Multi-junction all-perovskite tandem solar cells are a promising choice for next-generation solar cells with high efficiency and low fabrication cost. However, the lack of high-quality low-bandgap perovskite absorber layers seriously hampers the development of efficient and stable two-terminal monolithic all-perovskite tandem solar cells. Here, we report a bulk-passivation strategy via incorporation of chlorine, to enlarge grains and reduce electronic disorder in mixed tin–lead low-bandgap (~1.25 eV) perovskite absorber layers. This enables the fabrication of efficient low-bandgap perovskite solar cells using thick absorber layers (~750 nm), which is a requisite for efficient tandem solar cells. Such improvement enables the fabrication of two-terminal all-perovskite tandem solar cells with a champion power conversion efficiency of 21% and steady-state efficiency of 20.7%. The efficiency is retained to 85% of its initial performance after 80 h of operation under continuous illumination.

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The work at University of Toledo is financially supported by the US Department of Energy SunShot Initiative under the Next Generation Photovoltaics 3 programme (DE-FOA-0000990) for perovskite tandem device fabrication, the Office of Naval Research under contract no. N00014-17-1-2223 for device characterization, the Air Force Research Laboratory under the Space Vehicles Directorate (FA9453-11-C-0253) for wide-bandgap perovskite synthesis and the Ohio Research Scholar Program for device modelling and understanding. The work at the National Renewable Energy Laboratory is supported by the US Department of Energy SunShot Initiative under the Next Generation Photovoltaics 3 programme (DE-FOA-0000990) and under contract no. DE-AC36-08-GO28308 with the Alliance for Sustainable Energy, the Manager and Operator of the National Renewable Energy Laboratory.

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Author notes

  1. These authors contributed equally: Dewei Zhao, Cong Chen, Changlei Wang.


  1. Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, OH, USA

    • Dewei Zhao
    • , Cong Chen
    • , Changlei Wang
    • , Maxwell M. Junda
    • , Zhaoning Song
    • , Corey R. Grice
    • , Yue Yu
    • , Chongwen Li
    • , Biwas Subedi
    • , Nikolas J. Podraza
    •  & Yanfa Yan
  2. Key Laboratory of Artificial Micro/Nano Structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, China

    • Cong Chen
    • , Changlei Wang
    • , Xingzhong Zhao
    •  & Guojia Fang
  3. Ordered Matter Science Research Center, Nanchang University, Nanchang, China

    • Ren-Gen Xiong
  4. Jiangsu Key Laboratory for Science and Applications of Molecular Ferroelectrics, Southeast University, Nanjing, China

    • Ren-Gen Xiong
  5. Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, CO, USA

    • Kai Zhu


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D.Z. and Y. Yan conceived the project. D.Z. carried out single-cell and tandem-cell fabrication and characterization. C.C. prepared wide-bandgap perovskite film and devices. C.W. fabricated and characterized the single low-bandgap device. Z.S. participated in tandem-cell fabrication and characterization and conducted transient photocurrent measurement and modelling. M.M.J., B.S. and N.J.P. conducted PDS and spectroscopic ellipsometry measurements. Y. Yu participated in wide-bandgap perovskite film and device fabrication. C.R.G. and C.L. helped with the characterization. D.Z., Z.S. and Y. Yan analysed the data and wrote the manuscript. K.Z. provided helpful discussions during the project and helped with the manuscript preparation. X.Z., G.F. and R.-G.X. helped with the manuscript preparation. All of the authors discussed the results and commented on the manuscript. Y. Yan supervised the project.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Dewei Zhao or Yanfa Yan.

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