TiO2/Cu2O all-oxide heterojunction solar cells produced by spray pyrolysis

Here we present for the first time a TiO 2 /Cu 2 O all-oxide heterojunction solar cell entirely produced by spray pyrolysis onto fluorine doped tin oxide (FTO) covered glass substrates, using silver as a back contact. A combinatorial approach was chosen to investigate the impact of the TiO 2 window layer and the Cu 2 O light absorber thicknesses. We observe an open circuit voltage up to 350 mV and a short circuit current density which is strongly dependent of the Cu 2 O thickness, reaching a maximum of ~0.4 mA/cm 2 . Optical investigation reveals that a thickness of 300 nm spray pyrolysis deposited Cu 2 O is sufficient to absorb most photons with an energy above the symmetry allowed optical transition of 2.5 eV, indicating that the low current densities are caused by strong recombination in the absorber that consists of small Cu 2 O grains.