Growth of CuInS2 Nanotubes from Cu2S-CuInS2 Heterostructures as a Potential Photovoltaic Material

Abstract

Chemically synthesized nanostructures possess well-defined domains with an interconnected network, which helps the carriers to bypass the other material in the solar cell while moving to their respective electrodes. In this work, CuInS2 films constituting CuInS2 nanotubes and nanoparticles were fabricated using a hot-injection chemical technique, followed by sulfurization. Structural and microstructural investigations reveal Cu2S nanoparticle formation at an early stage of growth of nanotubes, serving as possible catalyst sites for the subsequent anisotropic growth of the heterostructured hexagons. The crossover takes place over a number of intermediate stages. This sharing of the heterostructure by the hexagonal Cu2S and chalcopyrite CuInS2 minimizes the lattice distortion. The Cu2S- CuInS2 interface in the heterostructure acts as the nucleation center for CuInS2 nanotubes. Optical absorption and Raman spectroscopy studies reveal better optical properties for CuInS2 nanoparticles as compared to CuInS2 nanotubes. Compared to all other nanostructures, nanowires or nanotubes tend to provide single-crystalline nanograins for direct characterization. These nanoparticles, especially the nanotubes, can be used to form an interconnected network structure of p- and n-type materials in bulk heterojunctions providing the key to improve solar cell efficiencies.