The physical and photoelectrochemical characterizations of a new inorganic-organic hybrid single crystal material, synthesized by hydrothermal route, based on alpha-Keggin-type polyoxotungstate and Cu(I)-(trz) coordination complex, namely [Cu-6(trz)6][alpha-PW12O40](2)center dot H2O, [trz=1H-1,2,4-triazole] are investigated for the first time. The crystal structure, determined by single-crystal X-ray diffraction, reveals a 3-D supramolecular host-guest structure with Keggin anion as template. The diffuse reflectance indicates an optical transition at 2.91 eV, directly allowed, attributed to the Keggin polyoxoanions. The physical characterization shows a semiconductor behavior and the conductivity follows an exponential type law associated to a small polaron hopping between neighboring ions. The thermo-power measurement indicates n-type conduction with an electron mobility (0.54 x 10(-6) cm(2) V-1 s(-1)), thermally activated. The photoelectrochemical study, performed in Na2SO4 medium, confirms n-type conduction with a flat band potential of -0.65 V-SCE and electrons density of 6.59 x 10(18) cm(-3). The electrochemical impedance spectroscopy reveals the predominance of the bulk contribution with a constant phase element and Warburg diffusion. As application, the photo-degradation of Rhodamine B upon sunlight and UV irradiation is achieved by the radicals 02(center dot-) and OH center dot. The improved activity is attributed to the wide depletion width (460 nm) and the potentials of the valence and conduction bands close to the radicals levels. (C) 2015 Elsevier B.V. All rights reserved.