Hybrid thermoelectric-photovoltaic (HTEPV) generators can be seen as an evolution of STEGs. In their structure the opto-thermal converter is constituted by a solar cells. The intention is to implement thermoelectric materials to recover the high fraction of heat losses occurring in solar cell, adding an extra output power to the system. HTEPV have been already shown to be able to enhance the efficiency of solar cells, even if researchers are still trying to make this approach good enough to become reality. In this paper we will analyse the layout and the achievable efficiency of this hybrid devices, highlighting the challenges and the strong points of this approach.