Probing of Maxwell-Wagner Type Interfacial Charging Process in Double-Layer Devices by Time-Resolved Second Harmonic Generation

摘要

The Maxwell-Wagner type interfacial charging processes were characterized by time-resolved second harmonic generation method (TR-SHG) using three typical organic double-layer devices, i.e., IZO/α-NPD/Alq3/Al for OLED and ITO/PI/α-NPD (or pentacene)/Au for MIM elements. Devices with a PI blocking layer represent one-carrier transport case, while the OLED is a typical two-carrier transport device. It is found that three devices show similar behavior of charging of the electrodes, however, interfacial charging behavior was different from case to case. On the basis of Maxwell-Wagner model, the different transients were analyzed with consideration of carrier species responsible for the interfacial charging. The observed TR-SHG well support the results of I-V measurements.