Influence of spin-coating rate and annealing method of water-soluble CuPc on blue organic light-emitting devices performance

Investigated in this work are the effects of the spin-coating rate of water-soluble copper phthalocyanine (WS-CuPc) and the annealing method of WS-CuPc films obtained at the optimal spin-coating rate on the performances of blue organic light-emitting devices (OLEDs). The OLEDs, eack with a configuration of ITO/WS-CuPc/NPB/Be(PP)2/LiF/Al, are fabricated by using WS-CuPc as hole injection layer, NPB as hole transport layer and Be(PP)2 as emission layer separately. In our experiments, a new annealing method of WS-CuPc is used first for heating the ITO glass, and then for spin-coating the WS-CuPc. The performances of the device prepared with the new annealing method are compared with those of the devices prepared with the traditional annealing method or no annealing treatment. And the effects of different annealing treatments on the surface topography are analyzed by atomic force microscope (AFM). The experimental results demonstrate that there exists an optimal spin-coating rate of WS-CuPc, about 3000 r/min. Based on the optimal spin-coating rate of WS-CuPc, the roughness of the film prepared with the new annealing method is lowest and the performances of the device are best.