Artificial sunlight to test solar cell efficiency

To help test solar cell properties and find ways to boost their efficiency, researchers have developed a laser-based instrument that generates artificial sunlight.

The device simulates sunlight well across a broad spectrum of visible to infrared light.

More flexible than conventional solar simulators such as xenon arc-lamps or light-emitting diodes (LEDs), the laser instrument can be focused down to a small beam spot.

"We can focus the light down to a spot less than two micrometer in diameter, despite the wide spectral content. You can not do this with sunlight," said Tasshi Dennis from National Institute of Standards and Technology (NIST) in the US.

"We then used this focused spot to scan across solar cell materials while monitoring the current the light generated," Dennis added.

This allowed scientists to create spatial maps (images) of the response of a solar cell at the micrometre level.

The instrument is based on a white light laser that uses optical-fibre amplifier technology to boost the power and a photonic crystal fibre to broaden the spectrum.

"The new simulator's capability to make rapid, accurate spectrum adjustments will help characterise the most efficient solar cells, which use multi-junction materials in which each junction is tuned to a different part of the spectrum," Dennis noted.