Synergistically improved photovoltaic performances of dye-sensitized solar cells with metal-free organic cosensitizer and hybrid rGO-TiO₂ photoanode

The photovoltaic performances of the dye-sensitized solar cells were considerably improved via comprising the device structure with the metal-free organic dye cosensitizer and the hybrid photoanode. The cosensitizer was composed of Eosin Y and Coumarin (EY-CM) dyes, and the hybrid photoanode was constructed with the reduced graphene oxide-anchored titanium dioxide (rGO-TiO₂) nanocomposites. Due to the aggregation of highly conductive rGO with semiconductive TiO₂, the nanocomposites exhibited the decreased interfacial resistance; hence, the electron transport could be improved in the solid-state medium of the photoanode. Meanwhile, the cosensitization of EY-CM dyes could give rise to the increased photon absorbance at the wide spectral range; and their energy level alignment with rGO-TiO₂ could lead to the enhanced hopping conduction of the photo-generated electrons. Furthermore, the configuration of rGO-TiO₂/EY-CM allowed us to increase the electron injection lifetime, which could reduce the photocarrier recombination at the photoanode/sensitizer interface. Owing to the synergetic effects from both the rGO-TiO₂ hybrid photoanode and the EY-CM cosensitizer, the fabricated dye-sensitized solar cell eventually showed the increased power conversion efficiency up to ∼6.14% under 1-Sun illumination with 100 mW/cm².