Combining wide-bandgap and narrow-bandgap perovskites to construct monolithic all-perovskite tandem solar cells offers avenues for continued increases in photovoltaic (PV) power conversion efficiencies (PCEs). However, actual efficiencies today are diminished by the subpar performance of narrow-bandgap subcells. Here we report a strategy to reduce Sn vacancies in mixed Pb–Sn narrow-bandgap perovskites that use metallic tin to reduce the Sn4+ (an oxidation product of Sn2+) to Sn2+ via a comproportionation reaction. We increase, thereby, the charge-carrier diffusion length in narrow-bandgap perovskites to 3 μm for the best materials. We obtain a PCE of 21.1% for 1.22-eV narrow-bandgap solar cells. We fabricate monolithic all-perovskite tandem cells with certified PCEs of 24.8% for small-area devices (0.049 cm2) and of 22.1% for large-area devices (1.05 cm2). The tandem cells retain 90% of their performance following 463 h of operation at the maximum power point under full 1-sun illumination.
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All data that support the findings in this study are present in the paper and the Supplementary Information. Additional data related to this study are available from the corresponding authors upon reasonable request.
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This work is supported by the National Key R&D Programme of China (grant no. 2018YFB1500102), the Thousand Talent Programme for Young Outstanding Scientists in China and the Fundamental Research Funds for the Central Universities (grant no. 0213/14380122). The work of C.Z. is supported by the National Key R&D Programme of China (grant no. 2017YFA0303703) and the National Natural Science Foundation of China (grant no. 91833305). The work of J.Z. is supported by the National Natural Science Foundation of China (grant no. 11574143). The authors thank Q. Shi at SIMIT (Shanghai) for his guidance on the J–V measurements of tandem solar cells.
The authors declare no competing interests.
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Lin, R., Xiao, K., Qin, Z. et al. Monolithic all-perovskite tandem solar cells with 24.8% efficiency exploiting comproportionation to suppress Sn(ii) oxidation in precursor ink. Nat Energy 4, 864–873 (2019). https://doi.org/10.1038/s41560-019-0466-3
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