Light Emission From Ambipolar Semiconducting Polymer Field Effect Transistors

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

TECHNICAL SUMMARY: Ambipolar polymer light emitting field-effect transistors (LEFETs) have been demonstrated. Direct imaging showed emission in a narrow region within the channel. The light intensity and the location of the emission zone are controlled by the gate bias. The emission zone is near the center of the channel at the crossover point where the electron and hole currents are equal. The gate bias induced shift in the emission zone and the ambipolar charge transport indicate that the device is truly a light emitting transistor. The funded research will focus on achieving a fundamental understanding of the operation of the light emitting field effect transistor with the goal of optimizing the emission brightness and efficiency. Specific tasks include the following: a. Lower the operating voltage for the polymer LEFET by increasing the capacitance of the gate dielectric (Ci) and by reducing the channel length of the LEFET. b. Spatially and spectrally resolve the light emission. c. Test different semiconducting polymers as the active layer in LEFETs and different metals for the source and drain electrodes. d. Push brightness to the highest level possible: e. Pulsed LEFET Operation All dielectrics break down at sufficiently high DC bias, based on dielectric strength and thickness. To further enhance brightness, even higher drive voltages will be explored through pulsed voltage operation. NON-TECHNICAL SUMMARY: Research on light emitting field-effect transistors is at the forefront of the interdisciplinary field of semidonducting and metallic polymers and the emerging field of plastic electronics. The demonstration of light emitting field-effect transistors fabricated from semiconducting polymers --- plastic light emitting field-effect transistors --- is a significant breakthrough in the field of plastic electronics. This progress provides an opportunity to study both the fundamental science and the applied science of this novel device concept. The fabrication and study of light emitting field effect transistors involves a combination of polymer science, condensed matter physics, device science, materials chemistry, interface chemistry and materials science. Consequently, research in this area is ideally suited for the interdisciplinary education and training of graduate students and post-doctoral researchers. A goal of the proposed research is the achievement of sufficiently high brightness to enable potentially important applications such as using each light emitting field-effect transistor as a pixel in a flat panel display comprising an array of such devices and/or using the architecture of the light emitting field-effect transistor to demonstrate injection lasers from semiconducting polymers.