Abstract
The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional fluorescence and phosphorescence. Recent research interest has focused on blue TADF emitters. In this study, we use quantum mechanics to reveal the relationship between the molecular structures and the photophysical properties of TADF emitters and derive a direction for the molecular design of highly efficient blue TADF emitters. Theoretical analyses show that the luminescence efficiency of TADF emitters largely depends on the overlap density (ρ10) between the electronic wave functions of the ground state and the lowest excited singlet state. By increasing ρ10, we develop an efficient sky-blue TADF emitter material, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (BCzT). When doped into a host layer, BCzT produces a high photoluminescence quantum yield of 95.6%. From the transient photoluminescence decays of the doped film, the efficiency of excited triplet state conversion into light is estimated to be 76.2%. An OLED using BCzT as a sky-blue emitter produces a maximum external quantum efficiency (EQE) of 21.7%, which is much higher than the EQE range of conventional fluorescent OLEDs (5-7.5%). The high EQE is a result of the high triplet-to-light conversion efficiency of BCzT. Our material design based on ρ10 distribution provides a rational approach for developing TADF emitters for high-efficiency blue OLEDs.
| Original language | English |
|---|---|
| Pages (from-to) | 26283-26289 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry C |
| Volume | 119 |
| Issue number | 47 |
| DOIs | |
| Publication status | Published - Nov 25 2015 |
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Energy(all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
Cite this
Highly Efficient Blue Electroluminescence Using Delayed-Fluorescence Emitters with Large Overlap Density between Luminescent and Ground States. / Shizu, Katsuyuki; Noda, Hiroki; Tanaka, Hiroyuki; Taneda, Masatsugu; Uejima, Motoyuki; Sato, Tohru; Tanaka, Kazuyoshi; Kaji, Hironori; Adachi, Chihaya.
In: Journal of Physical Chemistry C, Vol. 119, No. 47, 25.11.2015, p. 26283-26289.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Highly Efficient Blue Electroluminescence Using Delayed-Fluorescence Emitters with Large Overlap Density between Luminescent and Ground States
AU - Shizu, Katsuyuki
AU - Noda, Hiroki
AU - Tanaka, Hiroyuki
AU - Taneda, Masatsugu
AU - Uejima, Motoyuki
AU - Sato, Tohru
AU - Tanaka, Kazuyoshi
AU - Kaji, Hironori
AU - Adachi, Chihaya
PY - 2015/11/25
Y1 - 2015/11/25
N2 - The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional fluorescence and phosphorescence. Recent research interest has focused on blue TADF emitters. In this study, we use quantum mechanics to reveal the relationship between the molecular structures and the photophysical properties of TADF emitters and derive a direction for the molecular design of highly efficient blue TADF emitters. Theoretical analyses show that the luminescence efficiency of TADF emitters largely depends on the overlap density (ρ10) between the electronic wave functions of the ground state and the lowest excited singlet state. By increasing ρ10, we develop an efficient sky-blue TADF emitter material, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (BCzT). When doped into a host layer, BCzT produces a high photoluminescence quantum yield of 95.6%. From the transient photoluminescence decays of the doped film, the efficiency of excited triplet state conversion into light is estimated to be 76.2%. An OLED using BCzT as a sky-blue emitter produces a maximum external quantum efficiency (EQE) of 21.7%, which is much higher than the EQE range of conventional fluorescent OLEDs (5-7.5%). The high EQE is a result of the high triplet-to-light conversion efficiency of BCzT. Our material design based on ρ10 distribution provides a rational approach for developing TADF emitters for high-efficiency blue OLEDs.
AB - The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional fluorescence and phosphorescence. Recent research interest has focused on blue TADF emitters. In this study, we use quantum mechanics to reveal the relationship between the molecular structures and the photophysical properties of TADF emitters and derive a direction for the molecular design of highly efficient blue TADF emitters. Theoretical analyses show that the luminescence efficiency of TADF emitters largely depends on the overlap density (ρ10) between the electronic wave functions of the ground state and the lowest excited singlet state. By increasing ρ10, we develop an efficient sky-blue TADF emitter material, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (BCzT). When doped into a host layer, BCzT produces a high photoluminescence quantum yield of 95.6%. From the transient photoluminescence decays of the doped film, the efficiency of excited triplet state conversion into light is estimated to be 76.2%. An OLED using BCzT as a sky-blue emitter produces a maximum external quantum efficiency (EQE) of 21.7%, which is much higher than the EQE range of conventional fluorescent OLEDs (5-7.5%). The high EQE is a result of the high triplet-to-light conversion efficiency of BCzT. Our material design based on ρ10 distribution provides a rational approach for developing TADF emitters for high-efficiency blue OLEDs.
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U2 - 10.1021/acs.jpcc.5b07798
DO - 10.1021/acs.jpcc.5b07798
M3 - Article
AN - SCOPUS:84948677032
VL - 119
SP - 26283
EP - 26289
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 47
ER -