• Chinese Optics Letters
  • Vol. 19, Issue 10, 103001 (2021)
Junze Li, Junchao Hu, Jiaqi Ma, Xinglin Wen, and Dehui Li*
Author Affiliations
  • School of Optical and Electronic Information and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
  • show less

    Abstract

    Two-dimensional (2D) perovskites exhibit broadband emission due to strong exciton–phonon coupling-induced self-trapped excitons and thus would find important applications in the field of white-light emitting devices. However, the available identifying methods for self-trapped excitons are currently rather limited and complex. Here, we identify the existence of self-trapped excitons by Raman spectroscopy in both excited and non-excited states. Under excited states, the shifting of the Raman peak indicates the presence of the lattice distortion, which together with the extra Raman scattering peak reveals the presence of self-trapped excitons. Our work provides an alternative simple method to study self-trapped excitons in 2D perovskites.

    1. Introduction

    The strong coupling between the crystal lattice and excitons would lead to the generation of self-trapped excitons (STEs)[1,2], which are one type of bound state excitons. Unlike bound state excitons usually formed by binding to defects, STE can be produced even in a perfect crystal lattice, which is created by the deformation of the crystal lattice under the coupling effect due to the softness of the crystal lattice[1,3]. Once the excitation is removed, the coupling disappears, and the lattice will return to its original state, resulting in removal of STE[4]. Therefore, STE can be regarded as one type of trapped state that exists only under an excited state[4]. STE exhibits broadband emissions with a large Stokes shift below the bandgap, which is beneficial to the white-light emitting devices[510]. Identifying and investigating the basic physical properties of STE is the basis for designing optoelectronic devices and optimizing device performance.