Electrochemical characterization of newly synthesized polyterthiophene benzoate and its applications to an electrochromic device and a photovoltaic cell

A novel conjugated polymer bridged a benzene ring between polymer backbone and carboxylic acid, poly(2,2':5',2 ''-terthiophene-3'-p-benzoic acid) (pTTBA) has been synthesized and applied to an electrochromic device and a polymer-sensitized solar cell. The pTTBA is characterized as a photo sensitizer on a TiO2 layer, and the cell performance is compared with that of poly(5,2':5',2 ''-3'-carboxylic acid) (pTTCA), which does not contain the benzene ring. The conductivity of pTTBA is determined to be 0.24 S cm(-1) at 1.4 V. The spectroelectrochemical study shows that pTTBA switches to an opaque dark-blue in its oxidized state from transmissive yellow in its reduced state with a contrast of 53%. The polymer film exhibits a good optical switching time within 0.82 s. The pTTBA film has a band gap energy of 1.98 eV. The impedance results show that the pTTBA is the enhanced electron transfer process in the TiO2/polymer/electrolyte interface in comparison with that of pTTCA. A photovoltaic cell is assembled with pTTBA coated on the TiO2 electrode as an anode and Pt-counter electrode as a cathode. The electrolyte is used a propionitrile solution containing I-/I-3(-) as a redox couple. The higher energy conversion efficiency was achieved with the pTTBA based dye solar cell (3.97%) (active layer 0.24 cm(2)). (C) 2012 Elsevier Ltd. All rights reserved.