JPH06318721A - Solar battery - Google Patents

Abstract

PURPOSE:To obtain a highly reliable solar battery having excellent initial characteristics by providing a barrier layer having a higher resistance than a grid has and insulating layer between an upper electrode and grid electrode, with the insulating layer being formed so that the layer can surround the barrier layer area. CONSTITUTION:This battery is composed of a semiconductor layer having at least one pair of pin or p-n semiconductor junctions, transparent upper electrode 106 formed on the light incident side surface of the semiconductor layer, and grid electrode 108 formed on the electrode 106. In addition, a barrier layer area 107 having a higher resistance than the grid 108 has and insulating layer area 112 are formed between the electrodes 106 and 108, with the area 112 being formed so that the area 112 can surround the area 107. The specific resistivity of the layer 107 is set at 0.1-1,000cm and the transmissivity of the layer 112 against all kinds of light rays is controlled to 50% to 90%. Therefore, the manufacturing yield of the battery can be increased and the metal migration which occurs under a high-temperature, high-humidity condition can be prevented. In addition, the reliability of the battery can be improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a solar cell having excellent characteristics and high reliability. More specifically, the present invention relates to a grid electrode structure for a solar cell that prevents shunts and short circuits and has high reliability during long-term use.

[0002]

2. Description of the Related Art Solar cells have been widely applied as a power source for consumer equipment such as calculators and wristwatches, and have been attracting 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. .

A solar cell is a technique that utilizes the diffusion potential generated at a semiconductor junction such as a pn junction, a pin junction, and a Schottky junction of a semiconductor. A semiconductor such as silicon absorbs sunlight to generate electrons and holes. Photocarriers are generated, the photocarriers are drifted by an internal electric field generated by the diffusion potential of the junction, and the photocarriers are taken out to the outside. Examples of semiconductor materials for such solar cells include amorphous silicon, amorphous silicon germanium, and tetrahedral amorphous semiconductors such as amorphous silicon carbide. Thin-film solar cells using these materials have the advantages of being able to form a large-area film, having a small film thickness, and being able to be deposited on any substrate material, as compared to single-crystal solar cells. Has been done.

The structure of an amorphous silicon solar cell is
For example, p made of thin film amorphous silicon on the substrate
It is configured by laminating a layer, an i layer, and an n layer. In addition, a so-called tandem cell in which two or more pin junctions are stacked in series has been studied to improve conversion efficiency. A pair of electrodes, an upper electrode and a lower electrode, are provided on the light incident side and the back surface side of the semiconductor layer. In amorphous silicon solar cells, the sheet resistance of the semiconductor itself is generally high, so a transparent upper electrode is required over the entire surface of the semiconductor.
A transparent conductive film that functions as an antireflection film, such as SnO ₂ or ITO (In ₂ O ₃ + SnO ₂ ) is used. A comb-shaped grid electrode for collecting current is provided on the upper electrode so as not to prevent the incidence of light, and a bus bar for collecting the current of the grid electrode is further provided.

By the way, when a 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 with a conversion efficiency of 10% is used, it is 30.
An area of m ² and a large area solar cell are required. However, it is difficult to make a defect-free solar cell over a large area due to the manufacturing process of the solar cell. For example, a polycrystal has a low resistance part in the grain boundary part, or a thin film solar cell such as amorphous silicon. It is known that in forming a semiconductor layer, pinholes and defects are generated due to the influence of dust and the like, which causes shunts and shorts, and these shunts and shorts significantly reduce the conversion efficiency.

The cause of pinholes and defects and their effects will be described in more detail. For example, in the case of an amorphous silicon solar cell deposited on a stainless steel substrate, the substrate surface cannot be said to be a perfectly smooth surface, and scratches, dents,
Alternatively, since there are spike-like protrusions or a back reflector having irregularities is provided on the substrate for the purpose of irregularly reflecting light, a thin semiconductor layer having a thickness of several tens nm such as p and n layers is Such surface cannot be completely covered, or another cause is that pinholes are generated due to dust during film formation. The semiconductor between the lower electrode and the upper electrode of the solar cell is lost due to the pinhole and the lower electrode and the upper electrode are in direct contact with each other, the spike-like defect of the substrate is in contact with the upper electrode, and the semiconductor layer is If the shunt or short circuit has low resistance, if not completely lost, the current generated by light will flow in parallel to the upper electrode and flow into the low resistance part of the shunt or short circuit. Will be lost. Even with a minute defect, the current flowing into the defect is quite large. With such a current loss, the open-circuit voltage of the solar cell drops significantly, and especially 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 much, The open circuit voltage will decrease significantly. Furthermore, when the defect is located away from the grid electrode or bus bar, the resistance when flowing into the defect is large, so the current loss is relatively small, but when the defect is below the grid electrode or bus bar, the defect is defective. Therefore, the current that is lost becomes larger. On the other hand, in the pinhole-shaped defect portion, not only the charge generated in the semiconductor layer leaks to the defect portion, but also an ionic substance is generated due to the interaction with moisture, so that when the solar cell is used,
It can be seen that the electric resistance of the defective portion gradually decreases with the lapse of use time, and characteristics such as conversion efficiency deteriorate.

As a measure against such a problem, for example,
In US Pat. No. 4,598,306, a transparent electrode or a transparent electrode is provided by providing a material having a sufficiently high resistance as a barrier layer between a semiconductor layer and a transparent electrode layer in order to prevent a shunt or a short circuit at a defective portion. A method of increasing the contact resistance with the grid electrode or the bus bar and preventing a decrease in conversion efficiency is disclosed. In addition, US Pat. No. 4,59
As disclosed in Japanese Patent No. 0,327, a method of providing an insulating layer between the bus bar and the transparent electrode has been proposed.

[0008]

However, in the conventional solar cell disclosed above, since the barrier layer must be transparent, it is necessary to make it as thin as several hundred Å to several μm, and as a result, the barrier layer itself has to be pinned. Holes are likely to be formed, so that the production yield due to the shunt and leakage due to humidity during actual use cannot be prevented and there is a problem in reliability. Also, by providing an insulating layer under the busbar, shunting at the busbar can be prevented, but the lower part of the busbar is not in electrical contact with the upper electrode, so the current collection efficiency is reduced, and at the lower part of the grid electrode. There is a problem that the shunt cannot be prevented.

An object of the present invention is to solve the problems such as the shunt and reliability of a solar cell and to provide a highly reliable solar cell configuration with good characteristics.

[0010]

The solar cell of the present invention comprises a semiconductor layer having at least a pair of pin semiconductor junctions or pn semiconductor junctions, a transparent upper electrode formed on the light incident side of the semiconductor layer, In a solar cell including a grid electrode formed on an upper electrode, a barrier layer region having a higher resistance than the grid between the upper electrode and the grid electrode, and an insulating layer region surrounding the barrier layer region. Is provided.

The specific resistance value of the barrier layer is preferably 0.1 to 1000 Ωcm. The total light transmittance of the insulating layer is preferably 50% to 90%.

[0012]

FUNCTION AND EXAMPLE OF OPERATION In the solar cell of the present invention, a barrier layer region having a higher resistance than the grid electrode is formed between the upper electrode also serving as an antireflection layer and the grid electrode to prevent a short circuit or a shunt. Furthermore, since the insulating layer region is provided around the barrier layer region, the function of the barrier layer can be further improved by the synergistic effect of the barrier layer region and the insulating layer region, increasing shadow loss and series resistance. It is possible to prevent the initial shunt by preventing contact between the upper electrode and the lower electrode in the defective portion of the semiconductor layer while preventing the adverse effects such as the above. Therefore, it is possible to improve the manufacturing yield, prevent the migration of metal that occurs in a high temperature and high humidity environment during actual outdoor use, and improve the reliability.

The grid electrode is an electrode for taking out the electromotive force generated in the semiconductor layer, and the material of the grid electrode is Ti, Cr, Mo, W, Al, Ag, N.
A metal such as i, Cu, Sn, or Pt, an alloy thereof, solder, or the like is used. When using the solar cell outdoors,
The metal migrates depending on the type of each metal to some extent due to humidity and deteriorates solar cell characteristics.However, in the present invention, since a barrier layer having high resistance is provided between the grid and the semiconductor layer, migration is prevented. , The reliability of solar cells will be high.

As the material of the barrier layer, SnO ₂ , In ₂
A metal oxide such as O ₃ , ZnO, CdO, CdSnO ₄ , and ITO, a conductive paste containing the metal oxide as a filler, and a carbon paste are preferably used.

In the solar cell, defects such as a low resistance portion caused by unevenness of the substrate, dust during film formation, or the like, which is normal in the initial stage of manufacture but has a low resistance during use, have defects. 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. However, by providing a barrier layer having high resistance as in the present invention, 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, yet has sufficient conductivity with respect to the current generated by the solar cell and has a resistance value that does not impair the efficiency of the solar cell. is necessary. That is, the barrier layer does not resist the current generated by the solar cell, and at the same time, acts as a resistance when there is a defect and prevents a large leak. The resistance value of the barrier layer is
It is determined by the design of the grid, the current value at the operating point of the solar cell, the size of defects, etc., but when the film thickness is 10 μm, the specific resistance is preferably 0.1 Ωcm to 1000 Ωcm. Enough resistance,
Moreover, the resistance value is negligible with respect to the current generated in the solar cell. In addition, the barrier layer and the upper electrode must have ohmic characteristics.

The thickness of the barrier layer is determined by requirements such as no pinholes, sufficient barrier properties against humidity, adhesiveness and flexibility, but if it is 1 μm or less, it easily becomes pinholes, and if it is 30 μm or more. However, the flexibility is impaired, so about 1 to 30 μm is preferable. The morphology of the barrier layer region is usually formed smaller than the pattern of the grid electrode, but it may be different from the shape of the grid electrode, and may be formed in dots, for example. When the pattern formation in the barrier layer region is performed by screen printing, the viscosity of the paste is 1000 cps.
It is desirable to be about 100,000 cps.

In addition, when the solar cell is used outdoors, it is necessary to have weather resistance that can withstand humidity and temperature. Therefore, in the present invention, the insulating layer region is formed slightly wider than the grid electrode in order to prevent the migration of the metal used for the grid electrode due to the influence of humidity in the place below the grid electrode and without the barrier layer. It Further, in order to reduce shadow loss in the portion other than the grid electrode, it is preferable that the insulating layer is transparent with respect to a wavelength having a spectral sensitivity of the solar cell, and for example, the total light transmittance defined by JISK7105 is 50 to 50. 90% is desirable.

As the material of the insulating layer, polymer resin, ceramics, SiO ₂ , Si ₃ N _4, etc. are preferably used. As a forming method, a screen printing method, a sputtering method, a method of adhering a film-like insulating layer, or the like is used. Further, when the barrier layer region is formed of a conductive paste, the binder component of the conductive paste may have the function of the insulating layer.

The solar cell of the present invention has a structure in which current leakage due to a shunt or short circuit is reduced by forming a high resistance layer under the grid electrode, and it 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.

An example of the embodiment of the solar cell of the present invention will be described below with reference to the drawings.

A preferred example of the structure of the solar cell of the present invention is shown in FIGS.
6 schematically shows.

FIG. 1 shows a sectional view of the solar cell of the present invention.
FIG. 2 is a view of the solar cell of the present invention viewed from the light incident side,
In this figure, a linear barrier layer region is used. In FIG. 3, the barrier layer region is formed in a dot shape. FIG. 4 is an amorphous silicon solar cell of the present invention having a single cell structure in which light is incident from the side opposite to the substrate, FIG. 5 is a solar cell having a triple structure of the solar cell of FIG. 4, and FIG. 6 is a structure of FIGS. It is the figure which looked at the solar cell from the light incident side, and is about 10 cm.
The grid of the length is formed, and the bus bar is provided in the center. Further, although not shown, it goes without saying that the configuration using the idea of the present invention can be applied to a solar cell deposited on a glass substrate, a crystalline solar cell such as a single crystal or a polycrystal, or a thin film polycrystalline solar cell. .

In FIG. 1, 100A is a solar cell main body,
101 is a substrate, 102 is a lower electrode, 103 is an n layer, 10
4 is an 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,
Reference numeral 110 represents an extraction electrode, 111 represents a defective portion, and 112 represents an insulating layer.

When the substrate 101 is a thin film solar cell such as amorphous silicon, the semiconductor layers 103, 104, 1
05 is a member that mechanically supports and is also used as an electrode in some cases. The substrate 101 is the semiconductor layer 10
Heat resistance is required to withstand the heating temperature at the time of forming the films 3, 104, 105, and either conductive or electrically insulating material may be used. As the conductive material, specifically, Fe, N
i, Cr, Al, Mo, Au, Nb, Ta, V, Ti,
Metals such as Pt, Pb and Ti or alloys thereof, for example, thin plates such as brass and stainless steel and their composites, carbon sheets, galvanized steel plates and the like can be used. As 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, glass, ceramics and the like.

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 alone or an alloy, and a transparent conductive oxide such as ITO (TCO) or the like is used . Although the surface of the lower electrode 102 is preferably smooth, it may be textured if it causes irregular reflection of light. Further, when the substrate 101 is conductive, the lower electrode 102 need not be provided.

As a method of manufacturing the lower electrode, a method such as plating, vapor deposition, sputtering or the like is used. Further, as a method for manufacturing the upper electrode, a resistance heating evaporation method, an electron beam heating evaporation 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
So-called group IV and group IV alloy-based amorphous semiconductors such as C: H: F are used. As the semiconductor material forming the p layer 105 or the n layer 103, the i layer 1 described above is used.
It is obtained by doping the semiconductor material constituting 04 with a valence electron control agent. As the valence electron control agent for obtaining the p-type semiconductor, a compound containing an element of Group III of the periodic table is used, and as the element of Group III, B, A
1, Ga, and In may be used. As a valence electron control agent for obtaining an n-type semiconductor, a compound containing an element of Group V of the periodic table is used. Group V elements include P, N and A
s and Sb are fisted.

The amorphous silicon semiconductor layer can be formed by vapor deposition, sputtering, RF plasma CVD,
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, an RF plasma CVD method in which a source gas is decomposed by RF plasma and deposited on a substrate is preferably used. Further, in RF plasma CVD, the decomposition efficiency of the source gas is as low as about 10%, and the deposition rate is from 1Å / sec to 10Å / sec.
The microwave plasma CVD method is attracting attention as a film forming method that improves this point, though it has problems such as being 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. The solar cell of the present invention can also be used in a so-called tandem cell in which two or more semiconductor junctions are stacked for the purpose of improving spectral sensitivity and voltage.

The upper electrode 106 is composed of the semiconductor layers 103, 10
The electrodes are for taking out the electromotive force generated at 4, 105 and form a pair with the lower electrode 102. Upper electrode 1
06 is required 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. Also, the upper electrode 1
06 is also called a transparent electrode because it is required to be located on the light incident side and transparent. The upper electrode 106 preferably has a light transmittance of 85% or more in order to efficiently absorb light from the sun, a white fluorescent lamp, or the like in the semiconductor layer. Further, electrically, a current generated by light is used. Sheet resistance value is 10
It is preferably 0Ω / □ or less. As materials having such characteristics, SnO ₂ , In ₂ O ₃ , ZnO, Cd
Metal oxides such as O, CdSnO ₄ , and ITO (In ₂ O ₃ + SnO ₂ ) can be used.

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 magnitude of the sheet resistance of the semiconductor layer 105 or the upper electrode 106. It is required that the grid electrode 108 has a low specific resistance and does not become a series resistance of the solar cell, and a desired specific resistance is 10 ^-2.
Ωcm to 10 ⁻⁶ Ωcm, and the material is Ti, C
r, Mo, W, Al, Ag, Ni, Cu, Sn, Pt,
A metal such as Cu, an alloy thereof, or solder is used. As a method of forming the comb-shaped grid electrode 108, a method of forming a comb pattern having a desired shape by 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 A polymer binder and a solvent for the binder are mixed in an appropriate ratio, and screen printing of a so-called conductive paste in paste form is used, or the metal plating method is used, or the metal is laid in a wire form. The method of doing is mentioned.

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, and an electrode having a minimum width of about 50 μm can be formed. it can. 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. Drying oven is hot air oven or IR (infrared)
An oven is used.

The 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. As the electrode material, a metal such as Ag, Pt, Cu or the like or an alloy thereof can be used, and as the form, a wire-like or foil-like one is stuck, or a conductive paste similar to the grid electrode 108 is used. You may use. As the foil, for example, a copper foil, or a copper foil plated with tin, and in some cases, an adhesive is used.

As a method of 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 manufactured as described above is modularized by encapsulation by a known method in order to improve weather resistance and maintain mechanical strength during outdoor use. As a concrete encapsulation material,
As the adhesive layer, EVA (ethylene vinyl acetate) is preferably used in terms of adhesiveness with a solar cell, weather resistance, and buffering effect. Further, in order to further improve moisture resistance and scratch resistance, a fluorine-based resin is laminated as a surface protection layer. Examples of the fluorine-based resin include a polymer of tetrafluoroethylene TFE (such as Teflon manufactured by DuPont), a copolymer of ethylene tetrafluoride and ethylene ETFE (such as Tefzel manufactured by DuPont), and polyvinyl fluoride (Tedlar manufactured by DuPont). , 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.

[0035]

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

Example 1 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. 4 was prepared as follows.

First, SUS4 which has been thoroughly degreased and washed
Substrate made of 30BA (10 cm square, thickness 0.2 mm) 101
Was placed in a DC sputtering apparatus to deposit Ag to a thickness of 400 nm, and then ZnO was deposited to a thickness of 400 nm to form the lower electrode 102. The substrate 101 was taken out and placed in an RF plasma CVD film forming apparatus to deposit the n layer 103, the i layer 104, and the p layer 105 in this order. After that, put it in a resistance heating vapor deposition device,
Maintaining an internal pressure of 1 × 10 ^-4 Torr while introducing oxygen,
An alloy of In and Sn was vapor-deposited by resistance heating, and a transparent ITO upper electrode 106 also having an antireflection effect was deposited to a thickness of 70 nm.

Next, the barrier layer 107 was formed as follows. In this embodiment, the barrier layer is made of carbon paste of epoxy resin binder. The specific resistance of the carbon paste was 1000 Ωcm.

The substrate 101 is installed in the screen printing machine,
A barrier layer 107 made of a carbon paste having a width of 100 μm and a length of 10 cm was printed at intervals of 5 mm. Next, the temperature of the hot air oven was maintained at 120 ° C., the substrate 101 was put in, and the barrier layer 107 was cured.

Next, the insulating layer 112 was formed as follows. In this embodiment, the insulating layer is made of epoxy resin. The substrate 101 was placed in a screen printing machine, and an insulating layer 112 having a width of 100 μm was printed on both ends of the barrier layer 107. Next, the temperature of the hot air oven was maintained at 120 ° C., and the substrate 1
01 was added to cure the insulating layer. The total light transmittance of the insulating layer 112 was 80%.

After that, the substrate 101 was taken out of the oven and cooled, and then the substrate 101 was placed in a screen printing machine.
A grid electrode 108 made of a silver paste having a width of 200 μm and a length of 10 cm was overlaid on the barrier layer 107 and printed. After printing, the substrate 101 is placed in the oven at 160 ° C. for 30 minutes.
Hold for minutes to cure silver paste. Furthermore, width 5m
A copper foil bus bar 109 with an adhesive of m was adhered to produce a 10 cm × 10 cm square single cell shown in FIG.

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 and under the EVA.
After stacking (product name Tefzel manufactured by DuPont), it was put into a vacuum laminator and held at 150 ° C. for 60 minutes to carry out vacuum lamination. Further, ten samples were prepared by the same method.

The initial characteristics of the obtained sample were measured as follows.

[0044] First, to measure the voltage-current characteristic in the dark state of the samples were determined inclination shunt resistance from the vicinity of the origin, and 30KΩcm ² ~80KΩcm ^2, a rather good characteristics shunt, also variation in small It was

Next, the conversion efficiency was determined by measuring the solar cell characteristics using a pseudo solar light source (hereinafter referred to as a simulator) manufactured by SPIRE with a light amount of 100 mW / cm ^{2 in} the AM1.5 global sunlight spectrum. 5.8% ±
The characteristic was as good as 0.5% and there was little variation.

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

First, the sample is placed in a thermo-hygrostat whose temperature and humidity can be controlled, and from -40 ° C to + 85 ° C (85% relative humidity).
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 in the same manner as the measurement of the initial characteristics, the average conversion efficiency was reduced by 2% 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.

In this embodiment, a carbon paste of an epoxy binder is used as the barrier layer 107.
₂ O ₃ , SnO ₂ , Sb-doped SnO ₂ , ITO, Ti
The same effect can be obtained by using a paste composed of a powder of O ₂ , CdO, ZnO or the like and a polymer resin, and an epoxy resin is used as the insulating layer.
Confirmed that similar effects can be obtained with alkyd resin, urethane resin, styrene resin, butyral resin, polyester resin, polycarbonate resin, phenol resin, melamine resin, alkyd resin, urethane resin, polyester resin, polyimide resin, fluorine resin, etc. did.

(Comparative Example 1) Next, for comparison, a conventional solar cell 200 having no barrier layer shown in FIG. 7 was manufactured in substantially the same manner as in Example 1 as follows.

Similar to Example 1, the upper electrode 206 was formed on the substrate 201. Next, the grid electrode 208 was printed in the same manner as in Example 1. Further, a copper foil bus bar 209 with an adhesive was laminated to produce 10 single cells 200 of 10 cm × 10 cm square.

Next, the encapsulation of this sample was performed in the same manner as in Example 1.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 1, 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 of Example 1, 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 1. 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, the average resistance dropped to 1.3 KΩcm ² , and it was found that a shunt was generated 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-mentioned Example 1 and Comparative Example 1, in the solar cell of the present invention, the barrier layer 107 and the insulating layer 110 prevent shunting under the grid electrode 108, so that the initial efficiency is high and the reliability is good. It turned out that

Example 2 Next, a sample was prepared in the same manner as in Example 1 except that the material and forming method of the insulating layer 110 were changed. ZnO was used for the barrier layer 107 and SiO ₂ was used for the insulating layer.

Similar to Example 1, the upper electrode 106 was formed on the substrate 101. Next, the substrate 101 is placed in a DC sputtering apparatus, ZnO is deposited to a thickness of 5 μm, and the barrier layer 10 is formed.
Formed 7. The stoichiometric ratio is adjusted by optimizing the oxygen partial pressure during sputtering to adjust the specific resistance of the barrier layer 107 to 0.1Ω.
cm. The width and length of the barrier layer 107 were the same as in Example 1. Next, SiO ₂ is deposited by sputtering to form the insulating layer 11
Formed 2. The total light transmittance of the insulating layer 112 was 90%. Then, in the same manner as in Example 1, the grid electrode 1
08 and bus bar 109 are laminated, and 10 cm × shown in FIG.
Ten 10 cm square single cells 100B were produced.

Next, the encapsulation of this sample was performed in the same manner as in Example 1.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 1, it was 6.3% ± 0.2%,
The shunt resistance was 50 KΩcm ^{2 to} 70 KΩcm ² with good characteristics and little variation.

Next, the reliability test of this sample was performed in the same manner as in Example 1. When the solar cell characteristics of the sample after the temperature and humidity cycle test were measured, it was about 1.5% on average with respect to the initial value.
There was no significant deterioration. In addition, when the shunt resistance was measured, there was almost no change.

From the results of this example, it is understood that the solar cell having the constitution of the present invention has a good yield, good characteristics and good durability.

In this embodiment, ZnO is used as the barrier layer 107.
However, In ₂ O ₃ , SnO ₂ , and Sb-doped Sn were used.
The same effect can be obtained by using a thin film of O ₂ , ITO, TiO ₂ , CdO or the like, and the insulating layer 112 is made of SiO.
_{Although 2} was used, it has been confirmed that the same effect can be obtained by using Al ₂ O ₃ , Si ₃ N ₄ or the like.

[0065]

According to the present invention, that is, by providing a barrier layer region having a higher resistance than the grid between the upper electrode and the grid electrode and an insulating layer surrounding the barrier layer region, good initial characteristics can be obtained. It is possible to provide a highly reliable solar cell.

According to the second aspect of the invention, a solar cell having further improved photoelectric conversion efficiency and reliability can be obtained. Further, according to the invention of claim 3, it is possible to obtain a solar cell having further excellent initial characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the structure of a solar cell of the present invention.

FIG. 2 shows a barrier layer of the solar cell of the present invention, a grid electrode,
It is a top view which shows the structural example of an insulating layer typically.

FIG. 3 is a barrier layer of the solar cell of the present invention, a grid electrode,
It is a top view which shows the other structural example of an insulating layer typically.

FIG. 4 is a cross-sectional view schematically showing the structure of a single solar cell of the present invention.

FIG. 5 is a cross-sectional view schematically showing the structure of a triple solar cell of the present invention.

FIG. 6 is a plan view schematically showing the configuration of the solar cell of the present invention.

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

[Explanation of symbols]

 100,200 Solar cell main body 101,201 Substrate 102,112,122,202 Lower electrode 103,113,123,203 n layer 104,114,124,204 i layer 105,115,125,205 p layer 106,116, 126,206 Upper electrode 107,117,127 Barrier layer region 108,118,128,208 Grid electrode 109,119,129 Bus bar 110 Extraction electrode 111 Defective part 112 Insulating layer.

Front Page Continuation (72) Inventor Yuko Yokoyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. A semiconductor layer having at least a pair of a pin semiconductor junction or a pn semiconductor junction, a transparent upper electrode formed on a light incident side of the semiconductor layer, and a grid electrode formed on the upper electrode. In the solar cell
A solar cell, wherein a barrier layer region having a higher resistance than the grid and an insulating layer region surrounding the barrier layer region are provided between the upper electrode and the grid electrode. 2. The specific resistance value of the barrier layer is 0.1 to 1
The solar cell according to claim 1, wherein the solar cell has a resistance of 000 Ω · cm. 3. The total light transmittance of the insulating layer is from 50% to
It is 90%, The solar cell of Claim 1 or 2 characterized by the above-mentioned.