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Strategy for Exploiting Self-Trapped Excitons in Semiconductor Nanocrystals for White Light Generation

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journal contribution
posted on 05.04.2019, 00:00 by Timothy G. Mack, Lakshay Jethi, Patanjali Kambhampati
Semiconductor nanocrystals have seen much use for their narrow emission line widths for display and lighting applications. Recent progress on semiconductor nanocrystals has suggested the possibility of exploiting self-trapped excitons to create white light emitting materials. Specifically, charge carrier trapping at the surface or interface gives rise to broadened and red-shifted bands that can support the generation of white light. Most reported materials based on emission from self-trapped states suffer from poor intrinsic luminescent quantum yields at room temperature and have not considered the temperature dependence of the chromaticity. Here we show that such results stem from fundamental quantum considerations, which can be easily visualized in terms of a simple, albeit microscopic electron transfer theory. We show the temperature-dependent chromaticity trajectories and how one can design function. We rationalize the strong temperature dependence of the photoluminescence quantum yield. Our results identify potential paths toward tailoring surface structure of semiconductor nanocrystals for rational design of white light emitters. Specific implications for regarding efficiency limitations of the photoluminescence quantum yield for white light emitting CdSe nanocrystals are discussed.