In-situ Process to Form Passivated Tunneling Oxides for Front-surface Field in Rear-emitter Silicon Heterojunction Solar Cells

摘要： A novel approach involving CO2 plasma treatment of intrinsic hydrogenated amorphous silicon was developed to form ultra-thin silicon oxide (SiOx) layers, that is, passivated tunneling layers (PTLs), for the fabrication of passivated tunneling contacts. These contacts were formed by depositing the PTL/n-type hydrogenated nano-crystalline layer (nc-Si:H(n))/c-Si(n) stacks. The results indicated that a higher CO2 plasma treatment pressure was preferred for the formation of oxygen-richer components in the silicon oxide films, with Si2+, Si3+, and Si4+ peaks, and a smoother PTL/c-Si heterointerface. The PTLs with higher oxidation states and lower surface roughness exhibited advantages for the c-Si surface passivation, with a maximum implied open-circuit voltage of approximately 743 mV. The lowest contact resistivity of approximately 60 mΩcm2 was obtained using nc-Si:H(n)/PTL/c-Si(n) as the passivated tunneling contact. Most importantly, the in-situ process can help prevent the contamination of the heterointerface during device fabrication processes.