Degradation Phenomena of Quantum Dot Light-Emitting Diodes Induced by High Electric Field.

Quantum dots (QDs) have outstanding optoelectronic properties, such as narrow bandwidth, controllable wavelength, and compatible solution-based processing. However, several issues need to be resolved for efficient and stable operation in electroluminescence mode. In particular, as device dimensions become smaller, a higher electric field may be applied through the next-generation QLED devices which may induce further degradation of the device. In this study, we perform a systematic analysis of the degradation phenomena of a quantum dot light-emitting diode (QLED) device induced by a high electric field, using scanning probe microscopy (SPM) and transmission electron microscopy (TEM). A local high electric field is applied using an atomic force microscopy (AFM) tip on the surface of a QLED device, and the changes in morphology and work function are investigated in the Kelvin probe force microscopy (KPFM) mode. After the SPM experiments, TEM measurements are performed on the identical sample area degraded by the electric field of the AFM tip. The results demonstrate that a QLED device could be mechanically degraded by a high electric field and the work function changes significantly in the degraded areas. In addition, the TEM measurements illustrates that the In ions migrate from the indium tin oxide (ITO) bottom electrode to the top of the QLED device. The ITO bottom electrode is also significantly deformed, which may induce the work function variation. The systematic approach adopted in this study can provide a suitable methodology for investigating the degradation phenomena of various optoelectronic devices.&#xD.