Fabrication and photovoltaic characteristics of Cu ₂O/TiO ₂ thin film heterojunction solar cell

A p-Cu ₂O/n-TiO ₂ thin film heterojunction solar cell has been fabricated by electrodeposition of Cu ₂O on radio-frequency sputtered n-TiO ₂ thin film. The heterojunction solar cell was characterized by X-ray diffraction, scanning electron microscopy and UV spectroscopy. Capacitance-voltage (C-V) and current-voltage measurements were performed. The values of barrier height and carrier concentration were estimated from the reverse bias C-V. The transport mechanism is related to space charge limited current and a trapped charge limited current having slope values of 1.95 and 3.5. Impedance measurement showed that electrical resistance decreases when the voltage is increased. The energy band diagram shows that the main-band discontinuity forms in the valence band. The ideality factor, barrier height and series resistance, fill factor and efficiency were also measured. The heterojunction solar cell exhibits a maximum fill factor and a power conversion efficiency of about 0.35 and 0.15% respectively.