N-type single-crystalline Si solar cells: Front side metallization for solar cells reaching 20% efficiency

摘要

Screen printed front side contacts were investigated in n-type, high efficiency, single-crystalline Si solar cells with B doped emitters. Cells were processed identically and two different front side pastes were used: paste Ag-Al yielded efficiencies of 20.0%, and paste Ag, without Al, yielded 16.1% efficiency only. Cells contacted with paste Ag-Al yielded a continuous glass layer, a significantly higher density of Ag colloids, and an Al mole fraction of similar to 1 at%. In contrast, cells contacted with paste Ag revealed a thinner but continuous glass layer as compared to cells processed with paste Ag-Al. It contained a lower density of Ag colloids and Al was below the detection limit of the EDX microanalysis. In n-type cells pyramidal shaped Ag nanocrystals did not appear, whereas for p-type cells they are formed at intersections of differently {111} oriented surface planes at the Si emitter. We did not find Ag/Al spikes at the Si emitter for cells contacted with paste Ag-Al.