Efficiency enhancement of perovskite solar cells by fabricating as-prepared film before sequential spin-coating procedure

Graphical abstract: Schematic illustration of modified two-step spin-coating procedure for MAPbI₃ perovskite thin films. - Highlights: • An as-prepared CH₃NH₃PbI₃ and PbI₂ film was introduced before the traditional two-step process. • Smooth morphology and trace amount of remaining PbI₂ benefit the performance of solar cell. • The optimal as-prepared film introduced improves the efficiency of CH₃NH₃PbI₃ solar cells from 9.11% to 11.16%. - Abstract: Sequential spin-coating procedure is a widely adopted strategy to prepare CH₃NH₃PbI₃ on mesostructured TiO₂ electrode for organolead halide perovskite-based solar cells. However, this method suffers from the rough surface and excessively residual PbI₂ in the resulting perovskite film, deteriorating the device performance seriously. Herein, a facial modified sequential solution deposition method, by introducing an as-prepared CH₃NH₃PbI₃ and PbI₂ film before the traditional two-step process, was proposed to fabricate the perovskite-based solar cell with smooth morphology and trace amount of remaining PbI₂. The optimal as-prepared film introduced improves the efficiency of CH₃NH₃PbI₃ solar cells from 9.11% to 11.16%. The enhancement of device performance can be attributed to the increased light absorption ability and decreased recombination rate of carriers in CH₃NH₃PbI₃ absorber.