Status of Industrial Back Junction n-type Si Solar Cell Development

Abstract

Here we present the latest results of our double side contacted, all screen printed n-type mono silicon solar cell development. N-type Czochralski (n-Cz) silicon solar cell results are compared to those of standard p-type Cz (p-Cz) silicon and n-type epitaxial (np+ epi) wafers, produced by Crystal Solar, having an integrated epitaxial boron doped p+-silicon layer. The np+ epi and p-Cz wafers are processed applying the Hanwha Q CELLS Q.ANTUM technology process flow to make PERC cells in our production line including process adaptations to mono wafers while the n-Cz wafers are processed with an extended Q.ANTUM sequence including additional processing steps like cleaning steps and a BBr3 tube furnace diffusion to create the rear side boron p+-silicon layer. We achieve conversion efficiencies up to 21.8% for the n-type Cz silicon back junction solar cell with open circuit voltage values of 671mV. The p-type Cz silicon solar cell shows non-stabilized efficiencies up to 21.2%. The n-type epitaxial solar cells have efficiencies up to 21.7% with fill factor values of up to 82.1% due to the high rear side conductivity of the integrated epitaxial boron doped p+-silicon layer. The latter solar cell results demonstrate a new path to industrial solar cells with efficiencies >22% by combination of simple and robust solar cell processing and epitaxial wafer growth with built-in doping layers.