Fabrication and characterization of Cu/Cu₂O/CuO/ZnO/Al–ZnO/Ag heterojunction solar cells

Abstract

Glass/Cu/Cu2O/CuO/ZnO/Al–ZnO/Ag heterojunction solar cell structures have been successfully constructed by using a direct current magnetron sputtering technique. Photovoltaic (PV) solar cells fabricated as above indicated a conversion efficiency >5.6% and an open-circuit voltage (VOC) ∼0.57 V. Surface modification of CuO during ZnO deposition was identified as the limiting factor for obtaining higher performance heterojunction cells. Magnetron sputtering acted as a promising inexpensive and scalable technique for the fabrication of the above heterojunction for PV application. The diode quality factor for different cells fabricated here varied between 3.35 and 5.6 which were quite high (>2) compared to that for an ideal one. These are connected with mechanisms like interface recombination and tunneling enhanced interface recombination. Series resistance varied between 18.05 and 19.8 Ω cm2 while shunt resistance varied between 495 and 524 Ω cm2. The minority carrier life time ∼7 ms suggested lower recombination losses in our cells culminating in higher short circuit current density compared to copper oxide based cells fabricated by others.