The effect of oxygen pretreatment at hetero-interface on the photovoltaic properties of MoS2/Si heterojunction solar cells

Abstract In this work, we modify the n-type MoS 2 /p-type Si heterojunction interface by oxygen pretreatment at the initial stage of MoS 2 films deposition. Such a facile pretreatment process has effective effect on the defects recombination reduction and band alignment at the MoS 2 /Si heterojunction interface. By adding the O 2 into the sputtering gases and lasting 3-10 s, the oxygen vacancy defects at the hetero-interface significantly decreased and the built-in electric field greatly increased and exceeded 600 mV, which was benefit for reducing defects recombination losses and improving carrier extraction at MoS 2 /Si interface. Hence, the enhanced MoS 2 /Si heterojunction solar cells performance (V oc of 243 mV, FF of 58.71 and J sc of 32.35 mA/cm 2 ) were obtained with the optimized conversion efficiency of 4.62%. While, if the pre-sputtering time was over 20 s, the interface vacancy defects increased instead and the built-in potential was reduced to 582.7 mV, which leads to the poor carrier transport at MoS 2 /Si interface and adversely affects the cells electrical performance. The results demonstrate that the appropriate oxygen pretreatment could be a new and efficient way to enhance the photovoltaic properties of the MoS 2 /Si heterojunction solar cells by the interface modification effect.