Cu2MgxZn1-xSnS4 (0 ≤ x ≤0.6) thin films were prepared by a simple, low-temperature (300 °C) and low-cost sol-gel spin coating method followed by post-annealing at optimum conditions. We optimized the annealing conditions and investigated the effect of Mg content on the crystalline quality, electrical and optical performances of the Cu2MgxZn1-xSnS4 thin films. It was found that the Cu2MgxZn1-xSnS4 film annealed at 580 °C for 60 min contained large grain, less grain boundaries and high carrier concentration. Pure phase kesterite Cu2MgxZn1-xSnS4 (0 ≤ x ≤ 0.6) thin films were obtained by using optimal annealing conditions; notably, the smaller Zn2+ ions in the Cu2ZnSnS4 lattice were replaced by larger Mg2+ ions. With an increase in x from 0 to 0.6, the band gap energy of the films decreased from 1.43 to 1.29 eV. When the ratio of Mg/Mg + Zn is 0.2 (x = 0.2), the grain size of Cu2MgxZn1-xSnS4 reaches a maximum value of 1.5 μm and the surface morphology is smooth and dense. Simultaneously, the electrical performance of Cu2MgxZn1-xSnS4 thin film is optimized at x = 0.2, the carrier concentration reaches a maximum value of 3.29 × 1018 cm-3.
Keywords: Cu2MgxZn1−xSnS4; photoelectric performance; solar cell; sol–gel; sulfuration treatment; thin films.