Quantum Dot-based Infrared Sensors on Their Way...Quantum Dot Solar Cells, Not So Fast

Quantum dots advance various optoelectronic devices but at different paces

2 min read

This month’s Spectrum Magazine has an article available online written by Edward H. Sargent that discusses his work at the University of Toronto in applying quantum dots to the field of optoelectronics. Specifically Sargent discusses the work his group has done in using quantum dots for photovoltaics, infrared sensors and infrared modulators.

While the application of photovoltaics for quantum dots leads off the article, it is in terms of chronology likely to be the last of these three that will see commercial development.

Sargent rightfully bemoans the current state of photovoltaics in which we either have high efficiency and a high price or low efficiency and a low price.As far as which way to go, cheap or efficient, I like one of the comments on this blog that suggested we follow the McDonald’s model: “Make 'em cheap, make 'em fast, make 'em consistent, and have 'em ready when I'm hungry.” (Thank you, David Alexander).

And that is more or less what Sargent offers us with his painted on quantum dots for making photovoltaics. Now, I don’t want to argue with someone like Professor Sargent on this issue, but when he ventures out into the economics of such devices he is depending on the information provided by others.

They have warned him that organic polymer photovoltaic cells will need to achieve at least a 10-percent efficiency if they are ever to take off commercially. This may be correct. Even this blog has trotted out various per kilowatt numbers as thresholds for commercial acceptance, but I’m beginning to feel a little tug in the back of my mind that it may not be about the numbers.

At any rate, I hope that Sargent is correct and the fundamental science research is at the point where we can start looking at the engineering for some of these optolectronic devices because the persistent refrain of “…in five to 10 years” will soon lead us into the time frame suggested by George Crabtree and Nathan Lewis for crystalline materials meeting the requirements of efficiency and cost for photovoltaics.

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Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.


If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

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