Photovoltaic characteristics of dye-sensitized surface-modified nanocrystalline SnO2 solar cells

Zinc-modified nanocrystalline SnO2 electrodes are prepared by chemical treatment of the commercial SnO2 colloid with zinc acetate and their thickness effects on photovoltaic characteristics are investigated. Open-circuit voltage (Voc) and fill factor increase with increasing zinc concentration, while short-circuit photocurrent (Jsc) 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 10 mol.% Zn2+ with respect to Sn4+. As increasing thickness of the films based on 10 mol.% zinc-modified SnO2 ranging from 0.76 to 8.12 μm, Jsc increases, reaches maximum and then decreases without change in Voc. The highest conversion efficiency of about 3.4% is achieved under 1 sun of AM 1.5 irradiation for the ∼6.3 μm-thick 10 mol.% zinc-modified SnO2 film with Jsc of 9.09 mA/cm2, Voc 600 mV and fill factor 62%.