Molecular design featuring carbazole-decorated 15H-diindolo[2,3-b:1′,2′,3′-lm]carbazole for improved efficiency and lifetime of thermally activated delayed fluorescence emitters,Journal of Materials Chemistry C

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Molecular design featuring carbazole-decorated 15H-diindolo[2,3-b:1′,2′,3′-lm]carbazole for improved efficiency and lifetime of thermally activated delayed fluorescence emitters
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2020/01/07 , DOI: 10.1039/c9tc05855a
Rajendra Kumar Konidena _{1,

2,

3,

4} , Kyung Hyung Lee _{1,

2,

3,

4} , Jun Yeob Lee _{1,

2,

3,

4}

Affiliation

In this report, we developed a novel electron donor named 12-(9-phenyl-9H-carbazol-3-yl)-15H-diindolo[2,3-b:1′,2′,3′-lm]carbazole (CzDICz) by introducing a carbazole unit into the rigid 15H-diindolo[2,3-b:1′,2′,3′-lm]carbazole (DICz) donor for designing a stable green thermally activated delayed fluorescence (TADF) emitter, 5-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-(12-(9-phenyl-9H-carbazol-3-yl)-15H-diindolo[2,3-b:1′,2′,3′-lm]carbazol-15-yl)benzonitrile (CzDICzTrz). The effect of the additional carbazole unit in the CzDICz donor on photophysical and electroluminescence properties was unveiled by comparing the CzDICzTrz with the control molecule viz. 2-(15H-diindolo[2,3-b:1′,2′,3′-lm]carbazol-15-yl)-5-(4,6-diphenyl-1,3,5-triazin-2-yl)benzonitrile (DICzTrz) featuring the DICz donor. Photophysical analysis revealed that the CzDICzTrz exhibited small singlet–triplet energy splitting, a short delayed fluorescence lifetime (t_d), fast reverse intersystem crossing (RISC) and high photoluminescence quantum efficiency compared to DICzTrz. Therefore, the organic light emitting diode fabricated with CzDICzTrz showed superior device performance with a maximum external quantum efficiency (EQE) of 19.9% and a current efficiency of 62.3 cd A⁻¹ compared to its congener DICzTrz, which showed a maximum EQE of 12.9% and a current efficiency of 38.6 cd A⁻¹. Moreover, CzDICzTrz based devices achieved 40 times extended operational lifetime up to 80% of its initial luminance (L₀ = 1000 cd m⁻²) of 446 h compared to 11 h of DICzTrz due to its stable CzDICz donor, short t_d and fast RISC. We believe that the CzDICz donor can contribute to the development of efficient TADF emitters with long operational stability and uncompromised EQE.

中文翻译：

咔唑修饰的15H-二吲哚并[2,3-b：1'，2'，3'-lm]咔唑的分子设计可提高热活化延迟荧光发射器的效率和寿命

在本报告中，我们开发了一种新型的电子给体，名为12-（9-苯基-9 H-咔唑-3-基）-15 H-二吲哚并[2,3- b：1'，2'，3'- lm ]咔唑（CzDICz）通过引入咔唑单元到刚性15 ħ -diindolo [2,3- b：1'，2'，3'- LM ]咔唑（DICz）供体用于设计稳定的绿色热活化延迟荧光（TADF ）发射体，5-（4,6-diphenyl-1,3,5-triazin-2-yl）-2-（12-（9-phenyl-9 H -carbazol-3-yl）-15 H -diindolo [ 2,3- b：1'，2'，3' - lm ]咔唑-15-基）苄腈（CzDICzTrz）。通过将CzDICzTrz与对照分子viz进行比较，揭示了CzDICz供体中其他咔唑单元对光物理和电致发光性质的影响。2-（15 H-二吲哚并[2,3- b：1'，2'，3' - lm ]咔唑-15-基）-5-（4,6-二苯基-1,3,5-三嗪-2基）苯甲腈（DICzTrz）担纲DICz捐助。光物理分析表明，与之相比，CzDICzTrz具有较小的单重态-三重态能量分裂，较短的延迟荧光寿命（t _d），快速逆系统间穿越（RISC）和高光致发光量子效率。DICzTrz。因此，与同类物DICzTrz相比，用CzDICzTrz制成的有机发光二极管显示出优异的器件性能，最大外部量子效率（EQE）为19.9％，电流效率为62.3 cd A ^-1，后者的最大EQE为12.9％电流效率为38.6 cd A ^-1。此外，CzDICzTrz基础的设备实现40倍扩展的工作寿命直至其初始亮度的80％（大号₀ = 1000 CD米^-2 446ħ相比，11H）DICzTrz由于其稳定CzDICz供体，短吨_d和快速的RISC。我们相信CzDICz捐助者可以为开发具有长期运行稳定性和不折不扣的EQE的高效TADF发射器做出贡献。

更新日期：2020-02-20

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