Decoration of Textured ZnO Nanowires Array with CdTe Quantum Dots: Enhanced Light-Trapping Effect and Photogenerated Charge Separation

Abstract

A large-area, nest-like ZnO nanowires (NWs) array was prepared through the oxidation reaction between zinc foil and (NH4)2S2O8 at 150 °C for 18 h. CdTe quantum dots (QDs) were linked chemically to the array to form CdTe/ZnO heterostructures based on the good affinity of carboxyl to zinc ions. The molar content of CdTe in the heterostructures can be controlled at the level of 1.2%, 5.1%, and 11.4%, which depends on the soaking time of ZnO array in CdTe solution. The measurements of the optical properties of the as-prepared CdTe/ZnO heterostructures reveal that they can harvest incident lights more efficiently than can unmodified ZnO NWs arrays, whose reflectance was decreased about 20%. The good light-trapping effect and the attachment of CdTe QDs significantly improve the photovoltaic properties of the heterostructure and result in a good rectifying behavior. The photoanode based on the heterostructures has open-circuit voltages of 0.5−0.6 V and a short-circuit current of 0.3 mA/cm2.