Electronic States Modulation by Coherent Optical Phonons in 2D Halide Perovskites. Issue 11 (11th February 2021)

• Record Type: Journal Article
• Authors: Fu, Jianhui; Li, Mingjie; Solanki, Ankur; Xu, Qiang; Lekina, Yulia; Ramesh, Sankaran; Shen, Ze Xiang; Sum, Tze Chien
• Is Part Of: Advanced materials. Volume 33:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-11
• Subjects: coherent optical phonons -- deformation potential -- exciton–phonon coupling -- impulsive stimulated Raman scattering; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202006233
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Excitonic effects underpin the fascinating optoelectronic properties of 2D perovskites that are highly favorable for photovoltaics and light‐emitting devices. Analogous to switching in transistors, manipulating these excitonic properties in 2D perovskites using coherent phonons could unlock new applications. Presently, a detailed understanding of this underlying mechanism remains modest. Herein, the origins of the carrier‐phonon coupling in 2D perovskites using transient absorption (TA) spectroscopy are explicated. The exciton fine structure is modulated by coherent optical phonons dominated by the vibrational motion of the PbI6 octahedra via deformation potential. Originating from impulsive stimulated Raman scattering, these coherent vibrations manifest as oscillations in the TA spectrum comprising of the generation and detection processes of coherent phonons. This two‐step process leads to a unique pump‐ and probe‐energy dependence of the phonon modulation determined by the imaginary part of the refractive index and its derivative, respectively. The phonon frequency and lattice displacement of the inorganic octahedra are highly dependent on the organic cation. This study injects fresh insights into the exciton–phonon coupling of 2D perovskites relevant for emergent optoelectronics development. Abstract : The modulation of the excitonic properties of 2D perovskites by coherent optical phonons is investigated using comprehensive optical spectroscopy and theoretical modeling. A clear understanding of these phonon modulation mechanisms injects fresh insights into the exciton–phonon coupling in 2D perovskites, which may help unlock new optoelectronic applications.