Photoelectrical properties in poly(alkyl/alkoxy-terthiophenes): dependence on the alkyl-chain length

The length of the alkyl-groups affects both the spectrophotometric and the electrochemical properties of poly(alkoxy-alkyl-terthiophenes) films prepared by cyclic voltammetry. The maximum absorbance shifts towards higher wavelengths and the oxidation peak towards cathodic potentials as the alkyl-chain length increases. Moreover, it was found that the photoelectrical performance exhibited by poly(alkoxy-alkyl-terthiophenes)-based devices improved from poly(4,4 " -dipenthoxy-3-dodecyl-2,2':5',2 " -terthiophene) to poly(4,4 " -dipenthoxy-3'-hexyl-2,2':5',2 " -terthiophene), probably due to an increasing hopping mobility, and remained constant or somewhat decreased by going from poly(4,4 " -dipenthoxy-3'-hexyl-2,2':5,2 " -terthiophene) to poly(4,4 " -dimethoxy-3'-methyl-2,2':5',2 " -terthiophene) possibly for a lower planarity of polythiophene chains. (C) 2001 Elsevier Science B.V. All rights reserved.