EAGER: The Organic Permeable Base Transistor: A Nanoscale Organic Switch

Kent State University, Kent OH

Investigators

Abstract

Abstract Nontechnical: Organic Transistors hold the promise of enabling flexible and low-cost electronics. One of the latest additions to this field is the Organic Permeable Base Transistor. Only recently has it been found that Organic Permeable Base Transistors reach very high output currents and operate at very low driving voltages. However, until now this excellent performance has come at the expense of significant base currents leading to static power losses and ruling out the use of Organic Permeable Base Transistors in most cases. The project addresses this challenge. The origin of base currents is studied and approaches to suppress them are tested. If successful, the project will increase the switching speed of organic transistors by an order of magnitude, which will accelerate commercialization of flexible electronics. Additionally, the reduction of base currents of Organic Permeable Base Transistors will open new fields of application such as flexible backplanes for active matrix displays. To broaden the impact of the project, additional measures aim at leveraging the research and using it as a vehicle to improve STEM education. The PI will develop courses targeted at high school teachers offering "College Credit Plus" classes. These "College Credit Plus" classes allow high school students to earn college credit early and free of cost, which has the potential to increase the enrollment in STEM degrees. Furthermore, selected work-packages of the proposal will be offered as Senior Honors Project to a student majoring in physics and mathematics. Furthermore, graduate students will be trained in a socially important research area, which will make them part of a globally competitive workforce. Students will participate in a summer school jointly organized with Case Western Reserve University providing them with all necessary background in organic semiconductors, device physics, and device engineering. Technical: The goal of this project is to unravel the origin of base currents in Organic Permeable Base Transistors. The specific research objectives are a) to prove that a drift-diffusion simulation of the device can quantitatively reproduce the device behavior, in particular the magnitude of base currents and b) to test the hypothesis that a self-assembled monolayer on top of the base electrode can significantly reduce base leakage currents. A quantitative agreement between the drift-diffusion simulation and experiment will be reached by a thorough characterization of the morphology of the base electrode and of the charge transport in all layers of the Organic Permeable Base Transistor. In particular, the growth of the porous base electrode and the nature of base currents will be studied by scanning probe methods, transmission electron microscopy, and electrical characterization of test devices. Self-organized layers of insulating phosphonic acids will be grown on top of the base. Charge transport across these layers will be quantified and modeled, leading to a concise description of Organic Permeable Base Transistors operating at significantly increased current amplification and thus lower static power dissipation. As a result of the project, an experimentally validated model of the Organic Permeable Base Transistor will become available to the scientific community, which will significantly enhance the fundamental understanding of the device and will enable a rational design of Organic Permeable Base Transistors. Furthermore, the project will increase the knowledge on vertical charge transport in poly-crystalline organic films and will provide detailed charge carrier mobility models for standard materials used in Organic Permeable Base Transistors. Clarifying the nature of base currents will improve the understanding of injection into a disordered organic semiconductor and will lead to a quantitative description of injection from oxidized aluminum into the organic semiconductor C60.