Abstract
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.
| Original language | English |
|---|---|
| Article number | 032102 |
| Journal | Journal of Photonics for Energy |
| Volume | 8 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Jul 1 2018 |
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All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Renewable Energy, Sustainability and the Environment
Cite this
Solvent-dependent investigation of carbazole benzonitrile derivatives : Does the le 3 - CT 1 energy gap facilitate thermally activated delayed fluorescence? / Hosokai, Takuya; Noda, Hiroki; Nakanotani, Hajime; Nawata, Takanori; Nakayama, Yasuo; Matsuzaki, Hiroyuki; Adachi, Chihaya.
In: Journal of Photonics for Energy, Vol. 8, No. 3, 032102, 01.07.2018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Solvent-dependent investigation of carbazole benzonitrile derivatives
T2 - Does the le 3 - CT 1 energy gap facilitate thermally activated delayed fluorescence?
AU - Hosokai, Takuya
AU - Noda, Hiroki
AU - Nakanotani, Hajime
AU - Nawata, Takanori
AU - Nakayama, Yasuo
AU - Matsuzaki, Hiroyuki
AU - Adachi, Chihaya
PY - 2018/7/1
Y1 - 2018/7/1
N2 - 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.
AB - 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.
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U2 - 10.1117/1.JPE.8.032102
DO - 10.1117/1.JPE.8.032102
M3 - Article
VL - 8
JO - Journal of Photonics for Energy
JF - Journal of Photonics for Energy
SN - 1947-7988
IS - 3
M1 - 032102
ER -