The configuration of the OLED device is like this : ITO/PEDOT:PSS(Ag nanoparticle) /NPB/Alq3/Al
The effect of Ag nanoparticles in the hole injection layer on the performance of Organic Light Emitting Diodes(OLED) was investigated.
The hole mobility in the hole injection layer seems to be increased by Ag nanoparticles.
The increased current in the hole injection layer increased the emission efficiency of the OLED.
Initially, we try to incorporate silver nanoparticles(diameter:30nm) directly into the hole injection layer. However the Ag nanoparticles are aggregated into big particles, ( size 1∼2 μm). We can confirm this behavior by the optical microscope. Thus, PEDOT:PSS/Ag nanoparticles solutions were filtered before spin-coating and big particles were eliminated by this process.
The several silver nanoparticles concentration were selected (0.05, 0.1, 0.25 wt % of the silver nanoparticles was mixed with PEDOT;PSS solutions). Theses solutions were spin-coated on the ITO layer with 3000 rpm for 60 secs. The spin coated Ag, PEDOT:PSS solutions were heat treated at 100 °C in 30 min. The big Ag agglomerate was not observed in the optical microscope. Then the thermal evaporation of the NPB and Alq3 layer was conducted.
The current-voltage relation was measured for the device and compared with the OLED device without Ag particle. The lumninance of the devices are also measured. The Ag nanoparticle increases the deriving current and thus increases the quantum efficiency of the OLED.