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Nature Energy (2026)
Perovskite/Cu(In,Ga)Se2 (CIGS) tandem solar cells hold particular promise for flexible and lightweight applications, yet their efficiency still lags behind other perovskite-based tandem architectures. To achieve optimal spectral matching with the CIGS bottom cell, the perovskite top cell requires a wide bandgap, obtainable with a mixed-halide composition with high bromide content. However, perovskite films made with high bromide content suffer from inhomogeneous halide distribution, especially for scalable film fabrication method. Here we use 2-pyrrolidinone as the coordinating solvent to suppress the crystallization of the halide intermediates, maintaining a homogeneous halide distribution during ambient blade-coating of the perovskite film. We demonstrate a flexible monolithic two-terminal perovskite/CIGS tandem cell with a power conversion efficiency of 27.3%, with minimal efficiency loss over 500 h of operation.
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J.X. acknowledges support from the National Natural Science Foundation of China (grant no. 62274146), the Natural Science Foundation of Zhejiang Province of China (grant nos. LR24F040001 and DG25E020001), the Central Guidance Funds for Local Science and Technology Development Projects (grant no. 2025ZY01012) and the Fundamental Research Funds for the Central Universities. R.W. acknowledges a grant from the National Natural Science Foundation of China (grant no. 62474143), Natural Science Foundation of Zhejiang Province of China (grant nos. LD24E020001 and QKWL25E1301), the support from the Key R&D Program of Zhejiang (grant no. 2024SSYS0061), Zhejiang Key Laboratory of Low-Carbon Intelligent Synthetic Biology (2024ZY01025), Muyuan Laboratory (pro-gramme ID 14136022401) and the support by Scientific Research Innovation Capability Support Project for Young Faculty (grant no. SRICSPYF-BS2025014). E.B. acknowledges the grant from the Major Industrial Innovation Project of Anhui Province (grant no. AHZDCYCX-LSDT2023-10).
These authors contributed equally: Shaochen Zhang, Enbing Bi, Borui Lei.
State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
Shaochen Zhang, Borui Lei, Liuwen Tian, Xiaonan Wang, Xu Zhang, Donger Jin, Jingjing Zhou, Yuan Tian, Wei Fan, Yang Gui, Deren Yang & Jingjing Xue
Department of Materials Science and Engineering, School of Engineering, Westlake University, Hangzhou, China
Shaochen Zhang, Liuwen Tian, Xiaonan Wang, Xu Zhang, Jingjing Zhou, Yuan Tian, Wei Fan, Shenglong Chu, Qingqing Liu & Rui Wang
Xuancheng Advanced Solar Technology Institute Co., Ltd, Xuancheng, China
Enbing Bi, Chongyan Lian & Tie Guo
Zhejiang Key Laboratory of Precise Synthesis of Functional Molecules, Instrumentation and Service Center for Molecular Sciences and Research Center for Industries of the Future, Westlake University, Hangzhou, China
Xiaohe Miao
Zhejiang Provincial Key Laboratory of Intelligent Low-Carbon Biosynthesis, Westlake University, Hangzhou, China
Rui Wang
Division of Solar Energy Conversion and Catalysis at Westlake University, Zhejiang Baima Lake Laboratory Co. Ltd, Hangzhou, China
Rui Wang
Center for Interdisciplinary Research and Innovation, Muyuan Laboratory, Zhengzhou, China
Rui Wang
Shangyu Institute of Semiconductor Materials, Shaoxing, China
Jingjing Xue
Zhejiang Provincial Key Laboratory of Optoelectronic Functional Materials and Devices, Hangzhou, China
Jingjing Xue
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J.X. and S.Z. conceived the idea. S.Z. and B.L. performed the device fabrication, characterizations and data analysis under the supervision of J.X. E.B. fabricated the flexible CIGS cells. C.L. and T.G. provided helpful discussions on the fabrication of CIGS cells. L.T., X.M., X.W., X.Z., D.J., J.Z., Y.T., W.F., S.C., Q.L. and Y.G. assisted with the characterizations and device fabrication. R.W. and D.Y. provided helpful discussions on the project. J.X. wrote the paper. All the authors discussed the results and commented on the paper.
Correspondence to Jingjing Xue.
The authors declare no competing interests.
Nature Energy thanks the anonymous reviewers for their contribution to the peer review of this work.
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Supplementary Notes 1–3, Figs. 1–40 and Tables 1–6.
The source data of Supplementary Figs. 18a, 18b, 19, 23a, 23b, 24, 29, 30, 36, 37a, 37a-inset, 38a and 38a-inset.
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Zhang, S., Bi, E., Lei, B. et al. Crystallization suppression of mixed-halide intermediates for perovskite/Cu(In,Ga)Se2 tandem solar cells with improved efficiency. Nat Energy (2026). https://doi.org/10.1038/s41560-026-01975-1
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DOI: https://doi.org/10.1038/s41560-026-01975-1
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