Surface plasmon resonance of gold and silver nanoparticle (NP) layers is investigated by the experiment as well as simulations. Although the good agreement was found for gold NP film, a significant mismatch in the resonance energy for silver NP film was observed. The deviation was assigned to the presence of silver oxide (${\text{Ag}}_2\mathrm{O}$ ) in silver NPs. As an alternative to the NP size-dependent Drude model, the analysis based on effective medium approximation for refractive index of ${\text{Ag}-\text{Ag}}_2\mathrm{O}$ material system is carried out and compared with the core-shell model. Both Mie's model and numerical simulation results illustrate shift of the surface plasmon resonance due to silver NP surface oxidation.

By using the electric field induced optical second-harmonic generation (EFISHG) measurements, we probed the transient electric field in a double-layer indium zinc oxide (IZO)/N, ${\text{N}}^{\prime }\text{-di-}\left[\left(1\text{-naphthyl}\right)\text{-N},{\text{N}}^{\prime }\text{-diphenyl}\right]\text{-}\left(1,1^{\prime }\text{-biphenyl}\right)\text{-}4$ , $4^{\prime }\text{-diamine}\left(\alpha \text{-NPD}\right)/\text{tris}\left(8\text{-hydroxy-quinolinato}\right)\text{aluminum}\left(\text{III}\right)$ (Alq3)/Al electroluminescent (EL) diode. Results evidently showed that EL was initiated by the injected hole transport across $\alpha \text{-NPD}$ layer, and holes accumulated at the $\alpha \text{-NPD}/\text{Alq}3$ interface while EL was enhanced. Analysis based on the Maxwell–Wagner effect model well accounted for the hole accumulation. EFISHG measurement is useful as a tool for probing carrier behavior in organic EL devices.

Time-resolved microscopic optical second-harmonic generation (TRM-SHG) technique provides a different approach to study the dynamics of carriers in organic field-effect transistor (OFET). Different from many common methods, the TRM SHG directly probes the transient electric-field distribution in the channel of the OFET in high temporal and spatial resolutions. In this work we used this technique to quantitatively study migration of the peak of the electric field. We found that under a broad range of experimental conditions, the migration of the peak of the electric field follows a diffusionlike behavior; namely, the square of the peak position of $\overline{x}$ is proportional to time $t$. Based on a two-dimensional computational simulation and general carrier transport mechanism, we proposed that this behavior arises from a simple relation, $\mu \simeq \gamma {\overline{x}}^2/\left(t\left|V_{\text{gs}}\right|\right)$, where $\mu$ is the carrier mobility, $\gamma$ is constant about 0.5, and $V_{\text{gs}}$ is the gate voltage with respect to the source voltage. The experimental and simulation data well supported this relationship.

Electric field distribution in the pentacene organic field-effect transistor (OFET) channel is investigated using the microscopic optical second-harmonic generation (SHG). At the on- and off-states of the OFET, enhanced SHG signal was observed near the drain electrode and at the source and drain electrodes. Our analytical analysis indicates that the Laplace field formation is in the off-state of the OFET. The electric field profile in the on-state representing distribution by the space-charge formation in the channel due to injected carriers was calculated by the transmission line model. Theoretical models are confirmed by the experimental results and the result shows that pentacene can be used as a dielectric material. On the basis of estimated potential distribution in the on-state, a model for the evaluation of the drain-source current is proposed.