Bandlike Transport in Ferroelectric-Based Organic Field-Effect Transistors

The dielectric constant of polymer-ferroelectric dielectrics may be tuned by changing the temperature, offering a platform for monitoring changes in interfacial transport with the polarization strength in organic field-effect transistors (FETs). Temperature-dependent transport studies of FETs are carried out from a solution-processed organic semiconductor, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene), using both ferroelectric-and nonferroelectric-gate insulators. Nonferroelectric dielectric-based TIPS-pentacene FETs show a clear activated transport, in contrast to the ferroelectric dielectric polymer, poly (vinylidene fluoride-trifluoroethylene), where a negative temperature coefficient of the mobility is observed in the ferroelectric temperature range. The current-voltage (I-V) characteristics from TIPS-pentacene diodes signal a space-charge-limited conduction (SCLC) for a discrete set of trap levels, suggesting that charge injection and transport occurs through regions of ordering in the semiconductor. The carrier mobility extracted from temperature-dependent I-V characteristics from the trap-free SCLC region shows a negative coefficient beyond 200 K, similar to the trend observed in FETs with the ferroelectric dielectric. At moderate temperatures, the polarization-fluctuation-dominant transport inherent in a ferroelectric dielectric, in conjunction with the nature of traps, results in an effective detrapping of the shallow-trap states into more mobile states in TIPS-pentacene.