Effect of side chain length on the electrochemical and photoresponse characteristics of poly[3-(2′,5′-dialkoxyphenyl)thiophenes]

Poly[3-(2′,5′-dioctyloxyphenyl)thiophene] (PDOOPT), poly[3-(2′,5′-diheptyloxyphenyl)thiophene] (PDHOPT) and poly[3-(2′,5′-dibutyloxyphenyl)-thiophene] (PDBOPT) have been prepared electrochemically from their monomers within nanocrystalline titanium dioxide (nc-TiO2) porous surface deposited on indium doped tin oxide coated glass (ITO-glass) for solar cell application. The redox properties of the polymers were characterized using cyclic voltammetry. The energy levels of the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) have been estimated from their cyclic voltammograms and UV–vis absorption spectra. The poly[3-(2′,5′-dialkoxyphenyl)thiophenes] studied sensitize nc-TiO2 in liquid-state photoelectrochemical cells. Devices that consist of PDBOPT/nc-TiO2 photoactive electrode showed improved performance over those that consist of PDHOPT/nc-TiO2 and PDOOPT/nc-TiO2. PDBOPT/nc-TiO2 based devices produced an open-circuit voltage of 0.56 V, a short-circuit current of 45 μA/cm2, and a fill factor of 0.52 when illuminated with white light intensity of 80 mW/cm2.