Theoretical tuning of the singlet–triplet energy gap to achieve efficient long-wavelength thermally activated delayed fluorescence emitters: the impact of substituents

2017 ◽  
Vol 19 (32) ◽  
pp. 21639-21647 ◽  
Author(s):  
Lijuan Wang ◽  
Tao Li ◽  
Peicheng Feng ◽  
Yan Song
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Long Wavelength ◽  
Thermally Activated ◽  
The Impact ◽  
Electron Withdrawing Substituents

Long-wavelength TADF emitters could be achieved with both small ΔEST and high kr through introducing small electron-withdrawing substituents!

scholarly journals A Novel Design Strategy for Suppressing Efficiency Roll-Off of Blue Thermally Activated Delayed Fluorescence Molecules through Donor–Acceptor Interlocking by C–C Bonds

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1735 ◽  
Author(s):  
Tae Hui Kwon ◽  
Soon Ok Jeon ◽  
Masaki Numata ◽  
Hasup Lee ◽  
Yeon Sook Chung ◽  
...  
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Design Synthesis ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Display Performance ◽  
Commercial Applications

The short material lifetime of thermally activated delayed fluorescence (TADF) technology is a major obstacle to the development of economically feasible, highly efficient, and durable devices for commercial applications. TADF devices are also hampered by insufficient operational stability. In this paper, we report the design, synthesis, and evaluation of new TADF molecules possessing a sterically twisted skeleton by interlocking donor and acceptor moieties through a C–C bond. Compared to C–N-bond TADF molecules, such as CPT2, the C–C-bond TADF molecules showed a large dihedral angle increase by more than 30 times and a singlet–triplet energy-gap decrease to less than 0.22 eV because of the steric hindrance caused by the direct C–C bond connection. With the introduction of a dibenzofuran core structure, devices comprising BMK-T317 and BMK-T318 exhibited a magnificent display performance, especially their external quantum efficiencies, which were as high as 19.9% and 18.8%, respectively. Moreover, the efficiency roll-off of BMK-T318 improved significantly (26.7%). These results indicate that stability of the material can be expected through the reduction of their singlet–triplet splitting and the precise adjustment of dihedral angles between the donor–acceptor skeletons.

scholarly journals Kinetics of thermal-assisted delayed fluorescence in blue organic emitters with large singlet–triplet energy gap

2015 ◽  
Vol 373 (2044) ◽  
pp. 20140447 ◽  
Author(s):  
Fernando B. Dias
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Threshold Temperature ◽  
Intersystem Crossing ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Kinetics Of ◽  
Triplet Harvesting

The kinetics of thermally activated delayed fluorescence (TADF) is investigated in dilute solutions of organic materials with application in blue light-emitting diodes (OLEDs). A method to accurately determine the energy barrier (Δ E a ) and the rate of reverse intersystem crossing ( k Risc ) in TADF emitters is developed, and applied to investigate the triplet-harvesting mechanism in blue-emitting materials with large singlet–triplet energy gap (Δ E ST ). In these materials, triplet–triplet annihilation (TTA) is the dominant mechanism for triplet harvesting; however, above a threshold temperature TADF is able to compete with TTA and give enhanced delayed fluorescence. Evidence is obtained for the interplay between the TTA and the TADF mechanisms in these materials.

scholarly journals Highly Efficient Thermally Activated Delayed Fluorescence Emitters with a Small Singlet–Triplet Energy Gap and Large Oscillator Strength

2015 ◽  
Vol 44 (3) ◽  
pp. 360-362 ◽  
Author(s):  
Yuta Sagara ◽  
Katsuyuki Shizu ◽  
Hiroyuki Tanaka ◽  
Hiroshi Miyazaki ◽  
Kenichi Goushi ◽  
...  
Keyword(s):  
Oscillator Strength ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Highly Efficient

scholarly journals N-Rich Electron Acceptor: Triplet Harvesting in Multichromophoric Pyridoquinoxaline and Pyridopyrazine-Based Organic Emitters

2020 ◽  
Author(s):  
BAHADUR SK ◽  
Samarth Sharma ◽  
Anto James ◽  
Subhankar Kundu ◽  
Abhijit Patra
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet States ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
New Class ◽  
State Security ◽  
Linkage Position ◽  
Triplet Harvesting

<p></p><p>Control of nonradiative deactivation of triplet states and tuning the singlet-triplet energy gap (ΔE<sub>ST</sub>) are the major challenges to develop materials exhibiting thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP). Herein, we propose a new class of multichromophoric tridonor-acceptor (D<sub>3</sub>-A) compounds with rigid and flexible π-spacer having N-rich pyridoquinoxaline (PQ) and pyridopyrazine (PZ) acceptor core, respectively. The molecule with carbazole (Cz) donors at <i>meta</i> to quinoxaline (QX) nitrogen of rigid PQ core exhibits TADF. Whereas, the variation of the linkage position of Cz to PQ as well as twisted and flexible PZ core show predominantly RTP due to relatively higher singlet-triplet energy gap (ΔE<sub>ST</sub>). Increasing the donor strength with phenoxazine (PO) in PZ system leads to simultaneous TADF and RTP. Further, we demonstrate the promising scope of all-organic triplet harvesting materials in solid-state security encryption.</p><br><p></p>

scholarly journals N-Rich Electron Acceptor: Triplet Harvesting in Multichromophoric Pyridoquinoxaline and Pyridopyrazine-Based Organic Emitters

2020 ◽  
Author(s):  
BAHADUR SK ◽  
Samarth Sharma ◽  
Anto James ◽  
Subhankar Kundu ◽  
Abhijit Patra
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet States ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
New Class ◽  
State Security ◽  
Linkage Position ◽  
Triplet Harvesting

<p></p><p>Control of nonradiative deactivation of triplet states and tuning the singlet-triplet energy gap (ΔE<sub>ST</sub>) are the major challenges to develop materials exhibiting thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP). Herein, we propose a new class of multichromophoric tridonor-acceptor (D<sub>3</sub>-A) compounds with rigid and flexible π-spacer having N-rich pyridoquinoxaline (PQ) and pyridopyrazine (PZ) acceptor core, respectively. The molecule with carbazole (Cz) donors at <i>meta</i> to quinoxaline (QX) nitrogen of rigid PQ core exhibits TADF. Whereas, the variation of the linkage position of Cz to PQ as well as twisted and flexible PZ core show predominantly RTP due to relatively higher singlet-triplet energy gap (ΔE<sub>ST</sub>). Increasing the donor strength with phenoxazine (PO) in PZ system leads to simultaneous TADF and RTP. Further, we demonstrate the promising scope of all-organic triplet harvesting materials in solid-state security encryption.</p><br><p></p>

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