Short-wavelength solar cells have high external quantum efficiency

Feb. 1, 2011
Indium gallium nitride (InGaN)-based semiconductors have large bandgaps, which has allowed the creation of ultraviolet and bright blue-emitting LEDs and lasers.

Indium gallium nitride (InGaN)-based semiconductors have large bandgaps, which has allowed the creation of ultraviolet and bright blue-emitting LEDs and lasers. However, a large bandgap can be a plus for use in detectors and solar cells as well, because they have a high response to short-wavelength light (down to 370 nm). Researchers at the University of California–Santa Barbara and the École Polytechnique (Palaiseau, France) have demonstrated InGaN/GaN solar cells that have an internal quantum efficiency as high as 97% and a peak external quantum efficiency (EQE) of 72%—the latter achieved by inducing a 41 nm (root mean square) surface roughness during fabrication.

The cells, which were fabricated by metal-organic chemical vapor deposition on sapphire substrates, have an InGaN/GaN thickness of 360 nm. A palladium/gold grid collects the current; the open-circuit voltage is 1.89 V. Despite the high EQE, at least 20% of the incoming light is either reflected or transmitted through the cell, and thus there is room for further improvement in efficiency. This type of short-wavelength photovoltaic cell has potential as one component in very high-efficiency multijunction solar cells, where it would convert the highest-energy portion of the solar spectrum. Contact Elison Matioli at [email protected].

About the Author

Gail Overton | Senior Editor (2004-2020)

Gail has more than 30 years of engineering, marketing, product management, and editorial experience in the photonics and optical communications industry. Before joining the staff at Laser Focus World in 2004, she held many product management and product marketing roles in the fiber-optics industry, most notably at Hughes (El Segundo, CA), GTE Labs (Waltham, MA), Corning (Corning, NY), Photon Kinetics (Beaverton, OR), and Newport Corporation (Irvine, CA). During her marketing career, Gail published articles in WDM Solutions and Sensors magazine and traveled internationally to conduct product and sales training. Gail received her BS degree in physics, with an emphasis in optics, from San Diego State University in San Diego, CA in May 1986.

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