JPS59101880A - Thin film solar battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film solar cell having a telojunction made of mutually different elements in amorphous semiconductor layers forming the junction.

In recent years, amorphous semiconductors have attracted attention as new electronic materials, with amorphous silicon being a typical example, and its application to solar cells in particular is progressing. It has long been known that amorphous silicon can be obtained by vacuum evaporation, etc.
Defects (mainly dangling bonds where bonds between atoms are broken)
Because of the presence of a large number of , its properties as a semiconductor were very poor. However, by using the glow discharge decomposition method of monosilane (SiH4) gas, the amorphous silicon deposited on the substrate is neutralized (terminated) by the hydrogen incorporated into the film as a dangling bond, and furthermore, boron, phosphorus, etc. are added. This made it possible to control valence electrons. In addition to hydrogen, the terminator may be a halogen element such as fluorine.

Amorphous silicon whose dangling bonds are terminated with hydrogen or the like is a semiconductor with a forbidden band of about 1.7 eV, but on the other hand, it has a 1j-i-n type (Figure 1 shows the forbidden band width). The relationship between the theoretical efficiency of solar cells is shown, and as can be seen from this, the highest efficiency is obtained at a bandgap value around 1.4 eV.Also, the layer on the light incident side (p or n layer) improves the light transmittance. For example, by incorporating carbon, the forbidden band width can be increased,
The bandgap can be reduced by incorporating gelmaram.

However, in the heterojunction thus obtained, as in the case of a single crystal semiconductor, the defect force at the junction surface increases due to lattice mismatch, and the solar cell characteristics deteriorate.

An object of the present invention is to eliminate this drawback and provide a thin film solar cell having a heterojunction but without deterioration of characteristics due to lattice mismatch.

This objective is achieved by each adjacent layer of the amorphous semiconductor layer forming the heterojunction containing the same group (I) element.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a conceptual structural diagram of an embodiment according to the present invention. An ITO film 2 is deposited on a glass substrate 1, and nine amorphous films 3, 1 layer 4, and 1 layer 5 are formed thereon in this order. 9 layer 3 is S
The first layer 4 is formed by a mixed gas of iH4, CH4, GeH4 and B2H6, and the first layer 5 is formed by glow discharge decomposition of a mixed gas of SiH4 and PH3. By changing the respective gas ratios, Si,
p layer consisting of C, Ge, 81. The forbidden band width of one layer made of Ge is 1.8 to 2 eV and 1.4 to 1.5 eV, respectively.
is adjusted to The 9th layer 3 contains both St and Go, which are Group 2 elements in the 1st layer 4 formed subsequently, and p
It has the effect of greatly reducing the lattice mismatch at the −1 interface. Furthermore, the first layer contains the Group Ⅰ element St in the first layer 5, which similarly reduces lattice mismatch. If a metal electrode 6 is then vapor-deposited on the first layer 5, a solar cell is completed in which the photovoltaic force generated by the incident light 7 can be taken out from the connecting conductors 8, 9.

As described above, the present invention reduces the lattice mismatch at the junction interface of amorphous semiconductor layers forming a heterojunction by making the adjacent layers contain the same group Ⅰ element. It is possible to obtain a solar cell with good characteristics by taking advantage of the feature of a heterojunction in which the forbidden band width of each layer can be adjusted arbitrarily, and the obtained effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the conversion efficiency of a solar cell and the forbidden band width of the constituent semiconductors, and FIG. 2 is a conceptual cross-sectional view of an embodiment of the present invention. 1...Glass plate, 2...Transparent electrode, 3...81(
C, Ge) p layer, 4-8t(Ge) 1 layer, 5-Sin
layer. O 1 Figure 1 12 1.4 1.6 +, 8 2 Ban Eichu O 2 Figure Busy 7

Claims (1)

[Claims] 1) A thin film solar cell characterized in that adjacent layers of amorphous semiconductor layers forming a heterojunction each contain the same Group I element of the periodic table.