A New Coevaporation/Selenization Process for High Quality CuInSe₂ Devices

Abstract

A new technique was used to prepare polycrystalline films of CuInSe₂ for PV devices. The main purpose of the work is to find optimized preparation methods and conditions to prepare CIS films with high reproducibility on a large area avoiding H₂Se as process gas. The process is splitted into three stages: coevaporation of the metals, in situ selenization by physical vapour deposition (PVD) of Se and standard coevaporation of all three elements. The idea is to combine the advantages of different techniques: selenization for high quality and large grain crystals, coevaporation for refinement of electrical properties in the near surface region. Basic properties and growth kinetics are considered. Process parameters e.g. Cu/In-rate ratios of the first metal film and the final coevaporated film have been varied in a wide range. Results of devices with (Zn, Cd)S and chemical-bath-deposited CdS plus sputtered ZnO: Al show that it is possible to prepare PV devices with efficiencies around 10% with a variation of the Cu content in the selenized films between 23 and 25 at. % and η > 7% with 20 – 25 at. % Cu, respectively. The final coevaporated layer is less sensitive on Cu/In ratio. Post deposition treatments have been made and results are shown.