Spatial Identification of “Zeroth Defect” Formation in Organic Light-Emitting Diodes by Multispectral Mappings

In recently developed organic semiconductors, the continuously improving sample purity makes the stability of the chemical bonds of organic materials themselves become a key factor in device stability, which provides greater uncertainty for the generation of "zeroth defect", and the spatial resolution of performance at different positions becomes particularly important. In this work, complete maps of electroluminescent, photoluminescent, and Raman scattering in the same area on an organic light-emitting diode during its operation have been achieved with a confocal spectrometer with multiple laser sources. The different spectral characters help to establish different regions and suggest the mechanism of degradation. In particular, Raman scattering has been shown to be very sensitive in a multilayer device to a change in thickness of several nanometers. In amorphous films with few defects, the very weak film uniformity, including the thickness and degree of aggregation, would induce dramatic degradation. The relatively thin and/or loosely textured region easily locally overheats and has the highest probability of "zeroth defect" generation. This method has high spatial resolution, a low level of damage to samples, good reproducibility, and multiple interconnected pieces of information, which is significant for online quality prediction and mechanistic analysis.