  Nanostructures, especially of silicon, are of paramount importance for new
generation solar cell applications. The key material requirements for solar
cells are good electrical conductivity, confinement of excitons, and a tunable
band-gap that allows for tandem arrangements to absorb a maximally large
portion of the solar spectrum. However, to date, existing Si-based
nanostructures have addressed these requirements individually. The difficulty
is that these requirements are entangled in complex ways, so an effort to
improve one can lead to a major trade-offs in the others. In this study, we
report on a novel silicon nanostructure, where the key advance is that we have
managed to satisfy all the abovementioned requirements simultaneously: We
demonstrate that the excitons are confined, the bandgap is tunable, and the
electrons can freely travel along the nc-Si network.
