Lead (II) fluoride additive modulating grains growth of water-processed metal halide perovskites for enhanced efficiency in solar cells

Abstract The widespread manufacture of perovskite solar cells (PSCs) is hindered by the significant use of toxic solvents in the solution processing. Among the alternative synthesis routes, the newly developed water-processable approach stands out for its environmental friendliness and scalability. However, the performance of the water-processed PSCs still lag behind those fabricated using organic solvents. In this research, we advance the water-processing fabrication of PSCs using an additive engineering strategy. Specifically, PbF 2 is employed to regulate perovskite crystallization in the water-based perovskite synthesis process. The additive is found to not only accelerate the phase transformation rate, forming photoactive perovskite phase of the film, but also enhance the preferable crystal orientation of the resultant perovskite. The fluoride anion, with its strong electronegativity, creates robust passivation for the surface of perovskite grains, leading to improved optical and electrical properties. As a result, significant improvement in device performance is achieved, with an optimal power conversion efficiency (PCE) of 18.1% for the PbF 2 -added device compared to the pristine device (PCE of 16.3%). Additionally, the devices exhibit prolonged operational and environmental lifetimes.