Thin films of Cu₂ZnSnS₄ for solar cells: optical and structural properties

Abstract

The structure of Cu₂ZnSnS₄ films was investigated by Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, optical reflectance and photoluminescence. The films were formed by thermal annealing layers of copper, zinc and tin sulfides on glass substrates at different substrate temperature and ambient atmosphere. It was revealed that the films have the dominant structure of kesterite with possible inclusions of stannite Cu₂ZnSnS₄ structure. Under certain growth conditions, however, segregation of Cu₂₋xS occurs, as proved by registering the characteristic peak in Raman spectra. No traces of secondary phases of zinc or tin sulphides are found.