Evolution of the charge carrier lifetime characteristics in crystalline silicon wafers during processing of heterojunction solar cells

Abstract All process steps in the fabrication of amorphous crystalline a Si H c Si silicon heterojunction solar cells affect interface recombination and thus have an impact on the open circuit voltage of the final solar cell. Transient photoconductance decay is a convenient method to assess the charge carrier lifetime which is a direct measure for recombination and thus the interface quality. In this contribution we present a step by step analysis and evaluation of the charge carrier lifetime throughout the processing of the solar cells starting from the saw damage etched Si wafer to the complete solar cell device. Particular emphasis is put on the optimization of the random pyramid texture. For this, surface morphologies and a Si H c Si interface properties were quantitatively evaluated and optimized with respect to low recombination and large carrier lifetimes. Based on this optimization a Si H c Si heterojunction solar cells with conversion efficiencies exceeding 20 were prepared on c Si wafers textured in isopropanol IPA free alkaline solutio