Photovoltaic Properties of a-Si:H Films Grown by Plasma Enhanced Chemical Vapor Deposition: A Review

Amorphous silicon films are currently receiving a worldwide renewed and intense research and commercial focus for low-cost solar power generation. In this article we review the history and current status of hydrogenated amorphous silicon films (a-Si:H) for thin film photovoltaics, and the role of intrinsic a-Si:H films in heterojunction (a-Si:H/c-Si) solar cells. The focus of this article is on plasma enhanced chemical vapor deposition (PECVD) of these films from silane (SiH₄). Very high frequency (VHF) PECVD deposition and its limitations are discussed. Properties and requirements of intrinsic and doped a-Si:H films are presented. Light-induced degradation of a-Si:H films are reviewed in detail. Current status of single junction a-Si:H solar cells and factors influencing cell performance are also discussed. Since the efficiency and stability of thin film a-Si:H solar cells are low, a-Si:H films can be successfully used in other solar cell technologies such as c-Si based back heterojunction solar cells, where doped a-Si:H films are used at the rear side of the substrate for emitter and back surface field.