RESEARCHERS AT GEORGIA TECH PAVE THE PATH TO LOWER COSTS BY DEVELOPING EFFICIENT EMITTERS FOR OLEDS WITH SIMPLIFIED GEOMETRY
With the help of DOE funding, researchers at the Georgia Institute of Technology have developed a new generation of organic emitters that challenge conventional wisdom by yielding high performance when used as neat single-component layers in OLED devices with simplified geometry. The team's approach is based on the search for new molecules within the known class of materials that exhibit thermally activated delayed fluorescence (TADF), which provides an alternative to phosphorescent emission. (September 2019) Learn more.
RESEARCHERS AT COLUMBIA UNIVERSITY IMPROVE MANUFACTURING EFFICIENCY OF WARM-WHITE LEDS
With the help of DOE funding, researchers at Columbia University, OSRAM Opto Semiconductors, and Lawrence Berkeley National Laboratory have developed a new process to synthesize red-emitting quantum dots in a single-step manufacturing process. These materials achieve efficient red emission on LED lighting packages that achieve state-of-the-art reliabilities under the harsh conditions necessary for commercial adaptation. (September 2019) Learn more.
RESEARCHERS AT THE UNIVERSITY OF CALIFORNIA AT SANTA BARBARA DISCOVER A KEY TO IMPROVING THE EFFICIENCY OF GREEN AND AMBER LEDS
Using a computational approach based on landscape theory, researchers at the University of California at Santa Barbara have identified key factors in the LED’s semiconductor layer structure that impact the forward-voltage performance of green LEDs. The findings indicate that careful design of the semiconductor layers in or surrounding the LED active region is essential to avoid excess voltage in green LEDs. The number of quantum wells, the percentage of aluminum in the quantum barriers, and the InGaN/GaN superlattice structure below the LED active region can be optimized to reduce the forward-voltage penalty in green LEDs. (September 2019) Learn more.
THE NATIONAL RENEWABLE ENERGY LABORATORY ESTABLISHES A NEW METHOD TO ACHIEVE HIGH-EFFICIENCY AMBER AND RED LEDS
Most mass-produced red and amber LEDs on the market today are based on the elements aluminum, gallium, indium, and phosphide (abbreviated as AlGaInP when used in combination). The efficiency of these AlGaInP LEDs is limited by the loss of injected electrons through several pathways that are intrinsic to that kind of material system. With funding from DOE, researchers at the National Renewable Energy Laboratory (NREL), MicroLink Devices, and the South Dakota School of Mines and Technology have demonstrated that these pathways, and the losses they entail, can be reduced by switching to a related material system that’s based on aluminum, indium, and phosphide (AlInP). This new approach has the potential to enable improvements in amber (~580-590 nm) and red (~610-620 nm) LED efficiencies. (September 2019) Learn more.
SANDIA RESEARCHERS DEMONSTRATE TUNNELING-ENABLED HIGH-EFFICIENCY, HIGH-POWER, MULTI-JUNCTION LEDS
With the help of funding from the U.S. Department of Energy, a team of researchers at Sandia National Laboratories and The Ohio State University have demonstrated the feasibility of using multi-junction cascaded LEDs to increase external quantum efficiency (EQE, a measure of how efficient the LED is) at fixed current density. This approach avoids the common phenomenon known as current droop, in which the efficiency of the LED decreases as the electrical current density increases. Current droop remains a significant barrier to LED efficiency. (September 2019) Learn more.
LUMILEDS FURTHER EXCEEDS EQE MILESTONE IN AMBER LIGHT
With funding from DOE, researchers at Lumileds have achieved, in a laboratory prototype, an amber LED with external quantum efficiency (EQE) of 22% at current density of 35 A/cm2 and junction temperature of 25°C. Efficient red and amber LEDs are essential building blocks for next-generation lighting products, enabling the ultimate DOE efficacy targets and spectral design freedom in color-mixed white and color-tunable lighting applications. (September 2019) Learn more.
UNIVERSITY OF MICHIGAN DEVELOPS A METHOD TO INCREASE LIGHT EXTRACTION IN WHITE OLEDS
With the help of DOE funding, researchers at the University of Michigan have developed a method to increase the light extraction in white organic light-emitting diodes (OLEDs), thereby improving their performance and reducing their cost. Based on a sub-electrode microlens array, the method has increased the external quantum efficiency (EQE, the ratio of photons emitted from an OLED to the electrons injected from the electrodes) of electrophosphorescent white-emitting OLEDs (WOLEDs) to 70% – a significant improvement over past results. (July 2019) Learn more.
RESEARCH TEAM LED BY THE UNIVERSITY OF CALIFORNIA AT SANTA BARBARA DEVELOPS A SIMULATION TOOL TO HELP IMPROVE THE PERFORMANCE OF GREEN LEDS
Simulations are used to predict the performance and behavior of a system instead of relying solely on experimental understanding – thus reducing cost and shortening development time. With the help of DOE funding, researchers at the University of California at Santa Barbara, in collaboration with those at National Taiwan University, the University of Minnesota, and France’s École Polytechnique, have developed a numerical tool that allows the 3D simulation of Group III nitride devices. (May 2019) Learn more.