An analysis of temperature dependent current-voltage characteristics of Cu₂O-ZnO heterojunction solar cells

Carrier transport and recombination mechanisms in Cu₂O-ZnO heterojunction thin film solar cells were investigated through an analysis of their current-voltage characteristics in the dark and under various illumination intensities, as a function of temperature between 100 K and 295 K. The Cu ₂O-ZnO heterojunction solar cells were prepared by metal organic chemical vapor deposition of Cu₂O on ZnO films sputtered on transparent conducting oxide coated glass substrates. Activation energies extracted from the temperature dependence of the J-V characteristics reveals that interface recombination is the dominant carrier transport mechanism. Tunneling across an interfacial barrier also plays an important role in current flow and a thin TiO₂ buffer layer reduces tunneling. A high open circuit voltage at low temperature (∼ 0.9 V at around 100 K) indicates that Cu₂O-ZnO heterojunction solar cells have high potential as solar cells if the recombination and tunneling at the interface can be suppressed at room temperature.