3.3.4.2. Thin film transistors (TFTs)
Regioregular P3HT is one of most promising and most studied solution processable rod structures. Formation of ordered supermolecular structures in these regioregular materials correlates strongly with their excellent electrical conductance. By varying the non-conjugated coil segment, the electrical properties can be further improved for transistor devices based on P3HT-coil block copolymers. Such block copolymers can self-assemble into a number of nanscale morphologies for advanced nanoelectronic device applications. For example, the P3HT-b-PMA rod–coil block copolymers developed by the McCullough and coworkers showed good organic semiconductor characteristics with high field-effect mobilities (∼0.01 cm2/VS), comparable with that of regioregular P3HT, despite the presence of the nonconjugated segments ( Fig. 31) [51]. The driving force for the formation of a nanofibrillar structure is dictated by the immiscibility of PMA and P3HT. Therefore, the strong tendency of regioregular P3HT to self-assemble into nanofibrillar structure contributes to the relatively high mobilites. Using rod–coil block copolymers system opens a new route for organic TFT devices, to modify the interface between the functional nano-domain while preserving the ordering of the conjugated rod segment.