Deep-red and near-infrared organic light-emitting diodes (DR/NIR-OLEDs) showed a wide range of applications such as healthcare and night-vision. However, red emitters generally demonstrated severe non-radiative emission due to energy gap law, and the development of efficient deep-red and near-infrared thermally activated delayed fluorescence (DR/NIR-TADF) materials was still under-researched by now. Herein, we designed and synthesized a series of efficient red/DR TADF emitters. Their emission wavelengths were rationally regulated into DR region via introducing strong electron-withdrawing groups from pyridinyl (PY) to trifluoromethyl (CF3) and to cyano (CN). The internal conversion (IC) process of these emitters was suppressed greatly via the incorporation of fused polycyclic aromatics (dibenzo[a,c]phenazine). Furthermore, the structural relaxation of their excited states was also reduced due to the restricted σ bond rotation between donor (D) and acceptor (A) units. As a result, these red/DR emitters showed high photoluminescence quantum yields (PLQYs) and excellent electrofluorescence performance. Particularly, OLEDs based on CN-TPA showed remarkably high maximum external quantum efficiencies (EQEs) of 22.80% at 668 nm, 18.41% at 688 nm and 15.05% at 698 nm, which were among the best values for reported TADF emitters. This result may provide a straightforward design strategy for efficient DR/NIR TADFs through optimizing the acceptor strength of rigidified polyaromatic frameworks.

深红色和近红外有机发光二极管（DR / NIR-OLED）显示了广泛的应用，例如医疗保健和夜视。但是，由于能隙定律，红色发射器通常表现出严重的非辐射发射，并且目前仍在研究有效的深红色和近红外热激活延迟荧光（DR / NIR-TADF）材料的开发。在这里，我们设计并合成了一系列高效的红色/ DR TADF发射器。通过将强大的吸电子基团从吡啶基（PY）引入三氟甲基（CF3）和氰基（CN），可以将它们的发射波长合理地调节到DR区。通过结合稠合的多环芳族化合物（二苯并[a，c]吩嗪），大大抑制了这些发射体的内部转化（IC）过程。此外，由于施主（D）和受主（A）单元之间受限制的σ键旋转，它们的激发态的结构弛豫也降低了。结果，这些红色/ DR发射器显示出高的光致发光量子产率（PLQYs）和出色的电致荧光性能。特别是，基于CN-TPA的OLED在668 nm处具有22.80％的极高的最大外部量子效率（EQE），在688 nm处具有18.41％的极高外部量子效率，在698 nm处具有15.05％的极高外部量子效率，这是已报道的TADF发射器的最佳值。通过优化刚性聚芳构架的受体强度，该结果可为有效的DR / NIR TADF提供一种直接的设计策略。这些红色/ DR发射器显示出高的光致发光量子产率（PLQYs）和出色的电致荧光性能。特别是，基于CN-TPA的OLED在668 nm处具有22.80％的极高的最大外部量子效率（EQE），在688 nm处具有18.41％的极高外部量子效率，在698 nm处具有15.05％的极高外部量子效率，这是已报道的TADF发射器的最佳值。通过优化刚性聚芳构架的受体强度，该结果可为有效的DR / NIR TADF提供一种直接的设计策略。这些红色/ DR发射器显示出高的光致发光量子产率（PLQYs）和出色的电致荧光性能。特别是，基于CN-TPA的OLED在668 nm处具有22.80％的极高的最大外部量子效率（EQE），在688 nm处具有18.41％的极高外部量子效率，在698 nm处具有15.05％的极高外部量子效率，这是已报道的TADF发射器的最佳值。通过优化刚性聚芳构架的受体强度，该结果可为有效的DR / NIR TADF提供一种直接的设计策略。