Adamantyl Substitution Strategy for Realizing Solution-Processable Thermally Stable Deep-Blue Thermally Activated Delayed Fluorescence Materials
Adamantyl Substitution Strategy for Realizing Solution-Processable Thermally Stable Deep-Blue Thermally Activated Delayed Fluorescence Materials
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DOI：
10.1002/adma.201705641
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发表时间：
2018-02-22
影响因子：
29.4
通讯作者：
Kaji, Hironori
中科院分区：
文献类型：
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作者：
Wada, Yoshimasa;Kubo, Shosei;Kaji, Hironori
高效的溶液可加工发光体，特别是深蓝色发光体，是开发低成本和低能耗有机发光二极管（OLED）的迫切需要。最近开发的一类潜在的无金属发射体，热激活延迟荧光（TADF）材料，是有前途的候选人，但溶液可加工的TADF材料与有效的蓝色发射没有得到很好的研究。在本研究中，首先阐明了高效深蓝色TADF材料的设计要求，在此基础上，开发了金刚烷基取代的TADF分子。取代不仅赋予高溶解度和优异的热稳定性，而且通过推高分子的最低未占分子轨道能量和三重态能量对分子轨道具有关键影响。在OLED的应用中，实现了22.1%的外量子效率（EQE），蓝光发射具有国际照明委员会（CIE）坐标（0.15，0.19）。还实现了具有CIE（0.15，0.13）的更深的蓝色发射，其中EQE为11.2%。就已知而言，这些效率在CIE y < 0.20和y < 0.15的溶液处理的TADF OLED中是最好的。这项工作证明了金刚烷基取代的有效性，并为直接实现可溶液加工的高效深蓝色TADF发光体铺平了道路。
Highly efficient solution-processable emitters, especially deep-blue emitters, are greatly desired to develop low-cost and low-energy-consumption organic light-emitting diodes (OLEDs). A recently developed class of potentially metal-free emitters, thermally activated delayed fluorescence (TADF) materials, are promising candidates, but solution-processable TADF materials with efficient blue emissions are not well investigated. In this study, first the requirements for the design of efficient deep-blue TADF materials are clarified, on the basis of which, adamantyl-substituted TADF molecules are developed. The substitution not only endows high solubility and excellent thermal stability but also has a critical impact on the molecular orbitals, by pushing up the lowest unoccupied molecular orbital energy and triplet energy of the molecules. In the application to OLEDs, an external quantum efficiency (EQE) of 22.1% with blue emission having Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.19) is realized. A much deeper blue emission with CIE (0.15, 0.13) is also achieved, with an EQE of 11.2%. These efficiencies are the best yet among solution-processed TADF OLEDs of CIE y < 0.20 and y < 0.15, as far as known. This work demonstrates the validity of adamantyl substitution and paves a pathway for straightforward realization of solution-processable efficient deep-blue TADF emitters.