Characterising Optical Properties of Doped Metal Complex Nanocomposite Films with PVA/PVAC for Optoelectronics

This study investigates the optical properties of nanocomposite films made from polyvinyl alcohol (PVA), polyvinyl acetate (PVAC), and a 50/50 polyblend of PVA and PVAC, doped with varying concentrations 0, 3, 6, and 9 wt.% of the metal complex Fluoro pentaamine cobalt (III) fluoride [Co(NH₃)₅F]F₂ (FACF). The films were prepared using a solvent casting method and analysed with a computerised UVـــVISـــIR spectrophotometer over the wavelength range of 250–850 nm. Key optical parameters, including the refractive index, extinction coefficient, and optical conductivity, were determined through absorption studies. The optical absorbance increased with higher FACF concentrations. UV-Vis spectra were used to estimate the band gap energies and investigate the electronic transitions from the valence band to the conduction band. A decrease in the band gap for allowed direct transitions was observed: from 4.0 eV to 2.55 eV for PVA, 4.1 eV to 2.6 eV for PVAC, and 4.35 eV to 2.6 eV for the polyblend as the FACF content increased. Additionally, both the extinction coefficient and refractive index increased with higher FACF concentrations. These nanocomposite films show potential for use in photovoltaic cells, optical sensors, LEDs, photodetectors and other luminescent devices, though further research is needed. KEYWORDS absorbance spectrum, casting method, energy gap, polyblend, polyvinyl acetate, polyvinyl alcohol