JPH11220147A - Amorphous silicon solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize a short-wavelength light by forming a fluorescent film on a light incident surface. SOLUTION: A fluorescent film 1 is formed on a light incident surface of an amorphous Si solar cell 7. For forming the fluorescent film 1, the deposition method of a fluorescent material or method of dispersing it in a polymer binder and coating it may be used. For dispersing in a polymer binder and coating, the bar coat, spin coat, dip coat method or the light may be used. For the constitution of the amorphous solar cell, one formed on a transparent substrate 2 such as glass or opaque substrate may suffice, and it may suffice to from the fluorescent film 1 on its light incident surface. The fluorescent film 1 is of a fluorescent material having a fluorescent emission spectrum with an absorption spectrum image-inverted to a long wavelength and the long wavelength transform is made so that short wavelength lights can be effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an "amorphous silicon solar cell" having a high photoelectric conversion efficiency, and more particularly to an "amorphous silicon solar cell" in which a fluorescent thin film is provided on a light incident surface side to improve light use efficiency. Things.

[0002]

2. Description of the Related Art Conventionally, there have been many attempts to increase the use efficiency of incident light in order to obtain highly efficient amorphous silicon solar cells, and some of them are actually used. As an example, an amorphous silicon layer which is a photoelectric conversion layer composed of a p-type a-Si, an i-type a-Si, and an n-type a-Si layer is formed on a transparent electrode having large irregularities on a glass substrate. Further, there is a structure in which a back electrode is sequentially formed. Further, there is also a device provided with an antireflection coating layer such as MgF2 in order to reduce light reflection on the surface of the glass substrate.

[0003]

An amorphous silicon solar cell in which a transparent electrode having large irregularities is formed on a glass substrate and an amorphous silicon layer serving as a photoelectric conversion layer and a back electrode are formed on the transparent electrode is formed in the photoelectric conversion layer. Since light confinement of incident light occurs, light utilization efficiency is high, and photoelectric conversion can be performed effectively. The antireflection coating on the glass substrate surface has been established for a long time, and is effective in increasing the efficiency of a solar cell because it increases the amount of light incident on the photoelectric conversion layer.

However, in the above structure, 400
For short-wavelength light of nm or less, there is a problem that the amount of light incident on the photoelectric conversion layer decreases due to absorption or interference by the glass substrate or the transparent electrode. In addition, the collection efficiency of an amorphous silicon solar cell is highest for light having a wavelength of 500 nm to 600 nm, and there is a problem that conversion efficiency decreases for light having a shorter wavelength. That is, in the conventional amorphous silicon solar cell, light having a wavelength of 400 nm or less is not effectively used.

Accordingly, an object of the present invention is to provide a more efficient amorphous silicon solar cell by effectively utilizing short-wavelength light.

[0006]

SUMMARY OF THE INVENTION In order to achieve the foregoing object, the present invention forms a fluorescent thin film on a light incident surface of an amorphous silicon solar cell, thereby making it possible to use short-wavelength light having low utilization efficiency more efficiently. This is characterized in that the efficiency of light utilization is improved by converting the light into long-wavelength light, and that an amorphous silicon solar cell with higher efficiency is obtained.

A fluorescent material generally has a fluorescence emission spectrum in which the absorption spectrum is mirror-inverted to the longer wavelength side, and is a very effective material for performing long wavelength conversion of light. In addition, there are a wide variety of types including fluorescent whitening agents, and there are many commercially available materials, and the range of selection is wide. In addition, an almost arbitrary emission spectrum can be obtained from near ultraviolet light to visible light by selecting a material. Further, there are a wide variety of film forming means, such as a vapor deposition method and a method of coating by dispersing in a polymer binder. From these facts, even when used for a solar cell, it can be formed simply and inexpensively according to its structure and use.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention is characterized in that a fluorescent thin film is formed on a light incident surface of an amorphous silicon solar cell. Various methods such as a vapor deposition method of a fluorescent material can be used for forming the fluorescent thin film. Also, a method of dispersing a fluorescent material in a polymer binder and coating it is inexpensive and easy. Bar coating, spin coating, dip coating, and the like can be used to disperse and coat the polymer binder, and can be selected according to the structure of the solar cell, the production process, and the like. The structure of the amorphous silicon solar cell may be one formed on a transparent substrate such as glass or one formed in an opaque substrate, and a fluorescent thin film may be formed on the light incident surface. Hereinafter, embodiments of the present invention will be described.

[0009]

EXAMPLE An amorphous solar cell shown in FIG. 1 was formed. A glass substrate and a tin oxide film having irregularities were used as transparent electrodes. The photoelectric conversion layer includes p-type a-SiC: H, i-type a-Si: H,
Formed in the order of n-type a-Si: H, and Ti
A film was formed. As a material for a fluorescent thin film, a dichloromethane solution of polycarbonate in which 1,1,4,4-tetraphenyl-1,3-butadiene was dispersed at 40 wt% was prepared. 1,1,4,4-Tetraphenyl 1,3-butadiene is a material having a fluorescence emission peak at about 430 nm, and has excellent dispersibility in transparent resins such as polycarbonate. Using this solution, a fluorescent thin film of about 20 μm was formed on the glass surface of the amorphous silicon solar cell by a bar coating method. The sample was dried by heating at 80 ° C. for 12 hours to remove the solvent in the fluorescent thin film. Further, as Comparative Example 1, an amorphous silicon solar cell having no fluorescent thin film was prepared, and as Comparative Example 2, an amorphous silicon solar cell coated with about 20 μm of polycarbonate containing no tetraphenylbutadiene instead of the fluorescent thin film was prepared. The amorphous silicon solar cell used in the comparative example was manufactured under the same conditions as in the example.

These samples were prepared using AM1 (100 mW / cm
Under the irradiation light of 2), the photoelectric conversion characteristics were measured.
At that time, the short-circuit current (Jsc: μA / cm2) and the open-circuit voltage (Vo
c: V), fill factor (ff), and conversion efficiency (eff .:%) are shown below. The area of all the solar cell elements is 0.5 cm2. Comparative Example 1 Comparative Example 2 Present invention Jsc (mA / cm 2): 12.3 12.0 12.9 Voc (V): 0.86 0.86 0.87 ff: 0.62 0.62 0.62 eff. (%): 6.56 6.40 6.96

[0011]

From the results, it is understood that the present invention can improve the photoelectric conversion efficiency of the amorphous silicon solar cell inexpensively and easily. Further, it can be understood that this effect is exhibited not only by the polycarbonate thin film but also by having fluorescence.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent thin film 2 Glass substrate 3 Transparent electrode 4 Photoelectric conversion layer 5 Back electrode

Claims (1)

[Claims] 1. An amorphous silicon solar cell, wherein a fluorescent thin film is formed on a light incident surface.