Simulations of thermally activated delayed fluorescence organic light-emitting diodes

December 16, 2022

Christoph Hauenstein defended his PhD thesis at the department of Applied Physics on December 15th.

Christoph Hauenstein.

Organic light-emitting diode technology is at the heart of many of the most advanced TVs and smartphones currently available on the market. They offer unique advantages over other displays in terms of picture quality and enable completely novel applications such as flexible displays, as demonstrated in the recently available foldable smartphones from Samsung and Huawei. However, OLED displays are more expensive and consume more energy than other display technologies. Materials based on so-called emitters can address this, but the processes that govern their performance are not well known. Using physics-based simulations, Christoph Hauenstein set out to explore these processes as part of his PhD research.

Organic light-emitting diode (OLED) technology could become the go-to technology for displays in the future, but there are still some factors impeding their widespread use. The price, energy consumption, and durability of OLED displays is not yet as good as that of other established display technologies.

One class of materials that could help overcome these limitations is based on emitters that show “thermally-activated delayed fluorescence”. These materials can, in principle, convert all of the supplied electrical energy into light in a very efficient manner.

To perform in the best possible way, they must be combined with several other materials, which together form a complete OLED device structure. To make the next step in OLED devices and performance, the interplay between these materials must be well understood, optimized, and precisely controlled. However, experimentally studying all of the relevant parameters and processes, which occur at extremely small time and length scales, can be challenging or even outright impossible.

Physics-based simulations

For his PhD research, Christoph Hauenstein and his colleagues at the Molecular Materials and Nanosystems group used physics-based simulations to better understand those processes and interactions.

Hauenstein focused on processes that led to efficiency losses and irreversible material degradation. By disentangling the roles of the different physical processes, the simulations helped the researchers to gain additional on material and device measurements. Identifying and understanding the most important interactions then also allowed for the determination of concrete design rules for successful material combinations, thus minimizing the currently required experimental efforts.

Flexible workflow

The developed simulation methods and workflow were flexible and could, in the future, easily be extended to novel OLED materials and system design concepts. They could also be combined with other simulation methods, with the goal of establishing a predictive and fully virtual research and development workflow.

Hauenstein’s research contributes to the development of a multiscale computational toolchain that can reliably replace experiments, offering potentially enormous time and cost savings at the same time.

Title of PhD thesis: Simulations of excitonic processes in thermally activated delayed fluorescence organic light-emitting diodes. Supervisors: Reinder Coehoorn, Peter Bobbert, and Harm van Eersel.

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