Suppressing the formation of tin vacancy yields efficient lead-free perovskite solar cells

Tin hybrid perovskite solar cells (TPSCs) have emerged as the most promising candidate to the lead counterparts for the low toxicity and high theoretical efficiency. However, the easy Sn2+ oxidation and related defects hinder further efficiency and stability improvement. Therefore, a facile Lewis base molecule of 4-amino-3-hydroxybenzoic acid (4A3HA) is employed in the perovskite precursor to coordinate with the under-coordinated Sn2+ ions and passivate the Sn defects. The effective suppression of the formation of Sn vacancy also has been verified from the density functional theory calculations. The 4A3HA modification significantly suppresses the trap-mediated recombination of Sn perovskite film. Accordingly, these benefits deliver a high power conversion efficiency (PCE) of 13.43% for TPSCs with notably improved on-shelf and thermal stability.