Organic electroluminescent characteristics of compound PS:NPB hole transporting layer

Green organic light-emitting devices with the structure of indium-tin-oxide (ITO)/polystyrene (PS):N, N'-bis-(3-naphthyl)-N, N'-biphenyl-(1, 1'-biphenyl)-4, 4'-diamine (NPB)/tris-(8-hydroxyquinoline)-aluminum (Alq3)/Mg:Ag were fabricated. A doping system consisting of small-molecular hole transporting material NPB and polymeric matrix polystyrene (PS) was employed as the compound hole transporting layer (HTL), and the thin film preparation was simplified via the spin-coating technique. By adjusting the component ratio of the system, we constructed several devices with different concentration proportions of PS:NPB. The electroluminescent characteristics of the devices were investigated and discussed. The results demonstrate that the doping concentration of NPB has a remarkable impact on the optoelectric performance of both the HTL and the device. Optimum device performance could be obtained by choosing the best concentration proportion of PS:NPB to be 1:1. This contributes to the construction of compound functional layers of OLED devices and to the technical improvement.