Spray‐pyrolyzed Cd‐substituted kesterite thin‐films for photovoltaic applications: Post annealing conditions and property studies

Kesterite materials were investigated for their suitability as absorber layers for thin-film photovoltaic cells. Thin- films of copper cadmium zinc tin sulfide (Cu2CdxZn1-xSnS4) were prepared by spray pyrolysis on soda-lime glass. The obtained thin-films were subjected to post annealing treatment at 525 ◦C in a sulfur atmosphere to study the effects on morphology, stoichiometry, phase formation and optical properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and ultraviolet visible spectroscopy (UV–Vis). The XRD patterns revealed the presence of prominent kesterite peaks in the unannealed and annealed thin-films, with enhanced crystallinity in the annealed thin-films. The crystal sizes of the unannealed and annealed thin-films were estimated from the XRD data and ranged from 5 nm to 27 nm for unannealed thin-films and 13 nm–25 nm for annealed thin-films. The unannealed thin-films exhibited a non-uniformly shaped morphology, which was a mixture of cube-shaped and rod-shaped nanoparticles, while the annealed thin-films exhibited a uniformly shaped morphology of flake-shaped nanoparticles, indicating enhanced crystallinity