2023/12/13 by Abdullah Saud Abbas, Abbas, Abdullah S., Beiye C Li +11 · 1 citation
Engineering · Materials Science · Physics and Astronomy · #FOS: Physical sciences #Luminescence Properties of Advanced Materials #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Optical properties and cooling technologies in crystalline materials #Perovskite Materials and Applications
paper · pdf · doi:10.48550/arxiv.2312.07810
openalex publication_date 2023/12/13 · openalex created_date 2023/12/15 · openalex updated_date 2026/08/01
Lead halide perovskite nanocrystals demonstrate efficient up-conversion, although the precise mechanism remains a subject of active research. This study utilizes steady-state and time-resolved spectroscopy methods to unravel the mechanism driving the up-conversion process in CsPbBr3 nanocrystals. Employing above- and below-gap photoluminescence measurements, we extract a distinct phonon mode with an energy of ~7 meV and identify the Pb-Br-Pb bending mode as the phonon involved in the up-conversion process. This result was corroborated by Raman spectroscopy. We confirm an up-conversion efficiency reaching up to 75%. Transient absorption measurements under conditions of sub-gap excitation also unexpectedly reveal coherent phonons for the subset of nanocrystals undergoing up-conversion. This coherence implies that the up-conversion and subsequent relaxation is accompanied by a synchronized and phased lattice motion. This study reveals that efficient up-conversion in CsPbBr3 nanocrystals is powered by a unique interplay between the soft lattice structure, phonons, and excited states dynamics.