Rapid Phosphorus Diffusion on the Poly-Silicon Surface of Tunnel Back Contact Solar Cells via Silicon Paste

Abstract Phosphorus (P) diffusion is a critical process in the preparation of semiconductor materials, playing a key role in both solar cells and integrated circuits. Using Tunnel Back Contact (TBC) solar cells as an example, P diffusion is employed to form an N-type emitter layer. Based on first principles calculations, Materials Studio is used to simulate changes in the band gap at various doping concentrations. Combined with EDNA2 and PC1D simulations, the influence on short-circuit current density is analyzed. The results show that when the doping concentration reaches 3.97×1020 cm-3, the band gap narrows to 1.004 eV, resulting in a short-circuit current density of up to 41.23 mA/cm2. Guided by the simulation results, we conducted a P doping experiment by screen printing P-doped Si paste onto the polycrystalline Si (poly-Si) surface on the back side of TBC solar cells. A local P-doped layer was formed through a rapid thermal annealing process. Experimental results indicate that the maximum P doping concentration in the n+ layer reaches 1.72×1021 cm-3, with an effective junction depth of 281 nm. This method has the potential to replace the traditional mask diffusion process in TBC solar cells, thereby simplifying the process and reducing production costs.