The0.25-square-centimetre tandem cell, made of a gallium-indium phosphide cellatop a gallium-arsenide cell, was measured under the AM1.5 global spectrum at1,000 W/m2.
Thethin-film cell, covered on the front with a bilayer anti-reflection coating andon the back with a highly reflective gold contact layer, was grown inverted,similar to the NREL-developed inverted metamorphic multi-junction solar cell –and flipped during processing.
"Historically,scientists have bumped up the performance of multijunction cells by graduallyimproving the material quality and the internal electrical properties of thejunctions – and by optimising variables such as the bandgaps and the layerthicknesses," says NREL scientist Myles Steiner.
“Butinternal
