the conductive paint. The conductive paint is applied to the substrate and hardened thus forming a transparent electrode. A high resistance barrier layer 107 is interposed between the upper electrode 106 and the grid electrode 108 of a solar cell 100A wherein the transparent electrode is employed as the barrier layer 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent electrode having excellent characteristics and high reliability, and a method for forming the transparent electrode, and having a function of transmitting light, having excellent conductivity and high durability. The present invention relates to a solar cell which prevents short circuits and shunts by using a high barrier layer, has high initial characteristics, and has high reliability during long-term use.

[0002]

2. Description of the Related Art Conventionally, transparent electrodes have been used as electrodes for EL display devices, liquid crystal display devices, etc., and are usually manufactured by a vapor deposition method, a sputtering method or the like. Such a manufacturing method has a problem that the substrate temperature is relatively high from 200 ° C. to 400 ° C. and the deposition rate is slow, so that it takes a long time to obtain a thick film. As a method of improving this point, a method of screen-printing a conductive coating material in which a conductive filler is dispersed in a resin is disclosed in Japanese Patent Laid-Open No. 117-217.
It is proposed in Japanese Patent Publication No. 015.

In the above method, a conductive coating material having a conductive filler having a particle size of 0.4 μm or less dispersed in a resin is applied to a substrate by printing, and the surface resistance of the transparent electrode thus prepared is measured. And light transmittance are disclosed.

By the way, it can be considered that the transparent electrode is used as a constituent member of a solar cell.
The conventional techniques of solar cells are described below.

Solar cells have been widely applied as a power source for consumer appliances such as calculators and wristwatches, and have attracted attention as a technique that can be put to practical use as an alternative power source for so-called fossil fuels such as petroleum and coal. Such a solar cell is a technology that uses the diffusion potential generated at a semiconductor junction such as a pn junction, a pin junction, or a Schottky junction of a semiconductor, and a semiconductor such as silicon absorbs sunlight and is an optical carrier for electrons and holes. Is generated, the photocarrier is drifted by an internal electric field generated by the diffusion potential of the junction, and taken out to the outside. As a semiconductor material for such a solar cell, a tetrahedral amorphous semiconductor such as amorphous silicon, amorphous silicon germanium, or amorphous silicon carbide is used. Thin-film solar cells using such semiconductors are promising because they have advantages such as the ability to form a large-area film, the need for a thin film thickness, and the ability to deposit on any substrate material, as compared with single-crystal solar cells. ing.

The structure of an amorphous silicon solar cell is
For example, as shown in FIGS. 5 to 7, a p-layer 205 and an i-layer 20 made of thin film amorphous silicon are formed on a substrate 201.
4 and n layer 203 are laminated. In addition, a so-called tandem cell in which two or more pin junctions are stacked in series as shown in FIG. 6 has been studied to improve conversion efficiency. An upper electrode 2 is provided on the light incident side and the back side of the semiconductor.
06 and the lower electrode 202 are provided as a pair of electrodes. In an amorphous silicon solar cell, since the semiconductor itself generally has a high sheet resistance, a transparent upper electrode covering the entire surface of the semiconductor is required, and a transparent conductive film such as SnO ₂ or ITO is usually provided. The transparent conductive film also functions as an antireflection film. A grid electrode 208 for collecting current is further provided on the upper electrode, but it is formed in a comb shape so as not to prevent the incidence of light. Further, a bus bar 209 for collecting the current of the grid electrode is provided.

By the way, when the solar cell is used for supplying electric power to a general household, for example, an output of about 3 kW is required, and when a solar cell having a conversion efficiency of 10% is used, it is 30.
With an area of m ² , large-area solar cells are needed. However, it is difficult to manufacture a defect-free solar cell over a large area due to the manufacturing process of the solar cell. For example, in a polycrystalline semiconductor, a low-resistance portion is generated in a grain boundary portion, or amorphous silicon such as amorphous silicon is generated. It is known that in an amorphous semiconductor, pinholes and defects are generated due to the influence of dust during film formation of a semiconductor layer, which causes shunts and shorts, and these shunts and shorts significantly reduce conversion efficiency.

The cause of pinholes and defects will be described in more detail. For example, in the case of amorphous silicon solar cells deposited on a stainless steel substrate, the substrate surface cannot be said to be a completely smooth surface, and scratches and Due to the presence of dents or spike-like protrusions and the provision of a back reflector with unevenness for the purpose of irregularly reflecting light on the substrate, a thin film with a thickness of several tens nm such as a p-layer or an n-layer is formed. The semiconductor layer cannot completely cover such a surface. Another cause is that pinholes are generated due to dust during film formation.

When there is a pinhole or a defect, the semiconductor between the lower electrode and the upper electrode of the solar cell becomes a void due to the pinhole, the lower electrode and the upper electrode are in direct contact with each other, or the spike shape of the substrate is present. If the defect is a shunt or short with low resistance, even if it contacts the upper electrode or the semiconductor layer is not completely lost, the current generated by light will flow in parallel through the upper electrode and the shunt or short will be generated. It will flow into the low resistance part of the part and the generated current will be lost. Even with a minute defect, the current flowing into the defect is quite large. If there is such a current loss, the open circuit voltage of the solar cell will drop. In particular, when the light intensity is low, the magnitude of the current generated in the solar cell by the light and the leak current due to the shunt does not change so much, so that the open circuit voltage is remarkably lowered. Furthermore, when the position of the defect is distant from the grid electrode or the bus bar, the current loss is relatively small because the resistance when flowing into the defective part is large, but conversely, when the defective part is the grid electrode or When under the bus bar, the current lost due to the defect is higher. On the other hand, in the pinhole-shaped defect portion, the charge generated in the semiconductor layer not only leaks to the defect portion but also an ionic substance is generated due to the interaction with moisture. There is a phenomenon in which the electric resistance of the defective portion gradually decreases with the passage of time, and characteristics such as conversion efficiency deteriorate.

As a countermeasure against such a problem, there is a conventionally known configuration disclosed in, for example, US Pat. No. 4,598,306. The skeleton of the configuration is to increase the contact resistance with the transparent electrode, the grid electrode or the bus bar by providing a material having a high resistance sufficient to prevent a shunt or a short circuit at the defective portion between the semiconductor layer and the transparent electrode layer. , To prevent a decrease in conversion efficiency. Further, as another known configuration, US Pat.
As disclosed in Japanese Patent No. 590,327, a method of providing an insulating layer (barrier layer) between a bus bar and a transparent electrode has been proposed.

[0011]

However, in the technology of the conventional transparent electrode disclosed above, a specific and detailed manufacturing method and a preferable combination of the transparent conductive filler and the transparent binder are not mentioned. In general, the transparent electrode produced by the disclosed method had high resistance and only a low light transmittance was obtained. In addition, when used in an environment such as outdoors, there is a problem that the resistance value increases due to humidity.

On the other hand, regarding the structure of the solar cell, there is a problem in reliability because the production yield due to the shunt and leakage due to humidity during actual use cannot be prevented. In addition, when a barrier layer is provided between the semiconductor layer and the transparent electrode, it must be conductive enough not to interfere with light incidence and not to resist the current generated by the solar cell, so it becomes a thin layer and prevents shunt. Was insufficient to do so.

An object of the present invention is to overcome the above problems and provide a transparent electrode having good characteristics and high reliability, which can be used for solar cells and other devices, and a method for forming the same. Is.

Another object of the present invention is to solve the problems such as the shunt and reliability of the solar cell and to provide a structure of the solar cell having good characteristics.

[0015]

In order to solve the above-mentioned problems in the transparent electrode, the transparent electrode of the present invention is based on a conductive paint containing at least one kind of conductive filler and at least one kind of binder. The transparent electrode formed above has a feature that the average particle size of the conductive filler after dispersion is 0.5 μm or less.

In the method for forming a transparent electrode of the present invention, the conductive filler having an average particle diameter of 0.1 μm or less and at least one binder made of a resin having a small molecular weight necessary to prevent secondary aggregation. Is added to a solvent to disperse a conductive coating material, and then the conductive coating material is applied onto a substrate and then cured to form the conductive coating material.

Further, in the solar cell of the present invention, at least a pair of pin semiconductor junctions, a transparent upper electrode formed on the semiconductor layer located on the light incident side of the semiconductor junctions, and a grid formed on the upper electrodes. In a solar cell including electrodes, a barrier layer having a resistance higher than that of the grid is laminated between the upper electrode and the grid electrode.

[0018]

The transparent electrode of the present invention has been completed by observing the dispersed state of the conductive filler contained in the transparent electrode after curing, experimentally finding the conditions under which the transparent and conductive property is obtained, and conducting further experiments. The main point is that the average particle size of the conductive filler after dispersion is 0.5 μm or less.

The reason why the transparent electrode having good characteristics can be obtained by the present invention can be explained as follows.

When transparent particles having a particle size smaller than the wavelength of light are monodispersed with primary particles, light is transmitted by the diffraction effect, but when secondary aggregation of particles occurs, light is transmitted. Rayleigh scattering occurs, and the transmittance of light with a short wavelength is particularly impaired. On the other hand, electrically, the sum of the specific resistance of the filler and the contact resistance between the fillers is equal to the resistance value of the transparent electrode. Therefore, if the particle size of the filler is too small, the contact interface increases and the resistance increases. Further, the contact resistance is lower when secondary aggregation occurs.
From the above relationship, in order to combine transparency and low resistance, the particle size of the filler is from 0.1 μm to 0.0
The thickness is preferably 1 μm.

By the way, it is known that since ultrafine particles generally have high surface energy, secondary agglomeration of particles occurs due to ordinary dispersion methods and monodispersion cannot be achieved, and secondary agglomeration occurs. Therefore, in order to improve the dispersion, a dispersant is added or a disperser having a high shearing force is used, but the dispersant may sometimes have an unfavorable effect on the characteristics.

In the present invention, the transparent conductive filler has a particle diameter of 0.1 μm or less and a number average molecular weight of 1,000 so that compatibility with the filler is good.
The transparent binder having a small molecular weight is selected as 0 or less to prevent aggregation. By reducing the molecular weight, the transparent binder was sufficiently coated on the surface of the transparent conductive filler, and the entrainment of air was reduced, so that the particles were dispersed to the state of primary particles. Further, the transparent binder is effectively modified by providing a functional group having a polarity. The transparent binder in the present invention is considered to have a function of favorably dispersing the transparent conductive filler.

Further, in the present invention, paying attention to the dispersion state of the transparent conductive filler as a transparent electrode, the average particle size after dispersion is 0.5 μm or less, so that both transparency and conductivity are provided. It has been found that the characteristics become different. According to experiments conducted by the present inventors, if the average particle size after dispersion is 0.5 μm or less, the transparency is sufficient, but if it is more than that, the transparency is significantly impaired.

Further, in the solar cell of the present invention, a layer consisting of a barrier layer having a higher resistance than the grid electrode is formed between the upper electrode also serving as an antireflection layer and the grid electrode, thereby eliminating shadow loss and series resistance. There is no adverse effect such as increase, and the initial shunt is eliminated by preventing the contact between the upper and lower electrodes of the defective portion of the semiconductor layer, improving the manufacturing yield and at the high temperature and high humidity environment when actually used outdoors. This study was completed after further detailed study on the finding that reliability can be improved by preventing the migration of generated metal.

In a solar cell, a low resistance portion caused by unevenness of a substrate, dust during film formation, or the like, which is normal in the early stage of manufacture but has a reduced resistance during use, is a defect. Exists. The defective portion becomes a short-circuited portion between the upper electrode and the lower electrode and becomes a short circuit or a shunt. Since the grid electrode and the defective portion are in direct contact with each other, the solar cell characteristics are significantly deteriorated, but by providing a barrier layer having high resistance, short circuit can be prevented and deterioration of the solar cell characteristics can be prevented.

The barrier layer is required to have a higher resistance than the grid electrode, and has sufficient conductivity with respect to the current generated in the solar cell so that the efficiency of the solar cell is not impaired. It should be a resistance value of some degree. That is, the barrier layer is a high resistance layer for preventing a shunt, and does not become a resistance to the current generated by the solar cell, but if there is a defect, it functions as a resistance and can prevent a large leak. It is a thing.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The constituent features of the present invention will be individually described below as embodiments.

(Conductive Filler) In the present invention, as the conductive filler, a metal oxide semiconductor is preferably used as a transparent and conductive material. Wavelength 40
In order to be transparent to visible light from 0 nm to 800 nm, it is preferable that the band gap is about 2 eV or more and the absorption edge is 400 nm or less. Specifically, as such a material, In ₂ O _{3 can be used.} , SnO ₂ , ITO, T
Examples thereof include iO ₂ , CdO, ZnO and the like. Here, the chemical formula of the metal oxide is expressed by the stoichiometric ratio, but it goes without saying that the composition includes a composition slightly deviated from the stoichiometric ratio to improve conductivity.

The specific resistance of these materials as a bulk is 1
Although it is about 0 ⁻⁴ Ωcm to about 10 ¹ Ωcm, the conductivity may be improved by performing reduction treatment or oxidation treatment or doping as desired. In the case of doping, for example, SnO ₂ is doped with Sb or F, Z
A known method such as B doping of nO is possible.

(Impurities in Filler) When a transparent electrode is manufactured, if impurities such as metal ions remain in the metal oxide semiconductor, the impurities migrate due to the influence of humidity and the like, which is an unfavorable characteristic. Therefore, it is preferable that the amount of impurities in the conductive filler be 1% (wt%) or less. In this case, as a method of measuring the amount of impurities, it is possible to measure the electric conductivity of pure water in which the powder is suspended, and the electric conductivity is preferably 10 mScm or less.

(Shape of Metal Oxide) It is desirable that the size and shape of the metal oxide semiconductor be designed as follows from the requirement of being transparent and conductive. That is, in order to improve the light transmittance, it is necessary to design so that the light incident on the oxide semiconductor is not reflected at the interface between the oxide semiconductor and the binder, and therefore the particle size of the semiconductor is It must be designed smaller than the wavelength of light. Specifically, the primary particle diameter is preferably 0.1 μm or less. In addition, since the oxide semiconductor particles are brought into contact with each other to generate conductivity, the shape of the oxide semiconductor particles may be needle-like, flaky, potato-like or tuft-like in addition to the spherical shape so as to facilitate contact. It is preferable that

(Manufacturing Method of Metal Oxide) As a method of manufacturing the oxide semiconductor fine particles, a known method can be used. That is, fine particles are prepared by a wet method of oxidizing a solution of metal chloride or a dry method of ejecting and oxidizing fine particles of metal in a gas phase. The shape of the fine particles may be spherical or needle-like depending on the conditions at the time of formation, but the spherical fine particles may be made into a flaky shape by a known method using an apparatus such as a stamp mill or a ball mill.

(Binder) The binder has a function of transmitting light, binding and holding the conductive filler, and protecting it from humidity. It also has a function of adhering onto the substrate. An organic polymer resin is suitable as such a material, and a thermoplastic resin or a thermosetting resin is used as desired. Specifically, the thermoplastic resin is preferably an acrylic resin, an alkyd resin, a urethane resin, a styrene resin, a butyral resin, a polyester resin, a polycarbonate resin, or the like, and as the thermosetting resin,
Epoxy resin, phenol resin, melamine resin, alkyd resin, urethane resin, polyester resin, polyimide resin, fluorine resin and the like are preferable. At least one kind or two or more kinds of these resins can be selected and used.

In the case of a thermosetting resin, a suitable curing agent may be added, and a curing catalyst may be added depending on the case. Further, these polymers may be modified polymers for the purpose of imparting flexibility or weather resistance. The number average molecular weight of these resins before crosslinking is 10
It is preferably 000 or less. The binder has a glass transition temperature T _g 6 in the case where moderate flexibility is required.
It is preferably 0 ° C. or lower.

(Solvent) The solvent is appropriately selected depending on the compatibility between the conductive filler and the binder so that the conductive filler is preferably dispersed. The solvent, as another function, has a function of dissolving the binder to form a paste having an appropriate viscosity,
An appropriate solvent may be used depending on the desired paste state.

Examples of the solvent include aromatics such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as butyl acetate and ethyl acetate, cellosolves such as butyl cellosolve and ethyl cellosolve, isopropanol, and the like. An appropriate number of alcohols such as butanol and carbitols such as butyl carbitol and butyl carbitol acetate are added so that desired viscosity and volatility can be obtained. These solvents are selected so that they volatilize during curing and do not remain on the transparent electrode.

(Selective Additive) In the present invention, known additives may be selectively added in order to improve dispersibility. As the additive, for example, a metal salt of a saturated fatty acid, a metal salt of an unsaturated fatty acid, a higher aliphatic amine, an organic titanate compound, an organic phosphorus compound or the like may be used.

Further, known additives such as a viscosity adjusting agent, an anti-settling agent, a leveling agent, a silane coupling agent and a titanium coupling agent may be mixed after the transparent conductive coating material is prepared.

(Coating Method) A known method is used to form the above-mentioned paste on the substrate to form an electrode having a desired pattern. That is, in the case of a paste having a high viscosity, screen printing is possible and pattern formation can be performed using a plate having a desired circuit pattern. Further, in the case of a paste having a low viscosity, for example, a dipping method, a spray method, a spin coating method or the like is used. After coating, it is cured using a hot air oven or IR oven under desired conditions. The curing can be divided into pre-curing and main curing to prevent foaming due to bumping of the solvent.

(Barrier Layer) Material of Barrier Layer etc. Examples of the material of the barrier layer include SnO ₂ and In ₂
O ₃ , ZnO, CdO, CdSnO ₄ , ITO (In ₂ O ₃
A metal oxide such as —SnO ₂ ), a conductive paste containing the metal oxide as a filler, or a carbon paste is preferably used.

The specific preferable resistance value of the barrier layer is determined by the grid design, the current value at the operating point of the solar cell, the size of defects, etc., but the film thickness is 10 μm.
When m, the specific resistance is 0.1 Ωcm to 1000 Ωc
By setting m, the resistance is sufficient when a shunt is generated, and the resistance value is negligible with respect to the current generated in the solar cell. In addition, the barrier layer and the upper electrode are required to have ohmic characteristics.

Thickness of Barrier Layer The thickness of the barrier layer is required to be free of pinholes, have sufficient barrier properties against humidity, and have adhesiveness and flexibility. Easily, and if the thickness is 30 μm or more, flexibility is impaired, so 1 to 3
About 0 μm is preferable.

Width of barrier layer The shape of the barrier layer is formed in the same pattern as the pattern of the grid electrode, because alignment becomes easy when the grid electrodes are stacked, and due to the influence of humidity. In order to prevent migration of the metal used for the grid electrode, it is preferable to form it slightly wider than the grid electrode. Further, if the barrier layer is too wide, shadow loss occurs, so it is necessary to design the barrier layer to have an appropriate width. Therefore, the preferable width of the barrier layer is preferably 1 to 5 times.

Further, when the pattern formation is performed by screen printing, it is desirable that the paste has a viscosity of about 1000 cps to 100,000 cps.

Further, when the solar cell is used outdoors, it is necessary to have weather resistance that can withstand humidity and temperature. It is preferable that the barrier layer is transparent to a wavelength having a spectral sensitivity of the solar cell in order to reduce shadow loss in a portion other than the grid electrode. The transparent electrode according to the present invention is preferably used for such a purpose.

The solar cell of the present invention has a structure in which a high resistance layer is formed under the grid electrode to reduce current leakage due to a shunt or a short circuit, and thus can be suitably applied to an amorphous silicon solar cell. It goes without saying that the configuration based on the above concept can be applied to a solar cell using a single crystal, a polycrystalline system, or a semiconductor other than silicon, a Schottky junction type solar cell, and the like.

(Grid electrode) The grid electrode is an electrode for taking out electromotive force generated in the semiconductor layer. Materials for the grid electrode include Ti, Cr, Mo,
A metal such as W, Al, Ag, Ni, Cu, Sn, Pt, or an alloy thereof, solder, or the like is used. When the solar cell is used outdoors, the above-mentioned metal migrates depending on the type of each metal depending on the humidity, but the solar cell characteristics deteriorate. In the present invention, by providing a high resistance barrier layer between the grid and the semiconductor layer, migration is prevented and a highly reliable solar cell is obtained.

(Structural Example of Solar Cell) A structural example of an embodiment of the solar cell of the present invention will be described below with reference to the drawings. A preferred configuration example of the solar cell of the present invention is schematically shown in FIGS.

FIGS. 1 and 2 are single cell structure amorphous silicon solar cells in which light is incident from the side opposite to the substrate, FIG. 3 is a solar cell having a triple structure of the solar cell of FIG. 2, and FIGS. FIG. 3 is a view of the solar cell having the configuration 3 as viewed from the light incident side, in which three grids each having a length of about 10 cm are formed and a bus bar is provided at the center of each row.
1 to 4, 100 is a solar cell main body, 101 is a substrate, 102 is a lower electrode, 103 is an n layer, and 104 is i.
Layer, 105 is a p-layer, 106 is an upper electrode, 107 is a barrier layer, 108 is a grid electrode, 109 is a bus bar, 110
Indicates a defective portion.

Further, although not shown, the configuration using the idea of the present invention can be applied to amorphous silicon solar cells deposited on a glass substrate, crystalline solar cells such as single crystals and polycrystals, and thin film polycrystalline solar cells. Needless to say.

The substrate 101 is a semiconductor layer 103, 104, 1 in the case of a thin film solar cell such as amorphous silicon.
05 is a member that mechanically supports and is also used as an electrode in some cases. The substrate 101 is required to have heat resistance to withstand the heating temperature when the semiconductor layers 103, 104 and 105 are formed, but it may be a conductive material or an electrically insulating material. Is F
e, Ni, Cr, Al, Mo, Au, Nb, Ta, V,
Metals such as Ti, Pt, Pb, Ti or alloys thereof,
For example, brass, stainless steel and other thin plates and their composites and carbon sheets, galvanized steel plates, and the like, examples of the electrically insulating material, polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene,
Polyvinyl chloride, polyvinylidene chloride, polystyrene,
Films or sheets of heat-resistant synthetic resins such as polyamide, polyimide and epoxy, or composites of these with glass fibers, carbon fibers, boron fibers, metal fibers, etc., and different materials on the surface of thin plates of these metals, resin sheets, etc. Thin metal film and / or SiO ₂ , S
Examples thereof include those obtained by subjecting an insulating thin film such as i ₃ N ₄ , Al ₂ O ₃ , and AlN to a surface coating treatment by a sputtering method, a vapor deposition method, a plating method, and the like, and glass and ceramics.

The lower electrode 102 is composed of the semiconductor layers 103 and 10
It is one electrode for taking out the electric power generated at 4, 105, and is required to have a work function that makes an ohmic contact with the semiconductor layer 103. As the material, Al, Ag, Pt, Au, Ni, Ti, M
O, W, Fe, V, Cr, Cu, stainless steel, brass, nichrome, SnO ₂ , In ₂ O ₃ , ZnO, so-called metal simple substance or alloy such as ITO, and transparent conductive oxide (TCO) are used. . The surface of the lower electrode 102 is preferably smooth, but may be textured in the case of causing diffuse reflection of light. Also, the substrate 10
When 1 is conductive, it is not necessary to provide the lower electrode 102.

As a method of manufacturing the lower electrode, a method such as plating, vapor deposition and sputtering is used. As a method for producing the upper species, a resistance heating vapor deposition method, an electron beam heating vapor deposition method, a sputtering method, a spray method, or the like can be used and is appropriately selected as desired.

Examples of the semiconductor layer of the solar cell used in the present invention include amorphous silicon, polycrystalline silicon and single crystal silicon. In the amorphous silicon solar cell, as a semiconductor material forming the i layer 104, a-Si: H, a-Si: F, a-Si: H: F,
a-SiGe: H, a-SiGe: F, a-SiGe:
H: F, a-SiC: H, a-SiC: F, a-Si
Examples include so-called group IV and group IV alloy-based amorphous semiconductors such as C: H: F. The semiconductor material forming the p-layer 105 or the n-layer 103 can be obtained by doping the above-mentioned semiconductor material forming the i-layer 104 with a valence electron control agent. Further, as the raw material, a compound containing an element of the periodic table III is used as a valence electron control agent for obtaining a p-type semiconductor. As the third element, B,
Examples include Al, Ga, and In. As the valence electron control agent for obtaining the n-type semiconductor, a compound containing an element of the periodic table V is used. Group V elements include P, N, A
Examples include s and Sb.

As the film forming method of the amorphous silicon semiconductor layer, vapor deposition method, sputtering method, RF plasma CVD method,
Microwave plasma CVD method, ECR method, thermal CVD method,
A known method such as the LPCVD method is used as desired. As an industrially adopted method, RF plasma CV in which a raw material gas is decomposed by RF plasma and deposited on a substrate
Method D is preferably used. Furthermore, RF plasma CVD
In this case, the decomposition efficiency of the source gas is as low as about 10%, and the deposition rate is from 0.1 nm / sec to 1 nm / sec.
The microwave plasma CVD method has been attracting attention as a film forming method capable of improving this point, though it is a problem that it is relatively slow.

As a reaction apparatus for performing the above film formation, a known apparatus such as a batch type apparatus or a continuous film forming apparatus can be used as desired. In the solar cell of the present invention, a semiconductor junction is used for the purpose of improving spectral sensitivity and voltage.
It can also be used for a so-called tandem cell in which the above layers are stacked.

The upper electrode 106 is formed of the semiconductor layers 103, 10
Electrodes for extracting the electromotive force generated at 4, 105, which form a pair with the lower electrode 102. The upper electrode 106 is necessary in the case of a semiconductor having a high sheet resistance such as amorphous silicon, and is not particularly necessary in a crystalline solar cell since the sheet resistance is low. Further, since the upper electrode 106 is located on the light incident side, it needs to be transparent and is also called a transparent electrode. The upper electrode l
06 has a light transmittance of 85% or more in order to efficiently absorb light from the sun or a white fluorescent lamp in the semiconductor layer. Further, electrically, a semiconductor generates a current generated by light. It is desirable that the sheet resistance value is 100 Ω / □ or less so that the sheet flows laterally with respect to the layer. As materials having such characteristics, SnO ₂ , In ₂ O ₃ , Z
nO, CdO, CdSnO ₄ , ITO (In ₂ O ₃ + Sn
Metal oxides such as O ₂ ) may be mentioned.

Next, the grid electrode 108 is formed on the semiconductor layer 10
It is an electrode for taking out the electromotive force generated at 3, 104 and 105. The grid electrode 108 is formed in a comb shape, and a design such as a suitable width and pitch is determined depending on the size of the sheet resistance of the semiconductor layer 105 or the upper electrode 106. The grid electrode 108 is required to have a low specific resistance and not be a series resistance of the solar cell, and a desired specific resistance is 10 ⁻² Ωcm to 10 ⁻⁶ Ωcm.

Since the grid electrode 108 is comb-shaped, a mask pattern having a desired shape is used as a forming method.
A sputtering method, a resistance heating method, a CVD method or the like is used. Alternatively, a method of depositing a metal layer on the entire surface and then patterning by etching, a method of directly forming a grid electrode pattern by photo CVD, a method of forming a negative pattern mask of the grid electrode and then forming by a plating method, the metal powder Examples of the method include a method in which a polymer binder and a solvent for the binder are mixed at an appropriate ratio and screen printing of a so-called electrically conductive paste is used.

In the screen printing method, a conductive paste is used as a printing ink by using a screen in which a mesh made of polyester or stainless steel is subjected to desired patterning. The electrode width can be set to about 50 μm at the minimum. . A commercially available screen printing machine is preferably used as the printing machine. The screen-printed conductive paste is heated in a drying oven to crosslink the binder and evaporate the solvent. A hot air oven or an IR oven is used as the drying oven.

Bus bar 109 used in the present invention
Is an electrode for further collecting the current flowing through the grid electrode 108 at one end. Ag, Pt, C as electrode materials
It is possible to use a metal such as u or an alloy thereof, and as the form, a wire-shaped or foil-shaped one may be attached, or the same conductive paste as that of the grid electrode 108 may be used. As the foil-shaped material, for example, a copper foil, or a copper foil plated with tin, and an adhesive-attached material may be used in some cases.

As a method for forming the bus bar 109, a metal wire may be fixed with a conductive adhesive, a copper foil may be attached, or the bus bar 109 may be formed similarly to the grid electrode 108.

The solar cell produced as described above is modularized by encapsulation by a known method in order to improve weather resistance and maintain mechanical strength when used outdoors. Specifically, as an encapsulation material, for the adhesive layer, adhesiveness with solar cells, weather resistance,
EVA (ethylene vinyl acetate) in terms of buffering effect
Is preferably used.

Further, in order to further improve the moisture resistance and the scratch resistance, a fluorine resin is laminated as the surface protective layer. Examples of the fluorine-based resin include a polymer of tetrafluoroethylene TFE (such as Teflon manufactured by DuPont) and a copolymer of ethylene tetrafluoride and ETFE (manufactured by DuPont).
Tefzel, etc.), polyvinyl fluoride (Tedlar manufactured by DuPont, etc.), polychlorofluoroethylene CTFE (Neotron manufactured by Daikin Industries, Ltd.) and the like. Further, weather resistance may be improved by adding a known ultraviolet absorber to these resins.

As a method of encapsulation,
Using a known device such as a vacuum laminator,
A method of heating and pressing the solar cell substrate and the resin film in a vacuum is desirable.

[0066]

EXAMPLES The structures of the transparent electrode of the present invention and the solar cell of the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

(Example 1) A transparent electrode was prepared as follows using the manufacturing method of the present invention.

First, 100 parts by weight of ITO powder (manufactured by Sumitomo Metal Mining Co., Ltd.) of spherical particles having an average diameter of primary particles of 0.03 μm as a conductive filler and 5 parts by weight of an epoxy resin (number average molecular weight 5000) as a transparent binder. 100 parts by weight of butyl cellosolve acetate as a solvent and glass beads were mixed and dispersed for one day with a paint shaker. Then, the ITO cake thinly coated with the resin component was separated by suction filtration and collected.

100 parts by weight of the ITO cake and the epoxy resin were added, block isocyanate was added as a curing agent, and 50 parts by weight of butyl cellosolve acetate were mixed and kneaded using a three-roll mill to prepare a conductive paint. did. The conductive paint was printed on a Corning 7059 glass substrate with a screen printer, placed in a hot air oven (not shown) and cured at 180 ° C. for 30 minutes to prepare a transparent electrode. This sample was designated as S-11.

This sample was scanned with a scanning electron microscope (hereinafter referred to as SEM).
It is referred to as ") to observe the dispersed state of the particles. S in FIG.
An EM photograph is shown, but the size was about 0.2 μm. Moreover, the spectral transmittance from 400 nm to 800 nm was measured and shown in FIG. As shown in FIG. 8, the transmittance of the sample S-11 is good. The sheet resistance of the sample S-11 was measured by the four-terminal method to be 1500Ω / □.
And the electrical conductivity was good.

Then, the sample S-11 was prepared as follows.
The moisture resistance test was conducted. The sample was placed in an environmental tester at a temperature of 85 ° C. and a humidity of 85% based on JIS C0022 high temperature and high humidity test method, left for 1000 hours, and then the sheet resistance was measured by the four-terminal method in the same manner as above.
Ω / □, which was almost unchanged.

From the above results, it was found that the transparent electrode manufactured according to the present invention has good conductivity and light transmittance and has high reliability.

Comparative Example 1 Next, for comparison, a conductive coating material was prepared, coated and cured as follows to prepare a transparent electrode.

0.2 μm ITO as a conductive filler
Using an epoxy binder (number average molecular weight 35,000) and butyl cellosolve acetate as a solvent, dispersion kneading was carried out in the same manner as in Example 1 to prepare a conductive paint. The conductive paint was printed on a Corning 7059 glass substrate with a screen printer, placed in a hot air oven (not shown) and cured at 180 ° C. for 0 minutes to prepare a transparent electrode. This sample is It was set to 1-1.

The sheet resistance of the above sample was measured by the four-terminal method and found to be 5000 Ω / □. In addition, when the particle diameter was observed using a scanning electron microscope in the same manner as in Example 1, the particles were aggregated and were 2 μm or more. FIG. 10 shows a SEM photograph. Furthermore, as in Example 1, 4
The spectral transmittance from 00 nm to 800 nm was measured and shown in FIG. It can be seen that the transmittance of light having a short wavelength is worse than that in Example 1.

Next, the sample was subjected to a moisture resistance test in the same manner as in Example 1. When the sample was placed in an environmental tester having a temperature of 85 ° C. and a humidity of 85% and left for 1000 hours, the sheet resistance was measured, and it was found that the sheet resistance increased by about three times. This result shows that the transparent electrode according to the present invention has high reliability.

(Example 2) Next, a transparent electrode was prepared in substantially the same manner as in Example 1 except that the following conditions were changed.

First, transparent electrodes were prepared by changing the average diameter of the transparent conductive filler made of ITO to 0.1, 0.2, and 0.5 μm, and samples were prepared as S-21, S-22, and S-2.
3 and S-24. In addition, transparent conductive filler
A transparent electrode was prepared by changing O to In ₂ O ₃ , SnO ₂ , TiO ₂ , and ZnO, and samples were S-31, S-32, and S-3.
3 and S-34. Further, the above binder was changed from epoxy resin to acrylic resin, phenol resin, fluororesin, butyral resin, and the samples were changed to S-41,
S-42, S-4, and S-44.

The sheet resistance and the total light transmittance defined by JIS K7105 of the above sample were measured in the same manner as the sample S-11. In addition, the moisture resistance test conducted in Example 1 was performed in the same manner, and then the sheet resistance was measured. Table 1 shows the initial total light transmittance and the sheet resistance after the moisture resistance test. The sheet resistance shows the ratio of the value after the test to that before the test. From the above results, it was found that the transparent electrode manufactured according to the present invention has good conductivity and light transmittance and has high reliability.

[0080]

[Table 1]

Example 3 Next, a solar cell 100B having a pin junction type single cell structure with a bus bar and a grid length of 10 cm shown in FIG. 2 was produced as follows.

First, SUS4 that has been thoroughly degreased and washed
Substrate made of 0BA (width 10 cm x length 10 cm, thickness 0.
2 mm) 101 into a DC sputtering device (not shown)
g was deposited to 400 nm, and then ZnO was deposited to 400 nm to form the lower electrode 102. The substrate 101 is taken out and placed in an RF plasma CVD film forming apparatus (not shown) to form the n layer 1
03, i layer 104, and p layer 105 were deposited in this order. Then, it is put in a resistance heating vapor deposition device (not shown), and while maintaining the internal pressure of 1 × 10 ⁻⁴ Torr while introducing oxygen, In and S
n of alloy is vapor-deposited by resistance heating to form 70 n of transparent ITO upper electrode 106 having a function also as an antireflection effect.
m deposited.

Next, the substrate 101 was placed in a screen printing machine (not shown), and three rows of transparent conductive layers 107 having a width of 300 μm and a length of 10 cm were printed at intervals of 5 mm. At this time, 80 parts by weight of ITO powder having an average particle diameter of 0.08 μm and an epoxy-based binder 20 having a number average molecular weight of 3000 are used as the transparent conductive coating material.
10 parts by weight of butyl cellulose acetate as a solvent
A composition containing parts by weight was used. The manufacturing method used was that shown in Example 1.

Next, the temperature of the hot air oven (not shown) is set to 1
The temperature was maintained at 80 ° C., the substrate 101 was charged, and the ITO paste was cured. After that, the substrate 101 was taken out of the oven and cooled, and then the substrate 101 was placed in a screen printer (not shown), and grid electrodes 108 made of silver paste having a width of 200 μm and a length of 10 cm were printed at intervals of 1 cm. After printing, the substrate 101 is put in the oven at 160 ° C. for 3
Hold for 0 minutes to cure the silver paste. The thicknesses of the barrier layer (transparent conductive layer) 107 and the grid electrode 108 were both 10 μm. The barrier layer 107 had a total light transmittance of 80% and a specific resistance of 10 Ωcm.

Further, a bus bar 109 of copper foil with an adhesive having a width of 5 mm was adhered to produce a 10 cm × 10 cm square single cell shown in FIG. Further, ten samples were prepared by the same method.

Next, encapsulation of these samples was performed as follows. EVA is laminated on the upper and lower sides of the substrate 101, and the fluororesin film ETFE is formed on the upper and lower sides thereof.
After laminating (ethylene tetrafluoroethylene), put it in a vacuum laminator and hold at 150 ° C. for 60 minutes,
Vacuum lamination was performed. The obtained sample was Three
-1 to No. It was set to 3-10.

The initial characteristics of the obtained sample were measured as follows. First, the voltage-current characteristics of the sample were measured, and the shunt resistance was calculated from the slope near the origin. The shunt resistance was 55 kΩcm ^{2 to} 75 KΩcm ² , which was a good characteristic with little variation. Next, the solar cell characteristics were measured using a pseudo solar light source (hereinafter referred to as a simulator) having a light amount of 100 mW / cm ^{2 in} the AM-1.5 global sunlight spectrum, and the conversion efficiency was calculated to be 5.3%. ±
It was 0.5%, which was a good characteristic with little variation.

The reliability test of these samples was carried out according to the temperature and humidity cycle test A specified in the environmental test method and durability test method of the crystalline solar cell module of Japanese Industrial Standard C8917.
-2.

First, the sample was placed in a thermo-hygrostat capable of controlling temperature and humidity, and the temperature was changed from -40 ° C to + 85 ° C (relative humidity 85%).
The cycle test of changing to 10 was repeated 10 times. Next, when the solar cell characteristics of the sample after the test were measured using a simulator as in the initial stage, the average conversion efficiency was 1% lower than the initial conversion efficiency, and no significant deterioration occurred.
When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 8%.

From the results of this example, it is understood that the solar cell of the present invention using the transparent electrode of the present invention has good yield, good characteristics, and high reliability.

Comparative Example 2 Next, for comparison, a conventional solar cell 20 nm having the same structure as that of Example 3 but having no barrier layer was used.
(FIG. 5) was manufactured as follows.

Similar to the embodiment, the upper electrode 206 was formed on the substrate 201. Next, the grid electrode 208 was printed in the same manner as in Example 3. Further, a copper foil bus bar 209 with an adhesive is laminated and 10 cm × 10 shown in FIG.
Ten cm square single cells 200 were produced.

Next, the encapsulation of this sample was performed in the same manner as in Example 3. The obtained sample was analyzed by R. 2-1 to R.I. It was set to 2-10.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 3, the conversion efficiency was 4.8% ± 2.5.
%, The shunt resistance is 0.5 kΩcm ² to 50 kΩcm ²
The shunt resistance was lower than that in Example 3, and therefore the conversion efficiency was low and the variation was large.

Next, the reliability test of this sample was evaluated in the same manner as in Example 3. When the solar cell characteristics of the sample after the temperature / humidity cycle test were measured, the average value showed a decrease of 17% from the initial value, and significant deterioration occurred.

When the shunt resistance was measured, it was found that the average resistance dropped to 1.3 kΩcm ² and that shunt occurred after the reliability test.

The shunt portion of this sample was confirmed as follows. First, a reverse bias of 1.5 V was applied to the sample. At this time, current flows through the shunt portion to generate heat, but the normal portion does not generate heat due to the reverse bias because no current flows. When the surface of the sample was observed with an infrared camera in this state, a heat generating portion was observed and it was found that the sample electrode was shunted under the grid electrode 208.

From the above Example 3 and Comparative Example 2, it was found that in the solar cell of the present invention, the barrier layer 107 prevents the shunt at the lower part of the grid electrode 108, so that the initial efficiency is good and the reliability is good. It was

(Embodiment 4) The transparent conductive filler, the transparent binder, and the solvent constituting the barrier layer 107 are changed, and as shown in FIG.
A solar cell 100B having the layer structure shown in was prepared in substantially the same manner as in Example 3. The constituent materials of the barrier layer 107 are as follows. At this time, the total light transmittance of the barrier layer 107 is 7
It was 5% and the specific resistance was 450 Ωcm.

Constituent Material of Barrier Layer 107 Conductive Filler: SnO ₂ Powder 0.08 μm 100 parts by weight Transparent Binder: Polyester (number average molecular weight 5000) 20 parts by weight Solvent: Cellosolve acetate 10 parts by weight Width: 300 μm Thickness: 10 μm

After forming the barrier layer 107, a silver paste having a width of 200 μm and a length of 10 cm was printed in the same manner as in Example 3 to form a grid electrode 108 and an extraction electrode 109 was set. Next, the sample was laminated in the same manner as in Example 3. Ten similar samples were prepared. The obtained sample is N
o. 4-1 to No. It was set to 4-10.

The initial characteristics of the obtained sample were measured in the same manner as in Example 3. The conversion efficiency was calculated to be 6.1% ± 0.5
%, The characteristics were good and there was little variation.

When the reliability test of these samples was measured in the same manner as in Example 3, the average conversion efficiency was 2% lower than the initial conversion efficiency, and no significant deterioration occurred. Also,
When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

From the results of this example, it is understood that the solar cell of the present invention has good yield, good characteristics, and high reliability.

Example 5 A solar cell 100B was produced in the same manner as in Example 3 except that the conductive filler, binder and solvent constituting the barrier layer 107 were changed to those shown below. The barrier layer 107 had a total light transmittance of 85% and a specific resistance of 5 Ωcm.

Constituent material of barrier layer 107 Conductive filler: In ₂ O ₃ powder 0.05 μm 100 parts by weight Binder: Fluororesin (number average molecular weight 7000) 20 parts by weight Curing agent: Isocyanate solvent: Xylene 10 parts by weight Width: 300 μm Thickness : 5 μm

Ten samples were prepared and the obtained sample was
o. 5-1 to No. It was set to 5-10. The initial characteristics of the obtained sample were measured in the same manner as in Example 3.

The conversion efficiency was calculated to be 5.8% ± 0.4
%, The characteristics were good and there was little variation.

When a reliability test was conducted in the same manner as in Example 3, the average conversion efficiency was reduced by 1.5% with respect to the initial conversion efficiency, and no significant deterioration occurred. When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

From the results of this example, it can be seen that the solar cell of the present invention has good yield, good characteristics, and high reliability.

Example 6 A solar cell 100B was produced in the same manner as in Example 3 except that the conductive filler, binder and solvent constituting the barrier layer 107 were changed to those shown below. The barrier layer 107 had a total light transmittance of 75% and a specific resistance of 500 Ωcm.

Constituent material of barrier layer 107 Conductive filler: ZnO powder 0.05 μm 100 parts by weight Binder: Phenolic resin (number average molecular weight 7000) 30 parts by weight Solvent: Butyl cellosolve 10 parts by weight Width: 300 μm Thickness: 1.5 μm

Ten samples of the above were prepared, and No. 6-1
To No. It was set to 6-10. The initial characteristics of the obtained sample were measured in the same manner as in Example 3.

The conversion efficiency is 5.7. % ± 0.2%,
Even after the reliability test, the average efficiency was reduced by 3% with respect to the initial efficiency, and no significant deterioration occurred. When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 8%.

From the results of this example, it is understood that the solar cell of the present invention has good yield, good characteristics, and high reliability.

Example 7 A solar cell 100B was produced in the same manner as in Example 4 except that the conductive filler, binder and solvent constituting the barrier layer 107 were changed to those shown below. The barrier layer 107 had a total light transmittance of 75% and a specific resistance of 200 Ωcm.

Constituent Material of Barrier Layer 107 Conductive Filler: SnO ₂ Powder 0.08 μm 100 parts by weight Binder: Polyester (number average molecular weight 2000) 20 parts by weight Solvent: Cellosolve acetate 10 parts by weight Width: 300 μm Thickness: 10 μm

Ten samples were prepared and No. 7-1 to N
o. It was set to 7-10. The initial characteristics of the obtained sample were measured in the same manner as in Example 2.

The conversion efficiency was calculated to be 6.1% ± 0.5.
%, And after the reliability test, there was an average decrease of 2% with respect to the initial conversion efficiency, and no significant deterioration occurred. When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

From the results of this example, it is understood that the solar cell of the present invention has good yield, good characteristics, and high reliability.

Example 8 A solar cell 100B was produced in the same manner as in Example 4 except that the barrier layer 107 of ZnO was formed by sputtering. The barrier layer 107 had a total light transmittance of 75% and a specific resistance of 200 Ωcm.

Constituent Material of Barrier Layer 107 Barrier layer: ZnO Width: 300 μm Thickness: 10 μm

Ten samples were prepared and No. 8-1 to N
o. It was set to 8-10. The initial characteristics of the obtained sample were measured in the same manner as in Example 3.

The conversion efficiency was 6.3% ± 0.5%, and after the reliability test, there was an average decrease of 2.5% with respect to the initial conversion efficiency, and no significant deterioration occurred. When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

From the results of this example, it is understood that the solar cell of the present invention has good yield, good characteristics, and high reliability.

Example 9 A solar cell 100B was produced in the same manner as in Example 4 except that the barrier layer 107 was changed to carbon. The specific resistance of the barrier layer was 200 Ωcm.

Constituent Material of Barrier Layer 107 Conductive Filler: Carbon 100 parts by weight Binder: Epoxy 20 parts by weight Solvent: Cellosolve acetate 10 parts by weight Width: 200 μm Thickness: 10 μm

Ten samples were prepared and No. 9-1 to N
o. It was set to 9-10. The initial characteristics of the obtained sample were measured in the same manner as in Example 2.

The conversion efficiency was calculated to be 6.3% ± 0.5.
%, The characteristics were good and there was little variation.

When the reliability test of these samples was measured in the same manner as in Example 3, the average conversion efficiency was 2% lower than the initial conversion efficiency, and no significant deterioration occurred. Also,
When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

From the results of this example, it can be seen that the solar cell of the present invention has good yield, good characteristics, and high reliability.

(Example 10) Next, in Example 3, the solar cell is substantially the same as Example 3 except that the microwave plasma CVD method is used to form the semiconductor layer as the tortle type solar cell shown in FIG. A solar cell was manufactured by the method as described below.

First, a lower electrode 102 composed of an Ag layer and a ZnO layer is formed on a substrate 101, and then placed in a microwave plasma CVD film forming apparatus (not shown) to form an n layer 103,
The i layer 104 and the p layer 105 were deposited in this order to form a bottom layer. At this time, the i layer 104 was a-SiGe. Next, the n layer 113, the i layer 114, and the p layer 115 were deposited in this order to form a middle layer. The i layer 114 is a like the bottom layer.
-SiGe. Next, the n layer 123, the i layer 124, and the p layer 125 were deposited in this order to form a top layer. i layer 12
4 was a-Si. Next, as in the second embodiment, the transparent upper electrode 106 having a function also serving as an antireflection effect is formed by 70
0Å accumulated. As the upper electrode 106, In203 (I
O) was used.

Next, the substrate 101 is placed in a screen printing machine (not shown), and the barrier layer 1 having a width of 300 μm and a length of 30 cm.
07 were printed with a spacing of 5 mm. At this time, the transparent conductive coating is 70% (wt%) of ITO powder having an average particle diameter of 0.05 μm,
30 polyester binders with a number average molecular weight of 2500
% (Wt%), and a solvent having a composition containing 10% (wt%) of carbitol was used. Next, the temperature of a hot air oven (not shown) was maintained at 150 ° C., the substrate 101 was charged, and the ITO paste was cured. Then the substrate 10
After removing 1 from the oven and cooling, a base paste having a width of 200 μm and a length of 30 cm was printed at intervals of 5 mm in the same manner as in Example 3. After printing, a copper wire having a diameter of 100 μm was placed on the grid electrode 108. Furthermore, cream solder was printed.

Next, after melting the solder, the flux was washed. Further, a bus bar 109 is laminated, and the bus bar 109 shown in FIG.
A cm square triple cell was prepared. Similarly, ten samples were prepared.

Further, the encapsulation of this sample was performed in the same manner as in Example 2. The obtained sample was 5
-1 to No. It was set to 5-10.

The initial characteristics of the obtained sample are 6.5% ±
0.5% and shunt resistance is 35 kΩcm ^{2 to} 90 k
It was Ωcm ² and had good characteristics and little variation.

Next, the reliability test of this sample was performed in the same manner as in Example 3. When the solar cell characteristics of the sample after the completion of the temperature and humidity cycle test were measured, the average value was decreased by about 1.5% from the initial value and there was no significant deterioration. When the shunt resistance was measured, there was almost no change.

Comparative Example 3 Next, for comparison, a conventional triple solar cell 200B having no barrier layer shown in FIG. 6 was produced as follows.

Similar to Example 10, the upper electrode 206 was formed on the substrate 201. Next, the grid electrode 208 was printed in the same manner as in Example 10. Further, a copper foil bus bar 209 with an adhesive is laminated, and 10 cm × shown in FIG.
Ten 10 cm square triple cells 200B were produced.

Next, encapsulation of this sample was performed in the same manner as in Example 10. The obtained sample was analyzed by R. 3-1
To R. It was set to 3-10.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 10, the conversion efficiency was 5.3% ± 2.
1%, shunt resistance is 5.6 kΩcm ² to 32 kΩc
m ² and the shunt resistance was low as compared with Example 10, and therefore the conversion efficiency was low and the variation was large.

Next, the reliability test of this sample was evaluated in the same manner as in Example 10. When the solar cell characteristics of the sample after the temperature / humidity cycle test were measured, the average was 10% of the initial value.
, And significant deterioration had occurred.

From the above-mentioned Example 10 and Comparative Example 3, it was found that in the solar cell of the present invention, the barrier layer 107 prevents shunting under the grid electrode 108, so that the initial efficiency is good and the reliability is good. It was

[0145]

EFFECT OF THE INVENTION At least one kind of transparent conductive filler of the present invention and at least one kind of transparent binder made of an organic polymer resin are added and dispersed to prepare a transparent conductive paint. In a transparent electrode formed by applying and curing the above on a substrate, a transparent conductive filler having a primary particle diameter of 0.1 μm or less and an average particle diameter after dispersion of 0.2 μm or less is produced. The obtained transparent electrode has a low specific resistance and good transparency.

Further, when the transparent conductive filler is fine particles of metal oxide, and any one of In ₂ O ₃ , SnO ₂ , Sb-doped SnO ₂ , ITO, TiO ₂ , CdO and ZnO is used, the above effect can be obtained. It becomes even more remarkable. In addition, the average particle diameter of the fine particles of the metal oxide is 0.1 μm or less, and the shape is spherical, acicular, or scaly, so that transparency and electrical characteristics are further improved.

Further, when the number average molecular weight of the transparent binder is 10,000 or less, the dispersibility is improved.

In addition, at least a pair of pin semiconductor junctions of the present invention, a transparent upper electrode formed on the semiconductor layer located on the light incident side of the semiconductor junction, and a grid electrode formed on the upper electrode. In this solar cell, by laminating a barrier layer between the upper electrode and the grid electrode, a solar cell having good initial characteristics, good yield, and excellent moisture resistance can be obtained.

By setting the thickness of the barrier layer to be 1 to 30 μm, the barrier layer functions as a barrier layer having flexibility and no pinhole, and the above-mentioned effect becomes more remarkable. further,
When the width of the barrier layer is 1 to 5 times the width of the grid electrode, the above-mentioned effect becomes remarkable. By using the transparent electrode layer of the present invention as the barrier layer, there is an effect that the loss of incident light is small.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a solar cell according to an example of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a solar cell according to an example of the present invention.

FIG. 3 is a diagram schematically showing a configuration of a solar cell according to an example of the present invention.

FIG. 4 is a diagram schematically showing a configuration of a solar cell according to an example of the present invention.

FIG. 5 is a diagram schematically showing a configuration of a conventional solar cell.

FIG. 6 is a diagram schematically showing a configuration of a conventional solar cell.

FIG. 7 is a diagram schematically showing a configuration of a conventional solar cell.

FIG. 8 is a diagram showing light transmittances of a transparent electrode according to an example of the present invention and a conventional transparent electrode.

FIG. 9 is an SEM photograph of the transparent electrode of the present invention.

FIG. 10 is an SEM photograph of a conventional transparent electrode.

[Explanation of symbols]

100A, 100B, 100C, 100D, 200A,
200B, 200C solar cell body, 101, 201 substrate, 102, 112, 122, 202 lower electrode, 103, 113, 123, 203, 213, 223 n
Layers, 104, 114, 124, 204, 214, 224 i
Layers, 105, 115, 125, 205, 215, 225 p
Layers, 106, 116, 126, 206, upper electrodes 107, 117, 127 barrier layers, 108, 118, 128, 208 grid electrodes, 109, 119, 129, 209 busbars, 110 defective portions.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuko Yokoyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (20)

[Claims] 1. At least one conductive filler,
A transparent electrode in which a conductive coating material containing at least one kind of binder is formed on a substrate, and the average particle diameter of the conductive filler after dispersion is 0.5 μm or less. . 2. The transparent electrode according to claim 1, wherein the conductive filler comprises fine particles of metal oxide. 3. The metal oxide is In ₂ O ₃ , Sn
O ₂ , Sb-doped SnO ₂ , ITO, TiO ₂ , Cd
The transparent electrode according to claim 2, which is one or more of O and ZnO. 4. The transparent electrode according to claim 2, wherein an impurity of the metal oxide is 1% (% by weight) or less. 5. The transparent electrode according to claim 2, wherein the metal oxide has a spherical shape, a needle shape, or a scaly shape. 6. The binder comprises a polymer resin,
The transparent electrode according to any one of claims 1 to 5, wherein the number average molecular weight is 10,000 or less. 7. The thermoplastic resin as the binder is acrylic resin, alkyd resin, urethane resin, styrene resin, butyral resin, polyester resin, polycarbonate resin, and as the thermosetting resin, epoxy resin, phenol resin, melamine resin, 7. The transparent electrode according to claim 1, wherein at least one of alkyd resin, urethane resin, polyester resin, polyimide resin, and fluorine resin is selected and used. 8. A conductive filler having an average particle size of 0.1 μm or less and at least one binder made of a resin having a small molecular weight necessary to prevent secondary aggregation are added to a solvent and dispersed. By making a conductive paint,
Next, a method for forming a transparent electrode, characterized in that the conductive coating material is applied onto a substrate and then cured to form. 9. The method for forming a transparent electrode according to claim 8, wherein the conductive filler comprises fine particles of a metal oxide. 10. The metal oxide is In ₂ O ₃ , SnO.
₂ , Sb-doped SnO ₂ , ITO, TiO ₂ , Cd
The method for forming a transparent electrode according to claim 9, wherein the transparent electrode is one or more of O and ZnO. 11. The method of forming a transparent electrode according to claim 9, wherein the metal oxide has an impurity content of 1% (wt%) or less. 12. The shape of the metal oxide is spherical, acicular, or scaly.
2. The method for forming a transparent electrode according to any one of 1. 13. The method for forming a transparent electrode according to claim 8, wherein the binder is made of a polymer resin and has a number average molecular weight of 1,000 or less. 14. The binder is a thermoplastic resin such as acrylic resin, alkyd resin, urethane resin, styrene resin, butyral resin, polyester resin, polycarbonate resin, or thermosetting resin such as epoxy resin,
The phenol resin, the melamine resin, the alkyd resin, the urethane resin, the polyester resin, the polyimide resin, and at least one kind selected from the fluorine-based resins is selected and used. Method for forming transparent electrode. 15. A pair of at least a pin semiconductor junction or a pn semiconductor junction, a transparent upper electrode formed on a semiconductor layer located on the light incident side of the semiconductor junction, and a grid electrode formed on the upper electrode. A solar cell having a barrier layer having a resistance higher than that of the grid electrode between the upper electrode and the grid electrode. 16. The solar cell according to claim 15, wherein the barrier layer has a specific resistance value of 0.1 to 1000 Ωcm. 17. The total light transmittance of the barrier layer is 50%.
% To 90%, 16.
6. The solar cell according to 6. 18. The barrier layer has a thickness of 1 to 30 μm.
The solar cell according to any one of claims 15 to 17, wherein: 19. The solar cell according to claim 15, wherein the width of the barrier layer is 1 to 5 times the width of the grid electrode. 20. The solar cell according to claim 15, wherein the barrier layer comprises the transparent electrode according to any one of claims 1 to 7.