Integration of high sheet resistance homogeneous emitters in a process flow for PERC-type solar cells with Cu contacts

This paper presents the results of the integration of a high sheet resistance (120 Ω/sq) homogeneous emitter with an industrial feasible process flow on large area p-type CZ-Si PERC solar cells with plated Ni-Si/Cu front contacts. Focus is put on the junction isolation performed by either applying a mask prior to POCl₃ diffusion or by selectively removing the rear side emitter in an inline 1-sided wet-chemical etching tool after diffusion. A metallization sequence [1,2] applying Ni and Cu plating, is performed to contact the moderately doped emitters. The best experimental split in this comparison resulted in excellent average conversion efficiency of 20.2%.