A thin poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer enhances the AM1.5 power conversion efficiency of a PbSe quantum dot (QD)-containing photovoltaic device to 2.4%, from 1.5% for a standard PbSe QD device, a relative increase of 60%. Synchrotron X-ray reflectivity measurements reveal that the roughness of the interfaces between the various layers decreases dramatically in the presence of the PEDOT: PSS layer. In addition, the device life time under continuous simulated AM1.5 irradiation (100 mW cm(-2)), measured in terms of the time required to reach 80% of the normalized efficiency, for the PbSe QD device incorporating the PEDOT:PSS hole transport layer is six times longer than that of the standard PbSe QD device.