High Efficiency Fluorescent Electroluminescence with Extremely Low Efficiency Roll‐Off Generated by a Donor–Bianthracene–Acceptor Structure: Utilizing Perpendicular Twisted Intramolecular Charge Transfer Excited State,Advanced Optical Materials

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High Efficiency Fluorescent Electroluminescence with Extremely Low Efficiency Roll‐Off Generated by a Donor–Bianthracene–Acceptor Structure: Utilizing Perpendicular Twisted Intramolecular Charge Transfer Excited State
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2018-05-31 , DOI: 10.1002/adom.201800060
Yue Yu _{1,

2} , Lin Ma ₁ , Xiaolong Yang ₂ , Huixin Zhou ₁ , Hanlin Qin ₁ , Jiangluqi Song ₁ , Guijiang Zhou ₂ , Dongdong Wang ₂ , Zhaoxin Wu _{3,

4}

Affiliation

Although phosphorescent and thermally activated delayed fluorescence (TADF) emitters can break through the spin statistics rules and achieve nearly 100% radiative exciton production (η_r), the swift efficiency roll‐off as luminance increases due to the accumulation of lowest triplet excited states with relatively long lifetime is the fatal bottleneck for their lighting application. How to achieve high η_r and low efficiency roll‐off simultaneously is still a challenge. To address this issue, two metal‐free organic molecules are reported with a highly twisted donor–bianthracene–acceptor structure involving high‐lying twisted intramolecular charge transfer (TICT) intermediate excited states, by which electroluminescent (EL) devices with both high η_r and extremely low efficiency roll‐off could be realized. Significant low efficiency roll‐off is achieved with about 99.1% of the maximum external quantum efficiency (EQE) maintained even at a high current density of 100 mA cm⁻², corresponding to luminance of 23615 cd m⁻², along with maximum EQE of 7.13% (η_r of 64.82%) in a doped green EL device with 9‐(4‐{10′‐[4‐(4,6‐diphenyl‐[1,3,5]triazin‐2‐yl)‐phenyl]‐[9,9′]bianthracenyl‐10‐yl}‐phenyl)‐9H‐carbazole as a host. The state‐of‐the‐art low efficiency roll‐off and enhanced η_r would be attributed to spin mixing of high‐lying TICT singlet and triplet intermediate excited states, proving the great potential of such a host design strategy for their practical lighting application.

中文翻译：

供体-双蒽-受体结构产生的具有极低效率衰减的高效荧光电致发光：利用垂直扭曲的分子内电荷转移激发态

尽管磷光和热激活的延迟荧光（TADF）发射器可以突破自旋统计规则并实现近100％的辐射激子产生（_ηr），但由于最低三重态激发态的积累，随着亮度增加，效率迅速下降。较长的使用寿命是其照明应用的致命瓶颈。如何同时实现高_ηr和低效率滚降仍然是一个挑战。为了解决这个问题，据报道，两个无金属的有机分子具有高度扭曲的施主-双蒽-受体结构，涉及高度扭曲的分子内电荷转移（TICT）中间激发态，通过这种结构，电致发光（EL）器件既具有高_ηr并且可以实现极低的效率下降。即使在100 mA cm ^-2的高电流密度（对应于23615 cd m ^-2的亮度）下也能保持约99.1％的最大外部量子效率（EQE），仍可实现显着的低效率滚降。在带有9-（4- {10'-[4-（4,6-二苯基-[1,3,5] triazin-2-yl）-苯基]的掺杂绿色EL器件中，获得7.13％（_ηr为64.82％） ]-[9,9']双蒽基-10-基}-苯基）-9H-咔唑作为主体。先进的低效率滚降和增强的_ηr可归因于高层TICT单重态和三重态中间激发态的自旋混合，证明了这种主机设计策略在其实际照明应用中的巨大潜力。

更新日期：2018-05-31

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