Abstract Fully inorganic metal halide perovskite solar cells (PSCs) have become an emerging research hotspot in photovoltaics due to their high efficiency and excellent thermal stability. Unfortunately, HTL-free CsPbIXBr3−X devices suffer from surface traps on the perovskite films, which severely limits the power conversion efficiency and operational stability of the devices. In this work, we propose a multifunctional passivator, 2-cyano-5-fluorobenzene bromide molecule (2-C-5-FB), to passivate perovskite films by post-treatment, aiming to improve the quality of perovskite films, reduce interfacial defects and non-radiative complexes, enhance carrier separation kinetics, and improve the extraction of carriers, thus improving device performance. The C≡N in the molecular structure immobilizes the undercoordinated Pb2+ ions, thus passivating the defects in the perovskite films. In addition, the Br atoms on the ring can with the [PbI6]4− backbone through halogen bonding, and the F atoms form Pb-F and Cs-F, which can effectively reduce the film defects. We prepared passivated devices with the structure of FTO/TiO2/CsPbIXBr3−X/2-C-5-FB/Carbon, and the PCE of the passivated devices was improved compared with the pristine devices, and the cell efficiency was increased from 7.84% to 9.21% with a light intensity of 100 mW cm−2, and the stability of the devices was also improved. The experimental results indicate that the use of 2-cyano-5-fluorobenzene bromide passivation strategy has a positive effect on the performance enhancement of the perovskite devices, and is an effective way to realize efficient and stable PSCs.
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