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Perovskite solar cells (PSCs) have demonstrated a high power conversion efficiency, however, the large energy loss due to non‐radiative recombination is the main challenge for further performance enhancement. Here, a surface treatment strategy is developed by heat‐induced decomposition of a thin interlayer 2,7‐Naphthaleneditriflate (NAP) to in situ reconstruct perovskite energetics. It is verified that the reconstructed perovskite surface energetics match better with the upper hole transport layer compared to the intrinsic condition. Spontaneous generation of n/n− homojunctions between the perovskite film bulk and the surface region promotes hole extraction, enhancing built‐in electric field, and thus significantly suppresses charge recombination at such perovskite hole‐selective heterojunctions. Moreover, the surface decomposed fluorine‐rich complexes passivate the defects and improve the crystallinity of the perovskite film. These advantages are confirmed by a remarkably improved efficiency from 20.52% for the control device to 23.37% for the treated one with excellent stability. The work provides a promising approach of in situ reconstructing perovskite surface and interface for the design of highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution‐processed chromium multioxide (CrOx) is judiciously selected to construct a MAPbI3/CrOx/Spiro‐OMeTAD hole‐selective heterojunction. It is demonstrated that the inserted CrOx not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)‐HOMO offset between perovskite and Spiro‐OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect‐assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI3 based n–i–p planar PSCs reported to date. These findings of this work provide new insights into novel charge‐selective heterojunctions for further enhancing efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]