Tiny Solar Cells Show Huge Promise

U.S. solar energy company Semprius has utilised funding and expertise from the Department of Energy’s (DOE) Sunshot Incubator program to develop a high-efficiency solar cell less than 600 microns in diameter – smaller than the dot made by a ballpoint pen.
The cell is designed for use in concentrated photovoltaic (CPV) systems. During testing at the DOE’s National Renewable Energy Laboratory (NREL), engineers successfully demonstrated a greater than 41 percent efficiency for the tiny cells at a concentration of 1000 suns – one of the highest efficiencies recorded at this concentration according to the NREL.
In a CPV module, lenses concentrate sunlight up to 1,100 times onto the triple-junction Semprius cells, which only occupy 1-1000th of the entire module area, maximising the capacity of the system and reducing the cost of each module. 
Semprius was chosen to receive Sunshot Incubator funding in 2010. The DOE scheme provides $1-3 million for solar start-up companies to bring concepts to market readiness, along with access to technical expertise from NREL scientists. 
The company manufactures the micro solar cells using a patented printing assembly line process. Each tiny solar wafer is “grown” and then sliced from the surface of a bedrock layer of gallium-arsenide substrate, a flexible compound used in thin-film photovoltaics. This allows the original substrate to be used again and again, dramatically cutting costs. It also provides a way to handle very small cells.
Semprius was founded in 2007 by Professor John Rogers from the University of Illinois. Initially aimed at producing flexible electronic materials, Rogers decided that the rapidly growing solar power market was a better fit for his technology. 
The company has since attracted $7.9 million from the North Carolina government to help build a 50,000 square-foot manufacturing plant which will employ over 250 people when completed. The plant is expected to start operating next year, with an initial capacity of 5 megawatts, eventually growing to 35 megawatts.
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