Analysis of the photocurrent from CuO/TiO2 nanostructured photoelectrodes to elucidate the benefits of nanocrystal size decrease

CuO/TiO 2 nanostructured photoelectrodes obtained with a modified immersion technique are analyzed, and their photocurrents are compared in order to study the effect of nanocrystals size decrease; which leads to a favorable conduction bands alignment. For this purpose, very small precursor concentration and immersion times are selected for CuO/TiO 2 film fabrication. This affects the amount of CuO deposited inside the TiO 2 mesoporous film and decreases the number of absorbed photons, as well as, the number of generated electron–hole pairs. Calculations account for these effects. When CuO nanocrystals size is reduced, CuO/TiO 2 energy bands alignment improves electron injection from CuO to TiO 2 but internal surfaces and defects acting as traps increase. This study considers the interplay of these phenomena. Results indicate that it is beneficial to reduce nanocrystal size in spite of internal surface recombinations.