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Enhanced Solar Cells

Highly Efficient, Durable, Photovoltaic Cells Absorb and Trap More Light

Energy

Researchers at China Lake have come up with a new technology for increasing the efficiency and durability of solar cells by enhancing and trapping light absorbance.

Existing Technology
Solar cells and batteries are extensively used throughout the DoD in thousands of different applications. For example, solar cells and batteries are needed to keep smaller drones and unmanned systems loitering in the air for longer periods of time. Extended batteries allow for enhanced operations. Even minor improvements can achieve significant operational results. The goal was to create higher efficiency, low mass, durable photovoltaic cells; specifically, excitonic solar cells.

New Technology
Researchers at China Lake have come up with an evolutionary new technology for increasing the efficiency and durability of solar cells. New portable power for Warfighters could include extending the range of electric powered drones or power for distributed sensors (security cameras), etc. Trapping each color of the rainbow within nanoplasmonic cavities has proven useful. China Lake synthesized light-harvesting materials and used a layer-by-layer deposition technique (APD) that enabled precise (within a few nanometers) control over the film thickness, gradient, and precise positioning. Titania, polymer photoabsorbers, and carbon nanotube electrodes further enhanced trapping and light absorbance.

This work began in 2000 and has progressed since. In 2007, a power systems core Science and Technology (S&T) project produced the first designs of nanoplasmonic cavities filled with APD polymer photoabsorbers. The cavity resonances were optimally tuned to the color absorbed thus increasing the efficiency of the solar cell. Using materials designed for maximum compatibility, multi-layer nanostructures were fabricated allowing rapid scale-up for mass production of large area devices. China Lake’s advanced computer modeling led to optimum device designs. DoD applications could benefit unmanned systems by increasing loiter time to assist Intelligence, Surveillance, and Reconnaissance / Target Acquisition (ISR/TA) missions.

How It Works
The invention improves the efficiency of excitonic solar cells such as polymer bulk-heterojunction and Graetzl cells. Two key embodiments of the innovation fabrication process are electrostatic self-assembly of organic conjugated polyelectrolytes and atomic layer deposition of titania within nanoplasmonic cavities that enhance the trapping and absorbance of light. China Lake synthesized light-harvesting materials, electrolyte-substituted polythiophenes, and demonstrated self-assembly of conformal nanofilm coatings on titania. The layer-by-layer deposition technique (APD) enabled precise (within a few nanometers) control over the film thickness, the concentration gradient of each component of the film, and precise positioning of the maximum concentration of each component. The surface of titania is a well-known efficient charge-separation interface commonly used in dye-sensitized solar cells. The titania further serves to transport electrons. China Lake deposited titania using atomic layer deposition (ALD). ALD produces high-quality wide area films with nanometer control of thickness. Using materials designed for maximum compatibility, multi-layer nanostructures were fabricated by methods that have demonstrated a capability for rapid scale-up for mass production of large area devices. China Lake’s computer modeling of the transport of charge density waves through the nanofilm PV devices leads to optimum device designs.

Who Benefits
DoD and any other entity using photovoltaic batteries for any application.

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