OLED具有自发光、高亮度、高对比度、柔性超薄、低功耗、视角广等诸多优点，成为显示领域的新宠儿。有机发光材料是OLED显示技术的基础，必须具有优异的固态量子产率，高效的激子利用率，快速而平衡的载流子注入和传输以及良好的热稳定性等特点。与聚集发光猝灭（ACQ）材料相比，聚集诱导发光（AIE）材料在光电器件、生物探针和化学传感等领域表现出独特的优势，是非掺杂OLED器件的理想发光材料。目前所开发的大多数AIE材料仍然属于荧光材料，其在器件中的最大激子利用率只有25%，很大程度上限制了器件效率的进一步提高，所以在AIE材料中引入新的光物理机制，如热活化延迟荧光（TADF）、三线态-三线态激子湮灭、室温磷光等，才有望在AIE材料的激子利用率和器件效率等方面取得更大突破。

近期华南理工大学唐本忠院士团队开发出了一类以苯甲酰基为电子受体，以二甲基吖啶和二苯并噻吩为电子给体的新型发光材料（DBT-BZ-DMAC），实现了AIE和TADF两种特性的有机结合，在保证高效固态发光的前提下，提高了材料在器件中的激子利用率。相关工作发表在《Advanced Functional Materials》上。

利用DBT-BZ-DMAC制备的非掺杂OLED器件[ITO/TAPC (25 nm)/DBT-BZ-DMAC (35 nm)/TmPyPB (55 nm)/LiF (1 nm)/Al]的启动电压低至2.7 V，最大亮度、最大电流效率和最大外量子效率分别达到27270 cd m^‒2、43.3 cd A^‒1和14.2%。得益于材料的AIE特性，非掺杂器件的外量子效率从最大值到亮度为1000 cd m^‒2时的效率滚降几乎为零，是目前报道的非掺杂器件中最低的。该工作不仅开发出了一类结构简单，适合大规模生产的高效发光材料，而且为解决目前TADF材料器件效率滚降严重问题提供了新思路。高效非掺杂器件的获得，也有助于简化器件结构和制备工序，降低生产成本。

论文链接：http://dx.doi.org/10.1002/adfm.201606458

论文摘要：

Achieving High-Performance Nondoped OLEDs with Extremely Small Efficiency Roll-Off by Combining Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence

Luminescent materials with thermally activated delayed fluorescence (TADF) can harvest singlet and triplet excitons to afford high electroluminescence (EL) efficiencies for organic light-emitting diodes (OLEDs). However, TADF emitters generally have to be dispersed into host matrices to suppress emission quenching and/or exciton annihilation, and most doped OLEDs of TADF emitters encounter a thorny problem of swift efficiency roll-off as luminance increases. To address this issue, in this study, a new tailor-made luminogen (dibenzothiophene-benzoyl-9,9-dimethyl-9,10-dihydroacridine, DBT-BZ-DMAC) with an unsymmetrical structure is synthesized and investigated by crystallography, theoretical calculation, spectroscopies, etc. It shows aggregation-induced emission, prominent TADF, and interesting mechanoluminescence property. Doped OLEDs of DBT-BZ-DMAC show high peak current and external quantum efficiencies of up to 51.7 cd A⁻¹ and 17.9%, respectively, but the efficiency roll-off is large at high luminance. High-performance nondoped OLED is also achieved with neat film of DBT-BZ-DMAC, providing excellent maxima EL efficiencies of 43.3 cd A⁻¹ and 14.2%, negligible current efficiency roll-off of 0.46%, and external quantum efficiency roll-off approaching null from peak values to those at 1000 cd m⁻². To the best of the authors’ knowledge, this is one of the most efficient nondoped TADF OLEDs with small efficiency roll-off reported so far.

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