Structural, electronic and optical properties of a tetragonal-stannite Cu2CoGeS4 thin film synthesized by a low-cost spray method: Experimental and theoretical study

This work presents the synthesis of a new quaternary compound Cu2CoGeS4 (CCGS) thin film for the first time combined with first-principles calculations (DFT, WIEN2k). The synthesis was done via spray ultrasonic of Cu-Co - Ge precursors onto glass substrate followed by high - temperature (500 degrees C) sulfurization under inert atmosphere (Ar). A near 2:1:1:4 stoichiometry of Cu2CoGeS4 was confirmed from EDX analysis. X- Ray- Diffraction(XRD) analysis confirmed the formation of polycrystalline Cu2CoGeS4 (CCGS) thin film with a tetragonal stannite structure(1 (4) over bar 2m). Raman spectroscopy confirmed the purity of the film and showed the presence of the characteristic predominant peak (339 cm(-1)) of the tetragonal stannite structure. The band structure displayed a direct band - gap. The experimental and theoretical optical band gaps were found to be about 1.75 eV with high absorption-coefficient in the visible region of the solar spectrum. Electrical measurement confirmed the p-type conductivity with a resistivity of 0.89(Omega.cm(-1)) and a carrier concentration of 4.6 10(16 )cm(-3). These results and the photoresponse measurement make the Cu2CoGeS4 (CCGS) a potential material for solar cell application and will draw the attention to develop this material in several other applications.