Characteristics of water-soluble polythiophene:: TiO2 composite and its application in photovoltaics -: art. no. 094906

We have studied the characteristics of composites of an environmentally friendly water-soluble polythiophene sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (PTEBS) and TiO2. We observed that the ultraviolet-visible absorption spectrum of low molecular weight PTEBS is redshifted possibly due to the formation of aggregates. Cyclic voltammetry reveals the values of highest occupied molecular orbitals and lowest unoccupied molecular orbitals for PTEBS. A factor of 7 in photoluminescence quenching indicates that the exciton dissociation and charge separation occur successfully at the PTEBS:TiO2 (1:1 by weight) interface. This enhances the possibility that the separated charges will reach the electrodes before recombining. Scanning electron micrograph images show how the PTEBS and TiO2 are interconnected and form paths to the electrodes to improve charge transport. Photovoltaic devices with TiO2:PTEBS composite achieved an energy conversion efficiency of eta=0.015%, a short circuit current of J(SC)=0.22 mA/cm(2), an open circuit voltage of V-OC=0.72 V, and a fill factor of FF=0.29 under similar to 300 mW/cm(2) white light illumination. (c) 2005 American Institute of Physics.