Semiconductor Nanomembrane Based Flexible PV Power Sources

ABSTRACT: The purpose of the proposed Air Force Phase I STTR program is to fabricate semiconductor nanomembrane based photovoltaic (PV) power sources on flexible substrates, using Virginia Tech NanoCMOS Laboratory"s SOI silicon nanomembrane technique in combination with NanoSonic"s pioneering Polynanoguard antireflection copolymer nanocomposite materials, which afford high levels of antireflection, temperature and abrasion resistance, impact durability and hydrophobicity (self cleaning). NanoSonic"s Polynanoguard composites will be used not only as the substrates but also the antireflection coatings to enhance the device efficiency. Such an approach to form flexible PV materials and devices offers advantages over hydrogenated amorphous silicon based flexible PV devices, in that much higher energy efficiency can be obtained on flexible substrates with room temperature manufacturing and processing. By proper diffusion, silicon P-N junctions will be formed into the n-type or p-type Si membranes, and then be patterned and released from the engineered SOI wafers using wet chemical etching. The released Si P-N junction membranes will be transferred to NanoSonic"s highly transparent, super lightweight and mechanically robust Polynanoguard materials to be integrated into flexible PV devices. NanoSonic will additionally investigate high mobility PV membrane materials other than Si, such as Ge, SiGe and GaAs to further increase the energy conversion efficiency. In addition, NanoSonic"s QD-PMMA composite will be coated on the top of the PV devices as down-converters to shift the incident high-energy photons toward lower energies for which the PV cells work more efficiently. During Phase I, NanoSonic would work with academic and industry partners to demonstrate the ability to reproducibly form semiconductor membrane based flexible PV devices, and investigate methods to improve quantum efficiency, fabricate electrode interconnections and implement effective device packaging. BENEFIT: A broad band of applications of the proposed PV devices include solar cells, spectroscopy, photography, analytical instrumentation, optical position sensors, beam alignment, surface characterization, laser range finders, optical communications, and medical imaging instruments. Currently, the production of electricity from photovoltaic devices is uneconomical compared to fossil fuel or nuclear sources except for applications located off the electrical grid. NanoSonic"s research in the flexible PV field, to ease the energy access for military soldiers will show promise in producing cells of high efficiencies at reduced cost and load using crystalline silicon membranes fabricated from SOI wafers to replace amorphous silicon and conductive polymer materials. Installation costs would be lower because lightweight flexible PV cells could be handled more easily than heavy silicon panels.