Reverse Intersystem Crossing acceleration in blue TADF emitters: spectroscopic and computational studies Vladyslav Ievtukhov 1 , Michal Monka 2 , Olga Ciupak 3 , Estera Hoffman 2 , Piotr Bojarski 2 , Illia Serdiuk 2 1 Faculty of Chemistry, University of Gdansk,Wita Stwosza Str. 63, Gdansk, Poland 2 Faculty of Mathematics, Physics and Informatics, University of Gdansk, Wita Stwosza Str. 57, Gdansk, Poland 3 Faculty of Chemistry, Gdansk University of Technology, Gabriela Narutowicza 11/12, Gdansk, Poland Thermally Activated Delayed Fluorescence (TADF) emitters are promising organic materials that could be used in OLEDs. Such kind of emitters could be potentially more attractive for using in diodes because of their efficient and long-time performance without use of heavy metals. In our research we are focusing on the design and tests of series of blue TADF emitters. Our investigations are based on the studies of photophysical parameters of TADF emitters. One of the main key parameters is Reverse Intersystem Crossing (RISC). This process can be described as "returning" of excitons from T 1 to S 1 state with further light emission and transition to the S 0 state. The main goal of our research work is to accelerate RISC as much as possible in order to achieve new efficient and stable blue TADF emitter that could be commercially used. Our latest investigations have shown that torsion angle between donor and acceptor fragments has key influence on the quantum yield of fluorescence and RISC rate. Rotation along this angle provides distribution of the rotamers which explains the TADF mechanism. Therefore, we deliberately modify structures of our emitters by introducing key structural fragments. The purpose of such structural modifications is to accelerate TADF, which will increase the service life of blue OLEDs. This presentation will summarize our latest achievements towards high-RISC blue emitters. Research financed by the National Science Center under the SONATA 16 project, contract number UMO- 2020/39/D/ST5/03094. Quantum-chemical calculations were carried out with the use of computers of the Wroclaw Center for Networking and Supercomputing (WCSS). References 1. Michał Mońka, Daria Grzywacz, Estera Hoffman, Vladyslav Ievtukhov , Karol Kozakiewicz, Radoslaw Rogowski, Aleksander Kubicki, Beata Liberek, Piotr Bojarski, Illia E. Serdiuk. J. Mater. Chem. C, 2022,10, 11719-11729. 2. M. Mońka, I.E. Serdiuk, K. Kozakiewicz, E. Hoffman, J. Szumilas, A. Kubicki, S.Y. Park, P. Bojarski. J. Mater. Chem. C 2022, 10, 7925-7934. 3. I. E. Serdiuk*, M. Mońka, K. Kozakiewicz, B. Liberek, P. Bojarski, S. Y. Park. Journal of Physical Chemistry B 2021, 125, 10, 2696–2706. 4. F. B. Dias, K. N. Bourdakos , V. Jankus, K. C. Moss, K. T. Kamtekar, V. Bhalla, J. Santos, M. R. Bryce, A. P. Monkman. Adv. Mater. 2013, 25, 3707–3714.
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