Effect of Al doping on structural, morphological, optical, and electrical properties of Cu 2 ZnSnS 4 thin films prepared by sol-gel spin coating

•Al-free and -doped nanocrystal Cu2ZnSnS4 films by sol-gel spin coating are reported.•Effect of Al doping on structural, electrical and optical properties of the films are presented.•Al enhances the structural properties and changes the surface morphology.•Raman and FTIR spectra of the films are reported.•Applications of the films are lithium battery, solar cells, and counter electrode.