Self-Trapped Excitons in All-Inorganic Halide Perovskites: Fundamentals, Status, and Potential Applications

TLDR

Photoluminescence is the radiative recombination of electron‑hole pairs, and self‑trapped excitons (STEs) in soft‑lattice, strongly electron‑phonon coupled materials emit broad, Stokes‑shifted photons; recent halide perovskites with efficient STE emission show promise for solid‑state lighting. This Perspective reviews photoluminescence phenomena, focusing on the mechanisms and characteristics of STE‑derived emission. We discuss STE emission in hybrid halide perovskites, then detail the mechanisms in all‑inorganic double‑perovskite Cs₂AgInCl₆ and propose strategies to enhance efficiency. The review summarizes current photoluminescence and electroluminescence applications of STE emitters, highlights their potential in luminescent solar concentrators, and outlines future research directions.

Abstract

Photoluminescence is a radiative recombination process of electron-hole pairs. Self-trapped excitons (STEs), occurring in a material with soft lattice and strong electron-phonon coupling, emit photons with broad spectrum and large Stokes shift. Recently, series halide perovskites with efficient STE emission have been reported and showed promise for solid-state lighting. In this Perspective, we present an overview of various photoluminescence phenomena with the emphasis on the mechanism and characteristics of emission derived from STEs. This is followed by the introduction of STE emission in hybrid halide perovskites. We then introduce all-inorganic STE emitters and focus in particular on the mechanism of STEs in double-perovskite Cs2AgInCl6 and strategies for efficiency improvement. Finally, we summarize the current photoluminescence and electroluminescence applications of STE emitters as well as the potential in luminescent solar concentrators and provide an overview of future research opportunities.