Degradation analysis of organic charge generation layer by impedance spectroscopy

Abstract

Understanding the degradation mechanisms of the charge generation layer (CGL) is crucial for developing stable tandem organic light-emitting diodes (OLEDs). Using capacitance-voltage (C-V) measurements and modulus spectroscopy, we visualized the charge distribution within the CGL and analyzed its changes before and after aging. Results indicate that the degradation of the CGL is primarily driven by dopant diffusion, which induces impurity compensation at the interface and increases the driving voltage. Equivalent circuit fitting further quantified the changes in resistance and capacitance across layers, confirming the impact of dopant diffusion on CGL performance. Additionally, the role of spontaneous orientation polarization (SOP) in CGL stability was explored, suggesting its potential influence on the interface barrier height. These findings provide insights for optimizing the CGL design to enhance the long-term stability of tandem OLEDs.