Theoretical Rationalization of the Singlet-Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

Abstract : New materials for OLED applications with low singlet-triplet energy splitting have been recently synthesized in order to allow for the conversion of triplet into singlet excitons (emitting light) via a Thermally Activated Delayed Fluorescence (TADF) process, which involves excited-states with a non-negligible amount of Charge-Transfer (CT). The accurate modeling of these states with Time-Dependent Density Functional Theory (TD-DFT), the most used method so far because of the favorable trade-off between accuracy and computational cost, is however particularly challenging. We carefully address this issue here by considering materials with small (high) singlet-triplet gap acting as emitter (host) in OLEDs and by comparing the accuracy of TD-DFT and the corresponding Tamm-Dancoff Approximation (TDA), which is found to greatly reduce error bars with respect to experiments thanks to better estimates for the lowest singlet-triplet transition. Finally, we quantitatively correlate the singlet-triplet splitting values with the extent of CT, using for it a simple metric extracted from calculations with double-hybrid functionals, that might be applied in further molecular engineering studies.
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https://hal.archives-ouvertes.fr/hal-01411679
Contributor : Dominique Richard <>
Submitted on : Wednesday, December 7, 2016 - 4:20:51 PM
Last modification on : Tuesday, February 12, 2019 - 12:06:03 PM

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Monica Moral, Luca Muccioli, Wonjoon Son, Yoann Olivier, Juan-Carlos Sancho-Garcia. Theoretical Rationalization of the Singlet-Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character. Journal of Chemical Theory and Computation, American Chemical Society, 2015, 11 (1), pp.168-177. ⟨10.1021/ct500957s⟩. ⟨hal-01411679⟩

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