Impact of Al Doping on Surface Passivation of TiOx on Si

Abstract

Titania (TiOx) is re-emerging to be a passivating material for the surfaces of high-efficiency crystalline silicon solar cells. Numerous sources in the literature suggest that the surface passivation and thermal stability of TiOx deteriorates with increasing film thickness when the TiOx film is thicker than a sufficient thickness. To circumvent this limitation, this study presents a novel process of Al-doped TiOx (TiOx:Al) film, which demonstrates the potential for improved thermal stability and surface passivation. Based on grazing incident X-ray diffraction and UV-Raman measurements, the incorporation of Al impurity in TiOx effectively restrains the crystal phase transformation of the amorphous TiOx layer during deposition. Furthermore, the TiOx:Al films provide better thermal robustness up to 350 °C, which makes it highly compatible with Si solar cell fabrication processes.