An Ultrathin Ferroelectric Perovskite Oxide Layer for High-Performance Hole Transport Material Free Carbon Based Halide Perovskite Solar Cells

The hole transport material (HTM) free carbon based perovskite solar cells (C-PSCs) are promising for its manufactural simplicity, but they currently suffer from low power conversion efficiencies (PCE) largely because of the voltage loss. Here, a new strategy to increase the PCE by incorporating an ultrathin ferroelectric oxide PbTiO₃ layer between the electron transport material and the halide perovskite is reported. The resulting C-PSCs have achieved PCEs up to 16.37%, which is the highest record for HTM-free C-PSCs to date, mainly ascribable to the ferroelectric layer enhanced open circuit voltage. Detail measurements and analysis show an enhanced built-in potential in the C-PSCs as well as suppression of the non-radiative recombination due to the ferroelectric PbTiO₃ layer incorporation, accounting for the boosted V_OC and photovoltaic performance.