P3HT and Other Polythiophene Field-Effect Transistors

Long before the potential of poly(3-hexylthiophene) (P3HT) in bulk-heterojunction solar cells was discovered, this conjugated polymer was one of the first and strongest contenders as a high mobility, solution-processable semiconductor for organic field-effect transistors (FETs). Many of the fundamental charge transport properties that were investigated for P3HT-FETs have informed subsequent studies of P3HT-based solar cells and the development of other high-mobility polythiophene-based polymers. Here we will give a brief overview of P3HT transistors, including the general working principles of polymer FETs and the various factors that influence device performance, such as regioregularity, molecular weight, solvents, chain alignment, and doping. Strategies for tuning the P3HT nano-and microstructure by using blends and copolymers and ways to reach the limits of charge transport in P3HT at high carrier densities will be discussed. Finally, we will survey some of the new polythiophene derivatives that have been developed over the last decade and may replace P3HT as the most popular polymer semiconductor.