Qualification testing of 40% metamorphic CPV solar cells

Spectrolab is qualifying its fourth generation of terrestrial concentrator multijunction cells (C4MJ). Prototypes of this product have been tested with an average efficiency of 40% at 50 W/cm2 illumination. This new generation is a departure from previous production technology in that, for the first time, it employs metamorphic rather than lattice-matched technology. The amount of lattice mismatch that must be accommodated by the metamorphic buffer of the C4MJ cell is small. Nevertheless, the metamorphic structure is a new cell design, and as such poses some additional risk over traditional lattice-matched CPV cells. For that reason the C4MJ cell will be subjected to extensive reliability testing at Spectrolab. Spectrolab also has C4MJ cells in the field for on-sun testing, in cooperation with two customers.