JPH01236661A - Manufacture of thin film solar cell - Google Patents

Abstract

PURPOSE:To enhance photoelectric conversion efficiency without an increase in the manufacturing steps by a method wherein an anti-reflection layer is formed on the incident side of a translucent insulating substrate and a layer for preventing diffusion of alkaline ions from the opposite side of the substrate is formed of the same material. CONSTITUTION:Translucent insulating films 2 and 7, lower than the translucent insulating substrate 1 in refraction index, are simultaneously formed on both sides of a translucent insulating substrate 1, respectively. Further, a semiconductor photoelectric conversion layer 4 is formed on a translucent insulating film 2, with a transparent conductive film 3 between the transparent insulating film 2 and semiconductor photoelectric conversion layer 4. An incident light beam 6 is guided to the semiconductor photoelectric conversion layer 4 without a loss thanks to the anti-reflection effect of the low refraction index translucent insulating film 2. The resultant current is efficiently taken out after passing through the transparent conductive film, which is adequately reduced in resistance thanks to the alkaline ion diffusion prevention effect of the low refraction index translucent insulating film 2 formed on the rear side, where it experiences no undesired consumption. This design increases the photoelectric conversion efficiency without any new manufacturing steps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing thin film solar cells.

[Conventional technology] Thin-film solar cells are superior to crystalline solar cells in terms of resource and energy savings, and are especially superior to crystalline solar cells in terms of resource and energy savings.
) in the charge conversion layer are the mainstay of low-cost solar cells. Among these, those using glass for the substrate are common because of ease of handling. FIG. 2 shows a cross-sectional view of a typical amorphous silicon solar cell. According to the conventional technology, in manufacturing an amorphous silicon solar cell on glass, first a light-transmitting insulating (diffusion prevention) film 2, typically a silicon oxide film, is coated on at least one side of a soda lime glass substrate 1. to prevent alkali ions from diffusing from the substrate.

Next, a transparent conductive film 3, an amorphous silicon film 4, and a metal electrode film 5 are sequentially formed on the transparent insulating film to form a solar cell. However, the amorphous silicon solar cell produced in this manner has a problem in that its charge conversion efficiency is low. Therefore, in recent years, in order to improve the charge conversion efficiency of amorphous silicon solar cells, in addition to the above steps, an anti-reflection film is applied to the incident surface side, and the surface of the transparent conductive film is made uneven to trap the incident light. Various methods of efficiently utilizing incident light are being investigated, such as stacking amorphous germanium, which has a spectral sensitivity different from that of amorphous silicon.

[Problems to be solved by the invention] However, adding a new process to the normal manufacturing process of amorphous silicon solar cells increases the price of the solar cells, significantly reducing price competitiveness. I will let you
For this reason, there has been a need for an inexpensive and rational method for manufacturing highly efficient thin film solar cells.

[Means to solve problems].

In the present invention, in order to solve the above problems, an antireflection layer is first formed on the light incident side of a transparent insulating substrate. At the same time, by forming a layer made of the same material to prevent the diffusion of alkali ions from the substrate surface on the opposite side, it was possible to increase charge conversion efficiency without increasing the manufacturing process of thin-film solar cells. In other words, when inexpensive soda lime glass is used as a transparent substrate, its refractive index is approximately 1.52.
By simultaneously forming a film with a smaller refractive index on both sides of a translucent substrate, it is possible to have an antireflection effect and an effect of preventing alkali ion diffusion.The material for this film is fluorine. Aluminum oxides (ALFs), calcium fluoride (CaFz), lithium fluoride (LiF)
, magnesium fluoride (MgF, z), sodium aluminum fluoride (Na 5AJIF 6), sodium fluoride (NaF), etc., but magnesium fluoride is preferable from the viewpoint of durability. Various vacuum deposition methods, dipping methods, etc. can be considered as the forming method, but it is inexpensive and advantageous to use the dipping method in order to form the film on both sides of the substrate at the same time.

Note that the thickness of this low refractive index layer is preferably in the range of 50 to 150 nm, which provides a large antireflection effect.

[Function] By using the above-mentioned technical means, first, the incident light on the solar cell is guided to the charge conversion layer without being lost due to the antireflection effect of the low refractive index film formed on the surface. The generated current then passes through the transparent conductive film, which has a sufficiently low resistance due to the low refractive index film formed on the back surface, which prevents the diffusion of alkali ions, and is efficiently extracted without being wasted there. .

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an amorphous silicon solar cell of the present invention.

A soda lime glass plate was thoroughly washed and dried and used as a translucent insulating substrate 1. This substrate was attached to a dipping device, immersed in a solution containing magnesium fluoride sol, and then gently pulled up to form magnesium fluoride films 7 and 2 on both sides of the substrate.Next, this substrate was sufficiently dried. , and fired at 400° C. for 1 hour using an electric furnace. Note that during dipping, the pulling speed of the substrate was adjusted so that the thickness of the magnesium fluoride film after firing was approximately 1100 nm on both sides.

Next, a transparent conductive layer 1113 is placed on this substrate as follows.
was formed. A 5N02 film doped with fluorine was deposited on a substrate heated to 550°C by the CVD method using an adjusted gas mixture of i-tetrachloride (anhydrous) vapor, water vapor, oxygen gas, 1,1-difluoroethane gas, and nitrogen gas. Formed. The thickness of the obtained 5n02 film was 450 nm.

Using the substrate obtained in this manner, an amorphous silicon luminium n-layer 4 was produced in the following procedure. Monosilane (Si
H4) 170 using a raw material gas whose main component is gas
Using a capacitively coupled high-frequency glow discharge device under a pressure of approximately Pa, (1) p-type semiconductor layer (boron-doped a-3iC: H1
(2) An i-type semiconductor layer (a-8i: H1, approximately 500 nm thick) (3) An n-type semiconductor layer (phosphorus-doped microcrystalline St (μc-Si): H, approximately 50 nm thick) was formed. Subsequently, using a resistance heating type vacuum evaporation device, about 2000 ml of metal aluminum membrane film 5, which will become a back electrode, is deposited on the substrate.
A thickness of 0 nm was formed.

For comparison, an amorphous silicon solar cell having the structure shown in FIG. 2 was also fabricated in the same manner as above using a soda lime glass plate on which no magnesium fluoride film was formed. Table 1 shows the relative values of the characteristics of each solar cell.

From the results shown in Table 1 and above, the amorphous silicon solar cell produced according to the present invention has improved short circuit current and F, F, and has significantly increased charge conversion efficiency.

[Effects of the Invention] According to the present invention, as is clear from the examples, the charge conversion efficiency can be increased without adding any new steps to the conventional manufacturing process of amorphous silicon solar cells. Therefore, the present invention is suitable as a method for manufacturing thin film solar cells.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an amorphous solar cell manufactured according to the present invention. FIG. 2 is a cross-sectional view of an amorphous silicon solar cell manufactured by a conventional technique. 1... Transparent insulating substrate 2... Transparent insulating film (diffusion prevention film) 3... Transparent conductive film 4... Charge conversion layer 5... Metal electrode 6... Incident light 7 ...Transparent insulating film (anti-reflection film) Patent applicant Nippon Sheet Glass Co., Ltd.

Claims (3)

[Claims] (1) Step of simultaneously forming a light-transmitting insulating film having a refractive index smaller than that of the substrate on both sides of the light-transmitting insulating substrate, and forming a semiconductor charge conversion layer using a transparent conductive film at least on the substrate side. A method for manufacturing a thin film solar cell, which comprises steps. (2) The method for manufacturing a thin film solar cell according to claim 1, wherein the light-transmitting insulating substrate is a glass substrate, and the light-transmitting insulating film is a film containing magnesium fluoride as a main component. (3) The method for manufacturing a thin film solar cell according to claim 1 or 2, wherein the method for forming the transparent insulating film is a dipping method.