MgF_2缓冲层对蓝光OLED性能的影响

Effects of the MgF_2 buffer layer on the properties of bule organic light-emitting diodes

为了提高蓝光有机电致发光器件(OLED)的发光性能,将MgF2缓冲层插入ITO阳极与空穴传输层NPB之间,通过优化MgF2的厚度,制备了结构为ITO/MgF2(x nm)/NPB(50nm)/DPVBi:DSA-ph(30nm)/Alq3(30nm)/LiF(0.6nm)/Al(100nm)的高性能蓝光器件。实验结果表明,MgF2厚为1.0nm时,器件性能最佳,对应的器件最大电流效率达到5.51cd/A,最大亮度为23 290cd/m2(10.5V),与没有MgF2缓冲层的标准器件相比,分别提高47.3%和25.2%。对ITO表面的功函数测量结果表明,MgF2缓冲层可以有效修饰ITO表面,降低ITO与NPB之间的势垒高度差,改善空穴的注入效率,从而导致电子和空穴的注入更加平衡,激发机制更高效,实现了高性能的蓝光发射,为实现高效而稳定的全彩显示和白光照明奠定了基础。

In order to improve the luminescence properties of the blue organic li ght-emitting diodes （OLEDs）,a thin buffer layer of MgF2is sandwiched betwee n the indium-tin-oxide （ITO） and the hole transporting layer of NPB in OLEDs.The structure is ITO/MgF2（x nm）/NPB（50nm）/DPVBi：DSA-ph（30nm）/Alq3（30nm）/LiF （0.6nm）/Al （100nm）.By optimizing th e thickness of MgF2buffer layer,the optimized OLED with a 1.0nm MgF2is obtained.The expe rimental results indicate that the devices with MgF2thin layer of 1.0nm can achieve a peak cu rrent efficiency of 5.51cd/A and the maximum luminance of 23290cd/m2（ at 10.5V）,which are improved by 47.3% and 25.2%,respectively,compared with the standard device without MgF2buffer l ayer.At the same time,the results of the measurement of the surface work function of ITO show th at the buffer layer of MgF2can modify the surface of the ITO and effectively decrease the b arrier height between ITO and NPB,improve the hole injection efficiency,which results in bet ter balanced injection of electron and hole,and more efficient exciton formation.So the perf ormance of the blue OLEDs has been improved,which makes the foundation in order to achieve high efficiency and stable full-color display and white OLEDs.