Investigation of Luminance Degradation in Organic Light-Emitting Diodes by Impedance Spectroscopy

We characterize the degradation of organic light-emitting diodes (OLEDs) by employing the impedance spectroscopy. An integrated OLED is compared with the hole-only device (HOD) and the electron-only device to understand the degradation mechanism under voltage stress for 12 h in ambient conditions. Changes in impedance observed from the Cole-Cole plot of the HOD reveal that the degradation mechanism of the OLED is attributed to unbalanced recombination resulting from the deterioration of hole injection into the emissive layer.