Unraveling exciton processes in Ir(ppy)3:CBP OLED films upon photoexcitation

Sanderson, Stephen, Vamvounis, George, Mark, Alan E., Burn, Paul L., White, Ronald D., and Philippa, Bronson W. (2021) Unraveling exciton processes in Ir(ppy)3:CBP OLED films upon photoexcitation. Journal of Chemical Physics, 154. 164101.

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Abstract

Emissive layers in phosphorescent organic light-emitting diodes commonly make use of guest–host blends such as Ir(ppy)3:CBP to achieve high external quantum efficiencies. However, while the Ir(ppy)3:CBP blend has been studied experimentally, crucial questions remain regarding how exciton diffusion is dependent on the distribution of the guest in the host, which can currently only be addressed at the atomic level via computational modeling. In this work, kinetic Monte Carlo simulations are utilized to gain insight into exciton diffusion in Ir(ppy)3:CBP blend films. The effects of both guest concentration and exciton density on various system properties are analyzed, including the probability of singlet excitons being converted to triplets, and the probability of those triplets decaying radiatively. Significantly, these simulations suggest that triplet diffusion occurs almost exclusively via guest–guest Dexter transfer and that concentration quenching of triplets induced by guest–guest intermolecular dipole-dipole interactions has a negligible effect at high exciton densities due to the prevalence of triplet–triplet annihilation. Furthermore, results for vacuum deposited morphologies derived from molecular dynamics simulations are compared to the results obtained using a simple cubic lattice approximation with randomly distributed guest molecules. We show that while differences in host-based processes such as singlet diffusion are observed, overall, the results on the fate of the excitons are in good agreement for the two morphology types, particularly for guest-based processes at low guest concentrations where guest clustering is limited.

Item ID: 67904
Item Type: Article (Research - C1)
ISSN: 1089-7690
Copyright Information: © 2021 Author(s). Published Version can be made open access in an Institutional Repository after a 12 month embargo.
Funders: Australian Research Council
Projects and Grants: ARC Grant No. FL160100067, ARC No. DP180101421
Date Deposited: 19 Jul 2021 02:33
FoR Codes: 40 ENGINEERING > 4016 Materials engineering > 401608 Organic semiconductors @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280110 Expanding knowledge in engineering @ 100%
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