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



IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

Dexter Johnson
Madrid, Spain