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July 24, 2007

Solar cell efficiency record of 42.8%

Using a novel technology that adds multiple innovations to a very high-performance crystalline silicon solar cell platform, a consortium led by the University of Delaware has achieved a record-breaking combined solar cell efficiency of 42.8 percent from sunlight at standard terrestrial conditions. This beats the previous 40.7% record of Spectrolabs.


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UD researchers Christiana Honsberg and Allen Barnett

The consortium’s goal is to create solar cells that operate at 50 percent in production, Barnett said. With the fresh funding and cooperative efforts of the DuPont-UD consortium, he said it is expected new high efficiency solar cells could be in production by 2010.

The highly efficient VHESC solar cell uses a novel lateral optical concentrating system that splits solar light into three different energy bins of high, medium and low, and directs them onto cells of various light sensitive materials to cover the solar spectrum. The system delivers variable concentrations to the different solar cell elements. The concentrator is stationary with a wide acceptance angle optical system that captures large amounts of light and eliminates the need for complicated tracking devices.

The VHESC would have immediate application in the high-technology military, which increasingly relies upon a variety of electronics for individual soldiers and the equipment that supports them. As well, it is hoped the solar cells will have a large number of commercial applications.

Modern solar cell systems rely on the concentration of the sun’s rays, a concept similar to youngsters using magnifying glasses to set scraps of paper on fire. Honsberg said the previous best of 40.7 percent efficiency was achieved with a high concentration device that requires sophisticated tracking optics and features a concentrating lens the size of a table and more than 30 centimeters, or about 1 foot, thick.

The UD consortium’s devices are potentially far thinner at less than 1 centimeter. “This is a major step toward our goal of 50 percent efficiency,” Barnett said. “The percentage is a record under any circumstance, but it’s particularly noteworthy because it’s at low concentration, approximately 20 times magnification. The low profile and lack of moving parts translates into portability, which means these devices easily could go on a laptop computer or a rooftop.”

Honsberg said the advance of 2 percentage points is noteworthy in a field where gains of 0.2 percent are the norm and gains of 1 percent are seen as significant breakthroughs.


FURTHER READING:

Barnett's main page at the University of Delaware

The researchers provide a 6 page solar cell FAQ sheet

The US photovoltaics industry has a 16 page roadmap with a goal of providing half of all new electricity generation by 2025 They have a cost target of 3.8 cents per kwh and 200 GW of installed power

A past article on nuclear power, wind and coal

A prior article that compares the cost of all energy sources. Nuclear, hydroelectric, wind and coal power would still be less expensive than the solar industry target of 3.8 cents but solar would be competitive in many situations.


Here is Gen III Molecular Beam Epitaxy (MBE) that is used by the team for crystal growth which offers the ability to control material composition down to the atomic layer level.

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