All-perovskite tandem solar cells with 24.2% certified efficiency and area over 1 cm2 using surface-anchoring zwitterionic antioxidant

Monolithic all-perovskite tandem solar cells offer an avenue to increase power conversion efficiency beyond the limits of single-junction cells. It is an important priority to unite efficiency, uniformity and stability, yet this has proven challenging because of high trap density and ready oxidation in narrow-bandgap mixed lead–tin perovskite subcells. Here we report simultaneous enhancements in the efficiency, uniformity and stability of narrow-bandgap subcells using strongly reductive surface-anchoring zwitterionic molecules. The zwitterionic antioxidant inhibits Sn2+ oxidation and passivates defects at the grain surfaces in mixed lead–tin perovskite films, enabling an efficiency of 21.7% (certified 20.7%) for single-junction solar cells. We further obtain a certified efficiency of 24.2% in 1-cm2-area all-perovskite tandem cells and in-lab power conversion efficiencies of 25.6% and 21.4% for 0.049 cm2 and 12 cm2 devices, respectively. The encapsulated tandem devices retain 88% of their initial performance following 500 hours of operation at a device temperature of 54–60 °C under one-sun illumination in ambient conditions.This work is financially supported by the National Natural Science Foundation of China (61974063, 61921005), Fundamental Research Funds for the Central Universities (14380168), National Key R&D Program of China (2018YFB1500102), Natural Science Foundation of Jiangsu Province (BK20190315), Basic Research Program of Frontier Leading Technologies in Jiangsu Province, Program for Innovative Talents and Entrepreneur in Jiangsu and Thousand Talent Program for Young Outstanding Scientists in China. The work of Y.H., M.W. and E.H.S. is supported by US Department of the Navy, Office of Naval Research (N00014-20-1-2572). V.Y. and M.I.S. acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC)