Abstract:
Cuprous oxide (Cu2O) homojunction thin films on Ti substrates were fabricated by an
electrochemical deposition in which a p-Cu2O layer was deposited on an n-Cu2O layer by carefully
controlled bath conditions. It was found that the open-circuit voltage of the homojunction solar
cell was significantly influenced by the pH of the lactate bath. The variation of the pH was used to
achieve the best possible crystal orientation for homojunctions. The crystallinity and morphology of
the products were characterized by X-ray diffraction (XRD), high-energy x-ray diffraction (HEXRD),
and scanning electron microscopy (SEM). The current density voltage (J-V) analysis showed that the
sulfur treatment and annealing enhanced the photocurrent by ten-fold compared to the untreated
and unannealed homojunction solar cell. X-ray photoelectron spectroscopy (XPS) studies confirmed
that the sulfur treatment eliminated the surface CuO and formed a thin layer of CuS, which was very
useful to make the front Ohmic contact. Transient measurements confirmed that the p-type Cu2O layer,
which was subjected to sulfur treatment, significantly reduced the recombination, thus enhancing the
efficiency of the solar cell. The best sulfur treated annealed Ti/n-Cu2O/p-Cu2O/Au solar cell produced
an energy conversion efficiency of 2.64% with an open-circuit voltage of 490 mV and a short circuit
current density of 12.8 mA cm−2 under AM 1.5 illumination.
