Suppression of Structural Change upon S 1 -T 1 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

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

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 S 1 and T 1 states (ΔE ST ) 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 ΔE ST 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 S 1 -T 1 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.

Original languageEnglish
Pages (from-to)2475-2480
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume10
Issue number10
DOIs
Publication statusPublished - May 16 2019

Fingerprint

carbazoles
Fluorescence
retarding
Derivatives
fluorescence
Photoexcitation
photoexcitation
Molecules
molecules
Vibrational spectroscopy
Energy barriers
Organic light emitting diodes (OLED)
Precious metals
acceleration (physics)
noble metals
Infrared spectroscopy
light emitting diodes
Activation energy
carbazole
benzonitrile

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physical and Theoretical Chemistry

Cite this

@article{3d349874b01246489043eb357631ca65,
title = "Suppression of Structural Change upon S 1 -T 1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile Derivatives",
abstract = "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 S 1 and T 1 states (ΔE ST ) 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 ΔE ST 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 S 1 -T 1 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.",
author = "Masaki Saigo and Kiyoshi Miyata and Sei'Ichi Tanaka and Hajime Nakanotani and Chihaya Adachi and Ken Onda",
year = "2019",
month = "5",
day = "16",
doi = "10.1021/acs.jpclett.9b00810",
language = "English",
volume = "10",
pages = "2475--2480",
journal = "Journal of Physical Chemistry Letters",
issn = "1948-7185",
publisher = "American Chemical Society",
number = "10",

}

TY - JOUR

T1 - Suppression of Structural Change upon S 1 -T 1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile Derivatives

AU - Saigo, Masaki

AU - Miyata, Kiyoshi

AU - Tanaka, Sei'Ichi

AU - Nakanotani, Hajime

AU - Adachi, Chihaya

AU - Onda, Ken

PY - 2019/5/16

Y1 - 2019/5/16

N2 - 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 S 1 and T 1 states (ΔE ST ) 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 ΔE ST 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 S 1 -T 1 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.

AB - 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 S 1 and T 1 states (ΔE ST ) 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 ΔE ST 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 S 1 -T 1 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.

UR - http://www.scopus.com/inward/record.url?scp=85065850135&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85065850135&partnerID=8YFLogxK

U2 - 10.1021/acs.jpclett.9b00810

DO - 10.1021/acs.jpclett.9b00810

M3 - Article

C2 - 30973013

AN - SCOPUS:85065850135

VL - 10

SP - 2475

EP - 2480

JO - Journal of Physical Chemistry Letters

JF - Journal of Physical Chemistry Letters

SN - 1948-7185

IS - 10

ER -