May 3, 2013
Graphene Super-Materials Could Be Future Of Solar Cells, And More
Alan McStravick for redOrbit.com - Your Universe Online
In 2004, the pure carbon material known as graphene was isolated by two University of Manchester Nobel Laureates, Andre Geim and Professor Kostya Novoselov, quickly leading to the discovery of a whole new family of one-atom-thick materials.
Now researchers from the University of Manchester and National University of Singapore have shown that by building multi-layered heterostructures of graphene in a three-dimensional stack, materials engineers are able to produce an exciting physical phenomenon that could lead to a variety of new electronic devices.
These new structures could conceivably lead to photovoltaic structures that could be placed on the outer walls of buildings. They would absorb sunlight and convert that energy into electricity capable of powering the entire building. This breakthrough was published recently in the journal Science. In addition to collecting and converting energy, the new structures could factor in environmental conditions like temperature and brightness, directing the energy to change the transparency and reflectivity of individual fixtures and windows.
Graphene is the world´s thinnest, strongest and most conductive material. Products and applications such as smartphones, computer chips, ultrafast broadband and drug delivery are poised to experience major advances as a result of this material and its unique properties.
Graphene´s 2D crystals can demonstrate a host of unique properties. For example, they can aid in conduction or insulation and change from opaque to transparent. As researchers add new layers to the stacks, the structure adopts new functions. For this reason, the team says these heterostructures are ideal for creating novel, multifunctional devices.
Due to the fact the combination of 2D crystals allows researchers to achieve functionality above and beyond what could be available from any of the individual materials, the team says the addition of one to another creates an outcome greater than the sum of its individual parts.
The collaborative research team was able to expand the functionality of these heterostructures into the realm of optoelectronics and photonics. This was achieved through the combination of graphene with monolayers of transition metal dichalcogenides (TMDC). With this combination came the creation of extremely sensitive and efficient photovoltaic devices. Eventual uses for these new devices could be found in the fields of photodetection or much more efficient solar cells.
These new devices involved the layering of TMDC between sheets of graphene. This layering allowed for the combination of the properties of both types of 2D crystals. The TMDC layers are ultra-efficient light absorbers, while the graphene layers act as a transparent conductive structure. The combination of these characteristics allows for further integration of these photovoltaic devices into a much more complex, multifunctional material.
“We are excited about the new physics and new opportunities which are brought to us by heterostructures based on 2D atomic crystals,” said Novoselov. “The library of available 2D crystals is already quite rich, covering a large parameter space.”
"Such photoactive heterostructures add yet new possibilities, and pave the road for new types of experiments,” he continued. “As we create more and more complex heterostructures, so the functionalities of the devices will become richer, entering the realm of multifunctional devices."
Lead author of the study and University of Manchester researcher Dr. Liam Britnell added, “It was impressive how quickly we passed from the idea of such photosensitive heterostructures to the working device. It worked practically from the very beginning and even the most unoptimised structures showed very respectable characteristics.”
Professor Antonio Castro Neto, Director of the Graphene Research Centre at the National University of Singapore stated, “We were able to identify the ideal combination of materials: very photosensitive TMDC and optically transparent and conductive graphene, which collectively create a very efficient photovoltaic device.”
"We are sure that as we research more into the area of 2D atomic crystals we will be able to identify more of such complimentary materials and create more complex heterostructures with multiple functionalities,” he continued. “This is really an open field and we will explore it."