Investigation of XeF2 dry etching for contact isolation of screen printed IBC solar cell

Abstract

We demonstrated the use of Xenon Difluoride (XeF2) plasma less vapor etching for isolation of n and p regions in screen-printed interdigitated back contact (IBC) solar cell. The fabrication process is free from lithography process and carried out using standard conventional silicon solar cell equipment. A p-type CZ wafer was used as the starting material and POCl 3 furnace was used to form the emitter. Silver and Aluminum pastes were screen printed to form emitter and base contacts respectively. An automated XeF2 vapor etching system was used for blanket etching of doped region between emitter and base metal contacts. Solar cell LIV response was measured as a function of XeF2 etching. Open-circuit increased as a function of XeF2 etching indicating removal of doped silicon; however, solar cell response was poor presumably due to large un-passivated, junction-free regions between positive and negative contacts. In order to improve performance, an extra alignment step is needed to etch small regions only.