Interfacial Morphology and Photoelectrochemistry of Conjugated Polyelectrolytes Adsorbed on Single Crystal TiO2

The nanoscale morphology and photoactivity of conjugated polyelectrolytes (CPEs) deposited from different solvents onto single crystal TiO2 were investigated with atomic force microscopy (AFM) and photocurrent spectroscopy. CPE surface coverages on TiO2 could be incremenentally increased by adsorbing the CPEs from static solutions. The solvents used for polymer adsorption influenced the surface morpohology of the CPEs on the TiO2 surface. Photocurrent spectroscopy measurements in aqueous electrolytes, using iodide as a hole scavenger, revealed that the magnitude of the sensitized photocurrents was related to the surface coverages and the degree of aggregation of the CPEs as determined by AFM imaging. Absorbed photon-to-current efficiencies approaching 50% were measured for CPE layers as thick as 4 nm on TiO2. These results suggest that precise control of CPE morphology at the TiO2 interface can be achieved through optimization of the deposition conditions to improve the power conversion efficiencies of polymer-sensitized solar cells.