How a new kind of "black silicon" is revolutionizing solar cells

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Black silicon solar cells are a relatively new technological advance that allows for the absorption of light in the infrared spectrum — about 25% of incoming sunlight. These cells are capable of pulling in an incredible 99.7% of the light that hits their surfaces, compared to traditional cells which absorb 95%. And now, owing to a breakthrough by German scientists, these cells have had their efficiency doubled.

Black silicon was developed back in the 1980s. It's a semiconductor material in which traditional silicon has been modified to have extremely low reflectivity (hence its deep black coloring), enabling it to absorb both visible and infrared light. It has many potential applications, including photodetecting for various imaging and night vision technologies.

But it can also be used for high-efficiency solar cells. Unlike traditional solar cells, black silicon is capable of pulling in sunlight on cloudy days, while also being able to draw energy from the sun at extreme angles (i.e. early and late in the day). The end result is a black panel that can produce twice the amount of electricity of regular PV panels.


And it now appears that the potential for black silicon cells has been given an extra boost. Stefan Kontermann of Fraunhofer Institute for Telecommunications has devised a new technique in which he has doubled the efficiency of these cells.

He did so by changing the manufacturing process of black silicon. Normally, infrared light lacks the energy needed to raise the electrons in the so-called 'conduction band.' But by introducing sulphur into the process, he was able to create an intermediary step in which the electrons were able to jump at the required levels, after which they can be converted into electricity. The energy levels of the sulphur was modified through the use of a laser pulse, which is used to irradiate the silicon.


The next step for the researchers are to create algorithms that will help them optimize the process and maximize efficiency.

H/t: CleanTechnica. Top image via Fraunhofer Institute for Telecommunications.