Spontaneously Healing Buried Interfaces in n–i–p Halide Perovskite Photovoltaics

Accumulated halide defects on the buried interfaces of halide perovskite layers have exacerbated undesirable nonradiative recombination in the n–i–p perovskite photovoltaics, but are challenging to be passivated—the commonly used passivation molecules at buried interfaces of perovskite layers would be inevitably eroded in the solution processes of perovskite deposition. Regarding the solvent incompatibility, herein, the ZnO–EA/SnO2–Cl electron transfer layers (ETLs) terminated with functional sites (i.e., ethanolamine (EA) ligands on ZnO and Cl− ions on SnO2) to spontaneously heal the buried interfaces of perovskite layers are customized. The specialties of ZnO–EA/SnO2–Cl for defect passivation are revealed: 1) formation of ZnO–EA–Pb2+ coherent interlayers at the EA‐terminated ZnO‐perovskite interfaces effectively offsets the I vacancy defects of perovskites; and 2) spontaneous halide exchange between Cl−‐terminated SnO2 and unstable I−‐terminated perovskites enables the formation of FA2Sn(ICl)6‐like coherent interlayers. Thus, the customized termination of ETLs’ surface reduces the halide‐defect‐triggered nonradiative recombination at the buried surfaces of perovskite, enabling the fabricated n–i–p planar modules (6 × 6 cm2) with power conversion efficiencies approaching 18% and elevated stability. These findings provide desirable guidelines for interfacial carrier transport between perovskites and ETLs.