Efficient Bidentate Molecules Passivation Strategy for High-Performance and Stable Inorganic CsPbI2Br Perovskite Solar Cells

All inorganic mixed-halide CsPbI2Br perovskites with suitable bandgap and superior thermal durability have ignited rising interests in the field of perovskite solar cells (PSCs). However, the serious energy losses derived from deleterious trap-assisted defects-induced notorious nonradiative recombination and inferior moisture durability are still the primary hindrance on the way to develop high-performance CsPbI2Br PSCs. Herein, a novel passivation strategy is presented by introducing dual-functionalized bidentate molecule 2-(2'-thienyl)pyridine (2-ThPy) to modulate perovskite crystallization and passivate halogen vacancy defects. Compared with monodentate counterparts, 2-ThPy can anchor Pb2+ sites via S and N atomic bonding simultaneously, and the synthesized CsPbI2 Br films exhibit enlarged grain size, show advantages to passivate defect states, and dramatically reduce trap density, thereby lessening the detrimental carrier recombination. Consequently, a champion power conversion efficiency (PCE) of 12.69% with negligible hysteresis is delivered for the fabricated CsPbI2Br PSCs treated with 2-ThPy. Moreover, the moisture stability of CsPbI2Br PSCs with 2-ThPy is also greatly enhanced, and the device without encapsulation retains 92% of initial PCE value after 30 days aging under 25 degrees C and 40% relative humidity in ambient environment. The bidentate molecules passivation strategy paves a promising avenue to implement efficient and stable inorganic PSCs.