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.