Inkjet structured EWT silicon solar cells with evaporated aluminum metallization and laser-fired contacts

This work focuses on manufacturing inkjet structured Emitter Wrap-Through (EWT) silicon solar cells with a side selective emitter and an evaporated metallization. Inkjet structuring is a suitable technique for the formation of interdigitated structures used in back contacted silicon solar cells because it allows small feature sizes and has high alignment accuracy. Therefore all structuring steps in this EWT solar cell process are done with the help of inkjet masking. This includes the structuring of a silicon oxide passivation layer and the evaporated aluminum metallization. For all masking processes an acid-resistant inkjet hotmelt ink is used. An evaporated thick aluminum layer and laser-fired contacts (LFC) to contact the bulk region are introduced. Cell efficiencies above 15% prior to a forming gas anneal are reached. The best cell reaches an efficiency of 15.7% after a short annealing step on a hotplate.