Peptide-Mediated Deposition of Nanostructured TiO2 into the Periodic Structure of Diatom Biosilica and its Integration into the Fabrication of a Dye-Sensitized Solar Cell Device

摘要

Biological fabrication approaches were used to enhance the performance of a dye-sensitized solar cell (DSSC) device stack for the conversion of light to electricity. Diatoms are single-celled algae that make silica shells called frustules that possess periodic structures ordered at the micro-and nanoscale. Nanostructured TiO2 was deposited onto the frustule biosilica of the diatom Pinnularia sp. Poly-L-lysine (PLL) conformally adsorbed onto surface of the frustule biosilica. The hydrolysis and condensation of soluble Ti-BALDH to TiO2 by PLL-adsorbed diatom biosilica deposited 0.77 ± 0.05 g TiO2/g SiO2 onto the diatom biosilica. The periodic pore array of the diatom frustule served as a template for the deposition of ~20 nm TiO2 nanoparticles, which completely filled the 200 nm frustule pores and also coated the frustule outer surface. This material was then integrated into the DSSC device stack. Specifically, a single layer of diatom-TiO2 frustules was deposited to surface coverage 100ug/cm~2 on top of the 25 nm anatase TiO2 nanocrystal layer (2.5 mg/cm~2) that was doctor-bladed onto conductive FTO glass. The composite structure was thermally annealed in air at 400 °C, followed by addition of N719 dye, I_3~-/3I~-liquid electrolyte, and semi-transparent Pt back electrode sputter coated on FTO glass. The solar cell efficiency increased from 0.20% to 0.70% when the diatom-TiO2 layer was added to anatase TiO2 base layer of the semi-transparent device. The increase in efficiency cannot be attributed solely to the added TiO2, because the amount of TiO2 in the diatom-TiO2 layer contributed to only 3% of the total TiO2 in the device. Instead, it is proposed that the diatom-TiO2 layer may have helped to improve photon capture within the DSSC because of its periodic structure and high dielectric contrast.