Methylammonium-free, high-efficiency, and stable all-perovskite tandem solar cells enabled by multifunctional rubidium acetate
Xufeng Liao, Xuefei Jia, Weisheng Li, Xiting Lang, Jianhua Zhang, Xinyu Zhao, Yitong Ji, Qingguo Du, Chun‐Hsiao Kuan, Zhiwei Ren, Wenchao Huang, Yang Bai, Kaicheng Zhang, Chuanxiao Xiao, Qianqian Lin, Yi‐Bing Cheng, Jinhui Tong
Abstract
All-perovskite tandem solar cells (APTSCs) offer the potential to surpass the Shockley-Queisser limit of single-junction solar cells at low cost. However, high-performance APTSCs contain unstable methylammonium (MA) cation in the tin-lead (Sn-Pb) narrow bandgap subcells. Currently, MA-free Sn-Pb perovskite solar cells (PSCs) show lower performance compared with their MA-containing counterparts. This is due to the high trap density associated with Sn2+ oxidation, which is exacerbated by the rapid crystallization of MA-free Sn-containing perovskite. Here, a multifunctional additive rubidium acetate (RbAC) is proposed to passivate Sn-Pb perovskite. We find that RbAC can suppress Sn2+ oxidation, alleviate microstrain, and improve the crystallinity of the MA-free Sn-Pb perovskite. Consequently, the resultant Sn-Pb PSCs achieve a power conversion efficiency (PCE) of 23.02%, with an open circuit voltage (Voc) of 0.897 V, and a filling factor (FF) of 80.64%, and more importantly the stability of the device is significantly improved. When further integrated with a 1.79-electron volt MA-free wide-bandgap PSC, a 29.33% (certified 28.11%) efficient MA-free APTSCs with a high Voc of 2.22 volts is achieved. The high trap density associated with tin (II) oxidation impacts the device performance of methylammonium cation-free tin-lead perovskite solar cells. Here, authors employ rubidium acetate for defect passivation and achieve efficient and stable single-junction and all-perovskite tandem solar cells.