INTRINSIC TRANSPORT-PROPERTIES AND PERFORMANCE LIMITS OF ORGANIC FIELD-EFFECT TRANSISTORS

The field-effect mobility in thin-film transistors based on alpha-sexi thiophene (alpha-6T) and related materials displays a temperature depe ndence that is remarkably nonmonotonic. Above a transition temperature T-T (specific to a given material) the transport is thermally activat ed, whereas below T-T there is a very steep enhancement of the mobilit y. In the activated regime, the results are well described by the theo retical predictions for small polaron motion made by Holstein in 1959. An analysis of the transistor characteristics shows that the hopping transport in these devices is intrinsic. Performance limits for device s based on alpha-6T and related materials were established; these limi ts point to the strong possibility that better molecular materials for transistor applications may be designed from first principles.