Mechanism of Intersystem Crossing of Thermally Activated Delayed Fluorescence Molecules

Autor:	Toshinari Ogiwara, Tadaaki Ikoma, Yusuke Wakikawa
Rok vydání:	2015
Předmět:	education.field_of_study Spin polarization Chemistry Population law.invention Intersystem crossing law Excited state Physical and Theoretical Chemistry Atomic physics Triplet state Spin (physics) Electron paramagnetic resonance education Hyperfine structure
Zdroj:	The Journal of Physical Chemistry A. 119:3415-3418
ISSN:	1520-5215 1089-5639
DOI:	10.1021/acs.jpca.5b02253
Popis:	The spin sublevel dynamics of the excited triplet state in thermally activated delayed fluorescence (TADF) molecules have not been investigated for high-intensity organic light-emitting diode materials. Understanding the mechanism for intersystem crossing (ISC) is thus important for designing novel TADF materials. We report the first study on the ISC dynamics of the lowest excited triplet state from the lowest excited singlet state with charge-transfer (CT) character of TADF molecules with different external quantum efficiencies (EQEs) using time-resolved electron paramagnetic resonance methods. Analysis of the observed spin polarization indicates a strong correlation of the EQE with the population rate due to ISC induced by hyperfine coupling with the magnetic nuclei. It is concluded that molecules with high EQE have an extremely small energy gap between the (1)CT and (3)CT states, which allows an additional ISC channel due to the hyperfine interactions.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::835d88fdf64024232f3fc50a0661cac7 https://doi.org/10.1021/acs.jpca.5b02253 Zobrazit plný text záznamu