The development of highly efficient thermally activated delayed fluorescence (TADF) emitters is persistently pursued for the application of organic light-emitting diodes (OLED) in full-colour display and solid-state lighting. Herein, we present a heptagonal intramolecular-lock strategy to design high-performance TADF emitters. As a proof-of-concept, a new type of tribenzotropone (TBP) acceptor has been designed and synthesized by a cascade decarboxylative cyclization of aryl oxoacetic acid derivative with biphenyl boronic acid. Compared with the unlocked benzophenone (BP) acceptor, the TBP acceptor has a highly twisted heptagonal geometry with moderate rigidity and flexibility, which enables a high-performance TADF emitter with a small single-triplet energy gap(ΔE_ST) of 0.04 eV, a high photoluminescence quantum yield (Φ_PL) of 99% and a large horizontal orientation factor (Θ_//) of 84.0%. Consequently, highly efficient OLEDs with an external quantum efficiency as high as 33.8% are assembled, which is significantly higher than those of DPAC-BP with a highly rotatable BP acceptor (23.8%) as well as DPAC-FO with a rigid fluorenone (FO) acceptor (6.9%).

高效热激活延迟荧光（TADF）发射器的开发一直是有机发光二极管（OLED）在全彩显示和固态照明中的应用的追求。在此，我们提出了一种七边形分子内锁定策略来设计高性能 TADF 发射器。作为概念验证，通过芳基氧代乙酸衍生物与联苯硼酸的级联脱羧环化，设计并合成了一种新型三苯托酮（TBP）受体。与解锁的二苯甲酮（BP）受体相比，TBP受体具有高度扭曲的七边形几何形状，具有适度的刚性和柔性，这使得高性能TADF发射器具有0.04 eV的小单三重态能隙（Δ E _ST）， 99% 的高光致发光量子产率 ( Φ _PL ) 和 84.0% 的大水平取向因子 ( θ _// )。因此，组装了外量子效率高达33.8％的高效OLED，这明显高于具有高度可旋转BP受体的DPAC-BP（23.8％）以及具有刚性芴酮（FO）的DPAC-FO。 ）接受者（6.9%）。