NaCl-Induced PbI₂ Passivation Enhancement on Cs_0.17FA_0.83Pb(I_0.83Br_0.17)₃ Thin Films for Perovskite Solar Cells

Perovskite solar cells are one of the most attractive alternative photovoltaic technologies. Moreover, the cells can be manufactured simply and inexpensively using solution-based methods and low-cost precursors. However, solution-based methods frequently demonstrated various defects, such as the presence of unreacted PbI₂, which tend to limit the efficiency and accelerate the degradation of devices. The modification of the light absorption layer has been demonstrated to be an effective strategy for dealing with defects. In this paper, we propose a low-cost and effective method to improve the performance of carbon-based perovskite solar cells (C-PSCs) by modifying the light absorption layer with a sodium chloride (NaCl) additive. The modification leads to changes in the excess PbI₂ crystal structure and morphology, which improve the passivation effect on perovskite solar cells. As a result, the optimized amount of the NaCl additive can increase the built-in potential and decrease nonradiative recombination, leading to the enhancement of V_oc and FF parameters. The champion NaCl-modified C-PSCs in a homemade air-filled dry glovebox achieved a PCE of 14.69%. The improvement not only promoted the device’s PCE but also maintained excellent long-term stability. This approach is noteworthy for enhancing C-PSCs with negligible cost and might lead to profitable large-scale production.