Associate Professor The College of New Jersey, NJ, United States
Organic Thin-Film Transistors are simulated for gas sensing application both in a single transistor and circuit configurations. Because of their environmental toxicity, NO2 and NH3 gases are getting increasing attention. The current commercial sensors of these gases are based on inorganic metal oxide active materials. However, Organic Thin-Film Transistors (OTFTs) offer a potential of designing high selective, low-cost, low-power, and low-operating temperature gas sensors. For this work NO2 is chosen as the analyte of interest. P6 and P7 polymers are used as active material for the transistor channels. Results of simulation are compared with experiment. Drift-diffusion (DD) simulation model is used in which the basic equations used are similar to those used for a single-crystal device except that traps and defects are included in the model. Hoping transport model in the context of the effective transport energy was implemented with Gaussian density of states. The Gaussian distribution represents the intrinsic doping property of the organic semiconductor due to its structural defects. Gas sensing is accounted for by doping dependent mobility model in the organic active material. To simulate the humidity sensitivity of the transistor/circuits, we used a uniform trap distribution at a trap energy level of 0.4eV. The density of doping in the polymer and the quantity of traps and interface charges are extracted by matching the simulation I-V curves with experiment. Compared to P6 and P7 single transistor gas sensors, the sensor in circuit configuration has an advantage of maintaining a significant level of analyte sensitivity under humidity exposure.
W. Wondmagegna , Shwetha Rajua, Nathaniel McKeeverb, Tushita Mukhopadhyayab, Howard E. Katzb, Electrical and Computer Engineering Department, The College of New Jersey, NJ 08628, USA, Phone: (609)771-2772, E-mail: [email protected] Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218,United States
Keywords: Organic Thin Film Transistor; gas sensor; drift diffusion; humidity suppresion; Gaussian distribution; field effect mobility; NO2 gas