Chemical Bath Deposition of Co‐Doped TiO2 Electron Transport Layer for Hysteresis‐Suppressed High‐Efficiency Planar Perovskite Solar Cells

Planar hybrid perovskite solar cells (PSCs) attract great attention due to their obvious advantages of low‐temperature processing with a high power conversion efficiency (PCE) up to 23.32%. Here, Co‐doped TiO 2 (Co‐TiO 2 ) deposited by a straightforward low‐temperature chemical bath deposition (CBD) method is explored. Using Co‐TiO 2 as an electron transport layer (ETL) for the planar PSCs, the effects of doping on TiO 2 morphology, electronic properties, and solar cell performance are investigated. The PCE increases to 19.10% when the Co doping concentration is optimized at 5 mol%, an increase of 17.40% compared with that using the pristine TiO 2 . Meanwhile, the notorious J – V hysteresis is suppressed to a greater extent. Considering that the low‐temperature CBD is comparable with continuous roll‐to‐roll processing, it makes the process and the Co‐TiO 2 ETL potential candidates for low‐cost commercialization.