**5. Conclusion**

Single phase polycrystalline Cu2O thin films on Ti substrate can be electrodeposited using an acetate bath in a potential range of 0 to -300 mV Vs SCE. Thin films are well adherent to the Ti substrate and uniform having grain size of ~1-2 m. Cu2O deposited in an acetate bath at the pH of 6.6 produces n-type photoconductivity in a PV applications. The n-type photoconductivity of the as-grown Cu2O thin film can be converted to p-type by annealing the films at 300 oC in air. Therefore, it is reasonable to believe that the origin of the n-type Cu2O is the oxygen ion vacancies created in the crystal lattice, and the conductivity-type conversion is due to the increment of the oxygen content in the lattice with annealing in air. Single phase polycrystalline CuO thin films can be prepared by annealing the electrodeposited Cu2O at 500 oC for 30 min in air. Films produce p-type photoresponse in a PEC. Well covered n-type Cu2O thin film can be electrodeposied on Ti/CuO electrode at -550 mV Vs the SCE in an acetate bath. Films consist of microcrystallites of about 1 m and are well adherent to the CuO. By depositing a suitable mettle grid on the Cu2O thin film, p-CuO/n-Cu2O heterojunction solar cell can be fabricated. The Ti*/*CuO*/*Cu2O*/*Au heterojunction solar cell results in Voc of 210 mV and Jsc of 310 μA. This initial stage performance can be enhanced by depositing very thin Cu2O films leading to minimize the resistance of the Cu2O and choosing better ohmic contact to the Cu2O. Best ohmic contact to the n-type Cu2O may be Al but not the Au. X-ray diffractions and the X-ray absorption spectra, using the synchrotron radiation, reveal that Cu2O and CuO are high quality semiconducting thin films (free of amorphous phases) but amorphous structure is formed between CuO and Cu2O while Cu2O deposition on CuO.

#### **6. Acknowledgment**

Prof. W. Siripala, Professor of Physics, Department of Physics, University of Kelaniya, Sri Lanka and Prof. M. Hidaka, Department of Fundamental Physics, Graduate School of Science, Kyushu University, Japan are gratefully acknowledged for their invaluable advice, guidance and encouragement.
