Tri-Brominated Perovskite Film Management and Multiple-Ionic Defect Passivation for Highly Efficient and Stable Solar Cells

摘要

High-quality perovskite films with low imperfections, high hole mobility, and matching energy levels play a crucial role in enhancing performance of perovskite solar cells (PSCs) without hole-transporting materials (HTMs). Herein, it is demonstrated that the incorporation of a stable tetra-bisphenol A (TBBPA) with diphenyl ring, polybromides, and hydroxyl groups additive into a perovskite film can simultaneously manipulate the crystal growth and passivate the defects through coordination interaction between the functional group (-OH, -Br) and the unsaturated halogen and metal ions (Br~-, Cs~+, and Pb~(2+)), resulting in a reduced grain boundary as well as imperfection and increased hole mobility of the CsPbBr_3 perovskite film. In addition, the valence band of a perovskite film with TBBPA additive is shifted upward to approach the work function of the carbon electrode, thereby improving the energy level alignment. Consequently, a significantly boosted charge extraction and reduced charge recombination of the carbon-based HTM-free CsPbBr_3 PSCs is obtained after incorporating the TBBPA additive, yielding a maximum power conversion efficiency of up to 9.82% of the optimized device. Furthermore, the champion PSC without encapsulation displays a remarkable thermal and moisture stability after being kept in ambient air for 720 h at 85 °C and 85% relative humidity, respectively.