Morphological effects on optical and electrical properties of ZnO nanostructures

Morphology control of semiconductor nanostructures is of great interest in recent years owing to their unique capabilities in achieving desired chemical and physical properties as well as enabling great potential in electronic and optoelectronic applications. In this paper, we review our recent study on morphological control of ZnO nanocones and how the optical and electrical properties of such nanostructure-based photovoltaic solar cells are affected. The nanocone shape is obtained by altering the ratio of oxygen to argon gas during thermal chemical vapor deposition. The nanocones grown on Si substrates show antireflective properties in a broad spectral range. We further found that incident light was confined in the nanocones, which enhances the antireflective properties through multi-reflection/absorption. The performance dependency of a ZnO-CdTe solar cell on the morphology of ZnO was explored by introducing the nanocones. Small junction area and strong electric field at the tip of nanocones contribute to effective charge transport across the heterojunction, resulting in improved the conversion efficiency of solar cells.