Blue/red reflecting solar cell covers for GaAs cells

Advances in the state of the art for coatings have allowed the development of solar cell covers that can improve the performance of gallium arsenide (GaAs) cells on germanium host substrates by lowering the temperature. These coatings reflect away the unconvertible solar energy in the near infrared and the blue/ultraviolet portions of the solar irradiance to prevent unnecessary heating of the cell assembly. It is now possible to reflect a significant portion of the Sun´s energy in the infrared and the ultraviolet (UV) so that the solar absorbtance of the cover/cell assembly is greatly reduced. The resultant reduction in cell temperature can then lead to higher output for the array. The spectral performance for a blue/red reflector (BRR) coating is discussed. Measurements of the absorbtance of a cell and cover combination have been used to model the expected equilibrium temperature for the assembly. This modeling is done for an antireflection (AR) coated solar cell cover, a standard UV reflecting (UVR) solar cell cover, representative of the current state of the art, and for the new BRR cover to provide an estimate of the change in temperature attributable to the improved coating design. The AR coated cover is used as a baseline for comparison of the expected output increases for the UVR and BRR covered cells at equilibrium. The environmental durability of these covers is included. A version of the BRR coating applicable to Si cells is also discussed