Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff
Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff
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DOI：
10.1038/s41467-020-15558-5
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发表时间：
2020-04-14
影响因子：
16.6
通讯作者：
Adachi, Chihaya
中科院分区：
文献类型：
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作者：
Kim, Jong Uk;Park, In Seob;Adachi, Chihaya
具有热激活延迟荧光(TADF)的芳香族有机深蓝发光体可以捕获电生单态和三态中的所有激子作为光发射。然而，由于有机电致发光二极管(OLED)中激子的湮没，蓝色TADF发光体通常具有较长的激子寿命，导致在高电流密度和高亮度下的效率严重下降，即滚降。在这里，我们报道了一种采用简单的分子设计的深蓝色TADF发射体，其中激活能以及不同自旋多重数的激发态之间的自旋轨道耦合被同时控制。在不含重金属元素的施主-受主类型分子结构中实现了750 ns的极快激子寿命。采用这种TADF发射体的OLED显示出深蓝色的电致发光，CIE色度坐标为(0.14，0.18)，最大电致发光量子效率为20.7%。此外，即使在高亮度下，高最大效率仍保持在20.2%和17.4%。为了实现高亮度、高效率的有机电致发光，需要具有低激子寿命的深蓝光有机发光材料。在这里，作者报告了具有亚纳秒级激子寿命的热激活延迟荧光分子的深蓝色OLED。
Aromatic organic deep-blue emitters that exhibit thermally activated delayed fluorescence (TADF) can harvest all excitons in electrically generated singlets and triplets as light emission. However, blue TADF emitters generally have long exciton lifetimes, leading to severe efficiency decrease, i.e., rolloff, at high current density and luminance by exciton annihilations in organic light-emitting diodes (OLEDs). Here, we report a deep-blue TADF emitter employing simple molecular design, in which an activation energy as well as spin-orbit coupling between excited states with different spin multiplicities, were simultaneously controlled. An extremely fast exciton lifetime of 750ns was realized in a donor-acceptor-type molecular structure without heavy metal elements. An OLED utilizing this TADF emitter displayed deep-blue electroluminescence (EL) with CIE chromaticity coordinates of (0.14, 0.18) and a high maximum EL quantum efficiency of 20.7%. Further, the high maximum efficiency were retained to be 20.2% and 17.4% even at high luminance. Deep-blue emitting organic materials with low exciton lifetime are required to realize efficient organic light-emitting diodes (OLEDs) at high brightness. Here, the authors report deep-blue OLEDs featuring thermally activated delayed fluorescence molecules with subnano-second exciton lifetime.