B-doped a-Si:H contact improvement on silicon heterojunction solar cells and interdigitated back contact structure

Abstract

This study reports on the p-type a-Si:H emitter layer of silicon heterojunction (Si-HJ) solar cells and its contacting scheme. The influence of the ratio between p-type a-Si:H emitter width and its contact width is checked on Interdigitated Back Contact (IBC) Si-HJ both experimentally and by 2D modelling. A low emitter contact fraction value is found to be detrimental to the IBC Si-HJ cells efficiency due to distributed series resistance effects. This not only limits the cell fill factor (FF) but also its short circuit current density (Jsc). By increasing the emitter contact fraction an efficiency of 12.7% is obtained on 25 cm2 IBC Si-HJ solar cells. New B-doped a-Si:H emitter layers and contacts are also developed on inverted Si-HJ cells. Depending on the a-Si:H conductivity, we observe a great impact of the contact material on Si-HJ cells performance. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.