Merging thermally activated delayed fluorescence (TADF) and mechanochromic luminescence (MCL) into one single molecule is a promising strategy for developing multifunctional organic materials. Herein, a unique multifunctional molecule TPA‐DQP, comprising a large π‐conjugated diquinoxalino[2,3‐a:2′,3′‐c]phenazine (DQP) as the acceptor and triphenylamine (TPA) as the donor, is designed and synthesized. TPA‐DQP possesses polymorphism, efficient TADF emission as well as MCL property with high‐contrast in emission colors from 576 to 706 nm. Reversible crystal‐to‐crystal phase transitions in response to external stimuli such as vapor fuming and heating are realized on the basis of the two polymorphs of TPA‐DQP. The distinct crystal‐to‐crystal phase transition is attributed ultimately to the change of packing arrangements and intermolecular interactions of the two polymorphs under stimuli. Furthermore, TPA‐DQP‐based organic light emitting diode (OLED) device achieves external quantum efficiency as high as 18.3% at 676 nm, which represents the best performance for deep‐red OLEDs based on MCL‐active TADF emitters. This study reports a novel MCL‐active TADF material that exhibits crystal‐to‐crystal phase transition and brings insight into the underlying relationship between molecular packing modes and the photoluminescent behavior.

中文翻译：

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具有高对比度发光变化的可逆晶体到晶体的相变，用于热激活的延迟荧光发射器

将热活化延迟荧光（TADF）和机械致变色发光（MCL）合并为一个分子是开发多功能有机材料的有前途的策略。在此，一个独特的多功能分子TPA-DQP，包含一个大的π-共轭二喹喔啉[2,3-- a：2'，3'- c设计合成了吩吩嗪（DQP）作为受体，三苯胺（TPA）作为供体。TPA-DQP具有多态性，有效的TADF发射以及MCL特性，在576至706 nm的发射颜色中具有高对比度。在TPA-DQP的两个多晶型的基础上，实现了响应外部刺激（如蒸汽发烟和加热）的可逆晶相转变。晶体到晶体的独特相变最终归因于在刺激下两个多晶型物的堆积排列和分子间相互作用的变化。此外，基于TPA-DQP的有机发光二极管（OLED）器件在676 nm处实现了高达18.3％的外部量子效率，这代表了基于MCL有源TADF发射器的深红色OLED的最佳性能。