Formation of a phase pure kesterite CZTSe thin films using multisource hybrid physical vapour deposition

Copper Zinc Tin Selenide (CZTSe) absorber films were obtained by growing CZT films with simultaneous RF and DC magnetron sputtering followed by thermal evaporation of Selenium. The deposition of CZTSe films was performed with different sputter powers with in-situ and post annealing of the deposited films at 400 degrees C in order to get uniformity and phase purity. Detailed GIXRD analysis concluded that a phase pure CZTSe film was obtained for in-situ annealed sample with Cu-Sn deposited through RF sputter power of 250W and Zn deposited through pulsed DC power of 200W. In conclusion from Raman scattering measurements, phase pure Raman active A mode of Kesterite CZTSe was observed for the same sample. Compositional analysis by EDS and XPS clearly showed that the CZTSe films are having Cu poor and Zn rich composition, favoring shallow Cu-vacancy which is highly desirable as p-type absorber layers for solar cells. The optical bandgaps (Eg) of the films calculated using Tauc plots were within the reported bandgap value of 1.0-1.35eV. The present deposition approach using hybrid PVD tool helps to control individual fluxes (Cu-Sn, Zn, Se), more precisely without the need of extra selenization step, leading to one step reduction in production process.