Highly Efficient Thermally Activated Delayed Fluorescence via J-Aggregates with Strong Intermolecular Charge Transfer
Highly Efficient Thermally Activated Delayed Fluorescence via J-Aggregates with Strong Intermolecular Charge Transfer
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DOI：
10.1002/adma.201808242
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发表时间：
2019-07-01
影响因子：
29.4
通讯作者：
Qiao, Juan
中科院分区：
文献类型：
--
作者：
Xue, Jie;Liang, Qingxin;Qiao, Juan
高效、低成本有机发射材料和器件的发展本质上受到能隙定律和自旋统计的限制，特别是在近红外（NIR）区域。据报道，一种新颖的设计策略通过具有强分子间电荷转移（CT）的J聚集体实现高效热激活延迟荧光（TADF）材料。设计并合成了两种具有强平面受体的有机供体-受体分子，它们可以在固态下轻松形成具有强分子间CT的J聚集体，并表现出从黄光到近红外的宽调谐发射。实验和理论研究表明，这种J聚集体的形成混合了Frenkel激子和CT激子，这不仅有助于快速的辐射衰减率和缓慢的非辐射衰减率，从而在固体薄膜中实现几乎一致的光致发光效率，而且显着减小了最低单重态和三重态激发态之间的能隙（大约0.3 eV），即使在近红外区域也能产生高效的TADF。这些有机发光二极管的红光发射外量子效率为15.8%，近红外发射外量子效率为14.1%，这是基于TADF材料的近红外有机发光二极管（OLED）的最佳结果。这些发现为开发基于分子聚集体的高效有机发射材料和器件开辟了新途径。
The development of high-efficiency and low-cost organic emissive materials and devices is intrinsically limited by the energy-gap law and spin statistics, especially in the near-infrared (NIR) region. A novel design strategy is reported for realizing highly efficient thermally activated delayed fluorescence (TADF) materials via J-aggregates with strong intermolecular charge transfer (CT). Two organic donor-acceptor molecules with strong and planar acceptor are designed and synthesized, which can readily form J-aggregates with strong intermolecular CT in solid states and exhibit wide-tuning emissions from yellow to NIR. Experimental and theoretical investigations expose that the formation of such J-aggregates mixes Frenkel excitons and CT excitons, which not only contributes to a fast radiative decay rate and a slow nonradiative decay rate for achieving nearly unity photoluminescence efficiency in solid films, but significantly decreases the energy gap between the lowest singlet and triplet excited states (approximate to 0.3 eV) to induce high-efficiency TADF even in the NIR region. These organic light-emitting diodes exhibit external quantum efficiencies of 15.8% for red emission and 14.1% for NIR emission, which represent the best result for NIR organic light-emitting diodes (OLEDs) based on TADF materials. These findings open a new avenue for the development of high-efficiency organic emissive materials and devices based on molecular aggregates.