JPS60102773A - Amorphous base solar battery - Google Patents

Abstract

PURPOSE:To improve the photoelectric conversion ratio by cutting the light reflecting power down to ideal value by a method wherein an intermediate layer with refractive index different from those of a glass substrate and a transparent electrode is laid between said substrate and electrode. CONSTITUTION:An intermediate layer 5 with refractive index different from those of a glass substrate 1 and a transparent electrode 2 is laid between said substrate 1 and electrode 2 within an amorphous solar battery constituted to intake light into an amorphous layer through the intermediary of the glass substrate 1 and the transparent electrode 2. The intermediate layer 5 may be se lected from a composition of one or two kinds of mixed oxide of e.g. Ti, Si, Ta and Al, etc. making the light reflecting power minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an amorphous solar cell (eg, an amorphous solar cell including an amorphous silicon fat cell, an amorphous 5i-C layer, an amorphous 51-Gg layer, etc.).

[Background of the invention]

This type of amorphous solar cell, e.g. EVA amorphous silicon solar cell, is capable of lower costs and larger area than crystalline solar cells, and has been rapidly developed. The situation is such that they cannot catch up with the system.

Conventional amorphous silicon solar cells include those that use metal as a substrate and those that use glass as a substrate. In those that use glass as a substrate, for example, a transparent electrode is attached to the glass, and pm, It has a structure in which i-layer and n-layer amorphous silicon are stacked and aluminum electrodes are deposited.

In order to increase the photoelectric conversion efficiency of amorphous silicon solar cells using glass as a substrate, various efforts have been made as shown in the following examples.

(1) Even if carriers are generated in one layer on the light-receiving surface side, the influence of surface recombination is large, so they do not contribute effectively to photoelectric conversion. Therefore, in order to suppress light absorption in the first layer and allow more light to enter the second layer, amorphous silicon carbide with a large optical bandgap is used for the P layer.

(2) Amorphous silicon has low carrier mobility and low dark conductivity. As a result, the resistance of the solar cell layer, which does not receive much light, increases considerably, reducing the efficiency of the solar cell. Therefore, we microcrystallize the Le layer to lower the resistance.
In addition, the photoelectric conversion efficiency is increased by lowering the absorbance of the four layers and using light reflection from the aluminum on the back to return the transmitted light to the second layer.

(3) In order to effectively absorb sunlight, the spectral sensitivity of the photoelectric conversion element should match the spectrum of sunlight. Therefore, we formed a double pn junction using two types of semiconductors with different optical band gaps, and by combining them, we created a photoelectric conversion element with spectral sensitivity close to a wide range of sunlight spectra, increasing conversion efficiency. ing.

(4) In order to efficiently introduce incident light into the element, an anti-reflection film is formed on the glass surface to minimize reflectance, suppressing reflection on the glass surface and increasing conversion efficiency.

Although the photoelectric conversion efficiency of amorphous silicon solar cells has been improved through efforts such as those in the above examples, it is still insufficient.

Therefore, as a method to further improve efficiency, in order to suppress reflection at the interface between the glass substrate and the transparent electrode, efforts have been made to adjust the film thickness of the transparent electrode to reduce the reflectance.

In FIG. 1, the refractive index of the glass substrate 1 is rL2, the refractive index of the transparent electrode 2 is n1, the thickness is do, and the refractive index of the amorphous silicon layer 6 is yLo, then the reflectance R is the wavelength of light. In this case, the refractive index of the glass substrate is 1.
5, and the refractive index of the transparent electrode is around 20, so in order to minimize R and increase efficiency, the thickness of the transparent electrode should be selected appropriately.

However, the thickness of the transparent electrode cannot be freely selected. In other words, if the film thickness is too thick, the transmittance of incident light will decrease, and if it is too thin, the resistance value as an electrode will be too high.Therefore, it was not possible to lower the reflectance R to the ideal value. Ta.

[Purpose of the invention]

An object of the present invention is to provide an amorphous solar cell in which the light reflectance is reduced to an ideal value and the photoelectric conversion rate is improved.

[Summary of the invention]

The present invention provides an amorphous solar cell having a structure in which light is introduced into the amorphous layer through a glass substrate and a transparent electrode, in which an intermediate layer having a refractive index different from that of the glass substrate and the transparent electrode is interposed between the glass substrate and the transparent electrode. Configure.

Thereby, the light reflectance can be lowered to an ideal value and the photoelectric conversion rate can be improved. That is, the incident light passes through the transparent electrode from the glass, 4.

During the process, light is reflected at the interface between the glass and the transparent electrode, and if this is too thick, the amount of light that can be used effectively will be reduced. Therefore, an intermediate layer with a different refractive index is inserted between the glass and the transparent electrode. , to minimize the reflection of incident light between layers.

The refractive index of the glass substrate is Le 8, the refractive index of the intermediate layer is TL2,
When the film thickness is dt, the refractive index of the transparent electrode is dl, and the refractive index of an amorphous layer such as amorphous silicon is dl, the reflectance R is expressed by the following formula.

R= [l (yb(,-TL3)001iδICxB
δ.

((Sayuru Ribo δ1 mountain δ! 2 TL (1 le 3 +(yJ)sinδ1coSδ! )2]n.

/[((rLo×rL3)cosδ1cOsδ.

, (nQ n, -+Ruri μsδ1thδ2LR TLOrL8 +(-+rL,) Out δ Sum α4 δ2 )2 ] n
.

λ is the wavelength of the incident light.

In this equation, by appropriately selecting the refractive index rL2 and film thickness d2 of the intermediate layer, it is possible to reduce the reflectance R to an ideal value.

As the intermediate layer used in the present invention, for example, Tt.

The composition used is one or a mixture of two or more oxides such as Si, Ta, M, and PB.

Film formation methods include a method of coating a compound containing the above metal with a spinner and then baking it, a vapor deposition method, a sputtering method, a carbon
An example is the VD method.

Depending on the refractive index and film thickness of the transparent electrode, a material with an appropriate refractive index is selected from the above-mentioned combinations of metal oxides as the material for the intermediate layer.
By controlling the film thickness to an appropriate value, it is possible to suppress the reflectance R to a minimum value.

The glass substrate used in the present invention is soda glass.

・　7　・ There are no particular restrictions, such as white glass or Pyrex.

Further, the transparent electrode used in the present invention is made of ITO, 5n02, or a combination thereof.

[Embodiments of the invention]

Some embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a sectional view showing an example of the structure of the amorphous solar cell of the present invention. This amorphous solar cell has
An intermediate layer 5 having a refractive index different from those of the glass substrate 1 and the transparent electrode 2 is interposed between the glass substrate 1 and the transparent electrode 2.

This makes it possible to lower the light reflectance to an ideal value and improve the photoelectric conversion rate.

More detailed examples of the present invention will be described below.

Each of the following examples embodies the present invention by applying it to an amorphous silicon solar cell.

Example 1 A mixed solution of tetrabutyl titanate and ethyl orthosilicate was applied with a spinner onto soda glass with a thickness of 11 m, and
Heat at 80'O for 60 minutes, about -3.

A film of 1200A was formed and an intermediate layer 5 was formed. The refractive index of this film was determined using an ellipse meter and was found to be 1.90.

On top of this, ITO was deposited as a transparent electrode 11 by EB evaporation to a thickness of 200 mm.
0. Using this substrate, a Ptn layer was formed by the method described below to create an amorphous silicon solar cell.

As a film forming apparatus, a six-chamber separation type plasma CVD apparatus was used. 1st layer is SiE46sccM, CM414sccM
.

2.0% of He dilution B2. B62 zccM was flowing, the gas pressure was 0.5 Torr, and the substrate temperature was 300'0, r.
It was discharged for 60 seconds at f power of 4W. Next, 10% Si2B6500zccM diluted with He was poured into the second layer, and the layer was heated for 350'
The battery was discharged for 2 minutes at 0.01.2 T orr with an RF power of 80 W. Finally, the layer is SiE, i sccM , E
Flow 20zccM of 2 diluted 1007Pi pH3, 25
0 '01. OT orr and rf bar '7-80F 1
It was discharged for 5 minutes. In this way, as shown in FIG.
2 is a B-doped SiC film, layer 16 is an α-5i:H film,
The layer 14 was formed as a P-doped microcrystalline Si film.

When the efficiency of the amorphous silicon solar cell created in this way was measured, the open circuit voltage was 0.78 with an area of 025-
0V, short circuit current 14.77 mA/ctA, fill factor 0550, and a conversion efficiency of 6.35% was obtained.

As a comparative example, when a solar cell was created under the same conditions using a similar ITO substrate without an intermediate layer, O,2S=
The conversion efficiency was 6.05% for the area of , which was smaller than that of this example.

Example 2 In the same manner as in Example 1, a refractive index of 2.2 was prepared as an intermediate layer.
A TatOs film of 240 OA was formed.

5tR4 (5zccM
, CM414sccM, B, 1162.0%
(He dilution) Flow 2sccM, 300'0.0,5
Discharge for 35 seconds with rf power 4W at Torr, a-5i
A C film was formed.

Next, the second layer was made by flowing SiH4 for 1105 ec and 0.5
An α-5i:H film was formed by discharging at 350° Torr and RF power of 4 W for 30 minutes. Finally, as a layer, Si
Flowing 20sccM of H, 1gccM, PR, 100ppm (E! dilution), 1. OTorr, 250°0
A microcrystalline Si film was formed by discharging at γf power soF for 15 minutes. When an M electrode was formed on this by vapor deposition and the efficiency was measured in the same manner as in Example 1, a conversion efficiency of 8.90% was obtained for an area of 025-. As a comparative example, a case without the intermediate layer of Ta2O was measured under the same conditions, and the result was 8.40.
% conversion efficiency, and by forming the intermediate layer, an efficiency improvement of 1.06 times could be achieved.

〔Effect of the invention〕

According to the present invention, since reflection of incident light can be ideally reduced, there is an effect of improving photoelectric conversion efficiency in an amorphous solar cell.

Further, since the intermediate layer also serves as a base film for preventing Na+ diffusion from the glass substrate, the present invention also has the effect of improving the reliability of the quality of the solar cell.

Note that, as a matter of course, the present invention is not limited to the above embodiments. For example, in the example, an amorphous silicon solar cell is representatively used.

Although shown as a solar cell, the present invention is also applicable to those using 5i-Ge and other solar cells.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional amorphous silicon solar cell, and FIGS. 2 and 3 are sectional views of a solar cell according to an embodiment of the present invention. 1...Glass substrate 2...Transparent electrode (ITO) 3...
......Amorphous layer (amorphous silicon layer) 5...Intermediate layer 8...M electrode 12... ... 11 layers 16 songs... layer 14... le layer, 12. Figure 1 ↑ Continued from Figure 2, Page 1 of Notification Figure 3 [Phase] Inventor Akio Saito Inside the Kijutsu Research Institute, Totsuka-ku, Yokohama City

Claims (1)

[Claims] 1. In an amorphous film having a structure in which light is introduced into an amorphous layer through a glass substrate and a transparent electrode, an oil contact layer of the glass substrate is provided between the glass substrate and the transparent electrode. 1. An amorphous solar cell characterized in that an intermediate layer having an oil contact ratio different from that of the transparent substrate is interposed. 2. The amorphous solar cell according to claim 1, wherein the amorphous layer contains at least one of amorphous silicon, amorphous 5i-C, and amorphous 51-Gg. .