A organic light-emitting diode device with a structure of ITO/PEDOT:PSS/MEH-PPV/Al was fabricated. High electric field is applied vertically to the surface of the sample to polarize the PEDOT:PSS layer during the process of spin-coating. Due to the electric-field induced orientation of the PEDOT:PSS

the device with an appropriately treated PEDOT:PSS film as hole-injecting buffer layer exhibited significantly enhanced luminescence and decreased driving voltage. The results suggest that the electric field-induced orientation is useful for the improvement of device performance. And the polarized MEH-PPV layer exhibits a low resistance compared to the unpolarized layer. By looking at the PEDOT: PSS fabrication steps

it can be inferred that a gradient enrichment of negative PSS content can form at the top surface due to the attractive power of the external electric-field. This should aid charge injection into the MEN-PPV by gradually increasing the work function from the ITO surface to the MEN-PPV surface giving a graduated barrier to hole-injection.