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"Egg-Carton" Solution to Improving Efficiency of Quantum Dots

New deposition process for quantum dots ensures current flow directly through them with better light-emission yield

1 min read
"Egg-Carton" Solution to Improving Efficiency of Quantum Dots

The quantum dot has been held out as a potential game-changer in the field solid-state lighting for some time now.

However, if one were to offer a possible knock against quantum dot-based devices in this area, it could be at their lack of efficiency. What happens is that current flow escapes between the quantum dots (QD) in a QD layer rather than through the QDs themselves.

To combat this researchers at Harvard University have developed an atomic layer deposition process that deposits the QDs in a single layer along with an aluminum oxide (Al2O3) insulating layer.  According to Edward Likovich, the best metaphor for the new arrangement is that of a carton of eggs, with the eggs being the QDs.

“The process provides a mechanical and energetic barrier between adjacent quantum dots, so the current tends to flow perpendicularly as opposed to being dissipated among dots in the layer,” says Likovich in the Material Research Society article linked to above. “Also, because we have this mechanical barrier between the dots, we can do post-processing to remove the ligands while holding the dots in place, preventing agglomeration.”

The research, which was published in the journal Advanced Materials, essentially fills the interstices between the QDs with the insulating aluminum oxide forcing the current to flow through the QDs and thereby increasing the light-emission yield.

It will be interesting to see if this process will have an impact on the application of QDs in the areas of LEDs or in photovoltaics.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

1 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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