ZnO double layer film with a novel organic sensitizer as an efficient photoelectrode for dye-sensitized solar cells

A novel organic sensitizer, coded CR147, is applied to sensitize a ZnO-based dye-sensitized solar cell (DSSC). The common problem of ZnO dissolution and Zn²⁺/dye agglomeration, caused by the use of ruthenium-based dyes, is solved by the application of this CR147 dye. The highest power conversion efficiency (η) of 4.77% is achieved for the DSSC using a photoanode with a film of commercial ZnO nanoparticles (C-ZnO) and the CR147 dye, while the η is only 3.41% for the DSSC with the commercial N719 dye. The cell performance with the CR147 dye is further improved by using a photoanode with the double layer ZnO film (D-ZnO), composed of an underlayer with coral-like ZnO nanocrystals and an overlayer with hexagonal club-like ZnO submicrocrystals. The DSSC with the D-ZnO film exhibits an η of 6.89%, which is ca. 45% higher than that of the DSSC with the C-ZnO film (4.77%). This higher efficiency is attributed to the superior charge transfer and light-scattering abilities provided by coral-like ZnO nanocrystals and hexagonal clubs-like ZnO submicrocrystals, respectively, with reference to these parameters of C-ZnO.