Characteristics of Boron Decorated TiO₂Nanoparticles for Dye-Sensitized Solar Cell Photoanode

Abstract

Different boron weight percents on mixed-phase (anatase and rutile) TiO 2 nanoparticles were synthesized to investigate structure morphology, defect states, luminescence properties, and energy conversion. The measured results indicate that boron doping of TiO 2 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 TiO 2 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 TiO 2 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<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msub><mml:mrow><mml:mi>J</mml:mi></mml:mrow><mml:mrow><mml:mtext>sc</mml:mtext></mml:mrow></mml:msub></mml:mrow></mml:math>. Although the resistance of the electron recombination (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>k</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) between doped TiO 2 photoanode and the electrolyte for the doped TiO 2 sample is lower, a longer electron lifetime (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:math>) of 19.7 ms with a higher electron density (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:msub><mml:mrow><mml:mi>n</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) of 2.1 × 10 18 cm −3 contributes to high solar conversion efficiency.