Investigation of optical and electrical properties of copper oxide - polyvinyl alcohol nanocomposites for solar cell applications

Copper oxide nanoparticles (CuO-NPs) were synthesized at room temperature via a green method that is easy, efficient, eco-friendly, and low-cost. The aqueous extract of Bougainvillea leaves was used as a reducing and capping agent. Pure polyvinyl alcohol (PVA) and CuO-PVA nano-composite thin films of 13wt%, 30wt%, 40wt%, and 51wt% were prepared by the solution casting method. The optical and electrical properties of the prepared CuO-NPs, pure PVA, and CuO-PVA thin films were analyzed using a UV–visible spectrophotometer and Keithley electrometer. The band-gap energy (Eg) value for the synthesized CuO-NPs was determined to be 2.74 eV. This band separation lies in a range that is suitable for a variety of optical and optoelectronic applications such as solar cells for energy conversion. Further, increasing the dispersion of CuO-NPs in a PVA matrix extended the absorption spectrum of PVA distinctly into the visible region and decreased the optical band gap exponentially from 4.42 eV for pure PVA to 3.34 eV for 51wt% CuO-PVA. In addition, an increase in the DC electrical conductivity with CuO-NPs dispersion was observed. The decrease in the band gap energy was usually accompanied by an increase in the DC electrical conductivity making the CuO-PVA nanocomposite more applicable in thin-film solar cell applications.