Enhanced performance of organic light-emitting diodes by integrating quasi-periodic micro-nano structures.

To integrate a quasi-periodic micro-nano structure (PMS) to the organic light-emitting devices (OLEDs) is an efficient way to enhance the performance of OLEDs. In this paper, the PMS prepared by the phase separation of Polystyrene and Poly (methyl methacrylate) was integrated to the OLEDs with the structures of Glass/PMS/Ag (30 nm)/MoO (5 nm)/(NPB) (40 nm)/(Alq) (60 nm)/LiF (0.5 nm)/Al (150 nm). The maximum luminance intensity and external quantum efficiency increased to 10700 cd/m and 1.11 %, which is 48 % and 44 % higher than that of 7209 cd/m and 0.77 % of the planar reference device. The enhanced performance of OLEDs was ascribed to the attenuation of surface plasmon polariton loss caused by the PMS, which was testified by the Finite-Difference Time-Domain (FDTD) simulation. The PMS was also transferred to the hole transfer layer (PEDOT: PSS) of OLEDs by nano-imprinting lithography with the structure of Glass/(ITO) (100 nm)/PEDOT: PSS (100 nm) (with PMS)/NPB (10 nm)/Alq (50 nm)/LiF (0.5 nm)/Al (100 nm). The performance was also improved by the optimized PMS and the light out-coupling efficiency increased to about 49.5 %, which is much higher than that of 28.8 % in the OLEDs with PMS Ag anode and 20 % in the planar reference devices. This suggests that the PMS can improve the OLED device performance regardless of the functional layer in which the PMS is integrated.