Light-emitting ambipolar organic heterostructure field-effect transistor

Abstract

We have investigated ambipolar charge injection and transport in organic field-effect transistors (OFETs) as prerequisites for a light-emitting organic field-effect transistor (LEOFET). OFETs containing a single material as active layer generally function either as a p- or an n-channel device. Therefore, ambipolar device operation over a wide range of operating voltages is difficult to realize. Here, we present a highly asymmetric heterostructure OFET architecture using the hole transport material pentacene and the electron transport material N, N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C 13H 27). Efficient charge carrier injection is achieved by using Au as bottom contact for hole injection into pentacene and Mg as top contact for electron injection into PTCDI-C 13H 27. The device characteristic of this asymmetric heterostructure shows all features of ambipolar operation. For example, a typical transistor characteristic with a linear and saturation region is observed for small drain-source voltage V DS. For large V DS, the current increases due to additional injection of charge carriers of opposite sign from the drain contact. In that regime, both types of charge carriers are present in the device. Thus, the thin-film transistor can be operated in a mixed state in which both electron and hole currents are transported within the device and where the double injection regime is controlled by the gate voltage. Our device exhibits electron and hole mobilities of 3 × 10 −3 cm 2/Vs and 1 × 10 −4 cm 2/Vs, respectively. Investigation of a bulk heterostructure of a thienylene derivative and PTCDI-C 13H 27 results in a light-emitting field-effect transistor. The light emission is controlled by both the drain-source voltage V DS and the gate voltage V G.