Hydrogel-Mediated Semiconductor Bonding for Photovoltaic Applications

Hydrogel-mediated semiconductor wafer bonding has been demonstrated for low-cost fabrication of high-efficiency lattice-mismatched multijunction solar cells. Wafer direct bonding can be hardly applied in the presence of wafer surface roughness or particles. Our hydrogel bonding scheme benefits from high surface roughness and particulate tolerances, optical transmittance, and electrical conductivity by utilizing the hydrogels' versatile properties suitable particularly for photovoltaic applications. We have investigated three types of hydrogels and all of them exhibit sufficient transmittance, bonding strength, and conductivity for the fabrication of highefficiency multijunction solar cells.