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Fast Intrinsic Emission Quenching in Cs4PbBr6 Nanocrystals
Urko Petralanda1, Giulia Biffi1,2, Simon C Boehme3
1Nanochemistry Department, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
Nano Letters
|October 13, 2021
Summary
Conflicting reports on Cs4PbBr6 nanocrystals are resolved: green emission is thermally quenched below room temperature due to strong electron-phonon coupling, not vacancies.
Area of Science:
- Materials Science
- Solid State Physics
- Quantum Chemistry
Background:
- Conflicting reports exist on the photoluminescence (PL) of cesium lead bromide (Cs4PbBr6) zero-dimensional (0D) nanocrystals, with no consensus on the origin of green emission or quenching mechanisms.
- Existing literature presents contradictory findings regarding Cs4PbBr6's emissive properties at room temperature.
Purpose of the Study:
- To elucidate the mechanism behind the temperature-dependent photoluminescence in Cs4PbBr6 0D nanocrystals.
- To identify the source of the reported green emission and understand the quenching mechanisms.
- To investigate the role of electron-phonon coupling in Cs4PbBr6's optical properties.
Main Methods:
- Utilized ab initio molecular dynamics (AIMD) simulations to model the behavior of Cs4PbBr6.
- Employed temperature-dependent photoluminescence (PL) spectroscopy to analyze emission properties.
- Investigated two proposed green emission sources: bromide vacancies and impurities within the octahedral network.
Main Results:
- Demonstrated that Cs4PbBr6 0D nanocrystals exhibit thermal quenching of PL well below 300 K due to strong electron-phonon coupling.
- Showed that bromide vacancies lead to significant thermal quenching of emission at room temperature.
- Identified an impurity-based emitter, with reduced electron-phonon coupling, that suppresses nonradiative quenching in the lead bromide octahedral network.
Conclusions:
- The observed photoluminescence in Cs4PbBr6 0D systems is primarily governed by thermal quenching via strong electron-phonon coupling, occurring below room temperature.
- Bromide vacancies are unlikely to be the primary source of room-temperature green emission due to their strong quenching.
- An impurity-related mechanism, involving a modified octahedral network, offers a plausible explanation for suppressed nonradiative quenching and potential green emission in Cs4PbBr6 materials.
