Investigation and control of charge transport anisotropy in highly oriented friction transferred polythiophene thin films

Highly oriented thin films of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] PBTTT were prepared by friction transfer technique followed by their characterization using polarized absorption spectroscopy, angle-dependent polarized Raman spectroscopy and X-ray diffraction techniques. Orientation in high molecular weight (MW) polymers is hampered by chain folding/entanglements, which limits their macromolecular orientation. Interestingly, utilizing high molecular weight PBTTT (MW >50 kDa) and friction transfer technique, successful fabrication of highly oriented thin films with very high dichroic ratio (⁓30) was demonstrated. Role of the substrate’s surface energy and their impact on the field-effect mobility () of the oriented thin films was comprehensively investigated. Influence of annealing of the thin films as prepared on the bare and self-assembled monolayer (SAM) treated SiO2 surface exhibiting differential trends of  was systematically investigated. This was explained by partial and...