The US Department of Energy’s National Renewable Energy Laboratory (NREL) is carrying out research on reducing the reflectivity of PV solar panels to increase their efficiency.
Standard silicon solar cells (out of which solar panels are built) reflect around 35% of all the light which hits them – therefore one third of the solar energy hitting them is immediately lost. To reduce these losses, commercial solar cells receive an anti-reflective coating (gas molecule deposition) which brings down reflectivity to 7-10% typically. (It is this coating which makes solar cells appear blue). This process is toxic and the equipment used to achieve it is very expensive. Therefore NREL are looking at ways to reduces reflectivity of solar cells while at the same time reducing costs of manufacture.
NREL’s solution called black silicon uses an acid bath with a silver nitrate catalyst to put trillions of tiny holes into the surface of each 6×6 inch solar cell. These holes trap the photons of sunlight increasing the chance they will be absorbed by the solar cell and converted into electricity. With this technique reflectivity is reduced to less than 1.5% (which results in solar cells which appear black).
An added benefit is that solar cells treated in this way perform better in the morning and afternoon when the angle of the sun is further from the optimum (perpendicular), and they also perform well in overcast conditions.
NREL have exclusively licensed this black silicon technology to Natcore Technology specialists in thin film solar panel manufacturing. With further development they hope to make more efficient and cheaper solar panels than anything on the market today.