Graphene Combined with Quantum Dots Result in Efficient Photodetector

Graphene/quantum dot hybrid lifts graphene's light absorbtion efficiency from just three percent to twenty-five percent

2 min read
Graphene Combined with Quantum Dots Result in Efficient Photodetector

Graphene research has been turning increasingly towards its potential in optoelectronic applications.  This is not a surprise because graphene’s optical properties are as astounding as its electrical conductivity capabilities.

But just as graphene has the glaring Achilles Heel in electronics applications of lacking a band gap, it also suffers a couple of fatal flaws in optoelectronics. For example, while nearly every single photon the material absorbs generates an electron-hole pair, it doesn’t really absorb that much light. According to some estimates, it absorbs less than 3 percent of the photons falling on it.

So, researchers at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain thought about the possibility of combining graphene with quantum dots to see if they couldn’t overcome graphene’s shortcomings.

The research, which was published in the journal Nature Nanotechnology last week,  demonstrated that the combination of the two nanomaterials did the trick. Instead of absorbing just 3 percent of the light that hits it, the graphene/quantum dot hybrid material is capable of absorbing 25 percent of the light falling on it. This new absorption capability is due to the quantum dots, and when you combine that with the graphene’s ability to make every photon into an electron-hole pair, the potential for generating current is significant.

"In our work, we managed to successfully combine graphene with semiconducting nanocrystals to create complete new functionalities in terms of light sensing and light conversion to electricity," Gerasimos Konstantatos, co-leader of the team at the Institute of Photonic Sciences (ICFO) in Barcelona, told "In particular, we are looking at placing our photodetectors on ultrathin and flexible substrates or integrating the devices into existing computer chips and cameras," added co-leader Frank Koppens in the same article.

The researchers offer a range of applications for the graphene-and-quantum-dot combination, including digital cameras and sensors. But it seems the researchers seem particularly excited about one application in particular. They expect the material will be used for night-vision technologies in automobiles—an application I have never heard trotted out before in relation to nanotech.

"We expect that most cars will be equipped with night-vision systems in the near future and our arrays could form the basis of these," Koppens told

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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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