Environmentally Robust Quantum Dot Downconverters for Highly Efficient Solid-State Lighting

Lead Performer: Columbia University – New York, NY
Partners:

• Lawrence Berkeley National Laboratory – Berkeley, CA
• Oram Opto Semiconductors – Portland, OR

DOE Total Funding: $1,250,914
Project Term: June 1, 2019 – September 30, 2021
Funding Type: SSL R&D Funding Opportunity Announcement (FOA) (DE-FOA-0001823)

Project Objective

This project seeks to develop improved cadmium-free quantum dots (QDs) with greater efficacy and improved stability to flux and temperature, for phosphor-converted LEDs. QDs, which are semiconductor nanoparticle phosphors, have the potential to increase LED efficacy because they emit a larger fraction of their light in the visible spectrum. This advantage is an especially important in the red region of the visible spectrum, where the narrow emission spectrum can be finely tuned to improve both the color rendering and efficiency. A major challenge preventing the widespread adoption of QD LEDs is the harsh operating conditions (i.e., high irradiation, heat, humidity) that degrade the quantum dot material. A second challenge is that the most-efficient QDs contain the regulated toxic metal cadmium. The project aims to improve the environmental robustness of cadmium-free, red-emitting QDs and demonstrate high-efficacy QD LEDs with a warm spectrum and higher color quality. With a tunable library of synthesis precursors designed at Columbia University and high-throughput synthesis robotics developed at Lawrence Berkeley National Laboratory, the team will screen thousands of synthetic conditions to identify the optimal QD structures for stable, inexpensive, and high-efficacy solid-state lighting.

Project Impact

The team will develop cadmium-free quantum dots with thick, strongly absorbing shells, robust surface passivation, and ultrabarrier encapsulation that maintains at least 90% of their initial performance over 3,000 hours of operating life under accelerated testing conditions. These QDs will be combined with green phosphors and deposited on high-efficiency LEDs manufactured by Osram Opto Semiconductors to demonstrate solid-state lighting packages with good color quality and luminous efficacies of 200 lm/W. Such an achievement would exceed the state of the art in phosphor-converted LEDs for solid-state lighting and be a meaningful step toward the DOE goal of 225 lm/W devices by 2025. Stable QD LEDs will become the most-efficient, most-versatile, and highest-quality light source. Elimination of cadmium will spur global adoption, which is currently restricted by environmental regulations.

Contacts

DOE Technology Manager: Brian Walker, brian.walker@ee.doe.gov 
Lead Performer: Jonathan S. Owen, Columbia University