Photovoltaic (PV) technology converts the power of sunlight into electricity. Itis one of the most promising renewable energy solutions to reduce carbon emissions and mitigate climate change. Applications of polysilicon (poly-Si) passivating contacts on silicon-based solar cells have led to world-record energy conversion efficiencies above 26% and are under rapid commercialization. To further increase the practical efficiency limit and establish technological pathways to enable economical fabrication routes for these cell architectures, the PV community is exploring advanced solar cell architectures using poly-Si. An example being interdigitated all-back contact (ABC) solar cells. In this presentation we will describe our innovative solution based on inkjet printing for maskless localized doping of both n- and p-type poly-Si passivating contacts. This methodology aims to economically produce high-efficiency silicon solar cells.

We used the FUJIFILM Material Printer DMP-2850 to print a variety of shapes and features on the substrates. Starting with intrinsic poly-Si/SiOx/c-Si substrates and using boron and phosphorus-containing glass solutions as the “ink”, the dopants were incorporated into the substrates and activated by N2 annealing at high temperatures. Full-area printed control samples show promising passivation quality and electrical contacts, yielding an implied open circuit voltage (iVoc) of 729 mV with contact resistivity (ρc) of 5.4 mΩ·cm² for n-type poly-Si, and iVoc of 718 mV with ρc of 3.4 mΩ·cm² for p-type poly-Si after hydrogen passivation.

The methodology proposed was verified by multi-instrumental analyses combining optical microscopy, micro-photoluminescence (µPL) and Dynamic Secondary Ion Mass Spectrometry (D-SIMS). Optical microscopy shows that localized n- and p-type poly-Si passivating contacts with minimum feature sizes down to ~ 60 µm can be achieved by optimizing the printing parameters, much smaller than the 200 to 300 µm feature sizes used in conventional ABC solar cells. The application of µPL confirmed the effective surface passivation of the locally doped regions. The full width at half maximum of the µPL cross-section profile aligns with the width of the printed regions. D-SIMS measurements using a CAMECA IMS 7f-Auto provide excellent depth and lateral resolution performance while keeping good sensitivity. It is the tool of choice to obtain depth profiles of dopant atoms within the locally doped passivating contacts with the best detection limits. The mapping of boron and phosphorous using D-SIMS reveals elevated dopant concentrations ([B]≈1x1019 cm-3, [P]≈2x1020 cm-3) at the locally doped regions while the migration or diffusion across the unprinted region proved negligible. These findings underline the high potential of inkjet printing technology to enhance the flexibility in the design and fabrication of high-efficiency solar cells with novel cell architectures.