Low Resistance TiO(2)/p-Si Heterojunction for Tandem Solar Cells

Niobium-doped titanium dioxide (Ti(1−x)Nb(x)O(2)) 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 H(2) atmosphere for 30 min. It was shown that the Ti(0.72)Nb(0).(28)O(2)/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·cm(2). As the resistance dependence on temperature revealed, the current across the Ti(0.72)Nb(0.28)O(2)/p(+)-Si heterojunction was mainly determined by the band-to-band charge carrier tunneling through the junction.