We demonstrate a light-emitting organic field-effect transistor (OFET) with pronounced ambipolar current characteristics. The ambipolar transport layer is a coevaporated thin film of α-quinquethiophene (α-5T) as hole-transport material and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) as electron-transport material. The light intensity is controlled by both the drain–source voltage VDS and the gate voltage VG. Moreover, the latter can be used to adjust the charge-carrier balance. The device structure serves as a model system for ambipolar light-emitting OFETs and demonstrates the general concept of adjusting electron and hole mobilities by coevaporation of two different organic semiconductors.

Ambipolar charge injection and transport are a prerequisite for a light-emitting organic fieldeffect transistor (OFET). Organic materials, however, typically show unipolar charge-carrier transport characteristics. Consequently, organic thin-film field-effect transistors based on a single material as active layer can typically either be operated as p- or as n-channel device. In this article we show that by using a heterostructure with pentacene as hole-transport and N,N′-Ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27) as electron-transport material, ambipolar characteristics, i.e., simultaneous p- and n-channel formation, can be observed in a single device. An OFET structure is investigated in which electrons and holes are injected from Mg top and Au bottom contacts into the PTCDI-C13H27 and pentacene layers, respectively. Our device exhibits electron and hole mobilities of 3×10−3 and 1×10−4 cm2/V s, respectively. This device architecture serves as a model structure for ambipolar field-effect transistors, which are a prerequisite for light-emitting field-effect transistors.

No abstract

No abstract

We have investigated ambipolar charge injection and transport in organic field-effect transistors (OFETs) as prerequisites for a lightemitting 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,Nditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C 13 H 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 13 H 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 13 H 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 .