Interaction of squarylium cyanine with nanoparticle TiO 2 for photoelectric conversion

Abstract

Three squarylium cyanine dyes with different attaching groups on the heterocyclic nitrogen atom were designed and synthesized. For 1,3-bis (N-3-sulfopropyl-3,3-dimethyl-2-methylene indolenine) squarylium cyanine pyridyl salt (Sq3), the apparent association constant of 3788 mol −1 liter −1 with nanoparticle TiO 2 was determined from the data of Sq3 fluorescence quenching by TiO 2 colloids, and the fluorescence lifetimes of Sq3 with or without TiO 2 were used to elucidate the kinetic information for the quenching process. ESR study provides direct evidence that electron injection from the excited singlet Sq3 to the conduction band of TiO 2 occurs. The Sq3-modified nanocrystalline TiO 2 electrode gives an overall photoelectric conversion efficiency of 2.17% and a top incident monochromatic photon-to-photocurrent conversion efficiency (IPCE) value of 6.2% at 650 nm.