Development and Improvement of Fluorescent OLED Structures

OLEDs (organic light-emitting diodes) typically suffer energy loss when the drive or current voltage is increased, leading to decreased external quantum efficiencies (EQE) at higher voltages, which are required to attain high brightness levels. This drop is fundamental due to the molecular excited and relaxed (light emission) states. When potential, or current, is increased, a large amount of the emitting molecules in the emissive layer (EML) are excited. When the excitation migrates across the layer there is the chance it could collide with another exciton already on the molecule, or on an electron or hole that is transiting the EML. This collision results in the de-excitation of one or two of the excited states, resulting in the loss of efficiency - this is called "exciton annihilation” or "quenching" and this process also leads to molecule degradation and a decrease in OLED lifetime. Therefore, it is important to develop structures that are resistant to exciton annihilation and substance degradation. The goal of this specific research project was to develop and test fluorescent OLEDs. This poster will discuss several device structure types that were researched to look at their effect on the exciton flow through doping concentrations and thickness gradients.