A step closer to a next generation of solar cells
In 1997, researchers from of the Instituto de Energía Solar-IES (Solar Energy Institute) in Madrid, invented and patented the concept of intermediate band solar cells as a way to turn more of the sun’s rays into electricity. After several attempts to develop them, a group of researchers has revealed the capability of a new material to absorb infrared light. Their work, published in the journal Physical Review Letters, constitutes a new scientific step to reach the implementation of these solar cells.
Conventional solar cells are unable to soak up infrared; that gives them a theoretical absorption limit of just over 40% of solar energy.
In practice, they only absorb about 30%. The new material, though, can harness both visible and infrared photons, so it has a theoretical maximum efficiency of 63%, its creators say.
The performance of intermediate band solar cell (IBSC) relies on finding a way to use more of the solar spectrum. The researchers added titanium and vanadium to get a material that exhibits an intermediate band, half-full of electrons, within what -in ordinary semiconductors- constitutes the bandgap, EG. The group of researchers was led by Perla Wahnon, from the IES, and Jose Carlos Conesa, from the Institute of Catalysis of the Spanish National Research Council.
However, while the material’s theoretical absorption limit is 63 percent, that doesn’t mean the finished product would have that efficiency in the real world. Nevertheless, since the theoretical limit percentage is higher, you can also expect a higher real world efficiency percentage. Scientists are already working to develop solar cells made of the new material.
The Institute of Solar Energy pursues this line of research as part of a European program to extract the most of every single photon available in the full solar spectrum. Through the Professor Antonio Luque, it is the coordinator of the FullSpectrum project, that has reached several interesting milestones and efficiency records in other areas as well, such as multijunction solar cells.