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Hydrostatic pressure was applied to single-crystal rubrene photoconductors and p channel field-effect transistors. Under illumination from a GaInN light-emitting diode, we observed linear increases in photoconductivity, by up to a factor of 2.1 at 0.43 GPa. We also measured increases in the drain current of the single-crystal rubrene organic field-effect transistors (OFETs) with increasing pressure up to 0.52 GPa. Analyzing the transfer characteristics of the OFETs, we extracted the pressure dependence of the field-effect hole mobility. The different OFETs examined showed similar hole mobility increase ratios with pressure, although their atmospheric pressure mobilities varied by more than a factor of two. Threshold voltages shifts with pressure were small. All results were reversible, i.e., the measured currents returned to their atmospheric pressure values upon release of pressure unless complete device failure occurred at the highest pressure. [ABSTRACT FROM AUTHOR]

Large operating voltages are often required to switch organic field-effect transistors (OFETs) on and off because commonly used gate dielectric layers provide low capacitive coupling between the gate electrode and the semiconductor. We present here a pentacene OFET gated by a solution-deposited polymer electrolyte film in which the current was modulated over four orders of magnitude using gate voltages less than 2 V. A subthreshold slope of 180 mV per decade of current was observed during transistor turn on at a source-drain bias of -1 V; the estimated dielectric layer specific capacitance was 5 μF/cm2. Sweep rate-dependent hysteresis may be attributed to a combination of ion migration and charge carrier trapping effects. Strategies to improve switching speeds for polymer electrolyte-gated OFETs are also discussed. [ABSTRACT FROM AUTHOR]

In this letter we report the use of roughly polished aluminum substrates with spin-coated polymer-smoothing layers for the fabrication of pentacene field-effect transistors. Transistors with spin-coated poly(methylmethacrylate) gate insulator layers were fabricated and showed good performance. On the gate insulator surface, the root-mean-square roughness was found to be 0.18 nm, significantly smaller than the aluminum surface roughness, which is on the scale of tens of nanometers. Field-effect carrier mobilities extracted from the device data reached 0.75 cm2 V-1 s-1; the maximum on/off current ratio was near 5×106. [ABSTRACT FROM AUTHOR]

Single-crystal organic field-effect transistors (SX-OFETs) with channel lengths of 1 and 100 μm have been fabricated by adhering thin crystals of tetracene to freshly ashed SiO2 substrates containing countersunk gold contacts. The intrinsic transport properties of the tetracene single crystals, corrected for potential contact effects by using a standard four-probe configuration, have been measured from room temperature down to 4.2 K. These OFETs exhibit mobilities as high as 0.1 cm2 V-1s-1, subthreshold swings of <500 mV/decade, and Ion/Ioff ratios in excess of 109. The larger devices (L=100 μm,W=1000 μm) show thermally activated mobilities over the temperature range 200 K105 V/cm. [ABSTRACT FROM AUTHOR]