Growth of polycrystalline silicon on glass for thin-film solar cells

Polycrystalline Si (poly-Si) thin-film solar cells on glass feature the potential to reach high single-junction efficiencies at low costs. However, the preparation is challenging because the process temperatures are limited by the glass to about 600 °C. There are several methods to prepare poly-Si films on glass. So far, the best poly-Si thin-film solar cells on glass have been prepared by solid phase crystallization (SPC) of amorphous Si (a-Si). In this paper, we give an overview on the formation of poly-Si films by both SPC and the aluminum-induced layer exchange (ALILE) process (which is based on aluminum-induced crystallization (AIC) of a-Si). Due to the fact that the utilization of ZnO:Al-coated glass is an attractive option for future poly-Si thin-film solar cells, we discuss the influence of an additional ZnO:Al layer on the formation of poly-Si films. Such an additional ZnO:Al layer leads to enhanced nucleation. Thus, the time necessary to form the poly-Si film (process time) and the resulting grain size of the poly-Si film are reduced.