Aligned ZnO/CdTe Core−Shell Nanocable Arrays on Indium Tin Oxide: Synthesis and Photoelectrochemical Properties

Abstract

Vertically aligned ZnO/CdTe core−shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap (∼1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of ∼5.9 mA/cm² has been obtained under visible light illumination of 100 mW cm⁻² with zero bias potential (<i>vs</i> saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications.