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7109073 
Journal Article 
All-perovskite tandem solar cells with 24.2% certified efficiency and area over 1 cm(2)using surface-anchoring zwitterionic antioxidant 
Xiao, Ke; Saidaminov, MI; Gao, Y; Luo, Xin; Wang, Y; Gao, Han; Zhang, C; Xu, Jun; Zhu, Jia; Sargent, EH; Tan, H; Lin, R; Han, Q; Hou, Yi; Qin, Z; Nguyen, HT; Wen, Jin; Wei, M; Yeddu, V; , 
2020 
NATURE RESEARCH 
BERLIN 
870-880 
WOS:000575346600001 
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 Sn(2+)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-cm(2)-area all-perovskite tandem cells and in-lab power conversion efficiencies of 25.6% and 21.4% for 0.049 cm(2)and 12 cm(2)devices, respectively. The encapsulated tandem devices retain 88% of their initial performance following 500 hours of operation at a device temperature of 54-60 degrees C under one-sun illumination in ambient conditions.Ensuring both stability and efficiency in mixed lead-tin perovskite solar cells is crucial to the development of all-perovskite tandems. Xiao et al. use an antioxidant zwitterionic molecule to suppress tin oxidation thus enabling large-area tandem cells with 24.2% efficiency and operational stability over 500 hours.