In this study, the effect of ultraviolet treatment on the photovoltaic property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)/n-type Si (PEDOT:PSS/n-Si) diodes was examined. Power conversion efficiency of the PEDOT:PSS/n-Si diodes in the light (AM 1.5G, 100 mW/cm(2)) was improved by reducing the device series resistance by ultraviolet treatment. This study shows that conductivity of PEDOT:PSS plays an important role in PEDOT:PSS/n-Si photovoltaic devices. (C) 2010 Elsevier B.V. All rights reserved.