Various size CdS nanoparticles have been synthesized on the TiO2 nanorod arrays by chemical bath deposition method with annealing treatment at different temperatures. The size and morphology of CdS nanoparticles can be observed from scan electron microscope and transmission electron microscopy images. Based on UV vis absorption measurement and photocurrent density-voltage characterization, the results display that compared with the device with the uniform size particles, the device with various size CdS nanoparticles shows the better performance with higher short-circuit current density, open-circuit voltage, and power conversion efficiency (PCE). Furthermore, the device sensitized by quantum dot-dye bilayer is fabricated and the PCE of the device enhances up to 2.81%, which is 1.6 times higher than that of the device sensitized by quantum dots. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.