Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs.
Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs.
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DOI：
10.1038/srep08429
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发表时间：
2015-02-12
影响因子：
4.6
通讯作者：
Adachi C
中科院分区：
文献类型：
--
作者：
Furukawa T;Nakanotani H;Inoue M;Adachi C
最近，通过热激活延迟荧光（TADF）过程的三重态收获已被确立为一个现实的路线，以获得最终的内部电致发光（EL）的量子效率在有机发光二极管（OLED）。然而，三重激发态的相当长的瞬态寿命由于增加了不必要的化学反应的机会而降低操作稳定性的可能性一直是一个问题。在此，我们证明了通过采用TADF分子作为辅助掺杂剂和荧光分子作为末端发射体，在OLED中的EL效率和操作稳定性的双重增强。辅助掺杂剂和发射体分子的适当组合实现了单重态激子从TADF分子到荧光发射体的“单向”快速Förster能量转移，减少了TADF分子中的系间交叉（ISC）和反向ISC的循环次数，并导致与以TADF分子作为末端发射体的OLED相比，操作稳定性显著增强。此外，我们发现，这种快速的能量转移的存在显着抑制单重态-三重态湮灭。利用这种精细调谐的快速三重态激子上转换方案，OLED的性能和寿命大大提高。
Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved.
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影响因子：
4.6
作者：
Nakanotani H;Masui K;Nishide J;Shibata T;Adachi C
通讯作者：
Adachi C
影响因子：
3.7
作者：
Zhang, Yi;Grover, Tarun;Vishwanath, Ashvin
通讯作者：
Vishwanath, Ashvin
影响因子：
4
作者：
Burrows, PE;Forrest, SR;Michalski, L
通讯作者：
Michalski, L
影响因子：
3.2
作者：
Schroegel, Pamela;Langer, Nicolle;Strohriegl, Peter
通讯作者：
Strohriegl, Peter
影响因子：
3.2
作者：
Masui, Kensuke;Nakanotani, Hajime;Adachi, Chihaya
通讯作者：
Adachi, Chihaya