TY - JOUR
T1 - Blue thermally activated delayed fluorescence emitters incorporating acridan analogues with heavy group 14 elements for high-efficiency doped and non-doped OLEDs
AU - Matsuo, Kyohei
AU - Yasuda, Takuma
N1 - Funding Information:
This work was supported in part by Grant-in-Aid for JSPS KAKENHI Grant No. JP17K17937 (K. M.) and JP18H02048 (T. Y.), the Research Foundation for the Electrotechnology of Chubu (T. Y.), the Japan Research Institute of Industrial Science (T. Y.), and the Research Foundation for Opto-Science and Technology (T. Y.). K. M. is grateful for nancial support from the JSPS Research fellowship (Grant No. JP18J01692). The authors are grateful for Prof. Nobuo Kimizuka and Prof. Teppei Yamada at Kyushu University for their generous permission to use the X-ray crystallography facility, and also for the support provided by the Cooperative Research Program “Network Joint Research Center for Materials and Devices” and the computer facilities at the Research Institute for Information Technology, Kyushu University.
Publisher Copyright:
This journal is © The Royal Society of Chemistry.
PY - 2019
Y1 - 2019
N2 - Deep-blue thermally activated delayed fluorescence (TADF) emitters are promising alternatives for conventional fluorescence and phosphorescence materials for practical application in organic light-emitting diodes (OLEDs). However, as appropriate bipolar hosts for deep-blue TADF-OLEDs are scarce, the development of efficient deep-blue TADF emitters that are applicable to both doped and non-doped systems is an urgent task. In this study, we developed a new family of blue TADF emitters that demonstrated high photoluminescence (PL) and electroluminescence (EL) quantum efficiencies in both doped and non-doped (neat) systems. Four new donor-acceptor (D-A)-type TADF molecules incorporating phenazasiline, phenazagermine, and tetramethylcarbazole as weak D units and phenothiaborin as a weak A unit were designed and synthesized. By varying the structural rigidity/flexibility as well as the electron-donating ability of the D units, the resulting photophysical and TADF properties of the D-A molecules could be systematically regulated. A comprehensive photophysical investigation revealed that phenazasiline and phenazagermine-based emitters concurrently exhibit blue TADF emissions (464-483 nm), high PL quantum efficiencies (∼100%), extremely fast spin-converting reverse intersystem crossing rates (>107 s-1), and suppressed concentration quenching. These fascinating features in conjunction produced high-performance doped and non-doped blue TADF-OLEDs. The doped and non-doped TADF-OLEDs using the phenazasiline-based emitter demonstrated extremely high maximum external EL quantum efficiencies (ηext) of 27.6% and 20.9%, with CIE chromaticity coordinates of (0.14, 0.26) and (0.14, 0.20), respectively. Further, ultra-low efficiency roll-off behavior for both the doped and non-doped devices was demonstrated by their ηext as high as 26.1% and 18.2%, respectively, measured at a practically high luminance of 1000 cd m-2
AB - Deep-blue thermally activated delayed fluorescence (TADF) emitters are promising alternatives for conventional fluorescence and phosphorescence materials for practical application in organic light-emitting diodes (OLEDs). However, as appropriate bipolar hosts for deep-blue TADF-OLEDs are scarce, the development of efficient deep-blue TADF emitters that are applicable to both doped and non-doped systems is an urgent task. In this study, we developed a new family of blue TADF emitters that demonstrated high photoluminescence (PL) and electroluminescence (EL) quantum efficiencies in both doped and non-doped (neat) systems. Four new donor-acceptor (D-A)-type TADF molecules incorporating phenazasiline, phenazagermine, and tetramethylcarbazole as weak D units and phenothiaborin as a weak A unit were designed and synthesized. By varying the structural rigidity/flexibility as well as the electron-donating ability of the D units, the resulting photophysical and TADF properties of the D-A molecules could be systematically regulated. A comprehensive photophysical investigation revealed that phenazasiline and phenazagermine-based emitters concurrently exhibit blue TADF emissions (464-483 nm), high PL quantum efficiencies (∼100%), extremely fast spin-converting reverse intersystem crossing rates (>107 s-1), and suppressed concentration quenching. These fascinating features in conjunction produced high-performance doped and non-doped blue TADF-OLEDs. The doped and non-doped TADF-OLEDs using the phenazasiline-based emitter demonstrated extremely high maximum external EL quantum efficiencies (ηext) of 27.6% and 20.9%, with CIE chromaticity coordinates of (0.14, 0.26) and (0.14, 0.20), respectively. Further, ultra-low efficiency roll-off behavior for both the doped and non-doped devices was demonstrated by their ηext as high as 26.1% and 18.2%, respectively, measured at a practically high luminance of 1000 cd m-2
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U2 - 10.1039/c9sc04492b
DO - 10.1039/c9sc04492b
M3 - Article
AN - SCOPUS:85075739361
VL - 10
SP - 10687
EP - 10697
JO - Chemical Science
JF - Chemical Science
SN - 2041-6520
IS - 46
ER -