Development of low and high bandgap amorphous silicon without alloying by germanium and carbon and their feasibility as active layers in the solar cells

Abstract

Low and high bandgap amorphous silicon ( a-Si : H) materials have been developed in a high plasma power regime (γ-regime) of r.f. glow discharge (PECVD) at substrate temperature ∼200°C. Growth mechanisms for the deposition of low and high bandgap materials are completely different and it is also different from that of normal bandgap a-Si : H material. Growth of low bandgap material under helium dilution is governed by physical processes whereas development of high bandgap a-Si : H is controlled by chemical reactions. It is surprising that in spite of the presence of nanocrystals in the amorphous matrix, both the materials have photovoltaic quality. Low and high bandgap materials have been used as the intrinsic layers of single junction solar cells.