Hot-melt inkjet as masking technology for back-contacted cells

Two approaches for structuring thin metal layers for seed and growth metallization for back-contacted solar cells using hot-melt inkjet as masking technology are evaluated. The characteristics of a hot-melt printed image relevant for process development are discussed. A metal lift-off process and a metal etching process, both creating a meander-shaped opening in a metal layer - hence an interdigitated grid - based on hot-melt inkjet are established. The process sequences are characterized regarding the shunt resistance between the grids and the contact resistance to an underlying emitter layer on appropriate test structures. The contact resistance is found to be increased on samples fabricated by metal lift-off compared to samples fabricated by metal etching. The lift-off process is found to open lines with a width of around 120 ¿m reliably, whereas a line opening width in the range of 50 ¿m is reliably represented with the etching process sequence, whereas a high shunt resistance is considered the criterion for a successful process.