D2 小松君（Ryutaro Komatsu）の高効率純青色ピリミジン系 TADF 材料群に関する「Manipulating the Electronic Excited State Energies of Pyrimidine-Based TADF Emitters to Realize Efficient Deep-Blue Emission」と題する論文が ACS の Applied Materials and Interfaces (IF: 7.145) からオンライン出版されました。D2 小松君をはじめ、TADF チーム、B4 大澤、M1 中尾、M1 早坂、おめでとうございます！
Abstract: The development of efficient deep-blue emitters is one of the key issues in organic light-emitting devices (OLEDs) for environmentally friendly, large-area displays or general lighting. As a promising technology that realizes 100% conversion from electrons to photons, thermally activated delayed fluorescence (TADF) emitters have attracted considerable attention. However, only a handful of examples of deep-blue TADF emitters have been reported to date, and the emitters generally show large efficiency roll-off at practical luminance over several hundreds to thousands of cd m−2, most likely because of the long delayed fluorescent lifetime (td). To overcome this problem, we molecularly manipulated the electronic excited state energies of pyrimidine-based TADF emitters to realize deep-blue emission and reduced td. We then systematically investigated the relationships among the chemical structure, properties, and device performances. The resultant novel pyrimidine emitters called Ac–XMHPMs (X = 1, 2, and 3) contain different numbers of bulky methyl substituents at acceptor moieties, increasing the excited singlet (ES) and triplet state (ET) energies. Among them, Ac–3MHPM, with a high ET of 2.95 eV exhibited a high external quantum efficiency (EQE,max) of 18% and an hext of 10% at 100 cd m−2 with Commission Internationale de l’Eclairage chromaticity coordinates of (0.16, 0.15). These efficiencies are among the highest values to date for deep-blue TADF OLEDs. Our molecular design strategy provides fundamental guidance to design novel deep-blue TADF emitters.
