Low resistance tio2 /p-si heterojunction for tandem solar cells

Abstract

Niobium-doped titanium dioxide (Ti1−x Nbx O2 ) films were grown on p-type Si substrates at low temperature (170◦ C) using an atomic layer deposition technique. The as-deposited films were amorphous and showed low electrical conductivity. The films became electrically well-conducting and crystallized into the an anatase structure upon reductive post-deposition annealing at 600◦ C in an H2 atmosphere for 30 min. It was shown that the Ti0.72 Nb0 .28 O2 /p+-Si heterojunction fabricated on low resistivity silicon (10−3 Ω cm) had linear current–voltage characteristic with a specific contact resistivity as low as 23 mΩ·cm2 . As the resistance dependence on temperature revealed, the current across the Ti0.72 Nb0.28 O2 /p+-Si heterojunction was mainly determined by the band-to-band charge carrier tunneling through the junction.