Fine tuning emissions from quantum dots for better color displays

New MIT analysis should enable development of improved color displays and biomedical monitoring systems.
Tiny particles of matter called quantum dots, which emit light with exceptionally pure and bright colors, have found a prominent role as biological markers. In addition, they are realizing their potential in computer and television screens, and have promise in solid-state lighting.
New research at MIT could now make these quantum dots even more efficient at delivering precisely tuned colors of light.
These materials, also called “colloidal semiconductor quantum dot nanocrystals,” can emit any color of light, depending on their exact size or composition. But there is some variability in the spread of colors that different batches of nanocrystals produce, and until now there has been no way to tell whether that variability came from within individual particles or from variations among the nanocrystals in a batch.
That’s the puzzle an MIT team has now solved, using a new observational method. The results appear in the journal Nature Chemistry in a paper by chemistry professor Moungi Bawendi, graduate student Jian Cui, and six others.
For many applications — such as flat-panel displays — it’s important to make particles that emit a specific, pure color of light. So, it’s important to know whether a given process produces nanocrystals with an intrinsically narrow or broad spectrum of color emission.
“You need to understand how the spectrum of a single particle relates to the spectrum of the whole ensemble,” Cui says. But existing observational methods that detect an entire ensemble produce data that “is blurring the information,” and methods that attempt to extract data from single particles have limitations.