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High Efficiency Flexible Photovoltaics


OBJECTIVE: Develop and demonstrate photovoltaic arrays that are flexible and can achieve greater than 20% solar photon to electrical conversion efficiency in a lightweight configuration. DESCRIPTION: Photovoltaics (solar cells) are an attractive technology to provide renewable energy sources for forward operating bases, man-portable power sources, and tactical applications. Solar arrays can provide base power greatly reducing the need for logistical fuels, continuous battery recharging for warfighters on the move, and integrated power sources for remote, autonomous systems, e.g. UAVs. To be effective, solar arrays must be lightweight, flexible, and provide high power density. Flexible solar arrays based on thin film photovoltaics have been fielded for some military applications, but their usefulness has been limited by their low efficiency. Si panels have attained efficiencies as high as 22% but but are made of glass and Al. Flexible amorphous Si or polycrystalline CIGS panels are less than 15% efficient. Higher efficiency, flexible solar cells have been demonstrated for space applications, but their cost has hindered terrestrial applications. New materials and manufacturing methodologies are needed to produce a solar cell that is lightweight, flexible, high efficiency, and affordable. The goal of this topic is to develop cost-effective, photovoltaic technologies that display high efficiencies in a flexible format. PHASE I: Produce a design for a flexible (bend radius of 6"or less) solar cell and array that can achieve>20% terrestrial conversion efficiency at ~1W/g, with a cost target of $50/W or less using modeling and simulation supported by material parameter data and optoelectronic measurements on representative materials and test structures. PHASE II: Grow, fabricate and test the solar cell design developed in Phase I. Quantify the solar cell performance through illuminated and dark current vs. voltage measurements and spectral response measurements. Develop methods to improve solar cell performance and optimize the solar cell design accordingly. Demonstrate a solar array coupon consisting of at least 4 interconnected solar cells, measure the performance, and compare with predictions from Phase I. Develop methods to improve solar array performance and optimize the array design accordingly. PHASE III: Using the knowledge gained during Phases I and II, produce 5 prototype solar arrays that each produce at least 20W. Develop prototype production line for the fabrication of high efficiency, flexible solar arrays and commercialization plans. PRIVATE SECTOR COMMERCIAL POTENTIAL: Cost effective, high efficiency, flexible solar cells could be used as lightweight, portable power sources.
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