Lead Performer: Georgia Institute of Technology – Atlanta, GA
DOE Total Funding: $896,000
Project Term: September 1, 2017 – August 31, 2019
Funding Type: SSL R&D Funding Opportunity Announcement (FOA) (DE-FOA-0001613)
Project Objective
This project will research, develop, and demonstrate blue-emitting layers (blue-EML) capable of overcoming the existing device efficiency vs. device stability tradeoff in blue-emitting OLEDs, and enable next-generation stable white OLEDs (WOLEDs). The researchers will develop ambipolar hosts with a wide optical bandgap and an energy difference between their singlet and triplet excited states sufficiently small for efficient thermally activated reverse intersystem crossing (TA-RISC) at room temperature. They’ll also develop blue-emitting OLEDs that achieve power efficacies (PE) > 50 lm/W with low efficiency roll-off (ca. 15%) through the use of emissive layers comprising ambipolar thermally activated delayed fluorescence (TADF) hosts and conventional state-of-the art fluorescent guest emitters; and will develop WOLEDs that yield PE values > 50 lm/W, color rendering index (CRI) values > 90 and lumen maintenance (L70) larger than 50,000 h from an initial light output of 10,000 lm/m2.
Project Impact
A current roadblock in obtaining highly efficient and stable white OLED devices is the limited stability of blue-emitting materials that harvest both singlet and triplet excited states to yield high efficiency. The understanding of the degradation mechanism of these blue-emitting materials is not well understood, but recent studies suggest that high concentrations of excited states with long lifetimes and large photon energy (blue color) are likely to lead to high-energy excited states through various up-conversion processes from which degradation occurs. This project has identified a solution to this problem that employs methods based on efficient and selective energy transfer from intra- and intermolecular donor/acceptor material systems to a fluorescent emitter to reduce the excited-state lifetime and consequently reduce degradation while maintaining 100% internal quantum efficiency. These advances will enable stable and highly efficient WOLEDs that fulfill or exceed the 2020 DOE SSL target metrics for OLED technology. Hence, they have the potential to become a game changer and can rapidly move OLED lighting from laboratory to market. The use of all-carbon-based materials simultaneously offers a price advantage in addition to performance. The project will create a comprehensive knowledge to overcome the current performance/stability tradeoff in blue-emitting organic materials and generate the core background intellectual property to continue the development of this technology with leading U.S. academic and industrial partners, in order to bring it to market and create U.S. manufacturing jobs.
Contacts
DOE Technology Manager: James Brodrick, [email protected]
Lead Performer: Bernard Kippelen, Georgia Institute of Technology