Understanding the behaviour of space charge in a solid organic dielectric under electrical stress remains to be a challenge for the development of more compact and reliable systems in the fields ranging from high voltage engineering and microelectronics to space applications. One of the main difficulties remains to be understanding the charge generation processes in the solid dielectric at an interface, in contact either with a solid (metal, dielectric, semi-conductive layer) or with another medium (e.g., liquid, air in voids or vacuum for space application). This work couples atomic scale modeling, fluid models (unipolar transport model) and Kelvin Probe Force Microscopy measurements, in order to better describe a metal/dielectric interface and a semiconductor/dielectric interface as encountered in HVDC cables for power transmission.