Simultaneous Contacting of Boron and Phosphorus Doped Surfaces with a Single Screen Printing Paste
The contact formation by screen printed metal pastes is widely employed in standard solar cell production. To expand the use of screen printed electrodes to n-type solar cells, both boron and phosphorus doped surfaces need to be contacted. To do so with a single material has some advantages especially for IBC solar cells. In this study we test four different screen printing pastes on different boron and phosphorus dopings and in combination with different silicon nitride thicknesses. Phosphorus doping could be contacted over a wide range of sheet resistances, nitride thicknesses and fast firing conditions, leaving much freedom to target the boron contacts. Boron dopings are successfully contacted with all materials, if no capping silicon nitride layer was present. With silicon nitride capping an AgAl and an Ag paste are found to be suitable choices. The lowest contact resistivities with 100 nm SiNX capping determined in this study are C = 0.5 mΩ cm² on phosphorus (Ag) and C = 1.8 mΩ cm² on boron (Ag) doping with one single paste. These results enable highly efficient homojunction IBC cells at low cost.