Natural Sensitizer for Dye-sensitized Solar Cells Using Three Layers of Photoelectrode Thin Films With A Schottky Barrier

摘要

This study combines Au nanoparticles with TiO2 nanoparticles to form a Schottky barrier, and applies it to the photoelectrode thin film of dye-sensitized solar cells (DSSCs). Due to this Schottky barrier, electrons are unable to go back to the dye molecules or electrolyte, thus effectively enhancing the electronic conversion efficiency. First, commercial TiO2 powder (Degussa P25) is put into the alkaline solution to prepare TiO nanotubes (Tnt) by a hydrothermal process. Tnt are sintered at 550℃ to obtain TntC550 particles and fabricated into a translucent sol by two hydrothermal treatments and baked at 180℃ to acquire H180 particles. H180 and TntC550 are spread into transparent polymer films by a doctor blade. H180 serves as the first layer and TntC550 the second, with both are sintered at 450℃. The third layer uses hydrogen tetrachloroautate (HAuCl4) and trisodium citrate (C6H5Na3O7) to prepare Au nanoparticles by salt reduction. Spherical Au nanoparticles around 27nm are adhered to the TntC550 make a film by self-assembly to complete the preparation of the photoelectrode of DSSCs. Natural dyes of bougainvillea leaves for chlorophyll and blueberries for anthocyanin are employed in this study. Extracted chlorophyll and anthocyanin dyes are also blended in the proportion of 1: 1 as a mixed dye and these three different natural dyes are compared to compare their photoelectric conversion efficiencies. Electrolyte and counter electrode (Pt) are added to form the sandwich structure of DSSCs. After being sealed, DSSCs are tasted for fill factor, photoelectric conversion efficiency and incident photon-tocurrent conversion efficiency. Results from the experimental tests show that for the dye mixtures, photoelectric conversion efficiency of DSSCs in this study can reach 0.75% with the VOC of 0.56 V and JSC of 2.93 mA/cm2, and FF of 0.47.