Light emission from an ambipolar semiconducting polymer field effect transistor: Analysis of the device physics

Abstract

Light emitting field-effect transistors (LEFETs) were fabricated with a low work function metal (calcium) and a high work function metal (gold) as the source and drain electrodes. The goldelectrode serves as the source for holes into the π band and the drain for electrons from the π * band; the calciumelectrode serves as the source for electrons into the π * band and the drain for holes from the π band. For 65 V < V G < 103 V , the LEFET operates in the ambipolar regime. The emission zone has been spatially resolved (as it is moved across the channel by sweeping the gate voltage) using confocal microscopy; the full width at half maximum is 2 μ m . At the gate voltage extremes ( V G = 0 or V G = 150 V ), the electron (hole) density extends all the way across the 16 μ m channel such that the electron (hole) accumulation layer functions as the cathode (anode) for a light-emitting diode, with opposite carrier injection by tunneling; i.e., the carrier densities are sufficiently high that the accumulation layer functions as a low resistance contact, implying near metallic transport.