N-Type Building Blocks for Organic Electronics. A Homologous Family of Fluorocarbon-Substituted Thiophene Oligomers with High Carrier Mobility

A novel series of alpha,omega-diperflurorohexyl-substituted thiophene oligomers [DFH-nTs; C sub 6 F sub 13-(thiophene) sub n-C sub 6 F sub 13; n = 2 - 6] has been synthesized, and the impact of fluoroalkyl substitution and conjugation length assessed vis-a-vis the corresponding fluorine-free analogues [DH-nT; C sub 6 H sub 13-(thiophene) sub n-C sub 6 H sub 13; n = 4 - 6]. Trends in DFH-nT and DH-nT molecular packing, optical absorption, HOMO-LUMO gap, and pi-pi interactions are found to be strikingly similar. However, fluroalkyl substitution substantially enhances thermal stability, volatility, and electron affinity. FET measurements indicate that all the longer members of the DFH-nT series are n-type semiconductors with unoptimized mobilities and I sub on: I sub off ratios approaching 0.05 cm sup 2/Vs and 10 sup 5, respectively. This family represents the first example of a homologous series of variable core pi-conjugation length n-type OTFT components.