Hole-Blocking Crystalline-Silicon/Titanium-Oxide Heterojunction with Very Low Interface Recombination Velocity

摘要

We demonstrate a hole-blocking crystalline-silicon/titanium-oxide heterojunction that can be fabricated by a modified MOCVD process at only 100 °C substrate temperature. Ultra thin layers of only 1-4 nm TiO_2 can be reliably deposited on silicon with no pinholes. Band alignment at the Si/TiO_2, experimentally determined using surface spectroscopy, confirms that Si/TiO_2 interface has a large barrier at the valence band, which blocks holes. The hole-blocking characteristics allow the Si/TiO_2 heterojunction solar cells to achieve power conversion efficiencies > 7%. Finally, the electrical quality of the Si/TiO_2 interface was characterized in terms of interface recombination velocity. We show that annealed Si/TiO_2 interfaces can achieve recombination velocities of ～200 cm/s.