Asynchronous Photoexcited Electronic and Structural Relaxation in Lead-Free Perovskites

Document Type

Article

Language

eng

Publication Date

7-30-2019

Publisher

American Chemical Society Publications

Source Publication

Journal of the American Chemical Society

Source ISSN

0002-7863

Original Item ID

doi:10.1021/jacs.9b04557

Abstract

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.

Comments

Accepted version. Journal of the American Chemical Society, Vol. 141, No. 33 (July 30, 2019): 13074-13080. DOI. © 2019 American Chemical Society Publications. Used with permission.

Link to Full Text
huang_13628acc.docx (432 kB)
ADA Accessible Version

Share

COinS