Tan Hong-Ji, Yang Guo-Xi, Deng Ying-Lan, Cao Chen, Tan Ji-Hua, Zhu Ze-Lin, Chen Wen-Cheng, Xiong Yuan, Jian Jing-Xin, Lee Chun-Sing, Tong Qing-Xiao
Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province, Shantou University, Guangdong, 515063, P. R. China.
Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, SAR, China.
Adv Mater. 2022 May;34(18):e2200537. doi: 10.1002/adma.202200537. Epub 2022 Mar 29.
To achieve high-efficiency deep-blue electroluminescence satisfying Rec.2020 standard blue gamut, two thermally activated delayed fluorescent (TADF) emitters are developed: 5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,10-diphenyl-5,10-dihydrodibenzo[b,e][1,4]azasiline (TDBA-PAS) and 10-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9,9-diphenyl-9,10-dihydroacridine (TDBA-DPAC). Inheriting from their parented organoboron multi-resonance core, both emitters show very promising deep-blue emissions with relatively narrow full width at half-maximum (FWHM, ≈50 nm in solution), high photoluminescence quantum yield (up to 92.3%), and short emission lifetime (≤2.49 µs) with fast reverse intersystem crossing (>10 s ) in doped films. More importantly, replacing the spiro-centered sp C atom (TDBA-DPAC) with the larger-radius sp Si atom (TDBA-PAS), enhanced conformational heterogeneities in bulky-group-shielded TADF molecules are observed in solution, doped film, and device. Consequently, OLEDs based on TDBA-PAS retain high maximum external quantum efficiencies ≈20% with suppressed efficiency roll-off and color index close to Rec.2020 blue gamut over a wide doping range of 10-50 wt%. This study highlights a new strategy to restrain spectral broadening and redshifting and efficiency roll-off in the design of deep-blue TADF emitters.
为了实现满足Rec.2020标准色域的高效深蓝色电致发光，开发了两种热激活延迟荧光（TADF）发光体：5-(2,12-二叔丁基-5,9-二氧杂-13b-硼萘并[3,2,1-de]蒽-7-基)-10,10-二苯基-5,10-二氢二苯并[b,e][1,4]氮杂硅环戊二烯（TDBA-PAS）和10-(2,12-二叔丁基-5,9-二氧杂-13b-硼萘并[3,2,1-de]蒽-7-基)-9,9-二苯基-9,10-二氢吖啶（TDBA-DPAC）。这两种发光体继承了其母体有机硼多共振核心，均表现出非常有前景的深蓝色发射，半高宽相对较窄（在溶液中约为50 nm），高光致发光量子产率（高达92.3%），以及在掺杂薄膜中具有短发射寿命（≤2.49 μs）和快速反向系间窜越（>10 s）。更重要的是，用较大半径的sp³ Si原子（TDBA-PAS）取代螺中心的sp³ C原子（TDBA-DPAC），在溶液、掺杂薄膜和器件中观察到在大基团屏蔽的TADF分子中构象异质性增强。因此，基于TDBA-PAS的有机发光二极管在10 - 50 wt%的宽掺杂范围内保持了约20%的高最大外量子效率，同时抑制了效率滚降，且色指数接近Rec.2020蓝色色域。这项研究突出了一种在深蓝色TADF发光体设计中抑制光谱展宽和红移以及效率滚降的新策略。
