Development of Conductive SiC:H as a New Hydrogenation Technique for Tunnel Oxide Passivating Contacts

Conductive hydrogenated silicon carbide (SiC:H) is discovered as a promising hydrogenation material for tunnel oxide passivating contacts (TOPCon) solar cells. The proposed SiC:H layer enables a good passivation quality and features a good electrical conductivity, which eliminates the need of etching back of SiN:H and indium tin oxide (ITO)/Ag deposition for metallization and reduces the number of process steps. The SiC:H is deposited by hot wire chemical vapor deposition (HWCVD) and the filament temperature (T_f) during deposition is systematically investigated. Via tuning the SiC:H layer, implied open-circuit voltages (iV_oc) up to 742 ± 0.5 mV and a contact resistivity (ρ_c) of 21.1 ± 5.4 mΩ·cm² is achieved using SiC:H on top of poly-Si(n)/SiO/c-Si(n) stack at T of 2000 °C. Electrochemical capacitance-voltage (ECV) and secondary ion mass spectrometry (SIMS) measurements were conducted to investigate the passivation mechanism. Results show that the hydrogenation at the SiO/c-Si(n) interface is responsible for the high passivation quality. To assess its validity, the TOPCon stack was incorporated as rear electron selective-contact in a proof-of-concept n-type solar cells featuring ITO/a-Si:H(p)/a-Si:H(i) as front hole selective-contact, which demonstrates a conversion efficiency up to 21.4%, a noticeable open-circuit voltage (V_oc) of 724 mV and a fill factor (FF) of 80%.