Hole-blocking titanium-oxide/silicon heterojunction and its application to photovoltaics

In contrast to the numerous reports on narrow-bandgap heterojunctions on silicon, such as strained Si_1−xGe_x on silicon, there have been very few accounts of wide-bandgap semiconducting heterojunctions on silicon. Here, we present a wide-bandgap heterojunction—between titanium oxide and crystalline silicon—where the titanium oxide is deposited via a metal-organic chemical vapor deposition process at substrate temperatures of only 80–100 °C. The deposited films are conformal and smooth at the nanometer scale. Electrically, the TiO₂/Si heterojunction prevents transport of holes while allowing transport of electrons. This selective carrier blocking is used to demonstrate a low-temperature processed silicon solar cell.