JPH0652798B2 - Method of manufacturing thin film solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] In the present invention, a junction for photoelectric conversion is formed of amorphous silicon (hereinafter referred to as a-Si) or the like, and one electrode is formed of a printed electrode. Low cost thin film solar cells.

[Conventional technology]

In a conventional thin film solar cell using amorphous silicon, unit cells are usually connected in series to increase the output voltage.
The unit cell uses, for example, ITO (indium tin oxide) and SnO ₂ (tin oxide) on a transparent insulating substrate such as a glass substrate as a transparent electrode, and glow discharge decomposition of a mixed gas of hydrocarbons such as silane and acetylene and diborane. P layer with a thickness of about 200 Å, and about 0.5 due to glow discharge decomposition of silane gas
A metal thin film of about 1 μm sandwiching an a-Si layer with a pin structure of a non-doped layer with a thickness of μm and an n layer with a thickness of about 500 Å by glow discharge decomposition of a mixed gas of silane and phosphine. It has a back electrode made of. In order to connect in series, a transparent electrode film and a-Si are formed on one transparent insulating substrate.
A film and a back electrode film are formed on the entire surface, and each time patterning is performed to separate each cell and form an inter-cell connection portion. The patterning of the transparent electrode is performed by a photolithography method in which a film is formed by electron beam evaporation or sputtering, and then a printing method or a resist pattern is formed by exposure using a photomask and etching is performed. a
The patterning of the -Si film is performed by a photolithography method or a laser scribing method. The metal electrode film is formed by electron beam evaporation or sputtering, and patterned by photolithography.

[Problems to be solved by the invention]

Among them, in order to form the back electrode with a metal thin film, it is difficult to reduce the number of steps because an expensive vapor deposition apparatus and sputtering apparatus are used and a photolithography technique is applied. Therefore, in order to reduce the cost of the solar cell, it was considered to form the back electrode by a printed electrode on which film formation and patterning are simultaneously performed. In the case of crystalline Si or polycrystalline Si solar cells, apply a paste prepared by mixing Ag particles with epoxy resin and fire at 600-700 ° C to make electrical contact with the Si layer and form the electrode. You can However, when applied to an a-Si solar cell, for example, the characteristics shown by the line 10 in FIG. 2 are obtained, and the fill factor is 0.4 or less. This is because in the case of a-Si, the temperature cannot be raised to 200 ° C. or higher, so that the polymer resin cannot be skipped and sintered, and a sufficiently low contact resistance cannot be secured. Therefore, as a-Si electrode paint,
It is necessary to obtain a sufficiently low contact resistance by firing at about 0 ° C. In addition, the conventional printed electrode does not have good moisture resistance.

The object of the present invention is to solve the above-mentioned problems, and by baking at about 150 ° C., a printed electrode which can obtain a sufficiently low contact resistance with the a-Si layer and can withstand high temperature and high humidity is used as a back electrode. To provide a thin film solar cell.

[Means for solving problems]

In order to achieve the above object, the present invention provides a solar cell manufacturing method in which unit cells each having a transparent electrode and an a-Si layer having a junction and a back electrode are laminated in series are connected on a transparent insulating substrate. The electrode comprises a first resin containing Ni particles as a conductive substance and kneading a silicon coupling agent, and a second resin containing carbon particles as a conductive substance and kneading a silicon coupling agent. It is assumed that the first resin and the second resin are printed so as to be in contact with each other in this order and printed, and then baked.

[Action]

The back electrode printed by adding a silicon coupling agent to a resin mixed with Ni particles was a-Si by firing at a temperature of about 150 ° C.
It forms a low contact resistance with the layer, has a large fill factor, and has excellent stability of properties. However, there is a problem that the resin surface deteriorates and peels off when left for a long time.Therefore, a resin that contains carbon particles and is kneaded with a silicon coupling agent is overlaid to complement the physical stability such as appearance and contact. .

〔Example〕

Three embodiments of the present invention will be described below with reference to the drawings.

Example 1 In FIG. 1, ITO (indium tin oxide) or SnO ₂ (tin oxide) is deposited on the glass substrate 1 by electron beam evaporation or sputtering, and then transparent electrodes 21, 22, 23 are formed by photolithography. Pattern 24 ... Then, an a-Si layer having a pin structure is formed by the method described above, and one end of the transparent electrodes 21, 22,
Patterns 31, 32, 33, 34 that fill part of the space of 23, 24 ...
... to form. Subsequently, the pattern of the metal electrodes 41, 42, 43, and 44 was used as a filler, and a phenol resin containing Ni particles and a phenol resin containing amorphous carbon particles were laminated and formed by a printing method. As the phenol resin, a resin obtained by reacting phenol, formalin, rosin, and oil to esterify with glycerin and the like and mixing an alkyd resin with a phenol / alkyd ratio of 4/6 to 2/8 may be used. it can. As alkyd resin,
It was formed by adding linseed oil, tung oil, soybean oil and other drying oils, dehydrated castor oil or its constituent fatty acids to the system of phthalic anhydride and glycerin.

The Ni particles were formed into powder having a particle size of 6 to 10 μm using a ball mill or the like, and were mixed in a weight ratio of 1 to 5 times that of the resin. Further, 0.1 to 5% by weight of a silicone coupling agent such as γ-aminopropyltriethoxysilane manufactured by Toshiba Silicone, trade name TSL8331 and the like were added. Using ethylene glycol-based or diethylene glycol-based solvent or the like for this resin, the viscosity is adjusted to 100 to 400 poise, and after performing a roll dispersion treatment of passing the resin between rolls to adjust the particle size, 180 to 250 It was applied to a thickness of 10 to 20 μm using a mesh screen mask and cured at 120 to 180 ° C. for 20 to 60 minutes. This solar cell obtained a fill factor of 0.61, and in a high temperature and high humidity storage test at 60 ° C. and 90%, it decreased by about 2% in 500 hours, obtaining a 0.06 fill factor value. Ni particle size after roll dispersion is 3 to 20
was μm.

Next, a resin obtained by mixing the same phenol-modified alkyd resin as above with an epoxy resin was formed. Amorphous carbon and graphite are used as fillers in this resin so that the ratio is 0.5 to 1.0, and the resin is 0.3 to 2.0 times the filler, preferably 0.
The mixture was mixed to be 5 to 1.5 times. Also ITO or SnO ₂
Is pulverized to a particle size of 5 to 10 μm, 20 to 80% of the amount of amorphous carbon and graphite is added, and a silicon coupling agent of 0.1 to
After 5% by weight of the mixture was mixed and subjected to a roll dispersion treatment, printing and coating were performed on the film containing Ni as a filler. Baking is 120-180 ℃
I went there for 20 to 60 minutes.

This solar cell exhibited the characteristics shown by the line 20 in FIG. ² , and obtained a fill factor of 0.66 at 200 lx and 0.63 at 100 mW / cm ² . However, the absolute value of the electric current depends on the incident light. 60
Almost no deterioration under high temperature and high humidity conditions of 90 ° C and 90%, and after 500 hours, fill factors of 0.65 and 0.61 were obtained.

After coating the resin with Ni as filler, do not bake, but keep at room temperature for 10 ~
A slight improvement in the fill factor was observed when the second layer containing carbon as a filler was applied for 30 minutes and then baked. The initial fill factor was 0.67 at 200 lx and 0.65 at 100 mW / cm ² .

Example 2: A melamine alkyd resin was used as the resin for the second layer of Example 1. The melamine-alkyd resin can be prepared, for example, as follows. Formaldehyde (4-6 mol) and butanol were added to 1 mol of melamine, pH was adjusted to 6-8 with ammonia, and methylolation reaction was performed at 90-100 ° C for 30 minutes.
The butyl etherification reaction is carried out at 5 for about 1 hour. Then xylol is added and the water and butanol produced is distilled off. The product was diluted with xylol, butanol or a mixed solvent thereof to form a melamine resin liquid. A short oil length alkyd resin made by adding linseed oil, tung oil, soybean oil and other drying oils, dehydrated castor oil or its constituent fatty acids to a phthalic anhydride and glycerin system
45% mixed. The ratio of melamine to alkyd was 20:80 to 45:35. Amorphous carbon as the filler, the ratio of graphite is 0.5 to 1.0, 0.3 to 2.0 times the filler, preferably 0.5
Mix with ~ 1.5x resin. Further, ITO or SnO ₂ crushed to a particle size of 5 to 10 μm was added to the amorphous carbon and graphite in an amount of 20 to 80% of the total amount. Further, 0.1 to 5% by weight of a silicon coupling agent was added to carry out a roll dispersion treatment and then applied as a second layer. As a result, 0.6 at 200 lx
A fill factor of 0.61 was obtained at 5, 100 mW / cm ² . 60 ° C, 90
%, There was no deterioration under high temperature and high humidity conditions, and the same value was maintained after 500 hours.

Example 3: With the same configuration as in Example 1, ITO or Sn was used as the resin for the first layer.
Fine powder of O ₂ with a diameter of 5-10 μm against Ni filler 20-60
% Added. As a result, a fill factor of 0.6 at 200 lx
A fill factor of 0.65 was obtained at 7,100 mW / cm ² .

FIG. 3 shows a thin film solar cell having a structure different from that of FIG. 1, in which case the a-Si layer is a continuous layer 3 without being cut into individual unit cells. The cells are connected to each other by overlapping the lead-out portions of the rear surface electrodes 41, 42, 43, 44 ... On the lead-out portions of the transparent electrodes 22, 23, 24. Also in the solar cell having this structure, the various applied metal electrodes as described above are provided on the back electrodes 41, 42, 43, 44 ...
Can be

〔The invention's effect〕

According to the present invention, a phenol resin, a melamine alkyd resin, etc. mixed with Ni particles as a conductive filler, and a mixture of carbon particles mixed with a silicon coupling agent are kneaded and printed in this order. As a result, a back surface electrode that comes into contact with the a-Si layer with low resistance can be formed by firing at a low temperature, and a solar cell having a large fill factor and good heat and humidity resistance was obtained without using an expensive evaporation back surface electrode. Moreover, the deterioration of the back electrode of the resin containing Ni as a filler for a long time can be prevented without applying the protective film. Furthermore, the characteristics could be further improved by adding ITO and SnO ₂ additives to both layers.

[Brief description of drawings]

FIG. 1 is a sectional view of a solar cell according to one embodiment of the present invention, FIG. 2 is an output characteristic diagram of a solar cell according to one embodiment of the present invention and a conventional example, and FIG. It is a perspective view of a solar cell. 1: glass substrate, 21, 22, 23, 24: transparent electrode, 3, 31,
32, 33, 34: a-Si layers, 41, 42, 43, 44: printed electrodes.

Claims (2)

[Claims] 1. A method of manufacturing a unit cell in which an amorphous silicon layer having a junction with a transparent electrode and a back electrode are laminated in series on a transparent insulating substrate, wherein the back electrode uses Ni particles as a conductive substance. A first resin kneaded with a silicon coupling agent containing, and a second resin kneaded with a silicon coupling agent containing carbon particles as a conductive material so that the first resin is in contact with the amorphous silicon layer, A method for manufacturing a thin-film solar cell, which comprises stacking and printing a second resin in this order and then firing. 2. A method of manufacturing a thin film solar cell according to claim 1, wherein the first or second resin contains at least an oxide containing tin as a conductive substance. Method.