Reduced Surface Hydroxyl and Released Interfacial Strain by Inserting CsF Anchor Interlayer for High‐Performance Perovskite Solar Cells

Defects passivation strategy for the atop perovskite films is widely investigated, while the buried interface between the tin oxide electron transport layer and the perovskite active layer should gain more attention since the interfacial strains and surface hydroxyl are inevitable during the fabrication process which would affect the efficiency and stability of the fabricated perovskite devices. Herein, the CsF interlayer between SnO 2 and perovskite film is adopted to release the interfacial strain and decrease the surface hydroxyl through the atomic interaction and chemical doping. Furthermore, the CsF can tailor the energy level of SnO 2 for a more favorable alignment to reduce the energy loss and improve charge extraction. Correspondingly, the perovskite photovoltaic devices with the efficiency of 23.13% are achieved. Moreover, CsF‐doped devices demonstrate enhanced stability, which could maintain 87% of its initial efficiency after 1000 h under environmental storage. The developed CsF interfacial engineering provides a promising strategy for the interfacial modulation.