Study of the sulphurisation reaction of cu/in precursors for thin polycrystalline film CuInS<sub>2</sub> solar cells

Abstract

The details of the sulphurisation reaction of Cu/In metallic precursors layers for the preparation of CuInS 2 solar cells have been investigated. For this purpose, we have designed an experiment using a combined sequence of sulphurisation and selenization steps. Analysing the resultant layers by Raman Spectroscopy and Auger Electron Spectroscopy (AES) we could study the details of the chemical reaction. By this method we have been able to identify where the chemical reaction between the metallic species and the reactive atmosphere takes place. Besides, we have developed an experimental system to analyse the sulphurisation process in-situ by Raman spectroscopy. With this system we studied the evolution of the material structure during the sulphurisation process. The experimental results prove that the reaction takes place in the surface, forming in the firsts steps CuInS 2 in two different structures (chalcopyrite and CuAu ordering). Afterwards, the out-diffusion of the metallic atoms towards the surface allows the reaction between them and the sulphur vapour. Together with the sulphurisation process the improvement of the crystalline quality of the CuInS 2 forming a chalcopyrite CuInS 2 layer has been observed.