Performance of organic light emitting diodes with MoO3 and PEDOT:PSS as double hole injection layers

The carrier injection capability of organic light emitting diodes (OLED) has a big influence on its performance such as the brightness and efficiency. Poly(3,4- ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) is the most commonly used hole injection material in OLED. However, PEDOT: PSS is hygroscopic and acidic, so it will corrode the ITO electrode and deteriorate the long-term performance of the device. In this paper, a P-type metal oxide- MoO
3
is introduced between ITO and PEDOT:PSS by thermal evaporation, and MoO
3
films of different thicknesses are made to explore the influence of MoO
3
thickness on device performance. Studies show that the introduction of MoO
3
not only enhances the hole injection capability, but also acts as a buffer layer between ITO and PEDOT:PSS to prevent the acidic and hygroscopic PEDOT:PSS from corroding the electrode. The MoO
3
/PEDOT:PSS double hole injection layer improves the efficiency and stability of the device.