Metal halide perovskites are of great interest for various high-performance optoelectronic applications1. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency2,3,4. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions5,6,7. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability2 (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities8,9. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport10. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

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M.A.-J. thanks Nava Technology Limited and Nyak Technology Limited for their funding and technical support. Z.A.-G. acknowledges funding from a Winton Studentship, and ICON Studentship from the Lloyd’s Register Foundation. This project has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement number PIOF-GA-2013-622630, the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 756962), and the Royal Society and Tata Group (UF150033). We thank the Engineering and Physical Sciences Research Council (EPSRC) for support. XMaS is a mid-range facility at the European Synchrotron Radiation Facility supported by the EPSRC and we are grateful to the XMaS beamline team staff for their support. We thank Diamond Light Source for access to beamline I09 and staff member T.-L. Lee as well as U. Cappel for assistance during the HAXPES measurements. S.C., C.D. and G.D. acknowledge funding from the ERC under grant number 25961976 PHOTO EM and financial support from the European Union under grant number 77 312483 ESTEEM2. M.A. thanks the president of the UAE’s Distinguished Student Scholarship Program, granted by the Ministry of Presidential Affairs. H.R. and B.P. acknowledge support from the Swedish research council (2014-6019) and the Swedish foundation for strategic research. E.M.H. and T.J.S. were supported by the Netherlands Organization for Scientific Research under the Echo grant number 712.014.007.

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  1. Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK

    • Mojtaba Abdi-Jalebi
    • , Zahra Andaji-Garmaroudi
    • , Camille Stavrakas
    • , Johannes M. Richter
    • , Mejd Alsari
    • , Edward P. Booker
    • , Andrew J. Pearson
    • , Richard H. Friend
    •  & Samuel D. Stranks
  2. Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK

    • Stefania Cacovich
    • , Giorgio Divitini
    •  & Caterina Ducati
  3. Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden

    • Bertrand Philippe
    •  & Håkan Rensmo
  4. Department of Chemical Engineering, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands

    • Eline M. Hutter
    •  & Tom J. Savenije
  5. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK

    • Samuele Lilliu
  6. The UAE Centre for Crystallography, United Arab Emirates

    • Samuele Lilliu


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M.A.-J. and S.D.S. conceived and planned the experiments with additional input from R.H.F. M.A.-J. fabricated all samples and devices and performed and analysed the PLQE experiments, the photoluminescence stability experiments, the time-resolved photoluminescence, absorption and photothermal deflection spectroscopies, the SEM and the device characterisation measurements. M.A.-J., Z.A.-G. and C.S. obtained and analysed the confocal photoluminescence maps. S.C., G.D. and C.D. performed and analysed the STEM–EDX measurements. M.A. and S.L. performed the GIWAXS experiments and analysed the data. E.M.H. and T.J.S. performed the TRMC measurements and analysed the data. M.A.-J., B.P. and H.R. performed and analysed HAXPES measurements. M.A.-J. and E.P.B. performed X-ray diffraction measurements and J.M.R. calculated the internal PLQE and assisted with time-resolved photoluminescence measurement and analysis. M.A.-J. and A.J.P. carried out the device stability tests. M.A.-J. and S.D.S. took the lead in drafting the manuscript and compiled the figures. All authors discussed the results and provided feedback on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Samuel D. Stranks.

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