Chemical Bath Deposition of Cu2O Thin Films on FTO Substrates: Effect of Sequential Deposition.

Sequential deposition of Cu2O on FTO substrates was performed by chemical bath deposition to increase the thickness of the films. The variation of structural, optical, morphological, and electrochemical properties was studied as the number of deposits increased. The increase of thickness promotes an increase in the crystallite size and the lattice constant a, as well as a shift in the region of the absorption of light towards lower energies, reducing the band gap and the transmittance slightly. Also, it was estimated a change in the preferential orientation from the plane (111) to (200), caused a decrease in the structural disorder (Urbach energy) as a consequence of reducing the conductivity. On the other hand, during the electrochemical characterization a p-type behavior was observed in all the films, and as the thickness increased a shift towards more positive flat band potential values and a decrease in the carrier concentration was observed, which is the result of the decrease in structural disorder. The photocurrent measurements showed that the best performances were by the thinnest and the thickest films because some are the most conductive and the others absorb more light.