Polarity-dependant Performance of p-Cu2O/n-ZnO Heterojunction Solar Cells

Abstract

This work presents a simple electroplating route for tuning the degree of extended growth of ZnO nanostructures along the (0001) axis, subsequently producing regular hexagonal disk-like nanocrystals at one extreme and hexagonal rod of various lengths at the other. Heterostructural p-Cu2O/n-ZnO solar cells are fabricated by the consecutive electrochemical deposition of n-ZnO nanodisks or nanorods, followed by deposition of the p-Cu2O layer on a transparent conductive substrate. The two shapes of ZnO nanodisks and nanorods are synthesized in the electrolytes of NO3− and Cl-, respectively, which are attributed to the specific ion adsorption. Their XRD patterns reveal that the relative intensities of (100) and (002) peaks from the nanodisks and nanorods vary with the degree of polarity in the ZnO nanostructures. The cell performance measurements clearly indicate that the polar facets of nanodisks yields a conversion efficiency twice higher than that of ZnO nanorods with nonpolar-facets owing to the efficient charge separation in the polar surfaces that a possess strong spontaneous polarization. Importantly, the proposed strategy enhances the solar cell performance as achieved by electrochemical deposition is highly promising for use in producing inexpensive and environmentally friendly solar devices.