Dr. Mark Thompson presents “21st Century Alchemy Applied to Organic LEDs: Making Copper Act Like Iridium” on Friday, April 23rd, 2021, at 4:30 PM.
Heavy metal containing phosphors, especially iridium-based emitters, have become the standard in high performance mobile displays and televisions. The high spin orbit coupling in these compounds facilitates the efficient harvesting of both singlet and triplet excitons generated in the electroluminescent process. My talk will start with a basic introduction to organic LEDs (OLEDs), highlighting on the spin dependent processes that needed to be addressed to get the high efficiency devices we have today.
All commercial OLED displays use iridium-based emitters due to the high spin orbit coupling of iridium and its ability to promote rapid and efficient emission from triplet states. An alternative to Ir-based emitters were introduced to OLEDs about a decade ago that emit via Thermally Assisted Delayed Fluorescence (TADF). Heavy-metal (Ir) and TADF emitters give similar OLED performance, which stems from the fact that they have very similar radiative lifetimes and luminance quantum efficiencies. I will cover the similarities and differences between these two types of emitters in my talk, but to honest they are far more similar than they are different.
The second half of my talk will focus on our most recent results with two‑coordinate copper, silver and gold carbene complexes, i.e. (carbene)MI(donor), where the donor is an amide or aryl group. All of these compounds emit via a TADF mechanism and show high phosphorescence quantum yield (70 – 100%), with radiative lifetimes in 0.4-3 microsecond regime. I will focus on why the silver-based materials give markedly shorter lifetime than the copper and gold analogues. We have prepared organic LEDs with these dopants and achieved > 20% EQE for green emissive OLEDs and > 12% for blue emissive OLEDs, both at comparatively low drive voltages, making these Group 11 emitters good candidates to replace iridium-based emitters in future displays and solid-state lighting applications.
Join Zoom Meeting https://carleton.zoom.us/j/97062621266
Meeting ID: 970 6262 1266 Passcode: 945583
Would you like cookies* and tea (or hot chocolate packets) to snack on during the Chemistry Seminar? On Friday, stop by the Mohrig Lounge-2nd floor Anderson between 3:30-4:30. Alison Block will be there to greet you or you may need to wait for her. If you don’t know where the Mohrig Lounge is, it is the study space on the southeast corner of 2nd floor Anderson, bordered on the south by the offices of Deborah, Dani and Lanhao.
*gf, vegan, nut-free options available