Opto-electrical characterization of quaternary sputtered copper indium gallium selenide nanorods via glancing angle deposition

Abstract

Nanorod arrays have become an attractive alternative to their thin film and bulk counterparts in photovoltaic and photoconductivity research. This is mainly attributed to their superior optical and electrical properties. Light trapping and unique bandgap geometries in vertically aligned nanostructures result in high optical absorption and provide enhanced carrier collection by utilizing a fully depleted p-n junction between the anode and cathode via an isolated “capping” construction. The combination of these two features leads to the development of high efficiency nanostructured devices that can be utilized in solar cells and photodetectors. Optical absorption properties, geometry, and opto-electrical properties of nanorod arrays of CuInxGa(1−x)Se2 (CIGS), a p-type semiconductor with a wide bandgap ranging from 1.0 to 1.7 eV, are compared to their thin film counterparts. Utilizing a radio frequency sputtering system, a quaternary target, and glancing angle deposition technique, both isolated vertical arrays of CIGS nanorods and “core-shell” devices were fabricated, while conventional film devices were fabricated by normal incidence deposition. Scanning electron microscopy images indicated a successful growth of CIGS nanorods. Optical absorption and opto-electrical performance were found to be strongly improved by the presence of the isolated nanorod structures through spectroscopic reflectometry and responsivity testing under a solar simulator.