Graphene sensors will be 1000 times more sensitive to light, use ten times less energy and will be five times cheaper when mass produced

Cameras fitted with a new revolutionary sensor will soon be able to take clear and sharp photos in dim conditions, thanks to a new image sensor invented at Nanyang Technological University (Singapore) This will lead to cameras that use ten times less battery and will be five times cheaper.

The new sensor made from graphene, is believed to be the first to be able to detect broad spectrum light, from the visible to mid-infrared, with high photoresponse or sensitivity. This means it is suitable for use in all types of cameras, including infrared cameras, traffic speed cameras, satellite imaging and more.

Not only is the graphene sensor 1,000 times more sensitive to light than current low-cost imaging sensors found in today’s compact cameras, it also uses 10 times less energy as it operates at lower voltages. When mass produced, graphene sensors are estimated to cost at least five times cheaper.

Nature Communication – Broadband high photoresponse from pure monolayer graphene photodetector

The breakthrough is made by fabricating a graphene sheet into novel nano structures and was published this month in Nature Communications, a highly-rated research journal.

“We have shown that it is now possible to create cheap, sensitive and flexible photo sensors from graphene alone. We expect our innovation will have great impact not only on the consumer imaging industry, but also in satellite imaging and communication industries, as well as the mid-infrared applications,” said Asst Prof Wang, who also holds a joint appointment in NTU’s School of Physical and Mathematical Sciences.

“While designing this sensor, we have kept current manufacturing practices in mind. This means the industry can in principle continue producing camera sensors using the CMOS (complementary metal-oxide-semiconductor) process, which is the prevailing technology used by the majority of factories in the electronics industry. Therefore manufacturers can easily replace the current base material of photo sensors with our new nano-structured graphene material.”

If adopted by industry, Asst Prof Wang expects that cost of manufacturing imaging sensors to fall – eventually leading to cheaper cameras with longer battery life.

How the Graphene nanostructure works

Asst Prof Wang came up with an innovative idea to create nanostructures on graphene which will “trap” light-generated electron particles for a much longer time, resulting in a much stronger electric signal. Such electric signals can then be processed into an image, such as a photograph captured by a digital camera.

The “trapped electrons” is the key to achieving high photoresponse in graphene, which makes it far more effective than the normal CMOS or CCD (charge-coupled device) image sensors, said Asst Prof Wang. Essentially, the stronger the electric signals generated, the clearer and sharper the photos.

“The performance of our graphene sensor can be further improved, such as the response speed, through nanostructure engineering of graphene, and preliminary results already verified the feasibility of our concept,” Asst Prof Wang added.

ABSTRACT – Graphene has attracted large interest in photonic applications owing to its promising optical properties, especially its ability to absorb light over a broad wavelength range, which has lead to several studies on pure monolayer graphene-based photodetectors. However, the maximum responsivity of these photodetectors is below 10 mA W−1, which significantly limits their potential for applications. Here we report high photoresponsivity (with high photoconductive gain) of 8.61 A W−1 in pure monolayer graphene photodetectors, about three orders of magnitude higher than those reported in the literature, by introducing electron trapping centres and by creating a bandgap in graphene through band structure engineering. In addition, broadband photoresponse with high photoresponsivity from the visible to the mid-infrared is experimentally demonstrated. To the best of our knowledge, this work demonstrates the broadest photoresponse with high photoresponsivity from pure monolayer graphene photodetectors, proving the potential of graphene as a promising material for efficient optoelectronic devices.

Fabrication – a) A monolayer graphene was mechanically exfoliated onto a 285 nm SiO2/Si substrate. (b) The graphene photodetector was processed into a FET structure

7 pages of supplemental material

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