Thin-film silicon crystal growth on low cost substrates

Abstract

Thin films of crystalline silicon are being grown by us on dissimilar substrates for photovoltaic solar cell application. The approach offers the potential to combine the high performance and stability of crystalline silicon with the low cost of thin films. Growth from saturated solution is being used to meet the specific requirements of large grain growth, benign grain boundaries, and long minority carrier diffusion length. For a good quality crystalline overlayer on a substrate, the growth process consists of five steps: (1) wetting, (2) nucleation, (3) non-impinging crystal growth, (4) fill-in crystal growth, and (5) homoepitaxial film growth. Silicon films with crystals that have a width to thickness ratio of greater than 2 to 1 and an overall thickness of 20μm have been grown on steel and quartz substrates. These films have demonstrated the required morphological characteristics for a high performance thin-film polycrystalline silicon solar cell.