Transition metal oxides as hole selective contacts in silicon heterojunctions solar cells
Abstract This work reports on a comparative study comprising three transition metal oxides, MoO3, WO3 and V2O5, acting as front p type contacts for n type crystalline silicon heterojunction solar cells. Owing to their high work functions >5 eV) and wide energy band gaps, these oxides act as transparent hole selective contacts with semiconductive properties that are determined by oxygen vacancy defects (MoO3 x) as confirmed by X ray photoelectron spectroscopy. In the fabricated hybrid structures, 15 nm thick transition metal oxide layers were deposited by vacuum thermal evaporation. Of all three devices, the V2O5/n silicon heterojunction performed the best with a conversion efficiency of 15.7% and an open circuit voltage of 606 mV, followed by MoO3 (13.6% and WO3 (12.5% These results bring into view a new silicon heterojunction solar cell concept with advantages such as the absence of toxic dopant gases and a simplified low temperature fabrication process.