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Proceedings Paper

Explaining rISC and 100% efficient TADF (Conference Presentation)
Author(s): Andrew P. Monkman; Marc Etherington; David Graves; Przemyslaw Data; Paloma Lays Dos Santos; Roberto Nobuyasu; Fernando M. Baiao Dias

Paper Abstract

Detailed photophysical measurements of intramolecular charge transfer (ICT) states have been made both in solution and solid state. Temperature dependent time resolved emission, delayed emission and photoinduced absorption are used to map the energy levels involved in molecule decay, and through detailed kinetic modelling of the thermally activated processes observed, true electron exchange energies and other energy barriers of the systems determined with the real states involved in the reversed intersystem crossing mechanism elucidated. For specific donor acceptor molecules, the CT singlet and local triplet states (of donor or acceptor) are found to be the lowest lying excited states of the molecule with very small energy barrier between them  kT. In these cases the decay kinetics of the molecules become significantly different to normal molecules, and the effect of rapid recycling between CT singlet and local triplet states is observed which gives rise to the true triplet harvesting mechanism in TADF. Using a series of different TADF emitters we will show how the energy level ordering effects or does not effect TADF and how ultimate OLED performance is dictated by energy level ordering, from 5% to 22% external quantum efficiency. From this understanding, we are able to define three criterion for TADF in different molecules and these will be discussed.

Paper Details

Date Published: 4 November 2016
PDF: 1 pages
Proc. SPIE 9941, Organic Light Emitting Materials and Devices XX, 994108 (4 November 2016); doi: 10.1117/12.2236460
Show Author Affiliations
Andrew P. Monkman, Durham Univ. (United Kingdom)
Marc Etherington, Durham Univ. (United Kingdom)
David Graves, Durham Univ. (United Kingdom)
Przemyslaw Data, Durham Univ (United Kingdom)
Paloma Lays Dos Santos, Durham Univ. (United Kingdom)
Roberto Nobuyasu, Durham Univ. (United Kingdom)
Fernando M. Baiao Dias, Durham Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 9941:
Organic Light Emitting Materials and Devices XX
Franky So; Chihaya Adachi; Jang-Joo Kim, Editor(s)

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