Brian Theobald

Exploring the bounds of narrow-band quantum dot downconverted LEDs

Quantum dots are finding increasing commercial success in LED applications. While they have been used for several years in remote off-chip architectures for display applications, it is shown for the first time to our knowledge that quantum dots can withstand the demands of the on-chip architecture and therefore are capable of being used as a direct phosphor replacement in both lighting and display applications. It is well known that, to achieve improved color metrics in lighting as well as increased gamut in display technologies, it is highly desirable to utilize a downconverter with a narrow emission linewidth as well as a precisely tunable peak. This paper will discuss the results of on-chip use of quantum dots in a lighting product, and explore the opportunities and practical limits for improvement of various lighting and display metrics by use of this unique downconverter technology.

Improved color metrics in solid-state lighting via utilization of on-chip quantum dots

While Quantum Dots (QDs) have found commercial success in display applications, there are currently no widely available solid state lighting products making use of QD nanotechnology. In order to have real-world success in today’s lighting market, QDs must be capable of being placed in on-chip configurations, as remote phosphor configurations are typically much more expensive. Here we demonstrate solid-state lighting devices made with on-chip QDs. These devices show robust reliability under both dry and wet high stress conditions. High color quality lighting metrics can easily be achieved using these narrow, tunable QD downconverters: CRI values of Ra > 90 as well as R9 values > 80 are readily available when combining QDs with green phosphors. Furthermore, we show that QDs afford a 15% increase in overall efficiency compared to traditional phosphor downconverted SSL devices. The fundamental limit of QD linewidth is examined through single particle QD emission studies. Using standard Cd-based QD synthesis, it is found that single particle linewidths of 20 nm FWHM represent a lower limit to the narrowness of QD emission in the near term.