The p-Cu2O/n-ZnO system is studied for its potential use as a photoactive heterojunction able to highly perform under visible light The main application deals with the degradation of organic dyes such as Orange II and the effects of Cu2O amount, Orange II concentration and light intensity are investigated Results show that the kinetics of degradation follows a pseudo-first order and the optimum sensitization effect is obtained using a 70% concentration of Cu2O. The degradation rate reaches its maximum (R-initial = 22.45 x 10(-2) mg l(-1) min(-1)) at 15 mg l(-1) of Orange II. The effect of the irradiation intensity is also investigated taking the electrical energy consumption per order of magnitude (EE/O) as a figure of merit The highest efficiency is obtained at an irradiation intensity of similar to 122 x 10(-5) kW with k(OBS) = 14 97 x 10(-3) min(-1) and EE/O, which corresponds to 12 54 kW h m(-3) of energy consumption This heterojunction allows a similar to 25% saving of electrical energy in comparison to the p-Cu2O/n-ZnO system, demonstrating the important role of the collector (C) 2010 Elsevier Ltd All rights reserved