چكيده به لاتين
Abstract:
ZnS:Cu/SnS thin films were prepared on glass and flexible polymeric substrates (polystyrene) by using an indirect chemical bath deposition (CBD) method. For this purpose, first high quality ZnS thin films from the point of view high crystallinity, compactness, hemogenity, adhesion to the substrates and high transparency in the visible region, were deposited onto glass and polystyren substrates with 2, 4 and 6 hours deposition times by a facile and environmentally friendly CBD method. Optical, structural, morphological and electrical properties of the ZnS thin films were studied by ultraviolet -visible light (UV-vis) spectroscopy, Raman pectroscopy, X-ray diffractometer (XRD), X₋ ray photoelectron spectroscopy (XPS), field emission₋ scanning electron microscopy (FE₋SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. According to the investigations, because of the high optical transmittance in the visible regions (> 80%), wide band gaps around 3.77, 3.73 and 3.69 correspond to 2, 4 and 6h deposition time and very low reflection of light (< 5%), as₋ deposited ZnS thin films can be employed as flexible buffer layers and anti₋ reflecting coatings in the flexible solar cells and other photovoltaic and optoelectronic devices. Also, deposited ZnS thin films exhibited a hydrophilic nature. On the other hand, ZnS thin films showed a slight photocatalitic properties in the degradation of rhodamine B (water pollutant).
ZnS:CuS thin films were prepared by immersing ZnS thin films into the Cu ions solution for 0.5, 1 and 5 min. Optical, structural, morphological, electrical and photocatalitic properties of the prepared ZnS:CuS thin films were investigated by ultraviolet -visible light (UV-vis) spectroscopy, Raman pectroscopy, X-ray diffractometer (XRD), field emission₋ scanning electron microscopy (FE₋SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), I-V mesurment and four point probe systems. ZnS:CuS films had chemical compositions of Zn0.48Cu0.03S0.49, Zn0.45Cu0.06S0.49 and Zn0.05Cu0.48S0.47, light transmittance of 57-74, 56-70 and 38-47% in the 500 -700 nm and Sheet resistance of 7.7×103, 5.5×103 and 3.8×103 Ω/sq correspond to 0.5, 1 and 5 min immersion times, respectively. Sample with chemical composition of Zn0.45Cu0.06S0.49 showed a high optical transmittance (56₋70%) in the range 500₋700 nm and low sheet resistance (5.5×103 Ω/sq) with p₋ type electrical conductivity. TEM image of a typical ZnS:CuS sample proved formation of the ZnS:CuS nanocomposite.The prepared ZnS:CuS nanocomposite thin films showed a photocatalitic activity in the degradation of rhodamine B dyes (water pollutant). By increasing amount of Cu in the films and exposure time in the visible light, degradation percentage of the rhodamine B dyes were increased, so that the films obtained with o.5, 1 and 5 min immersion times, degradaded about 10%, 20% and 40% of rhodamine B dyes after 5h exposure time in the visible light because of the decrease in recombination of the electron – hole pairs.
For preparing ZnS:Cu/SnS thin films by CBD, ZnS:CuS thin films were placed into the solution containing Sn2+ and S2- ions. Optical, structural, morphological and electrical properties of the ZnS:Cu/SnS thin films were studied by ultraviolet-visible light (UV-vis) spectroscopy, Raman pectroscopy, X-ray diffractometer (XRD), field emission- scanning electron microscopy (FE₋SEM), atomic force microscopy (AFM), I-V measurement and four point probe systems. Energy-dispersive X-ray spectrometer (EDX) proved existence of Zn, Cu, Sn and S elements in the obtained CZTS films. The grazing incident X-ray diffractometer (GIXRD) pattern of the prepared flexible CZTS thin film showed two characteristic peaks at 2θ = 28.49 and 47° correspond to the (112) and (220) lattice planes of the tetragonal type kesterite structure of the Cu2CZTS4 (CZTS). The nanocrystalline size of the CZTS particles was estimated to be 33.2 nm by using Williamson-Hall formula.
Flexible CZTS films had a high optical absorbance in the visible region and the bandgap energy of the films were estimated to be 1.71 eV which was higher than that of the bulk CZTS. Investigation of the CZTS film surface morphology showed formation of compact layer with no cracks and pinholes. AFM and FE₋ SEM results were in good agreement. Sheet resistant (Rsh) and resistivity of the CZTS thin films with 800 nm thickness were obtained 1.1×103 Ω/sq and 8.0×10-2 Ω.cm, respectively and the CZTS films had a p₋ type conductivity. Contact angle measurement showed a hydrophilic nature for the CZTS absorber layers.
Keywords: ZnS thin film, Flexible, ZnS:CuS thin film, Photocatalist , hydrophilicity, CZTS thin film.