DOE OSTI · 2588215
Efficient up-conversion in CsPbBr 3 nanocrystals via phonon-driven exciton-polaron formation
Abstract
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 CsPbBr 3 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 CsPbBr 3 nanocrystals is powered by a unique interplay between the soft lattice structure, phonons, and excited states dynamics.
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Abbas, Abdullah S. [University of California, Berkeley, CA (United States); University of Chicago, IL (United States)] (ORCID:0000000183744993), Li, Beiye C. [University of Chicago, IL (United States) ] (ORCID:0000000267174318), Schaller, Richard D. [Northwestern University, Evanston, IL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM)], Prakapenka, Vitali B. [University of Chicago, IL (United States) ] (ORCID:0000000192702330), Chariton, Stella [University of Chicago, IL (United States) ] (ORCID:0000000155220498), Bian, Daqian [University of Chicago, IL (United States) ] (ORCID:0000000287743733), Engel, Gregory S. [University of Chicago, IL (United States) ] (ORCID:0000000267405243), Alivisatos, A. Paul [University of California, Berkeley, CA (United States); University of Chicago, IL (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)]. 2025-07-01. Efficient up-conversion in CsPbBr 3 nanocrystals via phonon-driven exciton-polaron formation. https://doi.org/10.1038/s41467-025-60992-y
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