Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices.
Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices.
复制标题
热激活延迟荧光器件中磁电致发光的客体浓度、偏置电流和温度依赖性符号反转
DOI：
10.1038/srep44396
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发表时间：
2017-03-15
影响因子：
4.6
通讯作者：
Xiong Z
中科院分区：
文献类型：
--
作者：
Deng J;Jia W;Chen Y;Liu D;Hu Y;Xiong Z
经历热激活延迟荧光（TADF）的器件中的非发射三重激发态可以经由反向系间穿越（RISC）上转换为单重激发态，这导致增强的电致发光效率。由于外磁场可以有效地抑制系间交叉，激子荧光器件总是表现出正的磁致发光。相反，TADF器件应表现出负MEL，因为RISC受到外部磁场的抑制。有趣的是，我们在TADF装置中观察到阳性MEL。此外，MEL的符号是正的或负的，并且取决于实验条件，包括掺杂浓度、电流密度和温度。从我们的TADF器件观察到的MEL表明，在主体材料中的ISC和客体材料中的RISC共存。这些竞争过程受实验条件的影响，导致MEL的符号变化。这项工作提供了重要的洞察TADF设备中的能量转移过程和激发态的演化。
Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices.