A Light Emitting Field-effect Transistor Based On Pentacene/Alq₃Vertical Heterojunction

OLEFETs are an emerging class of multifunctionaloptoelectronic devices that combine the electrical switching andcurrent modulating functionalities of a field-effect transistor(FET) with the capability of electroluminescence (EL) from anOLED in a single device architecture. As one of the simplest integrated organicoptoelectronic devices possessing unique EL properties, OLEFETs not only have potential applications in active matrix full colorelectroluminescent displays, optical communication systems, and elec-trically pumped organic lasers [4], but also provide a newway for the fundamental studies of optical and electronic characteristicsof organic semiconductors. We report a top-contact light emitting field-effect transistor based on an asymmetric vertical heteroj unction using pentacene as a field-effect layer and tris-(8-hydroxyquinolinato) aluminum (Alq3) as an electron transport and luminescent material, which is fabricated on an indium tin oxide (ITO)-coated glass substrate with poly (methyl methacrylate)(PMMA) as a gate dielectric. The Alq3layer underneath the drain electrode roughly occupies one half of the pentacene surface forming an asymmetric heterojunction with pentacene. A hole transport layer N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB) is introduced to occupy the other half of the pentacene surface underneath the source electrode to allow vertical hole transport in the device.We have realized the electrical switching functionality of a field-effect transistor (FET) and the control of electroluminescence (EL) simultaneously under ambient atmosphere. The device exhibits typical p-channel characteristics and green emission from Alq3is observed adjacent to the drain electrode. A working principle of the device is discussed in detail.Furthermore, this device configuration enables high-spatial-resolution fluorescence imaging of device.