Strong Triplet-Exciton-LO-Phonon Coupling in Two-Dimensional Layered Organic-Inorganic Hybrid Perovskite Single Crystal Microflakes

TL;DR

This study uncovers a strong coupling between triplet excitons and LO phonons in 2D layered hybrid perovskites, revealing fundamental many-body interactions that could influence future optoelectronic device development.

Contribution

It demonstrates the strong triplet exciton-LO phonon coupling in 2D hybrid perovskite microflakes, highlighting differences between triplet and singlet excitons and their interactions.

Findings

Triplet excitons show strong PL in thick microflakes.

Coupling strength of triplet exciton-LO phonon is 2-3 times greater than singlet.

LO phonon energy is approximately 21 meV.

Abstract

Two-dimensional (2D) layered hybrid perovskites provide an ideal platform for studying the properties of excitons. Here, we report on a strong triplet-exciton and longitudinal-optical (LO) phonon coupling in 2D (C6H5CH2CH2NH3, PEA)2PbBr4 perovskites. The triplet excitons exhibit strong photoluminescence (PL) in thick perovskite microflakes, and the PL is not detectable for monolayer microflakes. The coupling strength of the triplet exciton-LO phonon is approximately two to three times greater than that of the singlet exciton-LO phonon with a LO phonon energy of about 21 meV. This difference might due to the different locations of singlet excitons located in the well and triplet excitons located in the barrier in the 2D layered perovskite. Revealing the strong coupling of triplet exciton-LO phonon provides a fundamental understanding of many-body interaction in hybrid perovskites, which is useful to develop and optimize the optoelectronic devices based on 2D perovskites in the future.