Preparation Of PVP.BtB Thin Films by Spin Coating Technique and Study the Structural and Optical Properties for Optical Filters Application

Abstract

To fabricate optical filters, the pure Polyvinylpyrrolidone (PVP) polymer thin films doped with Bromothymol blue (BTB) dye at different doping concentrations (0.2, 0.4, and 0.6 %wt) were prepared by the spin-coating method. FE-scanning electron microscope examinations indicated that all the pure and doped thin films were highly homogeneous and almost free of morphological defects. X-ray diffraction examinations indicated that the pure PVP thin films initially had an amorphous structure, which transformed into a polycrystalline structure upon doping with BTB dye; the crystal size was 41.1 nm at 0.2%wt BTB and increased to 60.4 nm at 0.6 %wt BTB. Optical measurements indicated that the doped thin films have selective ability at wavelengths of 406 and 620 nm. The studies also indicated that the prepared films have indirect electronic transitions and that the optical energy gap decreases with increasing BTB doping concentration. From the above results, the prepared films can be effective and scientific in optical filter applications, as they can select wavelengths located at 406 and 620 nm of the visible spectrum.