Fabrication and characterization of electrodeposited Cu₂O p-n homojunction solar cells

Two device structures for electrodeposited Cu₂O p-n homojunction solar cells, substrate and superstrate, have been fabricated and characterized. The Cu₂O p-n homojunctions in these cells were prepared by a two-step sequential electrodeposition process. It was found that the open-circuit voltage of the cells was affected by solution pH during the deposition of the n-type Cu₂O layer. Solution pH controls oxygen incorporation and thus the native point defects in Cu2O, which in turn controls the flatband voltage of Cu₂O. A thermal stability study indicates that the performance of the Cu₂O solar cells is unstable at temperatures above 150 °C. For Cu₂O superstrate solar cells, it was found that the thickness of the p-type Cu₂O layer is critical to the performance of the cells. The opencircuit voltage, and thus the efficiency of the cells, is proportional to the thickness of the p-layer, and a 3 μm p-Cu₂O layer is necessary for good performance. The highest efficiency of 0.15 % is achieved in a Cu₂O substrate solar cell with an area of 0.01 cm².