An Acetylene-Containing Perylene Diimide Copolymer for High Mobility n-Channel Transistor in Air

A new solution-processable conjugated copolymer (P1) of perylene diimide (PDI) and dithienothiophene (DTT) incorporating acetylene spacers was synthesized by palladium(0)-catalyzed Sonogashira coupling reaction. Theory calculation reveals that introduction of rod-like ethynylene spacer in the polymer main chain promotes planarity and pi-conjugation of the polymer main chain. Relative to the conjugated copolymer (P2) of PDI and DTT without acetylene spacers, polymer P1 exhibits 0.1 eV down shift of LUMO level and 89 nm red shift of low-energy absorption band. Polymer P1 in top-contact bottom-gate organic field-effect transistors (OFETs) exhibits a saturation electron mobility of 0.06 cm(2) V-1 s(-1) in air, while P2 does not function in the same device in air. Additionally, a saturation electron mobility of 0.075 cm(2) V-1 s(-1) in air, and after six days storage in air, an electron mobility of 0.034 cm(2) V-1 s(-1) were observed for P1 in bottom-contact bottom-gate OFETs; while a saturation electron mobility of 0.038 cm(2) V-1 s(-1) in air, and after six days storage in air, an electron mobility of 0.013 cm(2) V-1 s(-1) were observed for P2 in the same device. The better air stability and higher electron mobility of P1 are attributed to densely ordered packing of the polymer chains excluding oxygen or water and the lower LUMO level of P1.