Exploring the optoelectronic potential of dip coated CuInS2 thin films via morphological, structural, and photoresponse insights

In this present study, the dip coating technique is adopted to deposit copper indium disulfide (CuInS₂) thin films onto a glass substrate. The scanning electron microscopy (SEM) shows that the film thickness is (1.18 ± 0.06) µm. The transmission electron microscopy (TEM) confirms the crystalline character of the CIS (CuInS₂) thin films having fringe spacing consistent with the CIS major crystallographic (112) plane lattice spacing. The atomic force microscopy (AFM) reveals the presence of surface roughness-related hills and valleys. The X-ray diffraction (XRD) data show that the film has a tetragonal unit cell structure and is in the CIS phase. The elemental stoichiometry is validated by energy-dispersive X-ray spectroscopy (EDS) analysis. From the results of the ultraviolet-visible-near infrared spectroscopy (UV–Vis–NIR), an optical bandgap (direct) of 1.62 eV is found. Three different monochromatic incident photon wavelengths (480 nm, 560 nm, and 670 nm) are used to investigate the photoresponse of the CIS photodetector. When exposed to 670 nm (red) light with 5 mW·cm^-2 intensity and 100 mV bias voltage, the peak responsivity and detectivity for CIS thin films are determined to be 2.14 mA·W^-1 and 1.54 × 10⁹ Jones, respectively. It validates that the dip-coated CIS thin film has the potential for usage in optoelectronic devices 1,2.