Effects of Na2SO4 on the optical and structural properties of Cu2ZnSnS4 thin films synthesized using co-electrodeposition technique

Abstract

In this paper, kesterite films have been prepared by sulfurization of co-electrodeposited Cu–Zn–Sn (CZT) precursor using Na2SO4 as a complexing agent. The structural, morphological, optical and electrical properties of the films have been investigated in details. Adherent layers and pure kesterite phase were obtained. XRD analysis revealed the formation of a tetragonal crystal structure CZTS phase with majors and intense peaks (112), (200), (220), (312) plans. Raman analysis, using different wavelengths laser, confirmed the presence of a pure kesterite phase with minor trace of secondary phases in depth layer. SEM analyses show uniform and compact surface morphology with well definite boundary submicron particles. The absorption coefficient is higher than 1 × 104 cm−1 in the visible region. Electrical measurements, performed in the temperature range of 300 K-100 K, confirmed the p-type conductivity with high free carrier concentrations. For temperatures higher than 200 K, the conductivity is ensured by the emission of free carriers above the potential barriers at the grain boundaries with activation energy close to 51 meV. For temperatures between 200 and 160 K, conduction is provided by nearest neighboring jumps (NNH) mechanism.