Potassium Doping Effect on Cu<sub>2</sub>ZnSn(S<sub>,</sub>Se)<sub>4</sub> Thin Film Absorber Layer Deposited via Spray Pyrolysis

This article reports on the role of potassium (K) as dopant in Cu2ZnSn (S,Se)4, CZTSSe thin film in context of optical properties. Thin film precursor solution is prepared in dimethyl sulfoxide (DMSO) solvent, and doped by K with six different concentrations. The prepared solution are deposited on heated soda lime glass (SLG) substrates using spray pyrolysis technique, followed by selenization process using three-step temperature approach. UV-Visible spectra show high absorption coefficient, α, more than 104cm-1 and bandgaps in narrow range 0.98eV to 1.10eV. X-ray diffractograms show that all samples exhibit kesterite structure with preferential orientation along (112) orientation. Field Emission Scanning Electron Microscopy was used to determine the morphologies of the K-doped CZTSSe thin films. 1.5 mol % of K has shown better characteristics as an absorber layer among other tested samples.