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.