Doubly p-functionalized zinc(II) porphyrin-sensitized TiO₂ solar cells

Functionalized porphyrin at β-positions with carboxylic acid groups was prepared to investigate the photovoltaic function as dye-sensitized nanocrystalline-TiO₂ solar cells. The electronic structures of the porphyrin macrocyclic core are strongly coupled with olefinic side chains so that the absorption spectrum exhibits broad and red-shifted Soret and Q-bands. 2b-Zn, which is a metallated porphyrin with 2-propenoic acid groups at two β-positions, exhibits the power conversion efficiency of 5.18 %. From such photovoltaic performance, we can suggest that multiple pathways through olefinic side chains at two P-positions enhance the electron injection efficiency. For improvement of the solar cell efficiency, we have employed empirical surface modification which is a post-treatment of the TiO₂ film by aqueous TiCl4. As a result, post-TiCl₄ treated cell exhibits the power conversion efficiency of 5.37 % and the maximum incident photon to current efficiency of 67.2 % in the Soret band region.