Researchers have created an ultra-sensitive photodetector that could revolutionize the telecommunications industry and many others. Using graphene, which is made from graphite, and semiconducting quantum dots, researchers at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain have created a photodetector that is a billion times more sensitive to light than previous graphene-based photodetectors.
Photodetectors are electronic components that convert light into electrical signals. They are used, for example, as receivers in fiber optic networks where they convert light information to the form of an electric signal, explained Michael Berger for Nanowerk, an online resource for nanotechnology. Photodetectors are currently made from semiconductors like silicon or gallium arsenide. An electrical current is created when photons strike these materials. Graphene makes use of the internal field that exists at the interface of graphene and metal, but its low optical absorption – about 2.3 percent – leads to low responsiveness in photodetectors. Researchers around the globe have been working on increasing the interaction length of light with graphene to enhance its optical absorption.
And that’s where ICFO researchers have made a breakthrough.
“We managed to successfully combine graphene with semiconducting nanocrystals to create complete new functionalities in terms of light sensing and light conversion to electricity,” lead ICFO researcher Gerasimos Konstantatos told ZDNet.
Higher graphene light absorption
Another ICFO researcher, Frank Koppens, explained to The Economist that his team has managed to increase graphene’s light absorption to more than 50 percent by spraying tiny crystals of lead sulphide onto the surface of the material. These crystals are so small – three to ten nanometers across, a nanometer being a billionth of a meter – that they are known as quantum dots.
The Economist explains that optoelectronic transistors are much harder to make than ordinary transistors, and are in great demand in the world’s telecommunications networks, “in which signals are processed locally as electrons but are transmitted long-distance as light.”
The ICFO said in a statement on its website that its research regarding graphene photodetectors “consists of low-cost materials that can be integrated with existing silicon technologies, and can be readily deposited onto any sort of substrates – rigid or flexible, crystalline or amorphous. The search for low-cost, ultra-sensitive photodetectors, in particular for light that is not visible with the naked eye (such as infrared light) has been a pressing challenge for physicists and engineers.”
Graphene at $20,000 a pound
While graphene is touted as a material that could change our lives, the steep cost of producing it means its miracles are only being seen in laboratories. At a cost of $20,000 a pound, commercial use of graphene is currently prohibitive.
“Different industries that have found uses for graphene but were stymied by the high cost of graphene, or sacrificed performance by using reduced graphene oxides have been contacting Grafoid,” Dr. Gordon Chiu, vice president and co-founder of Grafoid said in an interview last month. He did not give an indication of how much the price of graphene has fallen.
The research by the ICFO scientists has created, using graphene, the “guts” of a transistor that is regulated by light, the Economist explained. It is too early to tell what impact the growing use of graphene will have on demand for graphite, especially high-grade flake graphite.
The Mining Letter reported that between 2000 and 2011 total graphite consumption doubled from 600,000 tonnes to 1.2 million tones. Byron Capital Markets expects to see this figure increase to 2.6 million tonnes by 2020 as more graphite is used to produce lithium-ion batteries and other applications.
Securities Disclosure: I, Karan Kumar, hold no direct investment interest in any company mentioned in this article.