Development of Advanced Anti-Reflection Coatings for High Performance Solar Energy Applications

MicroLink and its subcontractor Magnolia Solar will develop and demonstrate advanced anti-reflection coating (ARC) designs that will provide a better broadband and angular response than that of current coatings. Advanced coatings of this nature are needed to realize the full potential forthcoming generation of multi-junction solar cells that will contain four or more junctions. We will undertake several approaches to this problem:* investigate new dielectric materials that will allow a refractive index intermediate between those of the materials that are currently in common use as ARCs;* investigate a dielectric codeposition processes that will allow the fabrication of materials with a wide range of refractive indices; and* investigate oxidation of Al-containing III-V semiconductor compounds as a mechanism for forming a more transparent window layer.Based on the results of these investigations, we will fabricate and test on III-V triple-junction solar cells the best-identified candidates for improved anti-reflection coating. If successful, the new coating designs will have a reflectance less than 5% over the spectral range 300 nm to 1800 nm and over a wide range of incident angles. The coatings will be completely compatible with inverted metamorphic (IMM) multi-junction solar cell technology and will be optically matched to IMM solar cells. We expect the new coatings will enable a relative efficiency increase of at least 7%, corresponding to a 2.5% absolute efficiency increase.