Gong Hao, Song Yixing, He Jingping, Wang Ping, Xiang Yuhao, Li Shuai, Yao Jiannian, Liao Bo, Liao Qing, Fu Hongbing
Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing, 100048, China.
College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang, Henan 473061, P. R. China.
Angew Chem Int Ed Engl. 2024 Mar 18;63(12):e202400089. doi: 10.1002/anie.202400089. Epub 2024 Feb 9.
Metal-organic phosphorescent complexes containing Ir or Pt are work horse in organic light-emitting diode (OLED) technology, which can harvest both singlet and triplet excitons in electroluminescence (EL) owing to strong heavy-atom effect. Recently, organic room-temperature phosphorescence (ORTP) have achieved high photoluminescence quantum yield (PLQY) in rigid crystalline state, which, however, is unsuitable for OLED fabrication, therefore leading to an EL efficiency far low behind those of metal-organic phosphorescent complexes. Here, we reported a luminescence mechanism switch from thermally activated delayed fluorescence (TADF) in single crystal microwires to ORTP in amorphous thin-films, based on a tert-butylcarbazole difluoroboron β-diketonate derivative of DtCzBF2. Tightly packed and well-faceted single-crystal microwires exhibit aggregation induced emission (AIE), enabling TADF microlasers at 473 nm with an optical gain coefficient as high as 852 cm . In contrast, loosely packed dimers of DtCzBF2 formed in guest-host amorphous thin-films decrease the oscillator strength of fluorescence transition but stabilize triplets for ORTP with a PLQY up to 61 %, leading to solution-processed OLEDs with EQE approaching 20 %. This study opens possibilities of low-cost ORTP emitters for high performance OLEDs and future low-threshold electrically injected organic semiconductor lasers (OSLs).
含有铱或铂的金属有机磷光配合物是有机发光二极管（OLED）技术中的主力军，由于强烈的重原子效应，它们能够在电致发光（EL）过程中同时捕获单线态和三线态激子。最近，有机室温磷光（ORTP）在刚性晶体状态下实现了高光致发光量子产率（PLQY），然而，这并不适用于OLED制造，因此导致EL效率远低于金属有机磷光配合物。在此，我们报道了一种发光机制的转变，即从单晶微线中的热激活延迟荧光（TADF）转变为非晶薄膜中的ORTP，这是基于一种二叔丁基咔唑二氟硼β-二酮衍生物DtCzBF2实现的。紧密堆积且晶面良好的单晶微线表现出聚集诱导发光（AIE），能够实现473nm的TADF微激光器，其光学增益系数高达852cm。相比之下，在客体-主体非晶薄膜中形成的DtCzBF2松散堆积二聚体降低了荧光跃迁的振子强度，但稳定了三线态以实现PLQY高达61%的ORTP，从而导致溶液处理的OLED的外量子效率（EQE）接近20%。这项研究为高性能OLED和未来低阈值电注入有机半导体激光器（OSL）的低成本ORTP发射体开辟了可能性。
