Time-resolved Microscopic Second Harmonic Generation Research Articles

Transient carrier visualization of organic-inorganic hybrid perovskite thin films by using time-resolved microscopic second-harmonic generation (TRM-SHG)

Abstract Based on the transient electric field migration directly probed by the time-resolved microscopic optical second-harmonic generation (TRM-SHG) technique, we successfully detected the transient hole transport in the perovskite for the first time. From the spectroscopic point of view, SHG signal resonantly enhanced at the fundamental wavelength of around 1560 nm through the band-transition under the voltage application. Square dependence of the SH intensity on the applied voltage at the wavelength of 1560 nm clearly indicated the electric field induced process of the SHG. We could visualize the carrier motion in the channel of perovskite field effect transistor (FET) with this wavelength. Carrier mobility was estimated as 0.02 cm2/V by analyzing the transient carrier motion. TRM-SHG technique was also employed to investigate the effect of traps on the transient carrier motion. Based on the peak of the transient electric field distribution, trap density, and dynamic carrier mobility were separately estimated.

Carrier Transport Mechanism in Single Crystalline Organic Semiconductor Thin Film Elucidated by Visualized Carrier Motion.

Time-resolved microscopic second harmonic generation (TRM-SHG) measurement was conducted to evaluate temperature dependence of the anisotropic carrier transport process in 6,13-Bis(triisopropylsilylethynyl) (TIPS) pentacene single crystalline domains for two orthogonal directions. Enhancement of the electric field induced SHG (EFI-SHG) signal at the electrode edge at low temperature suggests the presence of potential drop in the injection process. We directly evaluated temperature dependence of the carrier mobility by taking into account the potential drop, and concluded that the Marcus theory is appropriate to interpret the carrier transport in anisotropic TIPS pentacene thin film. TRM-SHG method is a facile and effective way to directly visualize transport process in anisotropic materials and to evaluate injection and transport processes simultaneously.