Chelate-Pb Intermediate Engineering for High-Efficiency Perovskite Solar Cells

Crystallization quality and grain size are key factors in fabricating high-performance planar-type perovskite photovoltaics. Herein, we used 1,8-octanedithiol as an effective additive in the [HC(NH2)2]0.95Cs0.05PbI3 (FA0.95Cs0.05PbI3) solution to improve the FA0.95Cs0.05PbI3 film quality via solution processing. 1,8-Octanedithiol would coordinate with lead to form the chelate-Pb compound, leading to smaller Gibbs free energy during the perovskite crystallization process, facilitating formation of high-quality perovskite films with larger grains, smoother surfaces, lower electron trap densities, and longer carrier lifetimes compared to the nonadditive ones. As a result, the champion efficiency for devices with 3% 1,8-octanedithiol-doped FA0.95Cs0.05PbI3 is raised to 19.36% from 18.39% of a device without the additive. The new technique is a promising way to fabricate perovskite photovoltaics with high performance.