Suppression of Structural Change upon S1-T1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile Derivatives

Masaki Saigo, Kiyoshi Miyata, Sei'Ichi Tanaka, Hajime Nakanotani, Chihaya Adachi, Ken Onda

研究成果: ジャーナルへの寄稿学術誌査読

46 被引用数 (Scopus)

抄録

Thermally activated delayed fluorescence (TADF) molecules are gathering attention for their potential to boost the efficiency of organic light-emitting diodes without precious metals. Minimizing the energy difference between the S1 and T1 states (ΔEST) is a fundamental strategy to accelerate reverse intersystem crossing (RISC). However, the lack of microscopic understanding of the process prevents adequate design strategies for efficient TADF materials. Here, we focused on four carbazole-benzonitrile (Cz-BN) derivatives that possess identical ΔEST but distinct TADF activities. We systematically compared their geometrical dynamics upon photoexcitation using time-resolved infrared (TR-IR) vibrational spectroscopy in conjunction with quantum chemical calculations. We found that the most TADF-active molecule, 4CzBN, shows little structural change after photoexcitation, while the TADF-inactive molecules show relatively large deformation upon S1-T1 conversion. This implies that the suppression of structural deformation is critical for minimizing the activation energy barrier for RISC in cases of the Cz-BN derivatives.

本文言語英語
ページ(範囲)2475-2480
ページ数6
ジャーナルJournal of Physical Chemistry Letters
10
10
DOI
出版ステータス出版済み - 5月 16 2019

!!!All Science Journal Classification (ASJC) codes

  • 材料科学一般
  • 物理化学および理論化学

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