Characteristics of Boron Decorated TiO₂ Nanoparticles for Dye-Sensitized Solar Cell Photoanode

Different boron weight percents on mixed-phase (anatase and rutile) TiO₂ nanoparticles were synthesized to investigate structure morphology, defect states, luminescence properties, and energy conversion. The measured results indicate that boron doping of TiO₂ both increases the crystallite size and rutile-phase percent in an anatase matrix. Decreasing the band gap by boron doping can extend the absorption to the visible region, while undoped TiO₂ exhibits high UV absorption. Oxygen vacancy defects generated by boron ions reduce Ti⁺⁴ and affect electron transport in dye-sensitized solar cells. Excess electrons originating from the oxygen vacancies of doped TiO₂ downward shift in the conduction band edge and prompt the transfer of photoelectrons from the conduction band of the rutile phase to the lower energy anatase trapping sites; they then separate charges to enhance the photocurrent and J sc. Although the resistance of the electron recombination (R k) between doped TiO₂ photoanode and the electrolyte for the doped TiO₂ sample is lower, a longer electron lifetime (τ) of 19.7 ms with a higher electron density (n s) of 2.1 × 10¹⁸ cm^-3 contributes to high solar conversion efficiency.