Spin-On SiO_x-Assisted Inkjet Printing for Interdigitated n+ and p+ Poly-Si/SiO_x Contacts in Silicon Solar Cells With Suppressed Unintended Doping

The fabrication of localized doped polycrystalline silicon (poly-Si) passivating contacts, such as in an interdigitated back contact (IBC) solar cell, is complex and costly. Inkjet printing offers a promising route to simplify this process; however, unintended doping and cross-doping from the liquid dopant sources remain a significant challenge. This study demonstrates the effectiveness of a spin-on SiO_x capping layer in suppressing unintended doping in unprinted regions and cross-doping between dopant species, enabling the simultaneous formation of localized n+ and p+ poly-Si passivating contacts using inkjet printing via a single high-temperature annealing step. Secondary ion mass spectrometry (SIMS) mapping reveals uniform doping concentrations within the printed lines, approximately 1 × 10²⁰ cm⁻³ for phosphorus and 2 × 10²⁰ cm⁻³ for boron in the poly-Si layers with minimal lateral diffusion at the line edges. More importantly, unintended doping is now reduced to below 9 × 10¹⁷ cm⁻³, just 0.5% of the source doping concentrations. Additionally, cross-doping in the printed region of opposite polarity remains below 5 × 10¹⁸ cm⁻³, which is less than 2.6% of the intended doping. These results pave the way for the potential adoption of inkjet printing in simplifying the fabrication of solar cells and other electronic devices.