A critical analysis on the role of back surface passivation for a-Si/c-Si heterojunction solar cells

Back surface passivation is a well-known method to reduce carrier recombination and hence improves the efficiency of crystalline silicon solar cells. In this manuscript, we critically analyze the role of this process for a-Si/c-Si heterojunction solar cells through a combination of device fabrication, multiple characterization techniques, and modeling. Curiously, our experimental results indicate that dark current characteristics of these devices do not scale in accordance with the improvements in carrier lifetime achieved through back surface passivation. Our results indicate these puzzling experimental results could be due to the possibility that carrier injection from crystalline silicon base significantly contributes to the dark current of these devices. This result has obvious and significant implications towards understanding the device physics and efficiency optimization of a-Si/c-Si heterojunction devices.