Asynchronous Photoexcited Electronic and Structural Relaxation in Lead-Free Perovskites

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Vacancy-ordered lead-free perovskites with more-stable crystalline structures have been intensively explored as the alternatives for resolving the toxic and long-term stability issues of lead halide perovskites (LHPs). The dispersive energy bands produced by the closely packed halide octahedral sublattice in these perovskites are meanwhile anticipated to facility the mobility of charge carriers. However, these perovskites suffer from unexpectedly poor charge carrier transport. To tackle this issue, we have employed the ultrafast, elemental-specific X-ray transient absorption (XTA) spectroscopy to directly probe the photoexcited electronic and structural dynamics of a prototypical vacancy-ordered lead-free perovskite (Cs3Bi2Br9). We have discovered that the photogenerated holes quickly self-trapped at Br centers, simultaneously distorting the local lattice structure, likely forming small polarons in the configuration of Vk center (Br2 - dimer). More significantly, we have found a surprisingly long-lived, structural distorted state with a lifetime of ∼59 μs, which is ∼3 orders of magnitude slower than that of the charge carrier recombination. Such long-lived structural distortion may produce a transient "background" under continuous light illumination, influencing the charge carrier transport along the lattice framework. ©


  • Cunming Liu
  • Yingqi Wang
  • Huifang Geng
  • Taishan Zhu
  • Elif Ertekin
  • David Gosztola
  • Sizhuo Yang
  • Jier Huang
  • Bin Yang
  • Keli Han
  • Sophie E. Canton
  • Qingyu Kong
  • Kaibo Zheng
  • Xiaoyi Zhang
Enheter & grupper
Externa organisationer
  • Argonne National Laboratory
  • Center for High Pressure Science &Technology Advanced Research (HPSTAR)
  • ELI-HU Non-profit Ltd
  • University of Illinois at Urbana-Champaign
  • Marquette University
  • Dalian Institute of Chemical Physics Chinese Academy of Sciences
  • German Electron Synchrotron (DESY)
  • Synchrotron SOLEIL
  • Technical University of Denmark

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Kemi
TidskriftJournal of the American Chemical Society
StatusE-pub ahead of print - 2019
Peer review utfördJa