Zinc-modified nanocrystalline SnO 2 electrodes are prepared by chemical treatment of the commercial SnO 2 colloid with zinc acetate and their thickness effects on photovoltaic characteristics are investigated. Open-circuit voltage (V o c ) and fill factor increase with increasing zinc concentration, while short-circuit photocurrent (J s c ) decreases. The normalized incident photon-to-current conversion efficiency (IPCE) shows that increase of zinc concentration utilizes long wavelength light. Concerning the conversion efficiency, optimal concentration within the present experiment is found to be 10mol.% Zn 2 + with respect to Sn 4 + . As increasing thickness of the films based on 10mol.% zinc-modified SnO 2 ranging from 0.76 to 8.12μm, J s c increases, reaches maximum and then decreases without change in V o c . The highest conversion efficiency of about 3.4% is achieved under 1 sun of AM 1.5 irradiation for the ~6.3μm-thick 10mol.% zinc-modified SnO 2 film with J s c of 9.09mA/cm 2 , V o c 600mV and fill factor 62%.