Efficient and stable tin-based perovskite solar cells by introducing π-conjugated Lewis base

Tin-based perovskite solar cells (TPSCs) as the most promising candidate for lead-free PSCs have incurred extensive researches all over the world. However, the crystallization process of tin-based perovskite is too fast during the solution-deposited process, resulting in abundant pinholes and poor homogeneity that cause serious charge recombination in perovskite layer. Here, we employed the pi-conjugated Lewis base molecules with high electron density to systematically control the crystallization rate of FASnI(3) perovskite by forming stable intermediate phase with the Sn-I frameworks, leading to a compact and uniform perovskite film with large increase in the carrier lifetime. Meanwhile, the introduction of the pi-conjugated systems also retards the permeation of moisture into perovskite crystal, which significantly suppresses the film degradation in air. These benefits contributed to a stabilizing power conversion efficiency (PCE) of 10.1% for the TPSCs and maintained over 90% of its initial PCE after 1000-h light soaking in air. Also, a steady-state efficiency of 9.2% was certified at the accredited test center.