Surface Passivation of Silicon Solar Cells using Amorphous Silicon Carbide Layers

Dielectric layers for the passivation of solar cell surfaces are a crucial component of future cell generations. Not only their electrical and optical properties are of importance but also the implementation into an industrial cell process. In this regard an easy preconditioning of the surface, low process temperature and high thermal stability are essential. Therefore, we have developed a new passivation process based on PECVD deposited SiC_x. The cleaning of the surface was performed in-situ in the plasma chamber. Excellent passivation quality (S<5 cm/s) was achieved even though no additional wet chemistry cleaning was applied. Although the deposition temperature is in the range of 300-400 degC, high thermal stability could be demonstrated. A solar cell structure with SiC_x as rear surface passivation exhibited an implied open-circuit voltage of 679 mV after a firing step of 800 degC. Cells using a single SiC_x layer and laser-fired contacts as rear surface structure have shown very high efficiencies of 20.2%