It has been a challenge for decades until the time being, to avid solar cell innovators and scientists, how to tweak the design and what material to use, just to completely absorbed the wide solar spectrum of about 300 to 2500 nanometer.
Commercial Silicon (Si) based Photovoltaic (PV) cell’s performance, ranges 17 to 20 percent efficient at its best. With band response of approximately 400 to 1000 nanometer sensitivity to solar irradiance, Silicon is at its limit. So, the basic solution is, to tandem Silicon with different type of materials like Ge, GaAs, InGa, InGaP and InGaAs, having its individual band response within the solar spectrum, other than Silicon’s. This set up is also known as multi-layered and multi-junction solar cell.
NREL or National Renewable Energy Laboratory recorded, just recently, the best efficiency attained so far, is at 46 percent. This is from a multi-junction concentrator type solar cell, which was developed at Fraunhofer ISE/Soitec Freiburg, Germany.
However, tandem or multi-junction solar cells is not cheap, as of the moment. So, it is basically impractical to market and mass produce. Professor Nate Lewis, chairperson of the Basic Research Needs for Solar Energy Utilization, cited from the GECP Research Symposium 2010 in Stanford, California, that a square centimeter (sq.cm) of this concentrator multi-junction type of solar cell would cost about $40,000.
But, new hope dawns on the cost related issue, for Silicon tandem cells. Perovskites, a low cost material captured the attention of a group of physicist led by Henry Snaith at Oxford. The new material composition that they developed, is a combination of Silicon and Perovskites. This could overcome today’s efficiency of commercial Silicon cell on the market, by 25 percent higher, they say. This may not be comparably high as high-performance semiconductor tandem devices of over 40 percent efficient, but the process of making Perovkites tandem is more simpler and way cheaper than semiconductors. Thus, this material is a big deal and a game changer to the Solar Industry.
Having a 25 percent more energy coversion from the previous solar cell technology, is not bad at all, especially, when you could buy it, at the same price, or even, a slightly higher but affordable cost.
Source: MIT Technology Review