Ruthenium(ii)-polypyridyl zirconium(iv) metal-organic frameworks as a new class of sensitized solar cells

A series of Ru(ii)L₂L' (L = 2,2'-bipyridyl, L' = 2,2'-bipyridine-5,5'-dicarboxylic acid), RuDCBPY, -containing zirconium(iv) coordination polymer thin films have been prepared as sensitizing materials for solar cell applications. These metal-organic framework (MOF) sensitized solar cells, MOFSCs, each are shown to generate photocurrent in response to simulated 1 sun illumination. Emission lifetime measurements indicate the excited state quenching of RuDCBPY at the MOF-TiO₂ interface is extremely efficient (>90%), presumably due to electron injection into TiO₂. A mechanism is proposed in which RuDCBPY-centers photo-excited within the MOF-bulk undergo isotropic energy migration up to 25 nm from the point of origin. This work represents the first example in which a MOFSC is directly compared to the constituent dye adsorbed on TiO₂ (DSC). Importantly, the MOFSCs outperformed their RuDCBPY-TiO₂ DSC counterpart under the conditions used here and, thus, are solidified as promising solar cell platforms.