ScholarWorks@성균관대학교

초록

This study develops ultrathin tunnel nitride (TN) layers for TOPCon solar cells using plasma nitridation via PECVD at 350 °C with NH3 or N2 plasma to form TN directly on crystalline silicon. This approach overcomes the limited passivation, thermal instability, and low permittivity of conventional SiO2. It enables controlled interfacial chemistry and improved carrier transport. Three growth regimes initial, densification, and saturation were identified and correlated with thickness, refractive index (R.I.), and bonding structure. Ellipsometry showed TN-NH3 evolving from 1.68 nm (R.I = 1.53) to 1.97 nm (R.I = 2.08), while TN-N2 thickened to 2.43 nm with R.I relaxing to 1.82. XPS and ToF-SIMS revealed a sharp SiN interface for TN-NH3 and a broader oxynitride gradient for TN-N2. AFM confirmed atomically smooth surfaces (RMS < 0.20 nm). Passivation quality was highest for TN-NH3 (τeff = 836 μs, iVoc = 739 mV), followed by TN-N2 (745 μs, 732 mV), both surpassing a ∼ 1.5 nm SiO2 reference as (τeff = 715 μs, iVoc = 728 mV). Temperature-dependent IV analysis confirmed direct tunneling behavior through the ∼2 nm TN layer. PECVD-TN layer based NH3/N2 plasma appears to be promising as compared to SiO2, providing tunable interfaces, strong passivation, and efficient tunneling.

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