“…Until now, the most used TCO is indium-doped tin oxide (ITO), which presents high transmission in the visible and an electrical resistivity of up to 120 µΩcm 3,4 , but its high cost and toxicity and the scarcity of indium drive the search for alternative materials. Among TCO's, zinc oxide (ZnO) is versatile owing to its properties such as a direct high energy band-gap (~3.3 eV), high exciton binding energy (60 meV) 5 , as well as being a material composed of cheap, abundant, non-toxic elements, and readily deposited by several techniques [6][7][8][9] . ZnO is an intrinsic n-type semiconducting material, and to improve its electrical properties a dopant that provides charge carriers is used.…”