Show description

9). Most interestingly, despite all these factors, X-ray diffraction patterns of P29 indicate very strong lamellar ordering, and FETs fabricated from these materials show high field-effect mobilities. All these results appear quite surprising in view of the previously mentioned findings on the role of side-chain interdigitation/ordering and indicate that strong interdigitation and formation of extended regular terrace-like structures are not necessary for high carrier mobility in polythiophene-like materials.

4). 5). Rasmussen and coworkers [34] pioneered the use of N-alkyldithieno[3,2-b:2′ ,3′ -d]pyrrole (DTP) as a very promising fused aromatic building block for electronic materials. This core exhibits a completely flat crystal structure, indicating good π conjugation across the fused rings. Upon polymerization, poly(N-alkyl dithieno[3,2-b:2′ ,3′ -d]pyrrole)s exhibit excellent stability in their oxidized state, have low band gaps, and show efficient red fluorescence in solution [35]. However, some Poly(dithieno[3,2-b:2′ ,3′ -d]pyrrole) (PDTPs) have low solubilities and low molecular weights, which greatly limit their use in devices.

Therefore, high I on :I off ratios for P3AT are consistently achieved by preparing and testing the devices in dry N2 [23]. To address these problems, new polythiophenes have been developed. Ong et al. reported a class of solution-processable regioregular polyquaterthiophenes (PQTs) that affords excellent FET performance under ambient conditions. This class of polythiophenes was designed on the basis of the following structural 10 1 Polymeric and Small-Molecule Semiconductors for Organic Field-Effect Transistors considerations: (i) presence long alkyl side chains for solution processability; (ii) structural regularity to induce and facilitate molecular self-assembly; and (iii) control of the π-conjugation extension to achieve a delicate balance between transistor functionality and oxidative doping stability.