Molecular Bonding Regulated Defect Passivation for Modulating Efficiency and Stability of Methylammonium Free Inverted Perovskite Solar Cells

Abstract Molecular passivation is a prominent approach for improving the power conversion efficiency and operation stability of perovskite solar cells. Herein, diammonium iodide functional molecules with an aryl or alkyl core are introduced on 3D-perovskite, and its interfacial passivation effect is explored. It showed that piperazine dihydriodide (PZDI) with alkyl core-electron rich -NH terminal is propitious to mitigate surface and bulk defects and modify surface chemistry or interfacial energy band leading to increase carrier extraction. Benefiting from superior PZDI passivation, the device efficiency has been scaled to 23.17% (area ~1 cm 2 ) with superior operational device stability. We also achieved a certified efficiency of ~21.50% (area ~1.024 cm 2 ). The theoretical calculation suggests that PZDI entangles onto the film’s surface with -NH 2 I anchor, and reinforces the adhesion. Device analysis corroborates that a stronger bonding interaction attenuates the defect densities in the perovskite film and suppresses ion migration, which is supported by the first-principle calculations. This work demonstrated that the bifunctional molecules with stronger surface adsorption play a crucial role in triggering defect mitigation, which paves the way for the design of bonding-regulated molecular passivation for enhancing device performance and stability.