De-doping buried interface in p-i-n perovskite solar cells by utilizing compositional heterogeneity in depth

Compositional heterogeneity in halide perovskite materials often leads to undesired physiochemical properties of the materials that hampers device efficiency and stability. In a perovskite film prepared via conventional 2-step method, we find excess PbI₂ are prone to locate at surface and buried interfaces, resulting in negative-type self-doping. To tailor this band alignment unfavored for p-i-n devices, we pre-deposited pyrrolidinium hydroiodide to react with residual PbI₂ at buried interface. It not only de-dopes the perovskite to obtain the desired band alignment, but also passivates negative-type defects, which improves the device efficiency and stability. Consequently, the target planar p-i-n PSCs achieve an efficiency of 24.5 % (certified 23.2 %) and a remarkable photostability with 13 % efficiency decline for 2800 h under 1-Sun white LED illumination. It is so far among the highest-efficiency p-i-n PSCs via 2-step fabrication. Therefore, we suggest an interface de-doping strategy to fabricate highly efficient and stable PSCs.