Enhancement of photoelectric properties of Cu2ZnSnS4 thin films by electronic excitations induced by swift heavy ions

• AFM and SEM images confirm the morphological changes in the irradiated sample. • Micro-Raman spectra reveal the presence of lattice defects in the Au irradiated sample. • UV–Vis results reveal a red-shift in absorbance spectra after O irradiation. • Maximum photosensitivity is found to be 62% for O irradiated thin films. The structural, optical, and current–voltage characteristics including photosensitivity of copper zinc tin sulphide (Cu 2 ZnSnS 4 ) thin films were modified significantly by the electronic excitations. These excitations were induced by swift heavy ion (SHI) beams of 100 –120 MeV of O, Ag, and Au. X-ray diffraction patterns confirm that the pristine and irradiated films crystallize in kesterite structure and the crystallite size increases after O, and Ag ion irradiations compared to Au ions. The micro-Raman spectra reveal the presence of lattice defects in the Au irradiated sample. The analysis shows that the crystallinity of the Cu 2 ZnSnS 4 thin film increases with O ion irradiation indicating that the density of defect states decreases after SHI irradiation. The maximum photosensitivity is found to be 62% for O irradiated thin films compared to other ion beams due to the reduction in the band gap.