In‐Situ Self‐Assembly Dipole Shielding Layer Toward Efficient and Stable Inorganic Perovskite Solar Cells

Abstract Despite CsPbI_2.75Br_0.25 inorganic perovskites exhibit high potential for single‐junction and/or tandem solar cells, unexpected non‐radiative recombination, and mismatched interfacial band alignment within the inorganic perovskite solar cells (PSCs) disadvantageously affect their photovoltaic performance. Rational design of the dipole shielding layer (DSL) is vital to realize a win–win situation for the defect passivation and band alignment. Herein, A‐site dipole molecules, that is, neopentylamine and 2‐methylbutylamine, are employed for in‐situ self‐assembly of a thus‐far unreported DSL at the interface between 3D perovskite and hole transport layer. The as‐prepared DSL demonstrates a 2D RP phase perovskite and the lattice‐matching structurally‐stable DSL@3D perovskite enables to alleviate the unexpected surface defects and suppress the spontaneous non‐radiative recombination by means of effectively tuning the surface work function via regulating the dipole moment length and Van der Waals gap. Accordingly, the top dipole‐modified inorganic PSCs exhibit a champion power conversion efficiency (PSC) as high as 19.77% and a fill factor over 83%. Equally importantly, the corresponding solar cells demonstrate a remarkable enhanced stability, maintaining 90% of its initial efficiency for more than 1200 h without encapsulation under a 20% ± 5% relative humidity.