Carrier dynamics in coupled silicon nanocrystal systems

The transition from conventional (fossil fuel based) energy generation methods to renewable energy variants is set in motion but can certainly use an additional impulse. A good example is the solar energy market which is struggling since industry "gray-current" electricity-prices are low enough to prevent a smooth and effective transition to a photovoltaic-dominated electricity market. One way of breaking the established equilibrium is to increase the conversion efficiencies of solar panels without inducing skyrocketing prices. Typically, high-energy (ultra-violet) solar photons are inefficiently converted into electricity due to thermalization and front surface recombination. A possible route towards the efficiency increase is to make use of spectral shaper layers, which are add-on devices that can be combined with solar cells in order to transform the solar spectrum into a range optimal for efficient conversion by the cell. This dissertation focuses on the investigation of Si nanocrystals for the purpose of being used in these spectral shapers. The nano-scale dimensions of the Si particles increase their interaction potential with light due to quantum confinement. As a result, changes are induced in (among others) the bandstructure, transition strength and the electron-photon coupling. By making use of the bandgap tunability of Si nanocrystals that arises from quantum confinement, the problem of front surface recombination can be completely surmounted; a result that can in principle also be obtained without the use of nano-materials. In contrast, Si nanocrystals might be able to circumvent the thermalization losses as well, by efficient dipole-dipole interactions between proximal nanocrystals.