A possibility of semiconductor-sensitized thin film solar cells have been proposed. Nanocrystalline In2S3-modified In2O3 electrodes were prepared with sulfidation of In2O3 thin film electrodes under H2S atmosphere. The band gap (E-g) of In2S3 estimated from the onset of the absorption spectrum was approximately 2.0eV. The photovoltaic properties of a photoelectrochemical solar cell based on In2S3/In2O3 thin him electrodes and I-/I-3(-) redox electrolytes were investigated. This photoelectrochemical cell could convert visible light of 400-700 nm to electron. A highly efficient incident photon-to-electron conversion efficiency (IPCE) of 33% was obtained at 410 nm. The solar energy conversion efficiency, eta, under AM 1.5 (100 mW cm(-2)) was 0.31% with a short-circuit photocurrent density (J(sc)) of 3.10 mA cm(-2) a open-circuit photovoltage (V-oc) of 0.26 V, and a fill factor (ff) of 0.38. (C) 2000 Elsevier Science B.V. All rights reserved.