High efficiency a-Si solar cells with a superlattice structure p-layer and stable a-Si solar cells with reduced SiH 2 bond density

Abstract

In order to improve the conversion efficiency of a-Si solar cells, a superlattice structure p-layer and the use of B(CH 3) 3 as a dopant gas have been investigated for the first time. The collection efficiency spectrum of a glass/TCO/p-superlattice structure (a-SiC/a-Si)/in/Metal cell shows a remarkable increase in the short wavelength region. This result suggests that the superlattice structure p-layer is an active photovoltaic layer. It is also found that the photoconductivity of p-type a-Si:H films increases by using B(CH 3) 3 as a dopant gas. A conversion efficiency of 10.0 % (module efficiency 9.02 %) is obtained for 10 cm × 10 cm integrated single junction a-Si solar cell submodule using B(CH 3) 3. As for reliability it is found that the light induced degradation of a-Si solar cells can be reduced by simultaneous reduction of the impurity concentrations in a-Si with the super chamber (separated UHV reaction chamber) and the SiH 2 bond density.