Aluminum Evaporation and Etching for the Front-Side Metallization of Solar Cells

In this paper, we report and discuss several strategies to produce solar cell front contacts by full-area metallization and etching (FAME). Our chemically structured contacts consume less expensive silver than screen-printed contacts. As a proof of principle for the FAME approach, we present a 148.6-cm²-sized silicon solar cell that has about 100-μm-wide front-side fingers. These fingers consist of a 15-μm-thick evaporated aluminum layer, supplying the electrical conductance, and a sputtered capping stack (200 nm Ni:V plus 20 nm Ag), providing solderability. The entire metal stack is first deposited on the full area of the solar cells, then locally protected by a wax pattern, and subsequently etched with commercial Ni:V etch and NaOH. The efficiency of the best solar cell is 19.3%, the fill factor is 78%, the open-circuit voltage is 666 mV, and the short-circuit current density is 37.1 mA/cm².