Excellent Passivation of Silicon Surfaces by Thin Films of Electron-Beam-Processed Titanium Dioxide

Abstract

Dielectric of a titanium dioxide thin film is currently re-emerging as a passivating material for high-efficiency crystalline silicon (c-Si) solar cells, owing to its good passivation quality and appropriate band offset when in contact with c-Si. Here, we demonstrate effective passivation on c-Si substrates by electron-beam-processed titanium oxide layers, which are obtained by low-temperature thermal oxidation of predeposited pure titanium thin films. A derived titanium oxide layer by 3.5-nm titanium at 250°C yields a surface recombination velocity down to 16 cm/s. Structural characterizations reveal that the resultant oxide layers are amorphous titanium dioxide. The passivation property is attributed to Si-O-Ti bonding at the Si-titanium dioxide interface as well as to the presence of an interfacial silicon dioxide layer. The easy processing and high-level passivation capability make these titanium dioxide thin films highly desirable to serve as a good passivating choice toward high-efficiency c-Si solar cells.