The enhanced properties of amplified spontaneous emission and organic light emitting diodes based on Ag NPs doped hole transfer layer

The organic semiconductor lasers (OSLs) have been seen as a promising light source for future applications. Lower amplified spontaneous emission (ASE) threshold of the organic gain medium and optimized device structures are key factors to realize electrically pumped OSLs. In this paper, the silver nanoparticles (Ag NPs) doped PEDOT: PSS buffer layer was used to improve the ASE performance of BUBD-1 molecule and the optoelectronic performance of the corresponding organic light-emitting diodes (OLEDs). Compared with the reference device with pure PEDOT: PSS buffer layer, the lowest ASE threshold was obtained in CBP: 45 wt%BUBD-1 blend film at the optimal volume ratio 1:3 of PEDOT: PSS: Ag NPs, decreased by 6 times. Then the Ag NPs doped PEDOT: PSS buffer layer was used as both buffer layer and the hole transport layer in the OLEDs devices with CBP: 45 wt% BUBD-1 blend films as the emission layer. At the optimal volume ratio of PEDOT: PSS to Ag NPs, the maximum brightness increased more than 2 times to 7823 cd/m², and the maximum EQE increased nearly 2 times to 2.81%. The improved ASE performance of CBP: 45 wt%BUBD-1 blend films and optoelectronic properties of corresponding OLED devices can be attributed to both the localized surface plasmon resonance (LSPR) effect and the increased hole mobility caused by the addition of Ag NPs. The introduction of Ag NPs to the hole transfer layer of OLED devices may provide a potential method to realize the electrically pumped OSLs with the planar structures.