Probing of interfacial charging and discharging in double-layer devices with a polyimide blocking layer by time-resolved optical second harmonic generation (original) (raw)

By using time-resolved electric field induced second harmonic generation, we directly probed interfacial charging and discharging in double-layer devices with an indium tin oxide ͑ITO͒/polyimide͑PI͒/N,NЈ-di-͓͑1-naphthyl͒-N,NЈ-diphenyl͔-͑1,1Ј-biphenyl͒-4,4Ј-diamine ͑␣-NPD͒ ͑or pentacene͒/Au structure, where PI serves as a blocking layer. The results showed that carriers injected from Au electrodes were responsible for interfacial charging and discharging, but different carrier behaviors were observed for pentacene and ␣-NPD devices, which implies that two devices have the different electrical properties. By analyzing the devices as a system of a Maxwell-Wagner effect element, we proposed a model that accounted for the difference in the charging and discharging processes in terms of carrier behavior.