Microscopic observation of efficient intergrain charge transport processes in organic transistors of semicrystalline poly(3-hexylthiophene)

Abstract

Carrier dynamics in polymer transistors were investigated microscopically using electron spin resonance (ESR) spectroscopy for poly(3-hexylthiophene), a typical semicrystalline conjugated polymer. Charge transport processes across crystalline grains, indispensable for enhancing macroscopic mobility, are highlighted. For this purpose, we used high-molecular-weight (∼500 000) polymers to connect the grains by tie chains. Motional narrowing effects in ESR spectra demonstrated that efficient intergrain charge transport takes place for transistors with self-assembled monolayer (SAM) treatment on SiO2 gate insulators. Meanwhile, transistors without SAMs showed un-narrowed signals, indicating that the surface treatment possibly controls molecular orientations of tie chains more favorable for intergrain charge transport.