INTERACTION OF SEMICONDUCTOR COLLOIDS WITH J-AGGREGATES OF A SQUARAINE DYE AND ITS ROLE IN SENSITIZING NANOCRYSTALLINE SEMICONDUCTOR-FILMS

The role of bis(2,4,6-trihydroxyphenyl)squaraine, Sq, in sensitizing large bandgap semiconductors has been investigated in the present study. The dye in its aggregate form readily interacts with the TiO2 colloids giving rise to a new charge transfer band in the red region. The apparent association constant for the dye aggregate and TiO2 colloid as determined from a Benesi-Hildebrand plot is 1600 M(-1). Nanocrystalline semiconductor films prepared from TiO2, ZnO, and SnO2 colloids have been modified with Sq to probe the photosensitization effects. Both dye monomers and aggregates were found to participate in the charge injection process. An incident photon-to-photocurrent efficiency up to 0.7% has been observed.