Interfacial exciton-polaron quenching (EPQ) in organic light-emitting diodes (OLED) refers to the remote and direct energy transfer from the excitons in the emission layer (EML) to the charges accumulated at the interface of the adjacent charge transport layers (CTLs). Here, interfacial EPQ is investigated by using a bilayer hole-only device (HOD), where an ultra-thin dopant layer is selectively introduced near the interface. At the heterointerface, positive-charge accumulation is induced due to the energy difference between distinct organic layers, while excitons are optically pumped in the dopants exclusively. The interfacial EPQ is characterized by measuring a shift in the photoluminescent intensity of the dopants. Such interfacial EPQ indeed depends on the interfacial energy offset and the distance between charges and excitons, and universally occurs regardless of the emission mechanism of OLEDs. We propose the device architecture to potentially reduce interfacial EPQ for achieving high-performance OLEDs.
The advent of virtual and augmented reality displays will completely reshape and better our lives in various aspects. The most suitable light sources to realize the corresponding displays have been believed to be micro-organic light-emitting diodes (µOLED) and micro-light-emitting diodes (µLED), respectively. In this talk, we will discuss the major technological challenge for each type; the electrical crosstalk in µOLEDs and the difficulty in achieving monochromatic and directional emission from µLEDs. We will also suggest the potential solutions to resolve these issues for both µOLEDs and µLEDs.
In this article, we briefly review our recent publication on the influence of trap positions on the current density-voltage characteristics of organic semiconductor devices (PRB, 107, 1652304 [2023]). The position of traps significantly affects the total charge density and electric field in the active organic layer, consequently impacting the operating voltage of the comprising devices. Our findings showed that as the position of traps moves from the charge extraction electrode (cathode) towards the charge injection electrode (anode), the required voltage to achieve a constant current density initially increases. However, a reversed trend in the operating voltage vs. trap position is observed when the traps are present in the vicinity of the anode. We figured out that this phenomenon originates from the trap position dependence of electric field distribution.
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