Heterostructures Aiding the Development of Ultra High Efficient Thin Film Solar Cells

Elias Assmann (left) and Karsten Held (right) demonstrate the idea behind the new solar cell

Layered oxide heterostructures are getting more common these days, all thanks to it's properties and this is leading to the development of Ultra High efficient Thin Films. 

Before going in depth into the Properties of heterostructures, basics need to dealt with. The basic working principle of a solar cell is the photoelectric effect, ie when a light falls on a semiconductor Material, a photon is absorbed and this phenomenon may cause an electron to leave its place and electric current starts to flow. And as the electron moves it's place, what we call a 'Hole' will be formed, which has a positive charge. These released electrons as well as the holes contribute to the electrical current.

If these released electrons and holes in the solar cell recombine, the process will not result in a fruitfull end, This is where the  use of the Layered oxide heteo structures come to the rescue. A team comprising of at the researches of Vienna University of Technology and other researchers from the USA and Germany, has identified that heterostructure, specifically layered oxide ones, can be utilized to produce a new breed of highly efficient ultra-thin solar cells. 

"The biggest Advantage of the Layered oxide heteo structures, is in a microscopic scale, there is an electric field inside the material, which shows the property of seperating Holes and Electrons". This increases the efficiency of the solar cell.

The oxides used to create the material are actually isolators. However, if two appropriate types of isolators are stacked, an astonishing effect can be observed: the surfaces of the material become metallic and conduct electrical current. “, says Karsten Held from the institute of Solid State Physics, 

Vienna University of Technology. Conventional solar cells made of silicon require metal wires on their surface to collect the charge carriers – but these wires block part of the light from entering the solar cell.

Not all photons are converted into electrical current with the same efficiency. For different colors of light, different materials work best. “The oxide heterostructures can be tuned by choosing exactly the right chemical elements”, says Professor Blaha (TU Vienna). In the computer simulations, oxides containing Lanthanum and Vanadium were studied, because that way the materials operate especially well with the natural light of the sun. “It is even possible to combine different kinds of materials, so that different colors of light can be absorbed in different layers of the solar cell at maximum efficiency”, says Elias Assmann.

Article written by Manu Krishnan