Effect of [Cu]/[Cu + In] ratio in the solution bath on the growth and physical properties of CuInS₂ film using one-step electrodeposition

Copper indium disulfide (CuInS₂) semiconductor layers were deposited on fluorine doped tin oxide coated glass substrates using one-step electrodeposition. The effect of the [Cu]/[Cu + In] molar ratio in the solution bath on the structural, optical, and electrical properties of samples was investigated. X-ray diffraction patterns and energy dispersive analysis of X-ray results reveal that the samples changed from the In-rich CuInS₂ phase to the Cu-rich CuInS₂ phase with an increase in the [Cu]/[Cu + In] molar ratio in the solution bath. The thicknesses and direct band gaps of the samples, determined from surface profile measurements and transmittance and reflectance spectra, are in the ranges of 844-1570 nm and 1.42-2.11 eV, respectively. The conduction type and flat band potentials of samples were obtained using open circuit potential measurements in the dark and under illumination. With a [Cu]/[Cu + In] molar ratio in the solution bath of less than 0.29, the samples were n-type semiconductors with flat band potential in the range of -1.08 to -1.22 V (vs. Ag/AgCl). With a [Cu]/[Cu + In] molar ratio in the solution bath of greater than 0.33, the samples were p-type semiconductors with flat band potentials in the range of -0.74 to -0.83 V (vs. Ag/AgCl). Compensated CuInS₂ can be obtained in the solution bath with a [Cu]/[Cu + In] ratio of around 0.32.