Toroidal ferroelectric cobalt-doped barium titanates as efficient energy conversion materials for solar cells and photocatalysis

Abstract

Doughnut-shaped ferroelectric barium titanate (BTDS) and cobalt-doped barium titanate (CBTDS) [Co_xBaTi_1−xO₃ (x = 0 or 0.05 mol%)] nanostructures have been synthesized from hydrogen titanate nanowires for use as efficient photon energy conversion materials in dye-sensitized solar cells (DSSCs) and photocatalytic dye degradation applications. The morphological and structural analyses have revealed that the perovskite BDTS and CBDTS nanostructures exhibit toroidal ferroelectric characteristics, which are reinforced by the formation of oxygen vacancies and Ti³⁺ ions within their lattices. The DSSC bilayer photoanodes constructed using mesoporous TiO₂ nanoparticles (TNP) as the underlayer and CBTDS as the light-scattering and charge-collecting upper layer have shown the highest photovoltaic efficiency of 10.29 ± 0.44% due to the greater light scattering, light absorption extended to the near-infrared region, and toroidal ferroelectric field-induced slower charge recombination effects that collectively boosted the photovoltaic performance. Moreover, the photocatalytic dye-degradation performance of the CBTDS photocatalyst has demonstrated a maximum dye degradation efficiency of 86.74% over 75 minutes, indicating a respectable photocatalytic activity compared to the BTDS photocatalyst. These results have confirmed that superior morphology control, oxygen vacancy, and Ti³⁺ ion formation in the BTDS and CBTDS nanostructures strongly influence toroidal ferroelectric field-induced charge separation and light-harvesting ability in dye-sensitized solar cells (DSSCs) and photocatalysts, leading to superior performance.