Winter in Finland: Black Solar Cells Achieve Record Breaking 22.1% Efficiency

Professor Hele Savin, Leader of the Black project

Professor Hele Savin, Leader of the black cell project

A joint project between the Aalto University of  Finland and the Universitat Politècnica of Catalunya, demonstrated that black silicon solar cells in Helinski in the winter can generate considerably more electricity than traditional cells: a whopping 4% increase in daily energy production   The nanostructuring of silicon surfaces—known as black silicon—is a promising approach to eliminate  reflection in photovoltaic devices without the need for a conventional antireflection coating. This might lead to both an increase in efficiency and a reduction in the manufacturing costs of solar cells.

Due to the ability of black cells to capture solar radiation from low angles, they generate more electricity already over the duration of one day as compared to the traditional cells.  This is a huge  advantage particularly in the north, where the sun shines from a low angle for a large part of the year.

In the near future, the goal of the team is to apply the technology to other cell structures – in particular, thin and multi-crystalline cells.

“Our record cells were fabricated using p-type silicon, which is known to suffer from impurity-related degradation. There is no reason why even higher efficiencies could not be reached using n-type silicon or more advanced cell structures,” Professor Hele Savin, the leader of the project, predicts.

 

All previous attempts to integrate black silicon into solar cells have resulted in cell efficiencies well below 20% due to the increased charge carrier recombination at the nanostructured surface. Here, the research shows that a conformal alumina film can solve the issue of surface recombination in black silicon solar cells by providing excellent chemical and electrical passivation.   This means that the surface recombination issue has truly been solved and black silicon solar cells have real potential for industrial production.



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