Research on Capping Layer for Top-emitting White OLED Micro-display Performance

We prepared top-emitting white organic light-emitting diode (OLED) devices using Alq3 and ZnSe as capping layers (CPLs). The basic structure of the OLED was ITO/NPB: LiQ(5%)(10 nm)/TCTA(20 nm)/FIrpic+3.5%Ir(ppy)3+0.5%Ir (MDQ)2(acac)(25 nm)/TPBI(10 nm)/LiF(5 nm)/Mg: Ag(10%)(12 nm)/ CPL. The brightness and current efficiency of OLED devices fabricated with Alq3 and ZnSe as CPLs are significantly better than those without capping layers. Moreover, the color coordinates (CIEX, CIEY) of the OLED devices prepared with ZnSe CPLs changed more smoothly with brightness, showing good color stability. Further, by changing the ZnSe thickness to optimize the device, when the CPL was 45 nm, the maximum current efficiency and maximum brightness of the device were 7.38 cd/A and 1410 cd/m², respectively, and the color coordinates were (0.30, 0.33).