Delayed Luminescence in 2-Methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole Derivatives
Delayed Luminescence in 2-Methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole Derivatives
复制标题
DOI：
10.1021/acs.jpca.2c05392
复制
发表时间：
2022-10-10
影响因子：
2.9
通讯作者：
Marder, Seth R.
中科院分区：
文献类型：
--
作者：
Cooper, Matthew W.;Zhang, Xiaoqing;Marder, Seth R.
2，5-二苯基-1，3，4-恶二唑已被广泛用作显示热激活延迟荧光（TADF）的供体-受体荧光团的受体部分，但类似的2-烷基-5-苯基-1，3，4-恶二唑的研究要少得多。在这里，咔唑取代的2-甲基-5-苯基-1，3，4-恶二唑的性能进行了比较，其2，5-二苯基类似物。前一种化合物的荧光均发生蓝移约。50-100 meV相对于后者，而类似的单重态-三重态能量分离（Δ EST）的估计值保持不变。特别是，2-甲基-5-（五（9-咔唑基）苯基）-1，3，4-恶二唑和2-甲基-5-（五（3，6-二叔丁基-9-咔唑基）苯基）-1，3，4-恶二唑的溶液荧光最大值分别为466和485 nm，估计Δ EST值分别为0.12和0.03 eV。在这两种情况下，从它们的溶液荧光行为推断的反向系间交叉（RISC）速率是相应的2-苯基衍生物的两倍以上。其中2-甲基衍生物用作发射体的有机发光二极管（OLED）产生高达23%的外量子效率（EQE）值。具有2-甲基-5-（五（9-咔唑基）苯基）-1，3，4-恶二唑和2-甲基-5-（五（3，6-二叔丁基-9-咔唑基）苯基）-1，3，4-恶二唑发光体的OLED相对于它们的2-苯基对应物在高电流密度下显示出降低的效率滚降，后者在1000 cd m-2下显示出16%的EQE。
2,5-Diphenyl-1,3,4-oxadiazole has been widely used as an acceptor portion of donor-acceptor fluorophores that exhibit thermally activated delayed fluorescence (TADF), but analogous 2-alkyl-5-phenyl-1,3,4-oxadiazoles have been much less widely investigated. Here the properties of carbazole-substituted 2-methyl-5-phenyl-1,3,4-oxadiazoles are compared to those of their 2,5-diphenyl analogues. The fluorescence of each of the former compounds is blue-shifted by ca. 50-100 meV relative to that in the latter, while similar estimated values of the singlet-triplet energy separation (Delta EST) are maintained. In particular, 2-methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole and 2-methyl-5-(penta(3,6-di-tert-butyl-9-carbazolyl)phenyl)-1,3,4-oxadiazole exhib-it solution fluorescence maxima of 466 and 485 nm and estimated Delta EST values of 0.12 and 0.03 eV, respectively. In both cases the reverse intersystem crossing (RISC) rates inferred from their solution fluorescence behavior are over twice those of the corresponding 2-phenyl derivatives. Organic light-emitting diodes (OLEDs) in which the 2-methyl derivatives are used as emitters yield external quantum efficiency (EQE) values of up to 23%. OLEDs with 2-methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole and 2-methyl-5-(penta(3,6-di-tert-butyl-9-carbazolyl)phenyl)-1,3,4-oxadiazole emitters show reduced efficiency rolloff at high current densities relative to their 2-phenyl counterparts, the latter exhibiting an EQE of 16% at 1000 cd m-2.