Improved light management in a-Si:H/a-Si1-xGex:H tandem cells by employing multi-functional n-type microcrystalline silicon oxide

Abstract

In this work, the development of plasma-enhanced chemical vapor deposition (PECVD) mu c-SiOx:H(n) and its application to a-Si:H/a-Si1-xGex:H tandem cells as the intermediate reflecting layer (IRL) and back reflector (BR) is presented. The n-type microcrystalline silicon oxide [mu c-SiOx:H(n)] was used as multifunctional layers in silicon thin-film solar cells owing to its wide bandgap and low refractive index. In the development of mu c-SiOx:H(n), increasing RF power increased film oxygen content, which widened the bandgap while reducing dark conductivity. Applying the mu c-SiOx:H to a-Si:H/a-Si1-xGex:H tandem cells as IRL and BR significantly improved cell performance. The mu c-SiOx:H(n) IRL increases the current of the top cell, thus improving the light management in a-Si:H/a-Si1-xGex:H tandem cells. On the other hand, the mu c-SiOx:H(n) can be used as the BR replacing the n-type a-Si:H and ITO layers. The mu c-SiOx:H increased cell conversion efficiency by 12.9% as IRL, and by 9.7% as BR, achieving 10.03% efficiency. (C) 2014 The Japan Society of Applied Physics