In Situ Interface Engineering of TiO2 Nanocrystals for Fully Ambient‐Processed Perovskite Solar Cells

By in situ anchoring of dopamine molecules onto TiO2 during the nanoparticle synthesis, ultrasmall and ultrafine dopamine‐modified TiO2 nanocrystals (DA‐TiO2) are prepared and used as a high‐performance electron transport layer (ETL) in fully ambient‐processed planar perovskite solar cells. A mesoporous PbI2 scaffold deposited on DA‐TiO2 ETL is achieved by the exposure of PbI2 film toward ambient moisture (≈50% relative humidity, RH), which enables efficient conversion of PbI2 to CH3NH3PbI3. The dopamine interlayer with terminal amino groups is deliberately incorporated between the TiO2 and perovskite interface, resulting in optimized interface band alignment and suppressed charge accumulation at the interface. The fully ambient‐processed planar CH3NH3PbI3 perovskite solar cell using DA‐TiO2 ETL delivers an optimized average power conversion efficiency of 16.94%.