Contacting n+ Poly-Si Junctions with Fired AZO Layers: A Promising Approach for High Temperature Passivated Contact Solar Cells

Abstract

Polysilicon (poly-Si) based passivating contacts are promising to improve silicon solar cells conversion efficiency. However, the use of Transparent Conductive Oxides (TCO) has to be considered to improve lateral conductivity while maintaining good optical and surface passivation properties especially for bifacial devices. In this work different Aluminum-doped Zinc Oxide (AZO) based layers have been investigated after high temperature firing steps to contact Phosphorus-doped poly-Si layers. Contact resistivity below 100 mΩ.cm2 at the AZO/n+ poly- Si interface and stable implied open circuit voltage values (> 715 mV) have been obtained for firing temperatures from 550°C to 900°C. Moreover, the use of capping layers allows to maintain highly conductive AZO layers upon annealing. This novel high temperature contacting method via indium-free TCOs, is particularly interesting for the industrial integration of poly-Si based passivated contacts and provides new perspectives for advanced homojunction solar cells.