The efficiency of solar cells based on the most common semiconductors, silicon, continues to creep up, edging ever close to that theoretical Shockley–Queisser limit of 33.7 percent. Earlier this week Germany’s Fraunhofer Institute pushed the efficiency of a multicrystalline silicon solar cell to 21.9 percent, surpassing the 21.3 percent efficiency record set by Trina Solar.
“We are very happy about this excellent result, which is due largely to the fact that Fraunhofer ISE’s expertise runs along the entire value chain of silicon photovoltaics,” said Institute Director, Andreas Bett. “At the Institute our expertise spans the entire range from the crystallization of silicon through to the quality assurance of PV power plants. The research areas of material development, characterization and cell technology all played a part in the development of the world record cell.”
The institute was able to produce the record cell with a highly antireflective cell, making the device look almost purely black with no discernible crystal that most multicrystalline cells exhibit. The cell is made of n-type HPM silicon with an area of 2 cm x 2 cm, and shows a higher tolerance to impurities than p-type silicon, according to the institute.
“In our Silicon Material TEchnology Center SIMTEC, we adjusted the crystallization process with the goal of creating a material optimized for the planned solar cell processing procedure. We worked closely and in constant exchange with our colleagues until we all achieved our common target of world record efficiency,” explained Stephan Riepe, head of the silicon—crystallization and epitaxy group at the institute.
Higher solar power efficiencies and better processing are key factors for pushing the cost of manufacturing solar panels down even further. Hence, even incremental performance increases in cell efficiency can have a big impact on the price of solar power. Currently the average efficiency of commercially available multicrystalline silicon cells are about 19 percent efficient, according to Fraunhofer.
The institute will continue pushing such boundaries. “Our goal is to develop an advanced cell technology for the n-type multicrystalline wafer that really demonstrates its full potential. The question is, how far can we get to closing the efficiency gap to monocrystalline material,” said project leader Jan Benick, who also is team leader of Innovative Clean Room Technologies for High Efficiency Silicon Solar Cells at the institute. The “multiTOP” project, which produced the new champion cell, will run up to March 2018.Tweet