MIT postdocs Hyesung Park and Sehoon Chang, associate professor of
materials science and engineering Silvija Gradečak, and eight other MIT
researchers have come up with a new kind of photovoltaic cell based on sheets of flexible graphene coated with a layer of nanowires.
This new approach could lead to low-cost, transparent and flexible solar
cells that could be deployed on windows, roofs or other surfaces. Currently all the Solar Cells are made of Silicon, which are highly purified and then made into crystals which can be later sliced into thin Fragments, which are costly. Many researchers are exploring alternatives, such as Nano Structured Solar Cells (link). Indium tin oxide (ITO) is used as a transparent electrode in these new solar cells.
Associate professor of
materials science and engineering Silvija Gradečak says “Currently, ITO is the material of choice for transparent electrodes,”. It is seen used in the touch screens in smartphones. But
the indium used in that compound is still expensive, while graphene is made
from ubiquitous carbon.
Alternative to ITO:
The Researches believe that it is a alternative to Indium Tin Oxide due to its lower cost. Also the Graphene cells also provides other advantages, including
flexibility, low weight, mechanical strength and chemical robustness.
Way to Graphene Cell Development was Hard:
Building semiconducting nanostructures directly on a pristine graphene
surface without impairing its electrical and structural properties has
been challenging due to graphene’s stable and inert structure, Gradečak
explains. In order to overcome this Challenge the Team utilized a series of polymer coatings to modify its
properties, allowing them to bond a layer of zinc oxide nanowires to it,
and then an overlay of a material that responds to light waves — either
lead-sulfide quantum dots or a type of polymer called P3HT.
Efficiencies Comparable to ITO:
The Team has demonstrated that devices based on graphene have a comparable
efficiency to ITO, and the structure has
an overall power conversion efficiency of 4.2 percent, which is less than the
efficiency of general purpose silicon cells, but competitive for
specialized applications.
How was the Graphene synthezised:
The graphene is synthesized through a process called chemical vapor deposition and then coated with the polymer layers.
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