Enhanced blue TADF in a D–A–D type naphthyridine derivative with an asymmetric carbazole-donor motif,Journal of Materials Chemistry C

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Enhanced blue TADF in a D–A–D type naphthyridine derivative with an asymmetric carbazole-donor motif
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2021-12-29 , DOI: 10.1039/d1tc05061c
Dovydas Banevičius ₁ , Gediminas Kreiza ₁ , Rokas Klioštoraitis ₁ , Saulius Juršėnas ₁ , Tomas Javorskis ₂ , Vytenis Vaitkevičius ₂ , Edvinas Orentas ₂ , Karolis Kazlauskas ₁

Affiliation

Efficient triplet-to-singlet conversion in conventional donor–acceptor TADF compounds relies on charge-transfer (CT) and locally-excited (LE) triplet state mixing as this provides the required spin–orbit coupling. In this work, an asymmetric carbazole-donor motif is shown to facilitate the coupling and spin–flip process in a naphthyridine-acceptor based TADF emitter due to the enhanced LE character of the lowest triplet state. This was revealed from the delayed fluorescence measurements, which clearly signified a doubled RISC rate (up to 1.33 × 10⁶ s⁻¹) and a shortened delayed fluorescence lifetime (down to 4.4 μs) in an asymmetric compound compared to those of symmetric or singly-carbazole-substituted compounds. The promising features of the asymmetric blue TADF emitter were demonstrated to result in high efficiency OLEDs (external quantum efficiency of 21%) with a reduced efficiency roll-off.

中文翻译：

具有不对称咔唑供体基序的 D-A-D 型萘啶衍生物中增强的蓝色 TADF

传统的供体-受体 TADF 化合物中有效的三重态到单重态转换依赖于电荷转移 (CT) 和局部激发 (LE) 三重态混合，因为这提供了所需的自旋轨道耦合。在这项工作中，由于最低三重态的 LE 特性增强，不对称咔唑供体基序被证明可以促进基于萘啶受体的 TADF 发射体中的耦合和自旋翻转过程。延迟荧光测量揭示了这一点，这清楚地表明 RISC 速率翻了一番（高达 1.33 × 10 ⁶ s ^-1) 和与对称或单咔唑取代化合物相比，不对称化合物中的延迟荧光寿命缩短（低至 4.4 μs）。证明了不对称蓝色 TADF 发射器的有希望的特性可以产生高效率的 OLED（外部量子效率为 21%），并降低效率滚降。

更新日期：2022-01-19

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