Passivating Contact with Phosphorus-Doped Polycrystalline Silicon-Nitride with an Excellent Implied Open-Circuit Voltage of 745 mV and Its Application in 23.88% Efficiency TOPCon Solar Cells

摘要

A P-doped polycrystalline silicon-nitride (n-poly-SiNx) as the electron selectivecollection layer in a tunnel oxide passivated contact (TOPCon) solar cell isreported. The nitrogen content is controlled by the active gas ratio of R = NH_3/(SiH_4 + NH_3) during the plasma-enhanced chemical vapor deposition (PECVD)process. The effects of R ratio on the material’s composition, crystallinity, surfacepassivation, and contact resistivity are investigated. The poly-SiN_x contactexhibits improved surface passivation in comparison with the reference poly-Siwithout N incorporation. The best double-sided passivated n-type alkaline-polishedcrystalline silicon wafer with the n-poly-SiN_x/SiO_x manifests the highestimplied open-circuit voltage (iV_(oc)) of ≈745mV, with the corresponding singlesidedsaturated current density of 1.7 fA cm~(-2) and the effective lifetime (τ_(eff) ) of10 ms at the injection level of ≈1 × 1015cm~(-2). In contrast, the controlled samplewith an n-poly-Si/SiO_x passivation contact has a maximal iV_(oc) of 738 mV.However, the primary drawback of the N doping is to raise the contact resistivity,but which is still in an acceptable range and shows little effect on the performanceof solar cell with full-area contact. The proof-of-concept TOPCon solar cell usingthe n-poly-SiN_x/SiO_x passivating contact has achieved an efficiency of 23.88%,indicating the potential of the n-poly-SiN_x for high-efficiency TOPCon solar cells.