Through-Epitaxial-Via Back-Contact Multi-Junction Solar Cells Fabricated Using Epitaxial Lift-Off

Back-contact solar cells potentially achieve higher efficiency by moving all the electrical connections to the rear of the cell, thus eliminating shadow losses as well as enabling new array assembly approaches. In spite of the many advantages of this technology, as demonstrated in commercial manufacturing of silicon cells, the process complexity to create through wafer vias has limited its use in III-V solar cells. We present a simple, three-mask process flow for fabricating through-epitaxial via (TEV) back-contact multi-junction epitaxial liftoff (ELO) solar cells in this paper. Electrical characterization showed 3J cells with 25.9% efficiency (1 sun AM1.5 spectrum) without AR coating and similar performance to standard top-contact devices.