Optical second-harmonic generation measurement for probing organic device operation

This is the authors' abstract. We don't add key points for this paper.

We give a brief overview of the electric-field induced optical second-harmonic generation (EFISHG) technique that has been used to study the complex behaviors of organic-based devices. By analyzing EFISHG images of organic field-effect transistors, the in-plane two-dimensional distribution of the electric field in the channel can be evaluated. The susceptibility tensor of the organic semiconductor layer and the polarization of the incident light are considered to determine the electric field distribution. EFISHG imaging can effectively evaluate the distribution of the vectorial electric field in organic films by selecting a light polarization. With the time-resolved technique, measurement of the electric field originating from the injected carriers allows direct probing of the carrier motion under device operation, because the transient change of the electric field distribution reflects the carrier motion. Some applications of the EFISHG technique to organic electronic devices are reviewed. A new optical method can be used to visualize the electric-field distribution and charge carrier motion in organic field-effect transistors. This technique, devised by Takaaki Manaka and Mitsumasa Iwamoto from Tokyo Institute of Technology in Japan and called electric-field-induced optical second-harmonic generation, will benefit research into the device physics and electronic properties of organic optoelectronic devices. The researchers demonstrate that the imaging method evaluates the vector electric field distribution in organic films by selecting a light polarization. Importantly, the scheme works during device operation as it relies on carriers being injected into the device. It offers high temporal and spatial resolutions of 5 nanoseconds and 0.5 micrometres, respectively. Furthermore, with appropriate adaptation it shows promise for analysing other important organic optoelectronic devices, such as light-emitting diodes and solar cells.