Optimisation of doped amorphous silicon layers applied to heterojunction solar cells

The optimisation of amorphous silicon layers (a-Si:H) is of key importance to obtain high efficiency heterojunction (HJ) solar cells. However, since many mechanisms take place in photovoltaic energy conversion, good electrical and optical properties of a-Si:H films do not always result in high efficiency HJ devices. This is principally due to the use of very thin layers were interfaces are of capital importance and bulk properties are not always the main guideline to best results on solar cells. In this work, we focus on the doping analysis of (n) and (p) a-Si:H layers directly and their impact on solar cell results. First, we have deposited and characterized simple (p) and (n) a-Si:H layers and then we have integrated them on full heterojunction solar cells. We have correlated the solar cells characteristics (Jsc, Voc and FF) with layer properties in order to understand the main mechanisms involved in the high performance of HJ devices. Finally, we have chosen the best layers to improve the efficiency of our heterojunction solar cells on (n) c-Si 125PSQ wafers up to 20% on an industrially-compatible process.