19.5%-Efficient Back-Contact Silicon Heterojunction Solar Cell With Self Aligned Metallization Using Multilayer Aluminum Foils

We present advances in a back-contact, back-junction metallization strategy using preformed multilayers of aluminum foil with a polymer insulator. The low-cost multilayer foils can be conductively bonded to substrates using nonconducting adhesives. The properties of this bonding process are discussed. We also demonstrate different cell structures based on multilayer foils. One approach leverages features of the multilayer foil to produce a self-aligned base contact, leading to a process with only a single alignment step. A champion silicon heterojunction cell with this foil metallization achieved 19.5% efficiency. We further show first results on a completely alignment-free back contact process enabled by multilayer foil metallization.