Influence of laser pulse energy on the microstructure and optical properties of Cu2ZnSnS4 films by one-step pulsed laser deposition

Polycrystalline Cu2ZnSnS4 (CZTS) films were deposited on ITO conductive glass substrates by one-step pulsed laser deposition. The influence of laser pulse energy on the microstructure and optical properties was investigated. The results indicate that all the films are rich in Sn, poor in S and well crystallized with dominant (1 1 2) preferred orientation. At laser pulse energies of 130, 165 and 180 mJ, SnS2 impurity phase exists in CZTS films, which is probably the reason for their larger bandgaps (1.61-1.67 eV) compared with that of a stoichiometric CZTS film (around 1.50 eV). While at the laser pulse energy of 150 mJ, an attractive Cu-poor and Zn-rich, large grain size and single-phase CZTS film can be obtained. In such a film, excess Cu vacancies reduce the valence band maximum (VBM) of CZTS, leading to the blue shift of its bandgap (1.60 eV).