In this Phase I program we propose to develop an innovative fabrication process to introduce backside contacts to MicroLink Devices' large-area, multi-junction epitaxial lift-off (ELO) solar cells. This will enable a new solar cell technology with potential benefits for future NASA solar electric propulsion (SEP) programs using very large solar cell arrays. Backside contacts are used in the highest efficiency silicon solar cells manufactured by SunPower (>24% efficiency in production) but have never been successfully applied commercially to multi-junction solar cells. Benefits for large-area space solar cell include: higher device efficiency by reducing topside grid shadow and resistive losses, new approaches for panel assembly by placing contacts on backside of solar cell, and reduced arcing in high-voltage arrays by eliminating topside interconnects. The proposed technology builds on MicroLink Devices' low-cost, lightweight ELO solar cell technology and previous experience with backside contact solar cells for CPV applications.