Abstract
Metal halide octahedra form the fundamental functional building blocks of metal halide perovskites, dictating their structures, optical properties, electronic structures, and dynamics. In this study, we show that the connectivity of bismuth halide octahedra in Cs3Bi2Br9 and Cs3Bi2I9 quantum dots (QDs) changes with different halide elements. We use first-principles calculations to reveal the key role of the connectivity of bismuth halide octahedra on the wave function symmetry, Huang-Rhys factor, and exciton-phonon interaction strength. Following QD synthesis via a ligand-mediated transport method, the effect of connectivity is verified with transient absorption spectroscopy, where we contrast Cs3Bi2Br9 and Cs3Bi2I9 QD exciton dynamics. In photoexcited Cs3Bi2I9 QDs, phonons related to the vibrational motions of face-sharing [BiI6]3- bioctahedra couple strongly to the electronic state and drive rapid carrier relaxation. Equivalent signals are not observed for photoexcited Cs3Bi2Br9 QDs, implying a lack of phonon involvement in band-edge absorption and subsequent exciton relaxation. Our findings suggest that structural engineering can effectively tune the exciton-phonon coupling and therefore influence exciton relaxation and recombination in perovskite nanomaterials.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 10359-10368 |
| Number of pages | 10 |
| Journal | ACS nano |
| Volume | 19 |
| Issue number | 10 |
| DOIs | |
| State | Published - Mar 18 2025 |
Funding
The authors would like to thank Yimei Chen for assistance with TEM measurements, Dr. Alexander Filatov and Di Wang for assistance with XRD measurements, Ping-Jui Eric Wu for discussions on data processing and excited state dynamics, Qijie Shen for discussions on phonon visualization, Zirui Zhou and Dr. Aritrajit Gupta for crystal visualization software Atomsk and VESTA, Dr. Elena A. Rozhkova for assistance with the floor centrifuge, and Dr. Karen Watters for scientific editing. S.S. thanks the Benjamin Ball Freud fellowship from the Department of Chemistry, University of Chicago for funding. H.C. thanks the QUAD undergraduate research grant and Metcalf fellowship. G.S.E. gratefully acknowledges the U.S. National Science Foundation (NSF) QuBBE Quantum Leap Challenge Institute (NSF grant no. OMA-2121044) and the Department of Energy (DOE) through award no. DE-SC0020131. Y.J. and G.G. are supported by MICCoM, as part of the Computational Materials Sciences Program funded by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences, and Engineering Division through the Argonne National Laboratory, under contract no. DE-AC02-06CH11357. J.P. is supported by a Chicago Prize Postdoctoral Fellowship in Theoretical Quantum Science. This work made use of the shared facilities at the University of Chicago Materials Research Science and Engineering Center, supported by the NSF under award number DMR-2011854. Work performed at the Center for Nanoscale Materials, a U.S. DOE Office of Science user facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. The use of the GSECARS Raman Lab System was supported by the NSF Major Research Instrumentation program (EAR-1531583). First-principles calculations in this work used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science user facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231, and resources of the University of Chicago Research Computing Center.
Keywords
- differential electron density
- excited state dynamics
- exciton−phonon coupling
- lead-free perovskite quantum dots
- nanoscience
- TDDFT
- ultrafast transient absorption spectroscopy
ASJC Scopus subject areas
- General Materials Science
- General Engineering
- General Physics and Astronomy