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 Cu2O–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.