Applying BaTiO₃-coated TiO₂ core–shell nanoparticles films as scaffold layers to optimize interfaces for better-performing perovskite solar cells

In this paper, we replaced mesoporous TiO₂ nanoparticles scaffold layers by BaTiO₃-coated TiO₂ core–shell nanoparticles films which obtained by treating pure mesoporous TiO₂ layers with 1.0 wt% barium nitrate solution, successfully realized the aim of optimizing interfaces bonding at TiO₂/CH₃NH₃PbI₃. Ultrathin BaTiO₃ shell layer can combine better with CH₃NH₃PbI₃ layer so as to reduce the existence of carrier recombination centers. Moreover, better optical absorption and larger fill factor were obtained in this manner by the reason of larger CH₃NH₃PbI₃ grain size and fewer crystal boundaries. Furthermore, photoluminescence spectra and electrochemical impedance spectroscopy verified that our core–shell scaffold material contributes to accelerate carrier separation and retard carrier recombination. As a result, average power conversion efficiency enhanced from 11.20 to 13.76% under ambient conditions, which realized almost a quarter improvement than the devices based on pure mesoporous TiO₂ layers. Such results have a certain guiding effect on solving interface defects and carrier recombination.