JPH01161777A - Manufacture of amorphous semiconductor solar cell - Google Patents

Abstract

PURPOSE:To improve the conversion efficiency of a P-I-N structure amorphous semiconductor solar cell having a P/I interface layer further by forming the P/I interface layer through a high hydrogen dilution method set under conditions in which high-frequency power density extends over a specific value or below and a deposition rate over a specific value or more. CONSTITUTION:When a P-I-N type amorphous semiconductor solar cell in which a P/I interface layer 4 composed of an amorphous silicon-carbon layer is interposed between a P-type amorphous silicon layer 5 and an I-type amorphous silicon layer 3 is manufactured, said P/I interface layer 4 is shaped by using a high hydrogen dilution method set under conditions in which high-frequency power density extends over 0.1w/cm<2> or below and a deposition rate over 1Angstrom /sec or more. The mixed gas of PH3 and SiH4 is decomposed by glow discharge and an N-type a-Si layer 2 is deposited onto a metallic substrate 1, the I-type a-Si layer 3 is deposited by SiH4 gas, and the P/I interface layer 4 is deposited by the mixed gas of SiH4, CH4 and H2. The P-type a-Si layer 5 is deposited by the mixed gas of B2H6, SiH4, CH4 and H2, and a transparent conductive film 6 and a comb-shaped Al electrode 7 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing an amorphous semiconductor solar cell using a high hydrogen dilution method.

Conventional technology> Various methods have been attempted to improve the photoelectric conversion efficiency of amorphous semiconductor solar cells having a pin structure.
It is known that forming a p/i interface layer between a layer and an i layer increases the conversion efficiency, especially the open circuit voltage, of a solar cell. The following two points are listed as requirements that the materials must meet.

(111ffl also has a wide optical bandgap.

(2) The requirement for the first term above is that the optical bandgap should be
The internal electric field of the device is created by reducing the amount of light toward the 1st layer.
This is because the electric field causes carriers to be pushed out toward the Lvi layer. Further, the requirement of the above-mentioned item 2 is necessary so that the generated carriers (electrons and holes) can be extracted to the outside as a current without being recrystallized in the p/i interface layer.

Conventionally, amorphous silicon carbon has been used as a p/i interface layer material that satisfies these requirements. This is formed by using silane gas as a raw material for silicon (St) and hydrocarbon gas as a raw material for carbon (O), and decomposing these raw gases using a high-frequency glow discharge method. .

Recently, as a method to form a high-quality amorphous silicon carbon film with a wide optical bandgap and high photoconductivity, a method of diluting the raw material gas with hydrogen at a high magnification (hereinafter referred to as the high hydrogen dilution method) became known as Friend.

<Problems to be Solved by the Invention> However, when a p/i interface layer made of high-quality amorphous silicon carbon is formed on the i-layer or p-layer using a high hydrogen dilution method, solar cells As for the characteristics, the fill factor decreased and the predicted improvement in conversion efficiency was not observed.

This is thought to be due to the fact that Maruki atoms and hydrogen ions generated due to decomposition of hydrogen during the formation of the p/i interface layer damage the underlying i-layer or p-layer.

<Background of the Invention> The above-mentioned damage is caused by the ratio of the emission intensity of the luminescent species (H') of hydrogen atoms observed in discharge plasma emission spectrometry to the deposition rate (hydrogen atoms reaching the film surface per unit time, The inventors have discovered that there is a correlation between the ratio of ions to atoms deposited as a film). This is shown in FIG. As is clear from the figures, in the region of high-frequency power density of 0.1 w/cd or higher, which has been conventionally adopted to increase the deposition rate, (H'O emission intensity)/(deposition rate) rapidly decreases. It has increased.

It has also been confirmed that the fill factor decreases accordingly.

On the other hand, setting the high-frequency power density to 0.1 wA or less is not currently desirable from an industrial standpoint because conventionally the deposition rate is extremely slow. It is also possible to reduce the dilution ratio of hydrogen in order to reduce damage, but with this method, the photoconductivity of the amorphous silicon carbon film will rapidly decrease.
As a result, the conversion efficiency of the solar cell also decreases. As above,
The establishment of a method for forming an amorphous silicon carbon film that is effective as a p/i interface layer has been a major issue for improving efficiency. The purpose of the present invention is to provide a manufacturing method that further increases the conversion efficiency of a pin structure amorphous semiconductor solar cell having a pin structure, while extremely reducing the high frequency power density and without reducing the deposition rate. It is characterized by producing a battery. That is, the object of the present invention is to suppress the high frequency power density to 0.1 w/aI or less when forming the p/i interface layer, while increasing the flow rate of the raw material gas and diluted hydrogen gas to increase the deposition rate t- 1^/s
This is achieved by forming a film by setting e c or more.

Examples> Hereinafter, taking a solar cell having the structure shown in FIG. 1 as an example,
One embodiment of the present invention will be described. In the structure shown in Fig. 1, an n-type amorphous silicon (a-St) layer 2 is deposited on a metal substrate I by glow discharge decomposition of a mixed gas of PH8 and SiH4, and then SiH4 or a trace amount of this is deposited. An i-type a-5i layer 3 is deposited with a gas mixture of 6ft of B2H, and then SiH4
A p/i interface layer 4 of a rainbow amorphous silicon carbon film is deposited in a mixed gas of , CH4 and H2. Furthermore, B2H6,
p-type a-S by mixed gas of SiH4, CH4 and H2
L9 is obtained by depositing on layer ii and finally forming a transparent conductive film 6 and a comb-shaped At electrode 7. Table 1 shows the difference in fill factor and conversion efficiency depending on the difference in raw material gas flow rate and deposition rate for producing this p/i interface layer.

Table 1 It is clear from Table 1 that the IA/se according to this embodiment
Solar cells with a p/i interface skin formed at a deposition rate of e or higher were found to have an improved fill factor and improved conversion efficiency.

In order to clarify that the improvement in the above characteristics is significant in reducing the damage caused by hydrogen atoms and hydrogen ions, the relationship between (H%) emission intensity)/(deposition rate) and deposition rate was shown in the following. Figure 2 shows that as the raw material gas is increased and the deposition rate is increased, the ratio (emission intensity of H rice)/(deposition rate) decreases, and by setting the deposition rate to t-IA/sea or higher, sufficient damage is caused. Although it is clear that the damage has been reduced, it has also been confirmed that the fill factor increases in response to the reduction in damage.

Furthermore, when the flow rate is increased in this way, the characteristics of the single layer film are as shown in Figure 3. Although the optical bandgap decreases slightly, the photoconductivity increases significantly, indicating that a high quality film is formed. Recognize.

In the above embodiments, a solar cell having a structure using a metal substrate was taken as an example, but the present invention can also be applied to a solar cell having a structure using a glass substrate. Further, the present invention is applicable not only to the p/i interface layer but also to the n/i interface layer.

<Effects of the Invention> In accordance with the above-described process, the present invention is capable of depositing a p/i interface layer using a high hydrogen dilution method at a low power density of 0.1 cm or less and a deposition rate of 1 Å/sec or more. By forming the solar cell through discharge, a solar cell with high conversion efficiency can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a solar cell for explaining one embodiment of the present invention. Figure 2 shows (
FIG. 3 is an explanatory diagram showing the relationship between luminescence intensity (emission intensity)/(deposition rate) and deposition rate of H rice. The third factor is an explanatory diagram showing the relationship between the optical bandgap and photoconductivity of the p/i interface layer according to the present invention. FIG. 3 is an explanatory diagram showing the relationship with density. 1... Metal substrate 2... N-type a-5t layer 3...
I-type a-3t layer 4...p/i interface layer 5...p-type a-5t layer 6...transparent conductive film 7...comb-shaped At electrode representative Patent attorney Takeshi Sugiyama (and others) 1 person) 1st
gl Deposition rate (A/5ec) Fig. 2 1・82・02.2 Optical band gate f” (eV) 3rd WJ

Claims (1)

[Claims] 1. Method for manufacturing a pin-type amorphous semiconductor solar cell in which a p/i interface layer made of an amorphous silicon/carbon layer is inserted between a p-type amorphous silicon layer and an i-type amorphous silicon layer , the p/i interface layer was heated to a high frequency power density of 0.1 w/
1. A method for manufacturing an amorphous semiconductor solar cell, characterized in that it is formed using a high hydrogen dilution method set to conditions such as cm^2 or less and a deposition rate of 1 Å/sec or more.