A New Molecular Design Based on Thermally Activated Delayed Fluorescence for Highly Efficient Organic Light Emitting Diodes
A New Molecular Design Based on Thermally Activated Delayed Fluorescence for Highly Efficient Organic Light Emitting Diodes
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DOI：
10.1021/jacs.5b10950
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发表时间：
2016-01-20
影响因子：
15
通讯作者：
Cheng, Chien -Hong
中科院分区：
文献类型：
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作者：
Rajamalli, Pachaiyappan;Senthilkumar, Natarajan;Cheng, Chien -Hong
合成了两种苯甲酰基吡啶-咔唑荧光材料DCBPy和DTCBPy，它们分别在苯甲酰基环的Meta和邻位碳上带有两个咔唑基和4-叔丁基咔唑基。这些分子显示出非常小的Δ E-ST为0.03和0.04 eV和瞬态PL特性，表明它们是热激活延迟荧光（TADF）材料。此外，它们在溶液和固态中显示出极其不同的光致发光量子产率：在环己烷中，该值分别为14%和36%，但在薄膜中，该值分别增加到88.0%和91.4%。使用DCBPy和DTCBPy作为掺杂剂的OLED发射蓝光和绿色光，EQE分别为24.0和27.2%，并且在实际亮度水平下具有低效率滚降。DTCBPy的晶体结构揭示了邻位给体（咔唑基）和受体（4-吡啶基羰基）单元之间的实质性相互作用。供体和受体取代基之间的这种相互作用可能对实现具有高光致发光量子产率的非常小的Δ E-ST起关键作用。
Two benzoylpyridine-carbazole based fluorescence materials DCBPy and DTCBPy, bearing two carbazolyl and 4-(t-butyl)carbazolyl groups, respectively, at the meta and ortho carbons of the benzoyl ring, were synthesized. These molecules show very small Delta E-ST of 0.03 and 0.04 eV and transient PL characteristics indicating that they are thermally activated delayed fluorescence (TADF) materials. In addition, they show extremely different photoluminescent quantum yields in solution and in the solid state: in cyclohexane the value are 14 and 36%, but in the thin films, the value increase to 88.0 and 91.4%, respectively. The OLEDs using DCBPy and DTCBPy as dopants emit blue and green light with EQEs of 24.0 and 27.2%, respectively, and with low efficiency roll-off at practical brightness level. The crystal structure of DTCBPy reveals a substantial interaction between the ortho donor (carbazolyl) and acceptor (4-pyridylcarbonyl) unit. This interaction between donor and acceptor substituents likely play a key role to achieve very small Delta E-ST with high photoluminescence quantum yield.