High Electron Mobility in Conjugated Polymers Processed with Nonchlorinated Solvents for Organic Thin Film Transistors

Herein, we report a series of conjugated polymers P1–P4, which were synthesized through aldol polymerization using toluene as the solvent and p-toluene sulfonic acid as the sole catalyst. We investigated their solubility, optical and electrochemical properties, wettability, and aggregation behaviors in (or treated with) 2-methyltetrahydrofuran (2-MeTHF) and o-dichlorobenzene (o-DCB). We found that the 2-MeTHF-treated thin films of P1–P4 have slightly different frontier molecular orbital energy levels in comparison with those of their o-DCB-treated counterparts, respectively. Moreover, 2-MeTHF-processed organic thin film transistors (OTFTs) based on these polymers exhibited a higher n-type transport performance. Notably, the P2-based device afforded the maximum electron mobility of 3.14 cm2 V–1 s–1, which is among the highest for the n-type polymer-based OTFTs processed with nonchlorinated solvents to date. Microstructure characterizations further revealed that all these 2-MeTHF-treated thin films have enhanced film morphology and molecular orientation stacking compared to those of their respective o-DCB-treated ones.