Using a 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.

That number is a significant advance from the current record of 40.7 percent announced in December and demonstrates an important milestone on the path to the 50 percent efficiency goal set by the Defense Advanced Research Projects Agency (DARPA). These recent results put the pieces in place for a solar cell module with a net efficiency 30 percent greater than any previous module efficiency and twice the efficiency of state-of-the-art silicon solar cell modules.

Allen Barnett, principal investigator and UD professor of electrical and computer engineering, and Christiana Honsberg, coprincipal investigator and associate professor of electrical and computer engineering are leading the research. The two direct the university’s High Performance Solar Power Program and will continue working to achieve 50 percent efficiency, a benchmark that, when reached, would mean a doubling of the efficiency of terrestrial solar cells based around a silicon platform within a 50-month span.

The consortium’s goal is to create solar cells that operate at 50 percent in production, Barnett said. He said he expects new high-efficiency solar cells to be in production by 2010.

The new solar cells use a 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.

Modern solar cell systems rely on the concentration of the sun’s rays, a concept similar to 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.

“This is a solar cell that works,” Barnett said. “This technology has the potential to change the way electricity is generated throughout the world.”    EC