Hierarchically porous hybrids of polyaniline nanoparticles anchored on reduced graphene oxide sheets as counter electrodes for dye-sensitized solar cells

Abstract

Hierarchically porous polyaniline–reduced graphene oxide hybrids have been developed via oxidative polymerization of aniline by MnO₂ on reduced graphene sheets under acidic conditions (named M-PANI@rGO). The formation mechanism of the above hybrids indicates that the MnO₂ undergoes oxidative disintegration and results in the porous structure of polyaniline (PANI) nanoparticle formation on the reduced graphene oxide (rGO) surface. The scanning electron microscopy (SEM) images and Brunauer–Emmett–Teller (BET) nitrogen sorption–desorption measurement clearly showed the nanoporous nature of the M-PANI@rGO hybrids. TEM-EDX confirmed the complete removal/degradation of MnO₂ during the oxidative polymerization of aniline. Just for comparison, PANI–rGO hybrids have also been prepared via conventional polymerization using (NH₄)₂S₂O₈ as the oxidant (named C-PANI@rGO). When these different architectural PANI@rGO hybrids were applied as the counter electrode for dye-sensitized solar cells (DSSCs), the short-circuit current density (J_sc) and power-conversion efficiency (η) of the DSSCs with C-PANI@rGO hybrids are measured to be 11.64 mA cm⁻² and 5.62%, respectively, while the corresponding values are 12.88 mA cm⁻² and 6.15% for the DSSCs with M-PANI@rGO hybrids, which is comparable to 6.73% for the cell with a Pt counter electrode under the same experimental conditions. The hierarchically porous M-PANI@rGO hybrid is thus a promising candidate to replace platinum as a counter electrode for DSSCs.