Molecular photosensors of self-assembled monolayers: electron acceptor-photosensitizer dyad on an ITO surface

Abstract

Self-assembled monolayers of di-(3-diaminopropyl)-viologen (DAPV) were prepared on a tin-doped indium oxide (ITO) surface as acceptor layers. Photoactive layers of Ru(2,2'-bipyridine-4,4'-dicarboxylic acid)(2)( NCS)(2) were formed on DAPV to give an acceptor - sensitizer dyad on ITO. The photon energy was monitored by measuring the ITO conductivity change. Under illumination, the ITO conductivity increased with the current increasing by increments of 8 nA indicating the construction of molecular photosensors on the ITO surface. The concept of a molecular photosensor was further applied to a molecular photovoltaic system. The presence of the viologen moiety bridges the energy levels between the LUMO of the Ru sensitizer and ITO, and improves the efficiency of a photovoltaic cell with a quantum yield of 18.4% at 3.3 mW cm(-2).