Effects of 1-(2-amino-5-bromophenyl)ethenone modification on CsPbI2Br films and perovskite solar cells

Abstract

Despite the remarkable thermal stability of inorganic CsPbI₂Br perovskites solar cells, their practical deployment is plagued by severe interfacial non-radiative recombination and black phase instability at room temperature. To address these challenges, we designed a novel multifunctional interfacial modifier 1-(2-Amino-5-bromophenyl)ethenone(2A5B). In this study, the interface of CsPbI₂Br perovskite/Spiro-OMeTAD hole transport layer was modified by 2A5B. The effects of 2A5B modification on the morphology, structure, optical absorption properties, defect density, carrier lifetime, hydrophobicity and energy level of CsPbI₂Br perovskite film, optoelectronic performance of the devices, and their mechanism were systematically studied, which were rarely reported. The oxygen atoms in the CO groups of 2A5B form coordination bonds with uncoordinated Cs⁺ ions, while the nitrogen atoms in the –NH₂ groups coordinate with Pb²⁺ ions on the surface of CsPbI₂Br, passivating interface defects, modulating interface energy levels matching, and thus inhibiting interface non-radiative recombination. Simultaneously, the hydrogen atoms in the –NH₂ groups interact with surface free I⁻/Br⁻ ions of CsPbI₂Br via hydrogen bonding, suppressing halide migration and stabilizing the perovskite structure. The efficiency of the device modified with 4 mg/mL of 2A5B prepared in an air environment with relative humidity of 50 % increased by 51.08 % compared with that of the unmodified device. And 4 mg/mL 2A5B modified device could maintain an initial efficiency of 70 % after 40 days of storage at RH 50 %, whereas the unmodified device only keeps 20 % of the initial efficiency. This study provides valuable insights of designing interfacial modifiers between the perovskite layer and the hole transport layer, and the photovoltaic conversion efficiency and stability of the all-inorganic perovskite solar cells were improved in a highly humid air environment.