Photovoltaic and photocatalytic properties of bismuth oxyiodide-graphene nanocomposites.

In this study, we evaluate the photovoltaic and photocatalytic properties of chemical vapor deposited bismuth oxyiodide (BiOI) and bismuth oxyiodide-graphene (BiOI-GR) nanocomposite thin films. The BiOI thin film has an average thickness of 574 nm and a bandgap of around 2 eV. The BiOI and BiOI-GR thin films exhibited nanoflake morphology. It was found that addition of graphene increases absorbance by causing vertical growth of nanoflakes, imparting anti-reflectance and light trapping properties. The photocatalytic activities of the thin films were evaluated by examining methylene blue (MB) degradation under visible light irradiation. BiOI-GR degraded 56.42% of MB in two hours while BiOI degraded 44.16%. Afterwards, FTO|BiOI|graphite|Al and FTO|BiOI-GR|graphite|Al solar cell devices were fabricated with photocurrent density values of 2.0 μA cm and 2.7 μA cm, respectively. The improved properties of BiOI-GR are attributed to the anti-reflecting and light trapping properties of vertical BiOI-GR nanoflakes and the enhanced carrier separation due to graphene as an electron acceptor.