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

Conductive hydrogenated silicon carbide (SiCx:H) is discovered as a promising hydrogenation material for tunnel oxide passivating contacts (TOPCon) solar cells. The proposed SiCx:H layer enables a good passivation quality and features a good electrical conductivity, which eliminates the need of etching back of SiNx:H and indium tin oxide (ITO)/Ag deposition for metallization and reduces the number of process steps. The SiCx:H is deposited by hot wire chemical vapor deposition (HWCVD) and the filament temperature (T-f) during deposition is systematically investigated. Via tuning the SiCx:H layer, implied open-circuit voltages (iV(oc)) up to 742 +/- 0.5 mV and a contact resistivity (rho(c)) of 21.1 +/- 5.4 m Omega.cm(2) is achieved using SiCx:H on top of poly-Si(n)/SiOx/c-Si(n) stack at T-f of 2000 degrees 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 SiOx/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%.