Mechanism of the Triplet-to-Singlet Upconversion in the Assistant Dopant ACRXTN

In this work, the photophysics of 3-(9,9-dimethylacridin-10­(9H)-yl)-9H-xanthen-9-one (ACRXTN) has been investigated by combined density functional theory and multireference configuration interaction quantum chemical methods. ACRXTN was recently utilized as an assistant dopant in a green emitting or...

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Published in:Journal of physical chemistry. C 2016-02, Vol.120 (7), p.3715-3721
Main Author: Marian, Christel M
Format: Article
Language:English
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Summary:In this work, the photophysics of 3-(9,9-dimethylacridin-10­(9H)-yl)-9H-xanthen-9-one (ACRXTN) has been investigated by combined density functional theory and multireference configuration interaction quantum chemical methods. ACRXTN was recently utilized as an assistant dopant in a green emitting organic light-emitting diode (OLED), increasing substantially the external electroluminescence quantum efficiency of the OLED. The efficient triplet-to-singlet upconversion, found experimentally in ARCXTN, cannot be explained solely on the basis of a small singlet–triplet energy gap. We find five interacting electronically excited states in a small energy interval: a charge-transfer excitation (triplet and singlet) from acridine to xanthone, a local xanthone triplet (ππ*) excitation, and a pair of triplet and singlet states originating from an nπ* excitation on xanthone. On the basis of calculated spin–orbit coupling constants and potential energy profiles, we propose here that the triplet (ππ*) state mediates the triplet-to-singlet upconversion in ACRXTN and that the carbonyl bond stretching motion plays an essential role in this process.
ISSN:1932-7447
1932-7455
DOI:10.1021/acs.jpcc.6b00060