Efficient Solid-State triplet-triplet annihilation up-conversion electroluminescence device by incorporating intermolecular intersystem-crossing dark sensitizer
Efficient Solid-State triplet-triplet annihilation up-conversion electroluminescence device by incorporating intermolecular intersystem-crossing dark sensitizer
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DOI：
10.1016/j.cej.2021.130889
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发表时间：
2021-06-25
影响因子：
15.1
通讯作者：
Lee, Jiun-Haw
中科院分区：
文献类型：
--
作者：
Chen, Chia-Hsun;Lin, Bo-Yen;Lee, Jiun-Haw
电子-空穴（e-h）对向三重态激子的有效转换是基于三重态-三重态湮灭上转换（TTAUC）的蓝色有机发光二极管（OLED）面临的一个挑战。产生单重态激子的25%的e-h对表示可以导致寄生红移发射的显著损失通道。在这项研究中，一个分子间的系统间交叉，依赖于一个“暗敏化剂”（DS）层组成的三-（8-羟基喹啉）铝（Alq 3）掺杂三[2-苯基吡啶-C2，N]铱（III）（Ir（ppy）3）被证明，以提高TTAUC过程。在Alq 3分子上形成载流子复合和激子产生。Alq 3单重态激子然后被Ir（ppy）3三重态猝灭，随后能量转移到Alq 3三重态。非发射的长寿命Alq 3三重态从敏化剂层迁移到发射体层，在那里它们经历TTAUC以给出蓝色荧光发射。该DS-TTAUC工艺保证了Alq 3不产生绿色发射。与标准TTAUC OLED相比，使用DS-TTAUC的蓝色OLED的效率提高了34.2%。此外，该器件显示出（0.15，0.09）的CIE坐标。此外，掺入高光致发光量子产率荧光发射体以增强发射体层中的单线态激子发射。在固态下，最大外量子效率为7.54%，TTAUC的量子产率（phi TTAUC）为37.6%。
The efficient conversion of electron-hole (e-h) pairs into triplet excitons is a challenge for blue organic lightemitting diodes (OLEDs) based on triplet-triplet annihilation upconversion (TTAUC). The 25% fraction of e-h pairs that create singlet excitons represents a significant loss channel that can lead to parasitic red-shifted emission. In this study, an intermolecular intersystem crossing that relies on a "dark sensitizer" (DS) layer consisting of tris-(8-hydroxyquinoline)aluminum (Alq3) doped with tris[2-phenylpyridinato-C2,N]Iridium(III) (Ir (ppy)3) is demonstrated to enhance the TTAUC process. Carriers recombination and excitons generation are formed on Alq3 molecules. Alq3 singlet excitons are then quenched by the Ir(ppy)3 triplet state, followed by energy transfer to the Alq3 triplet state. The non-emissive, long-lived Alq3 triplets migrate from the sensitizer layer to an emitter layer where they undergo TTAUC to give blue fluorescence emission. This DS-TTAUC process promises no green emission from the Alq3. The efficiency of a blue OLED utilizing DS-TTAUC was improved by 34.2% compared to a standard TTAUC OLED. In addition, the device exhibited CIE coordinates of (0.15, 0.09). Furthermore, a high photoluminescence quantum yield fluorescence emitter is incorporated to enhance the singlet exciton emission in the emitter layer. A maximum external quantum efficiency of 7.54% can be achieved with recorded-high quantum yield of the TTAUC (phi TTAUC) = 37.6% in solid state.