Solvent-dependent investigation of carbazole benzonitrile derivatives: Does the le 3 - CT 1 energy gap facilitate thermally activated delayed fluorescence?

Takuya Hosokai, Hiroki Noda, Hajime Nakanotani, Takanori Nawata, Yasuo Nakayama, Hiroyuki Matsuzaki, Chihaya Adachi

研究成果: Contribution to journalArticle査読

10 被引用数 (Scopus)

抄録

The photophysical properties of six types of carbazole benzonitrile (CzBN) derivatives are investigated in different solvents to examine the thermally activated delayed fluorescence (TADF) activation via reducing the energy gap between the singlet charge-transfer and triplet locally excited states, ΔEST(LE). Relative to the ΔEST(LE) values for the CzBN derivatives in the low polarity solvent toluene (ϵ∼2), a reduction of ΔEST(LE) for the CzBN derivatives in the polar solvent acetonitrile (ϵ∼37) was confirmed while maintaining fairly constant ΔEST values. Notably, TADF activation was observed in acetonitrile for some CzBN derivatives that are TADF inactive in toluene. A numerical analysis of various rate constants revealed the cause of TADF activation as an increase in the reverse intersystem crossing rate and a suppression of the non-radiative decay rate of the triplet states. The positive effect of ΔEST(LE) was limited, however, as an excessive decrease in ΔEST(LE) facilitates the nonradiative deactivation of the triplet states, leading to a loss of the TADF efficiency. This paper shows that ΔEST(LE) provides a measure of TADF activation and that appropriate regulation of ΔEST(LE) is required to achieve high TADF efficiency.

本文言語英語
論文番号032102
ジャーナルJournal of Photonics for Energy
8
3
DOI
出版ステータス出版済み - 7 1 2018

All Science Journal Classification (ASJC) codes

  • 原子分子物理学および光学
  • 再生可能エネルギー、持続可能性、環境

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