Hydrostatic pressure dependence of charge carrier transport in single-crystal rubrene devices

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.