NREL produces 31.1% efficient dual-junction solar PV cell

The record-setting cell is based on NREL's inverted metamorphic (IMM) PV cell design
The record-setting cell is based on NREL's inverted metamorphic (IMM) PV cell design

The US Department of Energy's National Renewable Energy Laboratories (NREL, Golden, Colorado, US) has achieved a 31.1% conversion efficiency using a dual-junction solar photovoltaic (PV) cell under one sun of illumination, a new world record.

The previous record of 30.8% for this technology and condition was set by Alta Devices (Sunnyvale, California, US) in March 2013. NREL's 0.25 square centimeter III-V PV cell comprises a gallium indium phosphide cell on top of a gallium arsenide cell, measured under the AM1.5 global spectrum at 1,000 watts per square meter.

 

Cell based on IMM design

The PV cell is based on NREL's inverted metamorphic (IMM) cell design, which involves inverting the usual growth order of layers, as well as engineering a transparent buffer layer to mitigate dislocations and removing the primary substrate/attachment to the secondary 'handle'.

 

Cell produced under F-PACE program

NREL developed the cell as part of the US DOE's Foundation Program to Advance Cell Efficiency (F-PACE), a project of the SunShot Initiative that aims to lower the cost of solar energy. The goal of the program is to create a PV cell with a 48% efficiency under concentration.

“Historically, scientists have bumped up the performance of multi-junction cells by gradually improving the material quality and the internal electrical properties of the junctions -- and by optimizing variables such as the band-gaps and the layer thicknesses,” stated NREL Scientist Myles Steiner.

However, NREL's focus has instead been on internal optics, which Steiner says plays an under-appreciated role in high-quality in III-V PV cells. “The scientific goal of this project is to understand and harness the internal optics.”

 

2013-06-25 | Courtesy: NREL | solarserver.com © Heindl Server GmbH

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