STRUCTURE AND ELECTRONIC-PROPERTIES OF POLYTHIOPHENE AND POLY(3-ALKYLTHIOPHENE) FILMS ELECTROPOLYMERIZED ON INDIUM TIN OXIDE (ITO) GLASS ATELEVATED POTENTIALS

Homogeneous and flexible films of polythiophene are known to be diffic ult to obtain electrochemically on indium tin oxide (ITO) glass electr odes using normal 1,6-1,7 V applied voltage. The situation is greatly improved by using higher voltage. 0,1 - 10 mum thick films of polythio phene (PT) and various poly(3-alkylthiophene)s (P3AT's) (alkyl = methy l (P3MT), hexyl (P3HT) and octyl (P3OT)) were electropolymerized on IT O-covered glass anodes under an applied voltage of 8 V vs. an Ag/AgCl reference eletrode. In this paper we report upon the properties of the se films compared to their chemically and at low-voltage electrochemic ally polymerized equivalents. Generally, the films have all the proper ties known for PT and P3AT's. Characteristics such as thermo- and solv atochromism, conductivity and electronic band structure as studied by ultraviolet photoemission spectroscopy and optical absorption were com parable to the properties shown by the reference samples. However, the structure of high-voltage films differs considerably from those repor ted for chemically polymerized samples. The high-voltage films contain a higher amorphous fraction, and the polymer is more cross-linked and branched.