Doping-free organic light-emitting diodes (OLEDs) have attracted continuous attention owing to reduced phase separation, better repeatability, and low cost. Despite demonstrating great potential for white OLEDs (WOLEDs), development of phosphorescent materials capable of achieving high performance with low voltage, high luminance, and low efficiency roll-off simultaneously, still remains a significant challenge. Herein, we design three orange-red Ir(III) phosphors employing functionalized 1,2-diphenylbenzimidazole as main ligands. Clear relationship between structures and electroluminescence (EL)-performances has been established by comprehensively studying their emission properties and intrinsic carrier transporting abilities. Designed phosphor SFIrbiq with spirobifluorene moiety showing negligible intermolecular interactions and balanced carrier transporting ability, not only achieves favorable monochromatic doping-free device but also high-performance doping-free WOLEDs. Optimized WOLED realizes low voltages (2.5 V at 1 cd m⁻², 3.3 V at 100 cd m⁻², and 4.2 V at 1000 cd m⁻²), maximum brightness of 34 505 cd m⁻² and efficiencies of 24.2 cd A⁻¹, 21.7 lm W⁻¹, 10.3%. Such doping-free hybrid WOLED also achieves low efficiency roll-off of 5% for external quantum efficiency (EQE) at 1000 cd m⁻². The device performance can be further improved by employing doping-free all-phosphorescent device structure, achieving maximum efficiencies of 33.3 cd A⁻¹, 32.4 lm W⁻¹, and 16.9%. The results are promising among reported doping-free three-color WOLEDs, paving a feasible way to development of efficient Ir(III) phosphors and doping-free WOLEDs.

由于减少了相分离，更好的可重复性和低成本，无掺杂有机发光二极管（OLED）引起了持续的关注。尽管显示了白色OLED（WOLED）的巨大潜力，但能够同时实现低电压，高亮度和低效率滚降的高性能磷光材料的开发仍然是一项重大挑战。在这里，我们设计了三个橙红色的Ir（III）荧光粉，采用功能化的1,2-二苯基苯并咪唑作为主要配体。通过全面研究其发射特性和固有的载流子传输能力，已经建立了结构与电致发光（EL）性能之间的明确关系。设计的具有螺二芴部分的荧光粉SFIrbiq显示出可忽略的分子间相互作用和平衡的载流子传输能力，不仅获得了良好的单色免掺杂器件，而且还实现了高性能的免掺杂WOLED。经过优化的WOLED可实现低电压（1 cd m时为2.5 V^-2，3.3 V以100cd米^-2，和在1000cd米4.2V，^-2），34 505 CD米最大亮度^-2和24.2 CD A的效率^-1，21.7流明w ^ ^-1，10.3％。对于1000 cd m ^-2的外部量子效率（EQE），这种无掺杂的混合WOLED还能实现5％的低效率滚降。器件的性能可以通过采用无兴奋剂的所有磷光器件结构，实现了33.3 CD A的最大效率进一步提高^-1，32.4流明w ^ ^-1，和16.9％。在报道的无掺杂三色WOLED中，这一结果令人鼓舞，为开发高效的Ir（III）荧光粉和无掺杂WOLED铺平了可行的途径。