Artificial sunlight tool helps to test the properties of solar cells

The system from the US National Institute of Standards and Technology is said to simulate sunlight well across a broad spectrum of visible to infrared light. According to NIST the laser instrument can be focused down to a small beam spot - with resolution approaching the theoretical limit - and shaped to match any desired spectral profile. It is also claimed to be more flexible than conventional solar simulators such as xenon arc lamps or light-emitting diodes.

The new simulator 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. NIST researchers used the simulator to measure the efficiency of thin-film solar cells made of gallium arsenide, crystalline silicon, amorphous silicon and copper-indium-gallium-selenide, and the results are said to have agreed with independent measurements.

‘We can focus the light down to a spot less than 2μm in diameter, despite the wide spectral content. You can’t do this with sunlight,’ NIST researcher Tasshi Dennis said in a statement. ‘We then used this focused spot to scan across solar cell materials while monitoring the current the light generated. This allowed us to create spatial maps (images) of the response of a solar cell at the micrometre level.