We present an energy band model and a method for filling p-type CuSCN in n-type porous TiO2 film. The energy band model is based on the interface energy levels between TiO2/CuSCN heterojunction and the aqueous electrolyte. The whole deposition process is divided into three stages: the uniform nucleation on the internal surface at positive potential, the crystal growth with the cathodic potential shifting negatively and the thermal activated growth at constant potential. This was demonstrated by the electrochemical experiment combining the hydrothermal process. It was found that the obtained TiO2/CuSCN heterojunction exhibited good rectification characteristics, indicating that an intimate electrical contact was formed between the large internal surface of TiO2 film and CuSCN. This novel hydrothermal-electrochemical method may be valuable for fabricating extremely thin absorber (eta)-solar cells and other semiconductor devices. (c) 2007 Elsevier Ltd. All rights reserved.