ZnO-CuO core-shell heterostructure for improving the efficiency of ZnO-based dye-sensitized solar cells

In this work, the integration of ZnO-CuO core-shell nanostructures shows improvement in the conversion efficiency of ZnO-based dye-sensitized solar cells (DSSCs). This is due to CuO acting as a secondary absorption layer that allows the absorption of near-infrared (NIR) light increasing the generated photocurrent in the device, and as a blocking layer that reduces electron-hole recombination. The ZnO core and encapsulating CuO shell are synthesized through chemical vapor deposition (CVD), and thermal oxidation of a Cu seed layer, respectively. The crystallinity of the synthesized ZnO and CuO is analyzed by X-ray diffraction (XRD). Scanning electron microscope (SEM) images show the change in morphology through the steps of Cu seed layer deposition and thermal oxidation of this layer. To determine optical properties of CuO on ZnO nanorods, UV-Vis-NIR photospectrocopy is used. The comparison of conversion efficiency of DSSCs using two different photoelectrodes (i.e. ZnO nanorods versus ZnO-CuO core-shell nanostructure) is performed by I-V measurements.