Electrochemical doping of alpha-ethyl-disubstituted oligothiophenes and electrical conductivities of the resulting radical-cation salts

Electrochemical doping of alpha-ethyl-disubstituted oligothiophenes and the electrical conductivity of the resulting radical-cation salts have been studied. 5,5'''-Diethyl-2,2':5',2 '':5 '':2'''-quaterthiophene (DEt4T) and 5,5''''-diethyl-2,2':5',2 '':5 '',2''':5''',2''''-quinquethiophe (DEt5T) are found to contrast with each other in the stoichiometry and electrical properties of the resulting solid radical-cation salts. The DEt4T and DEt5T radical-cation salts with a doping extent of ca. 100 and 50%, respectively, produced by electrochemical doping exhibited room-temperature conductivities of 9 x 10(-8) and 5 x 10(-3) S cm(-1) with activation energies of 0.54 and 0.11 eV, respectively.