Challenges in the Fabrication of a Glued III-V on Si Tandem Solar Cell Using a ZnO-Based TCA

On the route to a high efficiency glued tandem solar cell fabricated using a ZnO-based transparent conductive adhesive, several challenges were encountered. By lowering the pressure during the annealing of the adhesive to 0.3 or 1 kg/cm2, the III-V surface did not crack and only minor delamination along the samples edge was observed. A fabricated tandem solar cell showed limitations due to voids within the bond (low fill factor) and a low current density due to a missing anti-reflective coating and reflectance at the bond layer. A sputtered TiO2:Nb contact layer showed a low ohmic contact on p-GaAs and thereby is suitable for implementation at the bond/III-V interface, which would significantly lower the reflectance at the bond.