Analysis of organic multilayer structures using a combined grazing incidence X-ray fluorescence/X-ray reflectometry approach

摘要

Organic light-emitting diodes (OLEDs) continue to attract research interest due to their application in bright displays and solid-state lighting. The highest efficiency values are reached with multilayer devices. The morphology of these layers is important for device performance. A current field of development is the application of solution-based deposition techniques. In general, solution processed devices do not yet reach the performance of OLEDs with vapor deposited materials. In this study, we used typical OLED materials with a sulfur based small molecule host, which can be vapor deposited as well as solution processed, to prepare single and multilayer samples. Samples consisted of the host layer deposited on a hole transport and a buffer layer and were investigated with a combination of grazing incidence X-ray fluorescence (GIXRF) and X-ray reflectometry (XRR). Measurements were performed using a diffractometer with an added fluorescence detector. The angle curves obtained have been evaluated with the software package JGIXA. Significant differences between differently prepared samples have been observed for single layer and multilayer samples. Sulfur could be detected in the layers beneath the solution processed host layer, but not in the layers below the vapor deposited host. The obtained results demonstrate the combination of GIXRF and XRR as a suitable nondestructive analysis method for the characterization of organic thin films with little to no sample preparation required.