Peculiarities in electrical and optical properties of Cu$_{2}$Zn$_{1-x}$Mn$_{x}$SnS$_{4}$ films obtained by spray pyrolysis

Thin films of Cu$_{2}$Zn$_{1-x}$Mn$_{x}$SnS$_{4}$ (0 $\le x\le$ 1) solid solutions have been obtained for the first time by the spray pyrolysis of aqueous salt solutions (copper, zinc, manganese, and tin chlorides and thiourea) at a temperature of $T_S$ = 563 K. The films possess specific electric conductivities within $\sigma\approx$ 35–422 $\Omega^{-1}$ cm$^{-1}$ and optical bandgap width E opg that increases with the manganese content from 1.54 eV ($x$ = 0) to 2.25 eV ($x$ = 1). Electrical and optical properties of the obtained films have been studied and analyzed based on a model of polycrystalline materials with grain boundaries. The energy barriers Eb between grains have been determined. The dependence of the bandgap of Cu$_{2}$Zn$_{1-x}$Mn$_{x}$SnS$_{4}$ (0 $\le x\le$ 1) solid solutions on the composition has been established using the results of measurements of the optical transmission and absorption coefficients.