Phosphorus- and Boron-doped Poly-Si/Siox Passivating Contacts via Inkjet Printing

In this work, we utilize the advantages of inkjet printing technology to achieve maskless localized doping of both n- and p-type poly-Si/SiOx passivating contacts, offering flexibility and simplicity in the fabrication process for advanced structures, such as interdigitated back contact (IBC) solar cells. By using commercially available spin-on solutions, full-area printed samples show promising passivation quality and electrical contacts, yielding an iVoc of 729 mV with ρc of 5.4 mΩ·cm² for n-type poly-Si/SiOx, and iVoc of 718 mV with ρc of 6.1 mΩ·cm² for p-type poly-Si/SiOx after hydrogenation. Optical microscopy shows that localized n- and p-type dopant lines with minimum feature sizes down to ~ 60 μm can be achieved. We demonstrated the simultaneous formation of localized phosphorus- and boron-doped poly-Si/SiOx passivating contacts in a single annealing step. Micro-photoluminescence (μPL) mappings confirmed the improved surface passivation of the locally doped region. Besides, high-resolution dynamic secondary ion mass spectrometry (D-SIMS) measurements revealed elevated dopant concentrations ([B] ≈ 1×1019 atom/cm3, [P] ≈ 1×1020 atom/cm3) at the doped regions. Additionally, D-SIMS results indicated the presence of unintended doping, likely due to volatile dopant species entering the gas phase during the high-temperature annealing.