Close spaced vapor transport deposition of Cu2ZnSnS4 thin films: Effect of iodine pressure

• High quality Cu2ZnSnS4 ingot was obtained by cooling a molten stoichiometric mixture.
• CZTS thin films were prepared by Close spaced vapor transport deposition technique.
• Effect of iodine pressure on the properties CZTS films has been investigated.
• XRD and Raman spectra revealed the kesterite phase with a good crystalline quality.
• Crystallite size and band gap energy of CZTS films increase with the iodine pressure.

High quality Cu2ZnSnS4 (CZTS) ingots obtained by cooling a molten stoichiometric mixture have been deposited as thin films on soda-lime glass by Close Spaced Vapor Transport (CSVT). Iodine pressure is one of the important parameters for the CSVT process. The effect of iodine pressure on compositional, morphological, structural, electrical and optical properties of CZTS thin films has been investigated. X-ray diffraction and Raman spectroscopy results revealed the formation of polycrystalline CZTS with a (112) preferred orientation plane and Raman shift of 338 cm−1 respectively. Iodine pressure does not have a significant effect on the composition nor on the electrical properties as measured by Hall effect measurements. However, scanning electron microscopy (SEM) and UV–Vis–NIR spectrophotometer data revealed an increase of crystallite size and band gap energy (1.47–1.56 eV) with iodine pressure. The photoluminescence (PL) measurements at 77 K exhibit emission peaks around 1.30 eV. The origin of this luminescence is attributed to band-to-impurity (BI) recombination.