Electron Beam Evaporated Molybdenum Oxide As Hole-Selective Contact in 6-Inch C-Si Heterojunction Solar Cells

Electron beam (E-beam) deposited molybdenum oxide (MoOx) has been investigated for its potential to replace p-type hydrogenated amorphous silicon (a-Si:H) in Si heterojunction (SHJ) solar cells. Excellent passivation was achieved for our best MoOx/c-Si junction based device, reaching an average implied V-oc (iV(oc)) of 734 mV on textured, commercially available 6-inch Cz wafers. This confirms the compatibility of MoOx as a hole selective layer with industrial SHJ cell processing. A hole barrier was, however, observed for our MoOx-based solar cells due to inefficient hole extraction. The formation of this hole barrier can be related to annealing of MoOx and the presence of a native oxide grown on the intrinsic a-Si:H interface layer below. Pre-annealing, followed by an HF treatment on the a-Si:H(i) layer prior to MoOx deposition, proved to be useful to mitigate the formed barrier, while making it more stable under standard SHJ annealing conditions.