Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Explicit Defects and Electrostatics

Marcus D. Hanwell, Tamika A. Madison, Geoffrey R. Hutchison. “Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Explicit Defects and Electrostatics” J. Phys. Chem. C 2010 114(48) 20417-20423. DOI

The effects of defects and electrostatics on charge transport in realistic organic field effect transistors were studied using a combination of first principles quantum chemistry calculations and Monte Carlo simulations with explicit introduction of defect sites. The results show that electrostatic interactions dramatically affect the field and carrier concentration dependence of charge transport in devices that include a significant number of traps, as well as its “switch-on” characteristics. Our results also show that charge transport decreases linearly as a function of neutral defect concentration as conduction pathways are turned off. For charged defects, mobility of imperfect devices is lower relative to defect-free devices but is surprisingly unaffected by the concentration of charged defects. The exact statistics of electrostatic disorder introduced by charged defects is found to obey a Poisson distribution rather than Gaussian or exponential as previously assumed. We also demonstrate that without including electrostatic interactions, simulations of transistors exhibit an unphysical negative differential resistance at higher defect levels.