Three kinds of Cu2O/ZnO heterostructure solar cells fabricated with electrochemical deposition and their structure-related photovoltaic properties

Three kinds of heterostructures composed of n-type zinc oxide (ZnO) film or nanowires or nanotubes covered with a p-type cuprous oxide (Cu2O) thin film respectively were fabricated with a simple and low-cost electrochemical deposition method. Structural, optical, and electrical studies identified the formation of the three kinds of proposed Cu2O/ZnO p-n heterojunctions. Photovoltaic properties measurements demonstrated that the Cu2O/ZnO film/nanowire based solar cell exhibited an obviously enhanced performance in comparison with the corresponding planar film solar cell due to the increased p-n junction area and improved charge carrier collection ability by using ZnO nanostructures. As a result, the Cu2O/ZnO film/nanotube solar cell had a maximum short-circuit current density under the same conditions. But, the open-circuit voltage and conversion efficiency decreased a little as the formation of ZnO nanotubes through chemical etching caused short circuits between the Cu2O layer and the conductive glass substrate. This study demonstrates that the proposed strategy to improve the solar cell performance realized by electrochemical deposition has potential in producing cheap and environmentally friendly solar cells.