Excited State Dynamics in Semiconductor Nanostructures

Over the past two decades quantum-dot-based photovoltaic devices have been attracting
a lot of attention due to their potential high efficiencies and low cost fabrication.
Unlike conventional photovoltaic devices where the absorption of a single photon always
produces a single electron hole pair (exciton), quantum-dot-based devices can
generate multiple excitons from the absorption of just a single photon. Thanks to this
process, which is referred to as either carrier multiplication or multiple excition generation,
quantum-dot-based devices can potentially reach higher efficiencies breaking
the Shockley-Queisser limit. In addition, the colloidal synthesis techniques used to
fabricate these devices are potentially very cheap and scalable. Despite the intrinsic
potential of these devices, they are not currently at a stage where they can compete
with commercial photovoltaics. In this thesis various factors that effect the efficiency
of carrier multiplication are investigated. In addition new analytical methods are
developed to form a contribution to theoretical work in this field.