A new class of materials, known as layered oxide heterostructures, made by stacking single atomic layers of oxides, can be used to create a brand new kind of ultra-thin, super-efficient solar cells.
Researchers from the Vienna University of Technology, together with colleagues from the US and Germany, discovered the unique electronic properties of these materials by conducting a series of computer simulations.
The basic concept of the technology is not new. Albert Einstein explained it in 1905, proving that when a single photon is absorbed, it allows an electron to vacant its place, creating an electric current. The electron leaves the so-called “hole”, which is essentially a positively charged region.
Elias Assmann, the team member who carried out the computer simulations at TU Vienna, explained that these holes and electrons can recombine in the solar cell, instead of being transported away. The researcher adds that the new material has a microscopic electric field inside, which has the unique advantage to separate electrons and holes, which consequently increases the efficiency of the solar cells.
By stacking the oxides, which are also isolators, the material becomes metallic and can conduct electrical current. This effect allows the extraction of the charge carriers and creates an electrical circuit. Professor Karsten Held from the Institute for Solid State Physics, Vienna University of Technology explains that unlike conventional solar cells made of silicon, the new cells would not require wires to collect the charge carriers. This means that the full amount of incoming light would be able to enter the solar cell.
Another member of the team, Professor Blaha from TU Vienna, points out that another advantage of the new materials is the fact that the layered oxide heterostructures can be tuned by choosing the right chemical elements and can achieve maximum efficiency.
Based on their computer simulations, the team concluded that oxides, which contain Lanthanum and Vanadium, are most suitable. These elements in the materials operate very well with natural light of the sun. Elias Assmann stated that it is now possible to even combine different kinds of materials, so that different colours of light are absorbed in different layers of the solar cell, achieving maximum efficiency.
Currently, the new solar cell is in a process of building and testing. The scientists are certain that the thin structure and the high efficiency provided by these materials will stimulate solar cell manufacturers to replace the conventional silicon.
