Purely organic electroluminescent material realizing 100% conversion from electricity to light.
Purely organic electroluminescent material realizing 100% conversion from electricity to light.
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DOI：
10.1038/ncomms9476
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发表时间：
2015-10-19
影响因子：
16.6
通讯作者：
Adachi C
中科院分区：
文献类型：
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作者：
Kaji H;Suzuki H;Fukushima T;Shizu K;Suzuki K;Kubo S;Komino T;Oiwa H;Suzuki F;Wakamiya A;Murata Y;Adachi C
已经开发了使用含有稀有金属（例如铂和铱络合物）的发射体的高效有机发光二极管。然而，迫切需要开发由更丰富的材料组成的发射器。在这里，我们展示了一种用于有机发光二极管的热激活延迟荧光材料，其实现了大约100%的光致发光量子产率和大约100%的三重态到单重态激发态的上转换。该材料含有供电子的二苯氨基咔唑和受电子的三苯三嗪部分。通过微调最高占据分子轨道和最低未占据分子轨道分布，克服了有效发射和三重态到单重态上转换之间的典型权衡。单重态-三重态能隙几乎为零，小于室温下的热能，导致有机发光二极管的外量子效率为29.6%。当使用外耦合片时，获得了41.5%的外量子效率。即使在3，000 cd m-2的高亮度下，外部量子效率也为30.7%。 有机发光二极管为光源提供了更环保的未来，但许多使用稀有金属。在这里，作者提出了一种方法，通过实现从三重态到单重态激子的100%上转换，从而实现100%的辐射发射，实现超过40%的外量子效率。
Efficient organic light-emitting diodes have been developed using emitters containing rare metals, such as platinum and iridium complexes. However, there is an urgent need to develop emitters composed of more abundant materials. Here we show a thermally activated delayed fluorescence material for organic light-emitting diodes, which realizes both approximately 100% photoluminescence quantum yield and approximately 100% up-conversion of the triplet to singlet excited state. The material contains electron-donating diphenylaminocarbazole and electron-accepting triphenyltriazine moieties. The typical trade-off between effective emission and triplet-to-singlet up-conversion is overcome by fine-tuning the highest occupied molecular orbital and lowest unoccupied molecular orbital distributions. The nearly zero singlet–triplet energy gap, smaller than the thermal energy at room temperature, results in an organic light-emitting diode with external quantum efficiency of 29.6%. An external quantum efficiency of 41.5% is obtained when using an out-coupling sheet. The external quantum efficiency is 30.7% even at a high luminance of 3,000 cd m−2. Organic light-emitting diodes promise a more environment-friendly future for light sources, but many use rare metals. Here, the authors present an approach that achieves external quantum efficiency over 40% by realising 100% up-conversion from triplet to singlet excitons and thus 100% radiative emission.