ZnTeSe quantum dots (QDs), recognized as promising eco-friendly blue electroluminescent emitters, remain under-explored in light-emitting diode (LED) applications. Here, to elucidate the operation and degradation mechanisms of ZnTeSe blue QD-LEDs, stacked ZnTeSe QD layers with discernable luminescence are designed by varying Te doping concentrations, and the recombination zones (RZs) of the blue QD-LEDs are investigated. The RZs are identified near the hole-transport layer (HTL), confirmed by angular-dependent electroluminescence measurements and optical simulations. In addition, in order to investigate carrier dynamics in the process of recombination, the transient electroluminescence (tr-EL) signals of the dichromatic QD-LEDs are analyzed. As a result, it is inferred that the RZ initially formed near the electron-transport layer (ETL) due to the high injection barriers of electrons. However, due to the fast electron mobility, the RZ shifts toward the HTL as the operating current increases. After the device lifetime tests, the RZ remains stationary while the photoluminescence (PL) corresponding to the RZ undergoes a substantial decrease, indicating that the degradation is accelerated by the concentrated RZ. Thus this study contributes to a deeper understanding of the operational mechanisms of ZnTeSe blue QD-LEDs.

Colloidal quantum-dot (QD) light-emitting diodes (QLEDs) have been in the forefront of future display devices due to their outstanding optoelectronic properties. However, a complicated solution-process for patterning the red, green, and blue QDs deteriorates the QLED performance and limits the resolution of full-color displays. Herein, we report a novel concept of QD–organic hybrid light-emitting diodes by introducing an organic blue common layer (BCL) which is deposited through a common mask over the entire sub-pixels. Benefitted from the optimized device structure, red and green QLEDs retained their color coordinates despite the presence of the BCL. Furthermore, adopting the BCL improved the external quantum efficiency of green and red QLEDs by 38.4% and 11.7%, respectively, due to the Förster resonance energy transfer from the BCL to the adjacent QD layers. With the BCL structure, we could simply demonstrate a full-color QD–organic hybrid device in a single substrate. We believe that this device architecture is practically applicable for easier fabrication of solution-processed, high-resolution, and full-color displays with reduced process steps.