Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely used conductive polymer in organic light-emitting devices. However, its strong acidity and fluorescence quenching effect seriously affect the overall device performance. We report a cost-effective method to address the above concerns by diluting PEDOT:PSS with deionized water, which effectively reduced the film thickness and the acidity. Therefore, the fluorescence quenching occurring at the interface was alleviated. Using the modified PEDOT:PSS as the hole injection layer, the external quantum efficiency of the de...