Filling and coating of vertically aligned Zinc Oxide nanowire arrays with various semiconductor materials
Concluding M.Sc. seminar - Department of Chemistry, Ben-Gurion University
Michael Volokh (volokh@post.bgu.ac.il)
The ongoing effort to find an alternative to conventional solar cells is part of the growing demand for cheap renewable energy solid-state devices. Thus far, little success has been achieved in fabricating efficient solar cells using abundant, inexpensive, and environmentally benign materials that would allow for a facile production of large-scale devices.
Our research focuses on finding an appropriate chemical path to synthesize a composite of nanostructures based on vertically aligned ZnO nanowire arrays filled with semiconductor nanostructures for all-inorganic solar cells. The formed heterostructure has a coaxial morphology and type II band alignment (staggered energy levels alignment), which facilitates the charge separation between an electron-hole pair. Various groups have implemented this concept by developing all-inorganic core/shell systems. They use an expensive, high-temperature or high vacuum methods such as metal-organic chemical vapor deposition (MOCVD) or various physical vapor deposition (PVD) techniques.
Our approach is based on aqueous phase synthesis of vertically aligned ZnO nanowires carried out at 90˚C, in which the wires grow from a solution, containing only a soluble zinc salt and hexamine. Three different methods were used for the filling: 1) A method that is based on the drop casting of Cu2O, CdS, or CdTe nanocrystals. 2) The use of single source precursors, which decompose upon heating to form CdS or Cu2O shell. 3) Chemical vapor deposition of single source precursors under Ar to give a homogeneous and complete coating of the nanowires with CdS.
