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Scientists at the US Department of Energy’s National Renewable Energy Laboratory have developed a solar cell that can convert 40.8% of the sunlight it receives into electricity – a world record.

The new triple-junction solar cell has three layers of different photovoltaic material, which split the solar spectrum into three equal parts that are absorbed by each of the cell’s layers. This enables more of the sunlight hitting the cell to be converted into electricity, and therefore improves the cell’s conversion efficiency.

The cell has a unique design in that it is grown in an inverted formation, from the top down, and is then separated from its substrate wafer to make a light-weight, flexible-film device. This method of production also allows materials with a different crystalline lattice spacing to be used in the bottom layer of the cell, creating a mismatched latticed or metamorphic solar cell, which improves the cell’s conversion efficiency.

The world record efficiency was measured by exposing the cell to sunlight concentrated by a factor of 326 (326 suns) – one sun is approximately the amount of light that hits the earth on a sunny day.

The new cell would be particularly suited for use in space satellites, or for earth-based concentrated photovoltaic arrays, which use lenses or mirrors to focus sunlight onto the solar cells.

For further information:
www.nrel.gov/news/press/2008/625.html