Characterization of organic light emitting diodes (OLED) using depth-profiling XPS technique

During the industrial development of solution processed organic light-emitting diodes (OLEDs), it has been found that inter-diffusion of active components between multi-layers leads to poor performance and decreased lifetime. Hence, characterization and understanding of interfacial chemistries between layers are of vital importance. In this regard, a series of solution printing processed and PVD-deposited OLED devices with different performance have been investigated. X-ray photoelectron spectroscopy (XPS) has been applied to probe these complex organic layered systems and reveal their interfacial properties via polyatomic C-60 ion-beam chemical depth profiling. Our experimental results show that C-60 profiling technique can be successfully used to study organic layered materials while preserving the overall chemical structures. To better differentiate these thin OLED layers, we have further employed multivariate statistical methods to translate the depth chemical concentrations into layer behavior for the first time. The application of multivariate analysis to this data is able to elucidate the inter-diffusion across the interfaces for OLED devices. (C) 2018 Elsevier B.V. All rights reserved.