The influence of morphology of electrodeposited Cu2O and Fe2O3 on the conversion efficiency of TiO2 nanotube photoelectrochemical solar cells

Titania (TiO2) nanotubes have broad potential for photoelectrochemical solar cell applications for the production of hydrogen, due to their high surface area and 1D transport properties. However, TiO2's large bandgap of 3.2 eV limits its absorption to the UV portion of the solar spectrum. Two candidate materials investigated in this experiment are cuprous oxide (Cu2O) and hematite (α-Fe2O3). We have used electrodeposition to pair these narrow bandgap (∼2 eV) materials with TiO2 and investigated their photoelectrochemical response. We show that the photoelectrochemical performance in the visible can be enhanced with the addition of these two materials, resulting in integrated quantum efficiencies of up to 2%. We have also identified that there is a strong morphological link between the photoelectrochemical performance of Cu2O on TiO2 nanotubes due to a light shadowing effect, but that the Fe2O3 is more flexible in terms of what morphology can produce enhanced photocurrent efficiencies.