SOLAR TODAY July 5, 2012
Scientists at the U.S. Naval Research Laboratory (NRL) Electronics Science and Technology Division have developed high-bandgap gallium-indium phosphide (GaInP) solar cells capable of powering electronic sensor systems at depths of 9 meters (30 feet).
According to Phillip Jenkins, head of NRL’s imagers and detectors Section, underwater systems are limited by the endurance of their power sources. the intensity of solar radiation is lower under water, and the spectral content is biased toward the blue/green portion of the spectrum. the narrow spectrum can produce high conversion efficiency if the cell is well-matched to the wavelength range. GainP cells offer a higher bandgap than silicon, with good quantum efficiency in wavelengths between 400 and 700 nanometers (visible light) and intrinsically low dark current, which is critical for high efficiency in lowlight conditions.
Preliminary results at a maximum depth of 9.1 meters reveal output to be 7 watts per square meter, sufficient to demonstrate there is useful solar power to be harvested at depths commonly found in littoral zones.