A Heterogeneous Kinetics Model for Triplet Exciton Transfer in Solid-State Upconversion
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solid-state-upconversion-kinetics v7.pdf
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Author(s)
Geva, Nadav
Nienhaus, Lea
Wu, Mengfei
Bulovic, Vladimir
Baldo, Marc A
Van Voorhis, Troy
Bawendi, Moungi G
Date Issued
May 2019
Journal
Journal of Physical Chemistry Letters
Publisher
American Chemical Society (ACS)
Citation
Geva, Nadav et al. "A Heterogeneous Kinetics Model for Triplet Exciton Transfer in Solid-State Upconversion." Journal of Physical Chemistry Letters 10, 11 (May 2019): 3147–3152 © 2019 American Chemical Society
Version
Author's final manuscript
Abstract
High internal quantum efficiency semiconductor nanocrystal (NC)-based photon upconversion devices are currently based on a single monolayer of active NCs. Devices are therefore limited in their external quantum efficiency based on the low number of photons absorbed. Increasing the number of photons absorbed is expected to increase the upconversion efficiency, yet experimentally increasing the number of layers does not appreciably increase the upconverted light output. We unravel this mystery by combining kinetic modeling and transient photoluminescence spectroscopy. The inherent energetic disorder stemming from the polydispersity of the NCs means that the kinetics are governed by a stochastic transfer matrix. By drawing the rates from a probabilistic distribution and constructing a reaction network with realistic connectivity, we are able to fit complex photoluminescence traces with a very simple model. We use this model to explain the thickness-dependent performance of the upconversion devices and can attribute the reduced efficiencies to the low excitonic diffusivity of the exciton within the NC layers and increased back transfer of the created singlets from the organic annihilator rubrene. We suggest some avenues for overcoming these limitations in future devices.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Department of Chemistry
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1021/acs.jpclett.9b01058
