Development of Phosphorus-Doped Nanoscale Poly-Si Passivating Contacts via Inkjet Printing for Application in Silicon Solar Cells

Herein, high-quality localized phosphorus-doped polycrystalline silicon (poly-Si) passivating contacts containing nanoscale poly-Si film (∼100 nm) on an ultrathin SiO_x layer (∼1.5 nm) were fabricated via an inkjet printing technique. A detailed study of the impacts of inkjet printer settings, dopant concentration, and annealing temperature on the poly-Si passivating contact performance (represented by implied open-circuit voltage iV_oc and contact resistivity ρ_c) was carried out. By applying optimized process conditions on symmetrical industrially processed intrinsic poly-Si/SiO_x/n-type crystalline Si (c-Si) substrates, good surface passivation was achieved with an iV_oc of 699 mV, together with a low ρ_c of 6.4 mΩ·cm², after annealing at 975 °C. After a hydrogenation treatment via the deposition of aluminum oxide (AlO_x)/silicon nitride (SiN_y) stack and subsequent forming gas annealing (FGA), the optimum annealing temperature shifted to 950 °C and the iV_oc was further improved to an excellent value of 729 mV. Optical images reveal that a line width of 75 μm can be realized on a mechanically polished silicon wafer. Moreover, high-resolution micro-photoluminescence (μ-PL) maps clearly demonstrate the localization of the doped regions on the symmetrical substrate after annealing. These results show that inkjet printing is a promising technique for the fabrication of localized poly-Si/SiO_x passivating contacts in high-efficiency solar cells with high flexibility and simplicity.