Oled With Tungsten Trioxide Buffer Layer Research

Tungsten oxide thin film was deposited by DC reactive magnetron sputtering and pulsed plasma deposition, by using a metal tungsten target with the purity of99.99%and another target made of tungsten oxide powder, respectively. The structure and the surface morphology of the thin films were characterized by XRD, AFM. OLED devices with the structure of IWO/NPB/Alq3/LiF/Al and IWO/WO3/NPB/Alq3/LiF/Al were fabricated. The effects of WO3thin layers on these two configuration OLED device performance were investigated. And the mechanism of two kinds of buffer layers were discussed.The structure and surface morphology of WO3thin films were analyzed by the methods of XRD and AFM and It shows the amorphous structure with relatively smooth surface.The effect of the sputtered WO3thin film as anode electrode work function modification layer on the OLED device performance was investigated. It is found thatas the working voltage achieves20V, the luminance of the IWO-OLED device becomes8791cd/m2, while the luminance of the IWO/WO3-OLED device becomes16690cd/m2. As the voltage reaches19V, the power efficiency of IWO/WO3-OLED device achieves the maximum, which is1.58lm/W. For IWO-OLED device, as the voltage reaches20V, the power efficiency of IWO/WO3-OLED device achieves the maximum, which is only0.76lm/W, and which is only half of the maximum power efficiency of IWO/WO3-OLED device. As the current density increases, the luminance efficiency goes up gradually. As the current density gets to181.9mA/cm2, the maximum of luminance efficiency is4.83cd/A. For IWO/WO3-OLED devices, as the current density reaches128.5mA/cm2(as the working voltage is19V), the luminance efficiency achieves the maximum, which is9.56cd/A and is approximately as twice as the former one. Overall, the performance of the IWO/WO3-OLED device gets much better in the luminance, the power efficiency and the luminance efficiency.The effect of the PPD prepared WO3thin film as anode electrode work function modification layer on the OLED device performance was also investigated. It is found that as the working voltage achieves20V, the luminance of the IWO-OLED device becomes8791cd/m2, and the luminance of the IWO/WO3-OLED device becomes17360cd/m2, which is almost double of another device. It is proved that inserting tungsten oxide buffer layer makes the luminance of OLED much better. For power efficiencyand luminance efficiency, however, the device does not get better. Because of these results, it can be concluded that the performance of the devices depends on the thickness of the tungsten oxide buffer layer. It is thought that the OLED device performance is closely related to the thickness uniformity and surface smoothness of the modification layerThe primary experimental results show that WO3work function modification layer is good for performance improvement of the OLED device. And further studying is needed such as the optimization of thickness and uniformity of WO3thin films.