  Multi-terminal multi-junction solar cells (MJSC) offer higher efficiency
potential than series connected (two-terminal) ones. In addition, for
terrestrial applications, the efficiency of multi-terminal solar cells is less
sensitive to solar spectral variations than the two-terminal series-connected
one. In space, generally, cells are always illuminated with AM0 spectrum and no
impact is expected from spectral variations. Still, in space, the
multi-terminal approach offers some advantages in comparison with the
series-connected architecture approach derived from a higher end of life (EOL)
efficiency. In this work we review the potential of multi-terminal solar cells
for achieving extended EOL efficiencies with emphasis in the potential of the
three-terminal heterojunction bipolar transistor solar cell, a novel
multi-terminal MJSC architecture with a simplified structure not requiring, for
example, tunnel junctions.
