Measured and confirmed by the National Renewable Energy Laboratory (www.nrel.gov), solar cells developed by IMEC (Leuven, Belgium) reached a record conversion efficiency of 24.7%. IMEC realized this record on a single-junction gallium arsenide (GaAs) cell, grown epitaxially on a germanium (Ge) substrate with an improved microdefect distribution. The cell measures 0.25 cm² and exhibits the 24.7% efficiency with an open-circuit voltage of 999 mV and a fill factor of 83.2%. Umicore (Brussels, Belgium), a materials technology company, produced the Ge substrate through an optimized manufacturing process aimed at improving the intrinsic Ge crystal quality.

IMEC says that improving the efficiency of this single-junction GaAs cell is a further step in the development of a hybrid monolithic/mechanically stacked triple-junction solar cell consisting of stacks of solar cells made of different semiconductors, carefully chosen to absorb the solar spectrum as efficiently as possible. IMEC focuses on stacked cells consisting of top cells with III-V materials and bottom cells made from Ge, and is targeting a conversion efficiency of at least 35% for use in satellites and Earth-based concentrators. Contact Giovanni Flamand at giovanni.flamand@imec.be.

Tue Apr 01 00:00:00 CDT 2008