Investigation of sub-stoichiometric MoO_x hole-selective contacts for rear junction passivating contact silicon solar cells

Carrier-selective contacts play a crucial role in improving the performance of silicon solar cells by reducing recombination losses. This study explores the use of sub-stoichiometric molybdenum oxide (MoOx) as a hole-selective contact material deposited via thermal evaporation. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) analysis reveal diverse Mo-O bonding configurations and a low work function of similar to 5.02 eV for the MoOx film. The passivation properties of a cell-like structure with local MoOx contact are found to be comparable to those of a structure with a full front passivation layer, as evidenced by an implied open-circuit voltage (iV(oc)) of 703.2 mV. However, the conversion efficiency of the solar cell with MoOx contact is limited to 16.5 %, with reduced external quantum efficiency (EQE) at UV and visible wavelengths. The study proposes that optimizing the MoOx front contact's work function and passivation characteristics could improve the solar cell's efficiency to 21.8 %. This research demonstrates the potential of sub-stoichiometric MoOx as a promising hole-selective contact for silicon solar cells, highlighting the factors influencing its performance.