Structural Evolution of Cu-In-Se Thin Films Prepared by Spin Coating Technique

Abstract

A low cost and simple fabrication of Cu-In-Se polycrystalline thin film for copper indium diselenide solar cell was prepared in a two-step process. The first step, a Cu In precursor film was prepared from copper acetate monohydrate and indium acetate mixed solution. The solution was coated on molybdenum-coated soda lime glass using the spin coating technique at room temperature following annealing in air at 500°C for 20 minutes. The effect between spin parameters and film thickness of as-deposited Cu-In film were investigated. The second step, selenium was added in the precursor film by selenization process at 450°C in Se atmosphere for 30 minutes in a low vacuum tube furnace with background pressure of 10-2 mbar. The crystallographic properties of Cu-In-Se thin films were identified by X-ray diffractometer (XRD), the surface and cross-sectional morphology of films were observed by scanning electron microscopy (SEM). The chemical compositions of films were characterized by energy dispersive spectroscopy (EDS). It was found that the thickness of Cu-In films deposited on molybdenum-coated soda lime glass were approximately 1 μm. The EDS analysis showed the composition ratio in atomic % of Cu/In as approximately as 0.77. The XRD results reveal that the as-deposited Cu-In films consist of a mixture of copper oxide (CuO) and indium oxide (In2O3) phase at the annealing temperature of 500°C. Furthermore, CuO and In2O3 phase were converted to (112) oriented chalcopyrite copper indium diselenide after selenization process.