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Tönu Pullerits. Portrait.

Tönu Pullerits

Professor

Tönu Pullerits. Portrait.

Coherent Phonons, Localization, and Slow Polaron Formation in Lead-Free Gold Perovskite

Author

  • Sankaran Ramesh
  • Yonghong Wang
  • Pavel Chabera
  • Rafael Araujo
  • Mustafa Aboulsaad
  • Tomas Edvinsson
  • Feng Gao
  • Tönu Pullerits

Summary, in English

Lead-free metal halide perovskites are emerging as less-toxic alternatives to their lead-based counterparts. However, their applicability in optoelectronic devices is limited, and the charge transport dynamics remain poorly understood. Understanding photo-induced charge and structural dynamics is critical for unlocking the potential of these novel systems. In this work, ultrafast optical and Raman spectroscopy combined with band structure calculations are employed to investigate the coupled electronic and vibrational dynamics in Caesium gold bromide, a promising lead-free perovskite. It is found that the band-edge charge transfer states are strongly coupled to Au─Br stretching phonon modes, leading to frequency modulation of absorption by coherent phonons. Early-stage relaxation is characterized by dynamics of delocalized charge transfer excitation and slowly decaying coherent phonons. The electronic and vibrational relaxation reveals a slow formation of a localized polaronic state in the 10–20 ps timescale. Using a displaced harmonic oscillator model, the polaronic binding energy is estimated to be ≈80 meV following lattice relaxation along the phonon modes. Strong exciton-phonon coupling and slow polaron formation via coupling to lattice modes make this material a promising testbed for the control of coherent phonons and localized polaronic states using light.

Department/s

  • Chemical Physics
  • LTH Profile Area: Nanoscience and Semiconductor Technology
  • LU Profile Area: Light and Materials
  • NanoLund: Centre for Nanoscience
  • LTH Profile Area: Photon Science and Technology
  • eSSENCE: The e-Science Collaboration

Publishing year

2025-02-17

Language

English

Publication/Series

Advanced Optical Materials

Volume

13

Issue

10

Document type

Journal article

Publisher

John Wiley & Sons Inc.

Topic

  • Atom and Molecular Physics and Optics

Keywords

  • Coherent Phonon
  • Electron-phonon coupling
  • Lead-free perovskite
  • Polaron
  • Raman

Status

Published

ISBN/ISSN/Other

  • ISSN: 2195-1071