Developing high-performance pure-blue and white organic light-emitting diodes (OLED) is one of the biggest challenges for thermally activated delayed fluorescence (TADF) technology, although great efforts have been made in designing new blue TADF emitters. Herein, we demonstrate that by virtue of solvatochromic characteristics for TADF molecules, host engineering can provide a feasible alternative to realize the high color purity and the state-of-the-art efficiencies on the basis of conventional blue TADF dyes. An electron-withdrawing diphenylphosphine oxide (DPPO) group is introduced at 4 position of symmetrical spirobi[xanthene] to construct 9,9′-spirobi[xanthen]-4-yldiphenylphosphine oxide (SXSPO) with the asymmetry of configuration and optoelectronic properties. Besides forming the ambipolar property and suppressing quenching, the steric and inductive effects of DPPO are spatially confined, which prevents the formation of high-polarity charge transfer excited states and the interaction between polar PO group and TADF dopants. Based on a conventional TADF emitter bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS), SXSPO dramatically improves the color purity of its pure-blue and white devices and realizes the external quantum efficiencies (η_EQE) beyond 20%. The power efficiency of the white devices reaches to ∼60 lm W⁻¹, demonstrating the potential applications as lighting source.

尽管在设计新的蓝色TADF发射器方面已付出了巨大的努力，但开发高性能的纯蓝色和白色有机发光二极管（OLED）是热激活延迟荧光（TADF）技术面临的最大挑战之一。在此，我们证明，借助TADF分子的溶剂化特性，宿主工程可以提供一种可行的替代方法，以在常规的蓝色TADF染料的基础上实现高色纯度和最先进的效率。将吸电子二苯膦氧化物（DPPO）基团引入对称螺双[x吨]的4位，以构建9,9'-螺双[黄嘌呤] -4-基二苯基膦氧化物（SXSPO）以及配置和光电特性的不对称性。除了形成双极性性质并抑制猝灭外，DPPO的空间和感应效应在空间上受到限制，这阻止了高极性电荷转移激发态的形成以及极性P O基团和TADF掺杂物之间的相互作用。SXSPO基于传统的TADF发射体双[4-（9,9-二甲基-9,10-二氢ac啶）苯基]砜（DMAC-DPS），极大地提高了其纯蓝色和白色器件的色纯度并实现了外部量子效率（η _EQE）超过20％。白色器件的功率效率达到〜60 lm W ^-1，证明了潜在的应用作为光源。