Recombination suppression in TiO₂/boron-doped reduced graphene oxide-based dye-sensitized solar cells

Abstract

Fundamental operational principles of photoanode-based-dye-sensitized solar cells (DSSC) remain elusive. The modification in photoanodes affects the overall DSSC performance due to the behavioral changes in charge transport. In this work, we control the precursor concentrations to fabricate a boron-reduced graphene oxide (B-rGO) series with varied amounts of photoanodes. The DSSC incorporating 0.2 wt% B-rGO exhibits the highest efficiency and EQE, surpassing both lower and higher B-rGO concentrations. Electrochemical impedance spectroscopy reveals the lowest charge transfer resistance for the 0.2 wt% B-rGO DSSC, suggesting suppressed recombination processes. However, the observed trend in electron lifetime (longest for the reference DSSC and decreasing with B-rGO concentration) suggests the potential introduction of electron trapping sites even at low B-rGO levels. The optimal B-rGO concentration (0.2 wt%) facilitates efficient electron transfer from the excited dye to the TiO₂ conduction band, potentially enhancing light scattering or suppressing recombination.