Coordination-complex polymer as an organic conductor for organic light-emitting diodes

A coordination complex of poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) is used to enhance the performance of organic light-emitting diodes. Use of the coordination complex formed by copper results in more than doubling the device lifetime when the complex is used as the hole injection layer (HIL) in place of the usual HIL of PEDOT-PSS that is not treated. Of the possible coordination complexes of PEDOT-PSS, the coordination complex formed with copper gives the best performance. The optimal mass ratio of CuSO4 and PEDOT-PSS solution in forming the complex is found to be 0.533. Surface morphology of the organic film formed and conductivity enhancement are the main factors that determine the optimal mass ratio.