Perfluoroalkyl-Functionalized Thiazole Thiophene Oligomers as N-Channel Semiconductors in Organic Field-Effect and Light-Emitting Transistors

Abstract

Despite their favorable electronic and structural properties, the synthetic development and incorporation of thiazole-based building blocks into n-type semiconductors has lagged behind that of other pi-deficient building blocks. Since thiazole insertion into pi-conjugated systems is synthetically more demanding, continuous research efforts are essential to underscore their properties in electron-transporting devices. Here, we report the design, synthesis, and characterization of a new series of thiazolethiophene tetra- (1 and 2) and hexa-heteroaryl (3 and 4) co-oligomers, varied by core extension and regiochemistry, which are end-functionalized with electron-withdrawing perfluorohexyl substituents. These new semiconductors are found to exhibit excellent n-channel OFET transport with electron mobilities (mu(e)) as high as 1.30 cm(2)/(V center dot s) (I-on/I-off > 10(6)) for films of 2 deposited at room temperature. In contrary to previous studies, we show here that 2,2'-bithiazole can be a very practical building block for high-performance n-channel semiconductors. Additionally, upon 2,2'- and 5,5'-bithiazole insertion into a sexithiophene backbone of well-known DFH-6T, significant charge transport improvements (from 0.0010.021 cm(2)/(V center dot s) to 0.200.70 cm(2)/(V center dot s)) were observed for 3 and 4. Analysis of the thin-film morphological and microstructural characteristics, in combination with the physicochemical properties, explains the observed high mobilities for the present semiconductors. Finally, we demonstrate for the first time implementation of a thiazole semiconductor (2) into a trilayer light-emitting transistor (OLET) enabling green light emission. Our results show that thiazole is a promising building block for efficient electron transport in ?-conjugated semiconductor thin-films, and it should be studied more in future optoelectronic applications.