Highly Efficient Blue Electroluminescence Using Delayed-Fluorescence Emitters with Large Overlap Density between Luminescent and Ground States,The Journal of Physical Chemistry C

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Highly Efficient Blue Electroluminescence Using Delayed-Fluorescence Emitters with Large Overlap Density between Luminescent and Ground States
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2015-11-11 00:00:00 , DOI: 10.1021/acs.jpcc.5b07798
Katsuyuki Shizu _{1,

2,

3} , Hiroki Noda ₄ , Hiroyuki Tanaka ₁ , Masatsugu Taneda ₁ , Motoyuki Uejima ₅ , Tohru Sato _{5,

6} , Kazuyoshi Tanaka ₅ , Hironori Kaji _{2,

3} , Chihaya Adachi _{1,

3,

7}

Affiliation

The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional fluorescence and phosphorescence. Recent research interest has focused on blue TADF emitters. In this study, we use quantum mechanics to reveal the relationship between the molecular structures and the photophysical properties of TADF emitters and derive a direction for the molecular design of highly efficient blue TADF emitters. Theoretical analyses show that the luminescence efficiency of TADF emitters largely depends on the overlap density (ρ₁₀) between the electronic wave functions of the ground state and the lowest excited singlet state. By increasing ρ₁₀, we develop an efficient sky-blue TADF emitter material, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (BCzT). When doped into a host layer, BCzT produces a high photoluminescence quantum yield of 95.6%. From the transient photoluminescence decays of the doped film, the efficiency of excited triplet state conversion into light is estimated to be 76.2%. An OLED using BCzT as a sky-blue emitter produces a maximum external quantum efficiency (EQE) of 21.7%, which is much higher than the EQE range of conventional fluorescent OLEDs (5–7.5%). The high EQE is a result of the high triplet-to-light conversion efficiency of BCzT. Our material design based on ρ₁₀ distribution provides a rational approach for developing TADF emitters for high-efficiency blue OLEDs.

中文翻译：

高效的蓝色电致发光，使用延迟荧光发射体，在发光态和基态之间具有大的重叠密度

使用热活化延迟荧光（TADF）可以实现高效的有机发光二极管（OLED），并且是使用常规荧光和磷光的有希望的替代方法。最近的研究兴趣集中在蓝色TADF发射器上。在这项研究中，我们使用量子力学揭示了TADF发射器的分子结构与光物理性质之间的关系，并为高效蓝色TADF发射器的分子设计提供了方向。理论分析表明，TADF发射体的发光效率很大程度上取决于重叠密度（ρ ₁₀的基态的电子波函数和所述最低激发单重态之间）。通过增加ρ ₁₀中，我们开发一种有效的天蓝色TADF发射体材料，9-（4-（4,6-二苯基-1,3,5-三嗪-2-基）苯基）-9'苯基-9- ħ，9' ħ -3,3'-联咔唑（BCzT）。当掺杂到主体层中时，BCzT产生95.6％的高光致发光量子产率。根据掺杂膜的瞬时光致发光衰减，将激发的三重态转换成光的效率估计为76.2％。使用BCzT作为天蓝色发射器的OLED产生的最大外部量子效率（EQE）为21.7％，远高于传统荧光OLED的EQE范围（5-7.5％）。高EQE是BCzT的三重态到光的高转换效率的结果。我们的材料设计基于ρ ₁₀ 分布为开发用于高效蓝色OLED的TADF发射器提供了一种合理的方法。

更新日期：2015-11-11

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