Highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as transparent electrodes for organic light‐emitting diodes (OLEDs) are doped with a new solvent 1,3‐dimethyl‐2‐imidazolidinone (DMI) and are optimized using solvent post‐treatment. The DMI doped PEDOT:PSS films show significantly enhanced conductivities up to 812.1 S cm−1. The sheet resistance of the PEDOT:PSS films doped with DMI is further reduced by various solvent post‐treatment. The effect of solvent post‐treatment on DMI doped PEDOT:PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated PEDOT:PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped PEDOT:PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized PEDOT:PSS films with the new solvent of DMI can be a promising transparent electrode for low‐cost, efficient ITO‐free white OLEDs.
