Evolution of sprayed Cu2ZnSnS4

Cu2ZnSnS4 (CZTS) thin films have been prepared using a Spray pyrolysis technique. The evolution of CZTS, followed by an increase in thiourea concentrations [S] from 0.04 to 0.07 M, is investigated. EDX analysis exhibits a drastic increase of sulfur amount as the thiourea concentration increases. X-ray diffraction and Raman spectroscopy analysis confirmed the formation of CZTS kesterite structure with some spurious phases mainly at higher thiourea concentrations. Indeed, with further increase in [S], XRD reveals the appearance of a sharp and intense peak, which is assigned to Cu4Sn7S16. Optical analysis by means of transmission T(λ) and reflection R(λ) measurements allow to determine the optical absorption coefficient α for all CZTS compounds, it is larger than 104 cm−1. The direct band gap energy value Eg can be deduced; it ranges from 1.59 to 1.74 eV. The broadening of Eg might be attributed to the ZnS secondary phase.