Design and optimisation of nanorod based light emitting diodes (NR-LEDs) by COMSOL

The optimisation of charge transport through the interfaces in a device at the nanoscale is essential to improvements in the performance of optoelectronic devices. This is especially pertinent to light emitting diodes (LEDs). In electrically pumped colloidal nanocrystal (NC) LEDs, multiple NC layers are enclosed between electron and hole transport layers. As electrons and holes are injected from the opposing electrodes, non-radiative processes, such as Auger recombination, can occur in lieu of radiative recombination. These non-radiative processes lead to a reduction in the internal quantum efficiency (IQE) of the devices. Optimising the radiative processes and reducing the non-radiative processes is key to improving device operation. Do?ing so requires an understanding of the mechanisms governing these processes. In this project, a finite element simulation model to simulate electrically pumped LEDs based on colloidal semiconductor nanorod (NR) heterogeneous assembly was developed. When experimentally realising these devices, some of the issues are that nanocrystal LEDs (NC-LED) are brighter with thicker NC layers, which leads to in?effective carrier injection, and that an increased external quantum efficiency (EQE) requires balanced carrier injection and luminescent quenching to be reduced. The carrier recombination process and lifetimes will be simulated and studied using I-V simulations in COMSOL by looking at electrons and holes injected into, and emitting from, a cavity.