Vanadium Pentoxide as a hole selective contact for novel heterojunction solar cells based on n-type silicon

This work reports on the use of vanadium pentoxide as a low-temperature alternative to conventional p-doped emitters for silicon solar cells based on n-type wafers. Vanadium pentoxide is a transition metal oxide, whose semiconducting properties are determined by oxygen-vacancies created during the deposition process. Due to its high work-function (> 5 eV) and wide energy band gap (> 3 eV), this transition metal oxide acts as a transparent front-side hole-selective contact. On the rear side of the n-type wafer, two different passivated back contact strategies were compared. The first one uses locally-diffused point-contacts created by laser-firing, whereas the second is based on the heterojunction with intrinsic thin layer concept. Of both rear contact types, the heterojunction performed the best with a conversion efficiency of 14.8%. These results bring into view a new silicon heterojunction solar cell concept with advantages, such as the elimination of toxic dopant gases and a more simple low-temperature fabrication process.