Highly Efficient TADF OLEDs: How the Emitter-Host Interaction Controls Both the Excited State Species and Electrical Properties of the Devices to Achieve Near 100% Triplet Harvesting and High Efficiency
Highly Efficient TADF OLEDs: How the Emitter-Host Interaction Controls Both the Excited State Species and Electrical Properties of the Devices to Achieve Near 100% Triplet Harvesting and High Efficiency
复制标题
DOI：
10.1002/adfm.201400948
复制
发表时间：
2014-10-22
影响因子：
19
通讯作者：
Monkman, Andrew P.
中科院分区：
文献类型：
--
作者：
Jankus, Vygintas;Data, Przemyslaw;Monkman, Andrew P.
在有机电致发光二极管(OLED)中，需要能够捕获单态和三态激发态以实现100%电荷到光的内部转换的新的发射体，以取代Ir基荧光粉。具有电荷转移(CT)激发态的分子可能通过热激活延迟荧光(TADF)机制来实现这一点。结果表明，D-A电荷转移分子在固态时，不仅可以通过分子内电荷转移激发态发射，还可以通过分子与主体材料之间形成的激发态发射。基于先前研究的宿主TAPC中的D-A-D分子的OLED获得了14%的外部电致发光产率，并显示出近100%的三重态捕获效率。在这些设备中，明确地确定三重态是通过TADF获得的，但更有趣的是，这些结果被发现与发射体是ICT状态还是D-A-D/主机激基复合体无关。
New emitters that can harvest both singlet and triplet excited states to give 100% internal conversion of charge into light, are required to replace Ir based phosphors in organic light emitting diodes (OLEDs). Molecules that have a charge transfer (CT) excited state can potentially achieve this through the mechanism of thermally activated delayed fluorescence (TADF). Here, it is shown that a D-A charge transfer molecule in the solid state, can emit not only via an intramolecular charge transfer (ICT) excited state, but also from exciplex states, formed between the molecule and the host material. OLEDs based on a previously studied D-A-D molecule in a host TAPC achieves >14% external electroluminescence yield and shows nearly 100% efficient triplet harvesting. In these devices, it is unambiguously established that the triplet states are harvested via TADF, but more interestingly, these results are found to be independent of whether the emitter is the ICT state or the D-A-D/host exciplex.