Surface chemical polishing and passivation minimize non-radiative recombination for all-perovskite tandem solar cells

All-perovskite tandem solar cells have shown great promise in breaking the Shockley–Queisser limit of single-junction solar cells. However, the efficiency improvement of all-perovskite tandem solar cells is largely hindered by the surface defects induced non-radiative recombination loss in Sn-Pb mixed narrow bandgap perovskite films. Here, we report a surface reconstruction strategy utilizing a surface polishing agent, 1,4-butanediamine, together with a surface passivator, ethylenediammonium diiodide, to eliminate Sn-related defects and passivate organic cation and halide vacancy defects on the surface of Sn-Pb mixed perovskite films. Our strategy not only delivers high-quality Sn-Pb mixed perovskite films with a close-to-ideal stoichiometric ratio surface but also minimizes the non-radiative energy loss at the perovskite/electron transport layer interface. As a result, our Sn-Pb mixed perovskite solar cells with band-gaps of 1.32 and 1.25 eV realize power conversion efficiencies of 22.65% and 23.32%, respectively. Additionally, we further obtain a certified power conversion efficiency of 28.49% of two-junction all-perovskite tandem solar cells. We also verify the effectiveness of the surface reconstruction in module-level devices (champion module PCE 23.39% with an aperture area of 11.3 cm²) and demonstrate operational stability, with encapsulated tandem cells retaining 79.7% of initial PCE after 550 hours of MPPT in ambient air.

Yongyan Pan, Jianan Wang, Zhenxing Sun, Jiaqi Zhang, Zheng Zhou, Chenyang Shi, Sanwan Liu, Fumeng Ren, Rui Chen, Yong Cai, Huande Sun, Bin Liu, Zhongyong Zhang, Zhengjing Zhao, Zihe Cai, Xiaojun Qin, Zhiguo Zhao, Yitong Ji, Neng Li, Wenchao Huang, Zonghao Liu, Wei Chen