Probing and modeling of carrier motion in organic devices by electric-field-induced optical second-harmonic generation

Abstract

By probing dielectric polarization originating from dipoles and electrons in materials, we can study dynamical carrier behaviors in materials and also in devices. Maxwell displacement current (MDC) measurement allows us to directly probe orientational dipolar motion in monolayers, while electric-field-induced optical second-harmonic generation (EFISHG) measurement allows dynamical electron and hole transport in solids to be probed directly. By probing nonlinear polarization induced in solids by coupling with incident electromagnetic waves of laser beam and dc electric field that originate from moving carriers, long-range carrier motion is visualized. Experiments using a time-resolved EFISHG technique reveal carrier transfer in organic devices such as organic field-effect transistors, organic light-emitting diodes, organic memory devices, and organic solar cells, and thus enable us to model the carrier transport mechanism. We anticipate that this novel technique using EFISHG can be a powerful tool for studying carrier behaviors in organic devices as well as in organic materials.

Formation of structural defects and strain in electrodegraded Fe‐doped SrTiO3 crystals due to oxygen vacancy migration

“…As a non‐destructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite‐type oxide surfaces, interfaces, and bulk regions . Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe‐doped SrTiO 3 (Fe:STO) single crystals .…”

“…As a non-destructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite-type oxide surfaces, interfaces, and bulk regions. [26][27][28][29][30][31][32][33] Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe-doped SrTiO 3 (Fe:STO) single crystals. 26,28,34,35 Electrostriction effects have been discussed based on our initial electric field-induced SHG measurements at the anode interfaces of reduced and oxidized Fe:STO single crystals.…”

Local structural changes due to the electric field‐induced migration of oxygen vacancies at Fe‐doped SrTiO3 interfaces

“…As a nondestructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite‐type oxide surfaces, interfaces, and bulk regions . Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe‐doped SrTiO 3 (Fe:STO) single crystals .…”

Analysis of current-voltage characteristics of Au/pentacene/fluorine polymer/indium zinc oxide diodes by electric-field-induced optical second-harmonic generation

“…Accordingly, it is very helpful to develop a novel method that can directly probe the electric potential and electric field distributions in organic devices [9], and to use the developed method in combination with the I-V and C-V measurements. We have been developing method of electric-field-induced optical second-harmonic generation (EFISHG) measurement that can selectively and directly probe the electric fields in organic layers and in organic devices [10][11][12]. This motivated us to study the electrical carrier transport mechanism of a variety of organic double-layer diodes, while taking into account their electric field distribution.…”