Study of contact formation of printed contacts through different passivation layers on lowly doped emitters
The etching mechanism of silver pastes with glass frit through the SiNx anti reflection coating of a standard silicon solar cell during the fast firing step is well understood. In this paper we investigate the firing through behavior for different alternative dielectric layers or stacks that are of great interest for new high efficiency solar cell concepts. On n-doped surface SiO2 and TiO2 were compared with SiNx. On p-doped surface TiO2 and SiNx as single layers and as capping layers on a thin Al2O3 layer were compared. The contact formation was analyzed using contact resistance measurement and scanning electron microscopy. Generally, it turns out that SiNx is the most stable passivation layer during a firing process when compared with all other tested materials. However, stacked on Al2O3 the contact resistance is decreased. Contact resistances as low as roh c = 3 m omega cm2 were obtained on lowly doped boron surface with a surface concentration of NA = 2.3×1019 cm-3.