Layer-by-Layer Conjugated Extension of a Semiconducting Polymer for High-Performance Organic Field-Effect Transistor.

A donor-acceptor (D-A) semiconducting copolymer, PDPP-TVT-29, comprising a diketopyrrolopyrrole (DPP) derivative with long, linear, space-separated alkyl side-chains and thiophene vinylene thiophene (TVT) for organic field-effect transistors (OFETs) can form highly π-conjugated structures with an edge-on molecular orientation in an as-spun film. In particular, the layerlike conjugated film morphologies can be developed via short-term thermal annealing above 150°C for 10 min. The strong intermolecular interaction, originating from the fused DPP and D-A interaction, leads to the spontaneous self-assembly of polymer chains within close proximity (with π-overlap distance of 3.55 Å) and forms unexpectedly long-range π-conjugation, which is favorable for both intra- and intermolecular charge transport. Unlike intergranular nanorods in the as-spun film, well-conjugated layers in the 200°C-annealed film can yield more efficient charge-transport pathways. The granular morphology of the as-spun PDPP-TVT-29 film produces a field-effect mobility (μ_FET) of 1.39 cm² V^-1 s^-1 in an OFET based on a polymer-treated SiO 2 dielectric, while the 27-Å-step layered morphology in the 200°C-annealed films shows high μ_FET values of up to 3.7 cm² V^-1 s^-1 . [ABSTRACT FROM AUTHOR]