Influence of Multiple rISC Channels on the Maximum Efficiency and Roll-Off of TADF OLEDs.

Autor:	Dos Santos PL; Department of Electronic and Electrical Engineering, University of Sheffield, Mappin St, Sheffield S1 3JD, U.K., de Sa Pereira D; Department of Physics, Durham University, South Road, Durham DH1 3LE, U.K., Oh CS; School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Korea., Kukhta N; Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K., Lee HL; School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Korea., Lee JY; School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Korea.; SKKU Institute of Energy Science and Technology, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Korea., Monkman AP; Department of Physics, Durham University, South Road, Durham DH1 3LE, U.K.
Jazyk:	angličtina
Zdroj:	The journal of physical chemistry. C, Nanomaterials and interfaces [J Phys Chem C Nanomater Interfaces] 2024 Sep 19; Vol. 128 (39), pp. 16308-16319. Date of Electronic Publication: 2024 Sep 19 (Print Publication: 2024).
DOI:	10.1021/acs.jpcc.4c02993
Abstrakt:	In this work, we look into the detailed photophysical characterization of a multidonor-acceptor ( D-A ) family of thermally activated delayed fluorescent (TADF) emitters to find correlations with their device performance. Increasing the number of closely packed D s around the A core leads to changes in dihedral angles between D s and A, affecting the highest occupied molecular orbital (HOMO)/lowest unpccupied molecualar orbital (LUMO) separation and impacting the singlet-triplet energy gaps. Moreover, D-A dihedral angles change molecular conjugation affecting the spread of charge-transfer state energies as well as the energy of D local triplet states. The coupling between these triplet states and the dispersion in CT states lead to the appearance of multiple rISC channels, a phenomenon that is host-dependent, i.e., hosts with different rigidities twist the dihedral angles differently. We show that different subsets of rISC rates directly impact device performance, where faster rISC leads to external quantum efficiencies above 20% while slower rISC rates act as parasitic traps, severely affecting device roll-off. This explains why emitters with excellent peak external quantum efficiencies can also present very poor roll-off. Competing Interests: The authors declare no competing financial interest. (© 2024 The Authors. Published by American Chemical Society.)
Databáze:	MEDLINE
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