High-Temperature Rubbing: An Effective Method to Fabricate Large-Scale Aligned Semiconducting and Conducting Polymer Films for Applications in Organic Electronics

Conjugated polymers (CPs) are ubiquitous in plastic electronics in the form of semiconducting and conducting polymers that are central in devices such as solar cells, field effect transistors, and thermoelectric generators. Exploiting the anisotropic properties of such conjugated materials calls for advanced and effective methods of growth and orientation. First, this contribution reviews different alignment methods of conjugated polymers used in plastic electronics. Second, we present the state of the art for the method of high-temperature rubbing that was extensively used to fabricate aligned polymer semiconductors (PSC) and conducting polymer (CP) films. Examples are given to illustrate how this versatile method of large-scale orientation can be used to design devices with anisotropic opto-electronic properties. Finally, we emphasize the recent progress made in the fabrication of highly ordered and oriented CPs by controlled doping of well-crystallized PSCs such as regioregular poly(3-hexylthiophene-2,5-diyl) and poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene]. The way dopant molecules are introduced into and modify the crystal lattice of these PSCs is presented. The impact of the semi-crystalline structure of the polymers on doping and resulting thermoelectric performances of oriented thin films is discussed.