Impedance Spectroscopy of Multi-layered Organic Electronic Devices

Abstract

We present the impedance analysis of multi-layered organic electronic devices. We have developed a new analysis technique, Dynamic Modulus Plot (DMP), which is the combination of C-V measurement and Cole-Cole plot. It is applied to analyze the anomaly of color index change against the current density of a stacked Red/Green phosphorescent Organic Light Emitting Diode (OLED). DMP shows that electrons accumulate in the green emitting layer below the turn-on voltage. The anomaly of the color index is attributed to the quench of the triplet excitons by the electrons accumulated in the green emitting layer. The color index anomaly becomes less when the accumulation is reduced by optimizing the host material of the green emitting layer. We demonstrate that DMP is a useful method to investigate the layer-to-layer carrier dynamics of separated function devices.