A group of Japanese researchers led by Saki Sonoda, associate professor at the Kyoto Institute of Technology, have built a prototype of a solar cell that can harvest ultraviolet, visible and infrared light as well. This wide-band solar cell could offer tremendous increases in efficiency.

The announcement has been made on March 19, at the 57th Spring Meeting of the Japan Society of Applied Physics.

They realized the new wide-band PV cell by adding “3d transition metals”, including manganese (Mn) to transparent composite semiconductors who already had a wide bandgap, such as gallium nitride (GaN). Despite the fact that the new cell is not a multi-junction one, it would be highly-efficient.

The prototyped model doesn’t offer a high conversion efficiency, but its open voltage is as high as 2V.

Sonoda explained the “impurity band” model, which is mainly composed of Mn’s energy levels in the 3d orbit. There has been a technology to set a ladder to a forbidden band, to which electrons with small energy levels cannot climb, by adding impurities to a semiconductor material with a large bandgap so that light with a longer wavelength can be absorbed.

Harvesting the invisible radiation spectrum not only will increase the efficiency of the cell, but it will also make solar cells cheaper for the end consumer.

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