Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

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This work is primarily supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division under contract no. DE-AC02-05CH11231 (PChem KC3103). The GIWAX data were collected at the Stanford Synchrotron Radiation Light Source at SLAC National Accelerator Laboratory supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under contract no. DE-AC02-76SF00515. The XPS data was collected at the Advanced Light Source, with help from E.J. Crumlin, Q.Kong and H.Zhang, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The RED data was collected at the Berzelii Center EXSELENT on Porous Materials, the Swedish Research Council (Grant no. 2012-4681). J.L. acknowledges the fellowship support from Shanghai University of Electric Power. M.L. and C.X. acknowledges the fellowship support from Suzhou Industrial Park. C.S.K. acknowledges support by the Alexander von Humboldt Foundation. H.C. acknowledges the postdoctoral scholarship support from the Wallenberg Foundation through the MAX IV synchrotron radiation facility program. D.L. thanks the Camille and Henry Dreyfus Foundation for funding, Award EP-14-151. S.A.H. acknowledges the support from the DOE Office of Energy Efficiency and Renewable Energy (EERE) Postdoctoral Research Award under the EERE Solar Energy Technologies Office administered by the Oak Ridge Institute for Science and Education (DE-AC05-06OR23100). We thank M.F. Toney for discussions on the GIWAX data, Y. Wang for the work on the supplementary videos, and J. Kanady for proofreading the manuscript.

Author information

Author notes

  1. Jia Lin, Minliang Lai and Letian Dou contributed equally to this work.


  1. Department of Chemistry, University of California, Berkeley, California, USA

    • Jia Lin
    • , Minliang Lai
    • , Letian Dou
    • , Christopher S. Kley
    • , Hong Chen
    • , Dylan Lu
    • , Steven A. Hawks
    • , Chenlu Xie
    • , Fan Cui
    • , A. Paul Alivisatos
    • , David T. Limmer
    •  & Peidong Yang
  2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA

    • Jia Lin
    • , Letian Dou
    • , Dylan Lu
    • , Steven A. Hawks
    • , A. Paul Alivisatos
    • , David T. Limmer
    •  & Peidong Yang
  3. Department of Physics, Shanghai University of Electric Power, Shanghai, China

    • Jia Lin
  4. Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, USA

    • Letian Dou
  5. Berzelii Center EXSELENT on Porous Materials, Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden

    • Fei Peng
    •  & Junliang Sun
  6. Lawrence Livermore National Laboratory, Livermore, California, USA

    • Steven A. Hawks
  7. Kavli Energy NanoScience Institute, Berkeley, California, USA

    • A. Paul Alivisatos
    • , David T. Limmer
    •  & Peidong Yang
  8. Department of Materials Science and Engineering, University of California, Berkeley, California, USA

    • A. Paul Alivisatos
    •  & Peidong Yang


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J.L., M.L., L.D. and P.Y. conceived the idea and designed the study. J.L., M.L. and L.D. contributed to all the experimental work. C.S.K. performed the AFM measurements. H.C., F.P. and J.S. carried out the RED experiments and data analysis. D.L., S.A.H., C.X. and F.C. helped with the device characterizations. D.T.L. performed the molecular modeling. J.L. and P.Y. wrote the manuscript. All authors discussed the results and revised the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Peidong Yang.

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    Supplementary Figures 1–11, Supplementary Tables 1–3


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