Ultrathin Polythiophene Films Prepared by Vertical Phase Separation for Highly Stretchable Organic Field-Effect Transistors

Physically blending semiconducting conjugated polymers with elastomeric materials and precisely controlling the resulting film structure provides an effective strategy to obtain intrinsically stretchable semiconducting polymers. Here, vertically phase-separated ultrathin poly(3-hexylthiophene) (P3HT) and polystyrene-b-polyisoprene-b-polystyrene (SIS) blend films are developed for one-step fabrication of semiconductor and insulator layers of organic field effect transistors (OFETs). The phase-separated structure, surface morphology, and tensile deformation are characterized by UV-vis absorption spectroscopy, atomic force microscopy, and optical microscopy. The blend film device maintains 43% of its mobility compared with 0.1% mobility of the pristine P3HT films after 50% stretch. The deformability of the films is efficiently improved by blending proved by both the finite element analysis and the dichroic ratio measurements. The P3HT/SIS blended films possess reproducible properties under 200 continuous stretch-release cycles at a strain of 50% without significantly reduced mobilities. The fully-stretchable OFETs on polydimethylsiloxane substrate are also investigated and show a stretchability up to 70% and good electrical recovery properties after stretch-release process. The vertical phase-separated structure obtained by the blends provides an effective way to easily fabricate stretchable devices with a balance between their mechanical and electrical properties.

Automated summary

Physically blending semiconducting conjugated polymers with elastomeric materials and precisely controlling the resulting film structure provides an effective strategy to obtain intrinsically stretchable semiconducting polymers. The phase-separated ultrathin P3HT and SIS blend films maintain reproducible properties under 200 continuous stretch-release cycles at a strain of 50%, showing a balance between their mechanical and electrical properties. The deformability of the films is efficiently improved by blending, as demonstrated by both finite element analysis and dichroic ratio measurements.