Novel room temperature ionic liquids of hexaalkyl substituted guanidinium salts for dye-sensitized solar cells

A novel family of room temperature ionic liquids, N,N-diethyl-N-',N-'-dipropyl-N-''-hexyl-N-''-methylguanidinium iodide (SGI) and N,N,N-',N-'-tetramethyl-N-'',N-''-dipentylguanidinium tricyanomethanide (SGTM) were designed and synthesized. Due to the strong charge delocalization on the tricyanomethanide anion and, thus, weaker ion-pairing, SGTM has a lower viscosity than SGI salt that has iodide as an anion. SGI was successfully used as an iodide resource for dye-sensitized nanocrystalline solar cells. The device with a solvent-free, SGI-based electrolyte achieved a 5.9% power conversion efficiency under an air mass 1.5 incident light of 9.47 mW/cm(2).