A Novel Polyaniline Gadolinium Oxide Coated Reduced Graphene Oxide Nanocomposite: A Sustainable, Cost-Effective and High-Performance Counter Electrode for Dye-Sensitized Solar Cells

A novel ternary nanocomposite, comprising reduced graphene oxide/polyaniline/gadolinium oxide (RGO-PANI-Gd2O3), was successfully synthesized using the Hummers method, followed by in situ emulsion polymerization of polyaniline. The final composite was produced by hydrothermally adding gadolinium nitrate. The composite was subjected to a systematic analysis that included optical, microstructural, physical, and Raman spectroscopic analysis, as well as current-voltage (J-V) measurements. The morphology of this composite material was investigated using scanning electron microscopy (SEM). The addition of Gd2O3 nanoparticles decreases the band gap energy from 3.5 eV (PANI) to 2.7 eV (RGO-PANI-Gd2O3). The UV–Vis spectra revealed a redshift in the π-π* transition peak from 318 nm (PANI) to 346 nm, indicating increased conjugation length and synergistic effects. This eco-friendly material has excellent catalytic activity for triiodide reduction. The manufactured counter-electrode (CE) demonstrated remarkable transparency and conversion efficiency comparable to platinum, with a current density of 11.7 mA·cm−2 versus 8.2 mA·cm−2 for platinum. Under simulated solar light (AM 1.5 G, 100 mW·cm−2), the RGO-PANI-Gd2O3 based nanocomposite CE achieved an excellent 4.3% photo conversion efficiency. These findings indicate that RGO-PANI-Gd2O3 nanocomposites have potential as efficient, platinum-free counter electrodes in dye-sensitized solar cells (DSSCs).