11 JUN 2021
Now regarded as the gold standard, OLED (organic light-emitting diode) offers exceptional picture quality and energy efficiency. Philipp Stoessel, a Senior Scientist in our OLED-Research Laboratories, shares his experiences from a 20-year career creating leading-edge materials for OLED displays.
What motivates you?
I've always been a laboratory leader in the OLED field, but I’ve never tried to have a career in the classical sense. What I care about is the freedom to do what I think must be done or what is interesting — that's my main motivation. I love going into the lab. I need to see and feel things to get a better understanding of what's going on. Hands-on chemistry helps me stay grounded. It's one of my great motivators.
What does your research involve?
Over the years, I've worked on all the functional materials that make up OLEDs. But I now specialize in a specific type of luminescent material called triplet emitters, making iridium and platinum complexes that generate red, green and yellow colors. We’re aiming to achieve the ‘mighty three’ for a device— efficiency, lifetime, and color purity. But successfully transforming this into a material requires experience. You need a gut feeling about structural elements and how to combine them to end up with an intelligent material design. From the many materials we look at, we select those with the right properties — which we then need to synthesize and purify before sending to our device department for further testing.
What challenges do you face?
Getting everything we need into one molecule is a real challenge. We're talking about more than a dozen different properties like color, oxidation potential, reduction potential, processability and so on. Trust me, making it perfect — that’s hard! Another challenge is driving innovation — striking the right balance between novel research and the next best development target and fine-tuning the materials for customer applications. Personally, I like looking for new entities — these are rare and hard to find. You might make a hundred compounds and if you're lucky, you get one good one. But that's the fun of the game! I'm fortunate enough to be able to try new things and collect failure after failure. All people expect is that we do this with a clear rationale, to make materials better over time — and to secure new grounds by filing intellectual property. I think that's a fair trade-off for the freedom I have in the lab.
How do you hope your research will make a difference?
A standard light bulb only transforms 1-2% of electricity into photons. With modern OLEDs, in optimal cases that’s increased to around 80-90% (IQE = Internal Quantum Efficacy), and we are trying to catch the remaining 10%. That will be valuable for achieving a sustainable society — using resources as efficiently as possible. Many of the materials we sell today include some parts of me and my team — it’s important to emphasize that materials development is a team effort. It would be fantastic to see one of our cage-type dopants in a product. We reinvented these organometallic complexes and brought them to life. You can think of these a bit like a praline with a metal atom at the center and organic material surrounding it. We are approaching our goal, but we aren’t there yet. If we succeed, that would be a personal achievement I would enjoy.