Composition-controlled optical fingerprints and anisotropy of self-trapped excitons in double perovskites
Abstract
Double perovskites (DPs) offer a compositionally versatile platform for photocatalysis and optoelectronics, but their soft lattices favor strong exciton-phonon coupling and self-trapped excitons (STEs), which produce broad, red-shifted photoluminescence (PL). Here, we combine optical spectroscopy and ab initio calculations to study lead-free, Sb-doped Cs2BInCl6 nanocrystals with B-site alloying from Na to K. Alloying tunes the PL energy from about 2.48 to 2.70 eV, while absorption features near 3.8 eV remain nearly unchanged. Calculations reveal that Sb doping enables bright radiative recombination channels and delocalizes the excitonic wavefunction. We identify STEs responsible for the large PL red shift, associated with an upward shift of dopant-hybridized in-gap states. Na-to-K substitution selectively changes the STE lattice distortion, explaining why PL varies strongly with composition while absorption does not. Theory further predicts pronounced PL polarization anisotropy that reflects the STE wavefunction's spatial structure and depends on B-site composition. Time-resolved anisotropy measurements closely agree with these predictions, providing experimental fingerprints of the excitonic wavefunction and its evolution with alloying. Together, these results disentangle the roles of doping and alloying in lead-free DPs and establish polarization-resolved spectroscopy as a probe of STE wavefunctions.
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BibTeX
@misc{grillo2026compositioncontrolled,
title = {{Composition-controlled optical fingerprints and anisotropy of self-trapped excitons in double perovskites}},
author = {Simone Grillo and Offir Zachs Maishlos and Liya Koren and Rotem Strassberg and Rachel Lifer and Edi Maizenberg and Umberto De Giovannini and Angel Rubio and Yehonadav Bekenstein and Ofer Neufeld},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18665},
eprint = {2610.18665},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18665},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Composition-controlled optical fingerprints and anisotropy of self-trapped excitons in double perovskites
AU - Simone Grillo
AU - Offir Zachs Maishlos
AU - Liya Koren
AU - Rotem Strassberg
AU - Rachel Lifer
AU - Edi Maizenberg
AU - Umberto De Giovannini
AU - Angel Rubio
AU - Yehonadav Bekenstein
AU - Ofer Neufeld
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18665
UR - https://arxiv.org/abs/2610.18665
AB - Double perovskites (DPs) offer a compositionally versatile platform for photocatalysis and optoelectronics, but their soft lattices favor strong exciton-phonon coupling and self-trapped excitons (STEs), which produce broad, red-shifted photoluminescence (PL). Here, we combine optical spectroscopy and ab initio calculations to study lead-free, Sb-doped Cs2BInCl6 nanocrystals with B-site alloying from Na to K. Alloying tunes the PL energy from about 2.48 to 2.70 eV, while absorption features near 3.8 eV remain nearly unchanged. Calculations reveal that Sb doping enables bright radiative recombination channels and delocalizes the excitonic wavefunction. We identify STEs responsible for the large PL red shift, associated with an upward shift of dopant-hybridized in-gap states. Na-to-K substitution selectively changes the STE lattice distortion, explaining why PL varies strongly with composition while absorption does not. Theory further predicts pronounced PL polarization anisotropy that reflects the STE wavefunction's spatial structure and depends on B-site composition. Time-resolved anisotropy measurements closely agree with these predictions, providing experimental fingerprints of the excitonic wavefunction and its evolution with alloying. Together, these results disentangle the roles of doping and alloying in lead-free DPs and establish polarization-resolved spectroscopy as a probe of STE wavefunctions.
ER -