紫外有机发光器件的激子形成区域优化与掺杂调控

Optimization of Excimer Forming Zone and Doping Engineering in Ultraviolet Organic Light-emitting Device

采用空穴传输兼发光层CBP和电子传输兼发光层TAZ构建了紫外有机电致发光器件（UVOLED）,通过调控功能层厚度可以优化激子形成区域,进而改善器件性能。实验结果表明：CBP厚度的变化对器件性能影响甚微,而TAZ厚度变化则有显著影响。当CBP和TAZ厚度分别为50 nm和30 nm时,获得了最大辐照度为4.4 m W/cm2@270 m A/cm2、外量子效率（EQE）为0.94%@12.5 m A/cm2,发光来自于CBP主发光峰~410nm以及TAZ肩峰~380 nm的UVOLED器件。在此基础上,通过在CBP/TAZ界面引入超薄[CBP∶TAZ]掺杂层可以加速激子复合,降低器件驱动电压,同时还有利于改善载流子平衡性,提高发光效率（最大EQE达到了0.97%@20 m A/cm2）而不影响光谱特性。

Ultraviolet organic light-emitting devices （UVOLEDs） were constructed by using hole- transport-emitting layer of 4,4＇-bis （carbazol-9-yl） biphenyl （CBP） and electron-transport-emitting layer of 3-（4-biphenyl） 4-phenyl-5-tert-butylphenyl-1,2,4-triazole （TAZ）. The excimer forming zone was optimized by adjusting the functional layer thickness, which contriuted to device perform- ance improvement. Our results indicate that the thickness variation of CBP has negligible effect on device performance while that of TAZ shows considerable effect. The maximum radiance of 4.4 mW/cm2@ 270 mAfcm2 and external quantum efficiency （EQE） of 0.94% @ 12.5 mA/cm2 are achieved in UVOLED with optimal thickness of 50 nm CBP and 30 nm TAZ. The electrolumines- cence peak of -410 nm and shoulder of - 380 nm, resulted from CBP and TAZ, respectively, are observed. Moreover, an ultrathin layer of [ CBP： TAZ] inserted between CBP and TAZ accelerates exeimer recombination rate and reduces driving voltage. Meanwhile, the carrier balance is improved aud thus device efficiency is slightly promoted （ the maxinunn EQE reaches 0.97% @ 20 mA/cm2 ） without altering spectrum characteristics.