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Tuning the Structural and Optoelectronic Properties of Cs2AgBiBr6 Double-Perovskite Single Crystals through Alkali-Metal Substitution

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  • Masoumeh Keshavarz, KU Leuven
  • ,
  • Elke Debroye, KU Leuven
  • ,
  • Martin Ottesen
  • Cristina Martin, KU Leuven, University of Castilla-La Mancha
  • ,
  • Heng Zhang, Max Planck Institute for Polymer Research
  • ,
  • Eduard Fron, KU Leuven
  • ,
  • Robert Küchler, Max Planck Institute for Chemical Physics of Solids
  • ,
  • Julian A. Steele, KU Leuven
  • ,
  • Martin Bremholm
  • Joris Van de Vondel, KU Leuven
  • ,
  • Hai I. Wang, Max Planck Institute for Polymer Research
  • ,
  • Mischa Bonn, Max Planck Institute for Polymer Research
  • ,
  • Maarten B.J. Roeffaers, KU Leuven
  • ,
  • Steffen Wiedmann, Radboud University Nijmegen
  • ,
  • Johan Hofkens, KU Leuven, Max Planck Institute for Polymer Research

Lead-free double perovskites have great potential as stable and nontoxic optoelectronic materials. Recently, Cs2AgBiBr6 has emerged as a promising material, with suboptimal photon-to-charge carrier conversion efficiency, yet well suited for high-energy photon-detection applications. Here, the optoelectronic and structural properties of pure Cs2AgBiBr6 and alkali-metal-substituted (Cs1−xYx)2AgBiBr6 (Y: Rb+, K+, Na+; x = 0.02) single crystals are investigated. Strikingly, alkali-substitution entails a tunability to the material system in its response to X-rays and structural properties that is most strongly revealed in Rb-substituted compounds whose X-ray sensitivity outperforms other double-perovskite-based devices reported. While the fundamental nature and magnitude of the bandgap remains unchanged, the alkali-substituted materials exhibit a threefold boost in their fundamental carrier recombination lifetime at room temperature. Moreover, an enhanced electron–acoustic phonon scattering is found compared to Cs2AgBiBr6. The study thus paves the way for employing cation substitution to tune the properties of double perovskites toward a new material platform for optoelectronics.

Original languageEnglish
Article number2001878
JournalAdvanced Materials
Number of pages10
Publication statusPublished - Oct 2020

    Research areas

  • alkali-substitution, double perovskites, electron–phonon coupling, photophysical properties, X-ray response

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