Time resolved electric field-induced second harmonic generation imaging from organic thin-film devices

Transient electric field-induced second harmonic generation (EFISHG) method, based on the third-order susceptibility, allows direct and selective probing of dynamic carrier motion in the active channel region of a field-effect transistor (FET). This technique provides a powerful tool for visualizing the carrier transport and predicting the carrier mobilities, free from contact resistance issues and device geometrical factors. We have developed a nonlinear microscopic imaging system using a tunable femtosecond laser and a pulse compensation arrangement, which compensates for any group velocity dispersion of the pulses in the imaging system. We apply the EFISHG technique to pentacene and other polymer-based FETs. By varying the time delay between the laser and the voltage pulse, the carrier motion across the FET channel is observed from which the carrier mobilities are deduced.