We designed and synthesized a series of spiro-configured bipolar hosts (CSC, DSD, TST, and NSN) comprising electron-transporting 4,5-diazafluorene and hole-transporting carbazole or diarylamine with thorough characterizations of their thermal, photophysical, electrochemical properties, and carrier mobilities. Time-of-flight (TOF) measurements and single-carrier devices revealed these compounds had good hole and electron mobilities (10−5 − 10−7 cm2 V−1 s−1) together with promising physical properties, rendering them good host materials for efficient electrophosphorescence. The green PhOLED with (PPy)2Ir(acac) as the emitter incorporating CSC as the host exhibited a remarkable high brightness of 260 000 cd m−2 at 2400 mA cm−2 (11 V) with the maximum external quantum efficiency (ηext) of 17.1%, the ηext remained as high as 15.4% under a high brightness of 10 000 cd m−2 at a low operating voltage of 5.1 V even without p–i–n device configuration. The NSN-based PhOLED with the red dopant Os(bpftz)2(PPhMe2)2 has a maximum brightness of 77 900 cd m−2 at 1100 mA cm−2 (10 V) with the maximum ηext of 19.5%. The ηext remained as high as 19.1% under a practical brightness of 1000 cd m−2 (4.6 V). These results suggest that the spiro-configured D–A hosts are well-suited for achieving highly efficient PhOLED with limited efficiencies roll-off.
我们设计并合成了一系列由电子传输的
4,5-二氮杂芴和空穴传输的
咔唑或二芳基胺组成的螺构型双极宿主(CSC、D
SD、TST 和 NSN),并对其热学、光物理性质、电
化学性质和载流子迁移率进行了全面的表征。飞行时间(TOF)测量和单载流子装置显示,这些化合物具有良好的空穴和电子迁移率(10-5 - 10-7 cm2 V-1 s-1)以及良好的物理性质,是高效电致
磷光的良好宿主材料。以(PPy)2Ir(acac)为发射体、CSC为宿主的绿色PhOLED在2400 mA cm-2 (11 V)的条件下,亮度高达260 000 cd m-2,最大外部量子效率(ηext)为17.1%;在5.1 V的低工作电压下,亮度高达10 000 cd m-2,即使没有p-i-n器件配置,ηext仍高达15.4%。使用红色掺杂剂 Os(bpftz)2(PPhMe2)2 的基于 NSN 的 PhOLED 在 1100 mA cm-2 (10 V)条件下的最大亮度为 77 900 cd m-2,最大 ηext 为 19.5%。在实际亮度为 1000 cd m-2 (4.6 V)时,ηext 仍高达 19.1%。这些结果表明,螺纹配置的 D-A 主基非常适合于实现效率有限的高效 PhOLED。