Conversion-efficiency mark is a world record for a
two-junction solar cell measured under one-sun illumination
The Energy Department’s National Renewable Energy Lab has
announced a world record of 31.1% conversion efficiency for a two-junction solar
cell under one sun of illumination.
NREL Scientist Myles Steiner announced the new record June
19 at the 39th IEEE Photovoltaic Specialists Conference in Tampa, Fla. The
previous record of 30.8% efficiency was held by Alta Devices.
The tandem cell was made of a gallium indium phosphide cell
atop a gallium arsenide cell, has an area of about 0.25 square centimeters and
was measured under the AM1.5 global spectrum at 1,000 W/m2. It was grown
inverted, similar to the NREL-developed inverted metamorphic multi-junction
(IMM) solar cell – and flipped during processing. The cell was covered on the
front with a bilayer anti-reflection coating, and on the back with a highly
reflective gold contact layer.