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Issue 1, 2015
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Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics

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Abstract

We report on reversible, light-induced transformations in (CH3NH3)Pb(BrxI1−x)3. Photoluminescence (PL) spectra of these perovskites develop a new, red-shifted peak at 1.68 eV that grows in intensity under constant, 1-sun illumination in less than a minute. This is accompanied by an increase in sub-bandgap absorption at ∼1.7 eV, indicating the formation of luminescent trap states. Light soaking causes a splitting of X-ray diffraction (XRD) peaks, suggesting segregation into two crystalline phases. Surprisingly, these photo-induced changes are fully reversible; the XRD patterns and the PL and absorption spectra revert to their initial states after the materials are left for a few minutes in the dark. We speculate that photoexcitation may cause halide segregation into iodide-rich minority and bromide-enriched majority domains, the former acting as a recombination center trap. This instability may limit achievable voltages from some mixed-halide perovskite solar cells and could have implications for the photostability of halide perovskites used in optoelectronics.

Graphical abstract: Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics

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The article was received on 13 Oct 2014, accepted on 04 Nov 2014 and first published on 04 Nov 2014


Article type: Edge Article
DOI: 10.1039/C4SC03141E
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Citation: Chem. Sci., 2015,6, 613-617
  • Open access: Creative Commons BY license
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    Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics

    E. T. Hoke, D. J. Slotcavage, E. R. Dohner, A. R. Bowring, H. I. Karunadasa and M. D. McGehee, Chem. Sci., 2015, 6, 613
    DOI: 10.1039/C4SC03141E

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