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변성용,유지광,이준엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Two host materials for blue phosphorescent organic light-emitting diodes (PHOLEDs) were synthesized. One of the materials is composed of two electron donating moieties, and the other one is composed of one electron donating moiety and one electron withdrawing moiety. Each electron donating and withdrawing moieties are connected using conjugation confining linkage to obtain high triplet energy (ET). The host materials showed high ET above 2.91 eV, which appropriate to blue PHOLEDs. The external quantum efficiencies of the blue PHOLEDs with the two host materials were above 20 %.
변성용,이준엽 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1
Blue host materials for phosphorescent organic light-emitting diodes (PHOLEDs) were synthesized with donor-acceptor moiety as a core structure which was modified with three different units to control charge transport property. The materials showed high triplet energy above 2.85 eV, and their highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels are -5.90/-2.79, -5.90/-2.72 and -5.89/-2.67 eV, respectively, depending on the substituent of the core structure. Maximum quantum efficiencies of 23.4%, 19.6% and 17.4% were obtained with low driving voltage in blue PHOLEDs using the new host materials.
변성용,이준엽 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Bipolar host materials were successfully synthesized for blue phosphorescent organic light-emitting diodes (PHOLEDs). Two weak acceptors were interconnected to formulate core moiety, and two different kinds of the substituent groups were attached to the core moiety to control charge transport properties. The triplet energy of the two host materials was 2.85 eV, and the highest occupied molecular orbital (HOMO)/ the lowest unoccupied molecular orbital (LUMO) of the host materials were -5.97/-2.75 and -5.91/-2.81 eV. The host materials showed high maximum external quantum efficiencies of 17.5 and 16.1% in the blue phosphorescent devices.
변성용,이준엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
엑스플렉스 호스트를 이용하여 단일 호스트보다 50 % 수명이 향상된 녹색 인광 소자를 개발하였다. 호스트로는 TCTA(tris(4-(9H-carbazol-9-yl)phenyl)amine)와 TPBI(1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene)를 사용하였으며, 엑시플렉스를 형성하는 TCTA와 TPBI의 조성비는 1:1이다. 도판트로는 Ir(ppy)3 (Tris[2-phenylpyridinato-C2,N]iridium(III))를 사용하였으며, 도판트의 도핑농도는 질량대비 5 %이다. 1000 cd/m2휘도 기준에서 반감수명으로는 TCTA를 단일 호스트로 사용한 소자의 경우 5 h이며, TPBI를 단일 호스트로 사용한 소자의 경우 87 h, 엑시플렉스 호스트를 사용한 소자의 경우 138 h 으로 TPBI 단일 호스트 소자에 비해 약 150 % 개선되었다. 엑시플렉스를 활용하여 기존 호스트의 일중항 에너지 보다 낮은 에너지에서 엑시톤을 형성함으로써 호스트의 스트레스를 최소화하였으며, 이를 이용하여 녹색 인광 소자의 수명 특성을 개선하였다.
변성용,이준엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Novel 1-position of carbazole based host materials were synthesized, and applied in blue phosphorescent organic light-emitting diodes (PHOLEDs). The 1-position of the phenyl carbazole was connected via different positions of another carbazole to build 1-position of the carbazole based bicarbazole moiety, and diphenyltriazine moiety was introduced to control charge transport property. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were approximately -6.1 and -3.3 eV, respectively. The maximum external quantum efficiency of the green PHOLEDs was obtained to be 24.5 %.