Microstructures of Si multicrystals and their impact on minority carrier diffusion length

We carried out a systematic investigation of microstructures in a particular zone of Si multicrystals which shows a strong local variation in minority carrier diffusion length (MCDL). It was found that three typical regions with distinct microstructures correspond to the microscopic origins of the local MCDL difference. The region with perfect twin structure (Sigma 3 boundaries) has a high MCDL, while the regions with either high-angle grain boundaries (Sigma 9 and Sigma 27 boundaries) or sub-grain boundaries (high density dislocation) exhibit lower minority carrier diffusion. The relationships between the microstructures and the corresponding MCDLs are briefly discussed. This study has implications for developing improved Si multicrystals with appropriate microstructure for application in solar cells. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.