Carbazole or acridan-substituted dibenzo[a,c]phenazines (CzDbp and AcDbp, respectively) were synthesized and investigated exploiting the donor-acceptor-donor (D-A-D) architecture expecting thermally activated delayed fluorescence (TADF) in both cases. Unexpectedly, while experimental microseconds-lived TADF behaviour was observed for AcDbp efficiency of which was found to be dependent on environment, CzDbp exhibited nanosecond-lived fluorescence complemented by triplet-triplet annihilation (TTA). Theoretical calculations by means of the ωB97XD functional with optimally tuned range separation parameter ω, were performed for both molecules, supporting their experimentally established electrochemical, optical and photophysical properties. Using the same emitter and device structure, CzDbp as the bipolar host allowed to achieve by 12.5% better external quantum efficiency and better roll-off efficiency of organic light-emitting diodes (OLEDs) in comparison to that of OLEDs based on the commercial host 1,3-bis(N-carbazolyl)benzene (mCP). In optimized OLED structure, device based on CzDbp host showed higher external quantum efficiency reaching 15.9% and lower roll-off efficiency in comparison to that of reference devices containing commercial hosts. This achievement can be explained by both the fast TTA triplet harvesting enhancing the substantial fluorescence efficiency of CzDbp, and by relatively high charge mobilities exceeding 10^-3 cm²/V·s for holes and 10^-4 cm²/V·s for electrons. CzDbp and AcDbp as TADF/TTA emitters were used, respectively, external quantum efficiencies of 19.4% and 22.1% for doped yellow and orange devices were achieved. The detailed discussion on TADF mechanism is presented, and the new “dynamical” state-energy diagram is proposed as the means allowing to better understand the TADF mechanism and the experimental results.

合成并研究了咔唑或a啶取代的二苯并[a，c]吩嗪（分别为CzDbp和AcDbp），并利用了供体-受体-供体（DAD）结构，期望在两种情况下均能热激活延迟荧光（TADF）。出乎意料的是，虽然观察到AcDbp效率的实验微秒级TADF行为，但发现其效率取决于环境，而CzDbp呈现出纳秒级荧光，并由三重态-三重态an灭（TTA）补充。借助于具有最佳调节范围分离参数ω的ωB97XD官能团，对两个分子进行了理论计算，从而支持了它们在实验上建立的电化学，光学和光物理性质。使用相同的发射极和器件结构，与基于商用主机的OLED相比，作为双极主体的CzDbp可以使有机发光二极管（OLED）的外部量子效率提高12.5％，并且滚降效率更高。 ，3-双（N-咔唑基）苯（mCP）。在优化的OLED结构中，基于CzDbp的设备与包含商用主机的参考设备相比，该主机显示出更高的外部量子效率，达到15.9％，并且具有更低的滚降效率。这一成就可以通过二者来解释快速TTA三重收获增强的实际荧光效率CzDbp，并且通过相对高的电荷迁移率超过10 ^-3厘米² / V·s的空穴和10 ^-4厘米² / V·s的电子供。使用CzDbp和AcDbp作为TADF / TTA发射体，掺杂的黄色和橙色器件的外部量子效率分别为19.4％和22.1％。提出了关于TADF机制的详细讨论，并且新的提出“动态”状态能图作为更好地了解TADF机理和实验结果的手段。