NREL August R&D IssueEngineers at the National Renewable Energy Laboratory have developed a way to assess the quality of solar cells at a speed that is orders-of-magnitude faster than previous methods.

The 2011 R&D 100-winning instrument, Real-time QE, licensed and further developed by Tau Science Corp. as FlashQE, uses light-emitting diodes (LEDs), high-speed electronics, and mathematical algorithms to measure the quantum efficiency of solar cells up to 1,000 times faster than other technologies.

With the instrument, quantum efficiency (QE) measurements, which used to take 20 min—and therefore could be done only with random samples of cells—now can be done in 1 sec.

QE measurements indicate how well a solar cell converts the various wavelengths of sunlight into electricity. Today's solar cell manufacturing lines test each cell to determine useful cell parameters such as how much current and voltage is generated. But those tests give no information about how the cell responds to each color of light in the solar spectrum.

FlashQE's ability to also test for each cell's response to color allows crucial extra information to be fed back into the production line. It does it so fast, that cells of the same current and the same response to particular colors can be sorted into particular bins. From these sorted bins, spectrally matched modules can be made to optimize the energy produced throughout a day.

The FlashQE system uses an electronically controlled full-spectrum light source composed of an array of LEDs that illuminate the cell simultaneously, rather than the serial approach of a conventional system.

National Renewable Energy Laboratory,