Benzamidine Derivative as a Multifunctional Additive in Pb–Sn Perovskite Solar Cells

Mixed Pb–Sn perovskite has attracted considerable attention owing to its lower toxicity and broader light absorption range than pure Pb-based perovskite. However, easy oxidation of Sn2+ into Sn4+ and uncontrollable crystallization of the Pb–Sn perovskite severely limit efficiency and stability of Pb–Sn perovskite solar cells (PSCs). Herein, a benzamidine derivative 4-aminobenzamidine dihydrochloride (4-ABD) was employed as a multifunctional additive in the Pb–Sn perovskite layer, as it simultaneously improved crystallinity, inhibited the oxidation of Sn2+, stabilized the crystal structure, and passivated defects. As a result, a power conversion efficiency of 22.33% with excellent operational stability has been achieved because the incorporation of 4-ABD not only accelerated carrier transport and extraction but also suppressed carrier recombination in the Pb–Sn PSCs. Moreover, the 4-ABD-modified Pb–Sn PSCs performed excellent thermal stability and storage stability. This work provides a promising, effective strategy for achieving high-efficiency, stable Pb–Sn PSCs.