It is reported herein that the co-adsorption of chenodeoxycholic acid (CDCA) with the D-p-A organic dyes (E)-3(5-(4-(bis(4-(hexyloxy) phenyl) amino) phenyl) thiophen-2-yl)-2-cyanoprop-2-enoic acid (Dye-O) or (E)-3-(5(4-(bis(4-(hexylthio) phenyl) amino) phenyl) thiophen-2-yl)-2-cyanoprop-2-enoic acid (Dye-S) has a significant influence on the ground state absorption spectra of sensitized TiO2 thin films. In the absence of CDCA, evidence for aggregation was observed at even the lowest measured surface coverages. The presence of CDCA also had a significant and very beneficial influence on the unwanted charge recombination reaction between TiO2(e) and oxidized cobalt mediators. (C) 2013 Elsevier B.V. All rights reserved.