This thesis aims to use quantum dot solar cells (QDSC) to realise the IBSC and, hence, achieve the 63.2% ultra-high power conversion efficiency. The approach is to epitaxially grow the QDSC using the most advanced epitaxial growth technique—molecular beam epitaxy (MBE). The nature of quantum dots (QDs) exhibits 3-dimensional (3D) carrier confinement and have discrete energy levels, a perfect candidate to implement the intermediate energy levels required for IBSCs. In this thesis, the practical implementations, physical limitations and technical difficulties are addressed and reviewed in detail.