Self-Assembled Liquid-Crystalline Ion Conductors in Dye-Sensitized Solar Cells: Effects of Molecular Sensitizers on Their Performance.

Dye-sensitized solar cells employing nonvolatile liquid-crystalline (LC) electrolytes that form nanostructures capable of efficient ion transport are reported. The LC electrolyte consists of a cyclic carbonate-functionalized mesogen and an iodide-based ionic liquid that nanosegregates into lamellar structures exhibiting over four times higher ion conductivities parallel to the layers than perpendicular to the layers. The self-assembled ion pathways allow efficient ion transport in the semi-solid LC state. When used together with organic dyes, DSSCs employing these LC electrolytes show higher power conversion efficiency (PCE) than metal-organic dyes. This behavior is not observed for devices containing standard liquid electrolytes. The higher PCEs of the LC-based devices can be attributed to longer electron lifetimes (τ) and higher electron densities in the photoelectrodes. The high concentration of iodide ions in the nanostructured pathways of the LC electrolyte is thought to induce reductive quenching of the ruthenium-based sensitizer, which competes with the electron injection process and lowers the τ and electron densities of the TiO2 .