New Record Set for Black Silicon Solar Cells

[Guest_Jim_*]

Black silicon is a special form of silicon that has surface features that cause it to absorb much of the light that hits it, hence the name. Naturally there is interest in using it for solar cells and now researchers at Aalto University and Universitat Politècnica de Catalunya have set a new efficiency record of 22.1%.

To achieve this record the researchers used atomic vapor deposition to add a thin passivating film onto the black surface structures and by moving the metal contacts to the back of the cell. The film had the effect of limiting surface recombination, instead of it limiting the energized electrons that can be pulled away by the contacts for work. This is the first time the recombination issue of black silicon has been removed from such a system. Additional work may actually push the efficiency higher as the type of silicon used, p-type, is known to suffer from impurity-related degradation, so n-type silicon or more advanced cell structures could go even higher.

While the improved efficiency is definitely important and noteworthy, there is more to the operation of black solar cells than that. When tested against traditional solar cells of similar efficiency, the researchers found the black silicon cells generated more electricity because they are better at capturing light at low angles. This is important in northern areas, where the Sun shines at lower angles for a good portion of the year.

Source: Aalto University

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