A new conversion efficiency world record for black silicon solar cells was recently set by researchers at the University of Aalto in Finland. The new record of 22.1% conversion efficiency marks a nearly 4% increase in efficiency — which was achieved by addressing (to some degree) one of the primary issues with the technology, carrier recombination.
For those that don’t know — carrier recombination is when the electron freed by the action of a photon hitting a silicon atom simply recombines with another silicon atom, rather than generating a current. As carrier recombination is proportional to the surface area of the silicon in a cell, and black silicon solar cells possess substantial surface area, the issue has remained a barrier with regard to improving conversion efficiencies.
Also worth noting, real-world performance was improved pretty notably as well — as black silicon solar cells can better harvest photons from low angles, as compared to conventional cells. Altogether, black silicon cells can harvest roughly 3% more electricity over a day than a conventional solar cell with the same nameplate efficiency.
The researchers were able to address carrier recombination via the application of a thin aluminum film (which functions as a chemical + electronic shield), as well as the integration of all the metal contacts on the back side of the cell, thereby improving absorption. These actions resulted in carrier recombination dropping to just 4%, down from 50%. According to the researchers, there is still much room for improvement in this regard — with notably higher conversion efficiencies being within reach.
The research concerning the new record was detailed recently in the journal Nature Technology.
Image Credit: Aalto University
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