Hybrid photovoltaic thermal PVT solar collectors are a good option to produce electrical power and thermal energy simultaneously from solar radiation, where the transfer uid circulating in this system works as a coolant, and at once, it gains additional heat to produce heat. This study is based on a numerical investigation, and aims to improve the performances of a hybrid photovoltaic thermal (PVT)collectorby using porous media, and taking into account the air buoyancy force effect (i.e., natural convection effect).For this purpose, the impacts of panel tilt angle (α), Richardson number (Ri), thickness of the porous layer (Ep) and Darcy number (Da) on the PVT system performances including its velocity contours, thermal eld, thermal and electrical e ciencies are examined. The obtained results showed that by taking into account the buoyancy force, an enhancement in both electrical and thermal e ciencies is observed which can reach up 9.88% and 10% respectively if the PVT is erected without porous layer. Moreover, in the case of the buoyancy force is neglected, the integration of porous media under speci c values of the studied parameters can enhance both electrical and thermal e ciencies by more than 26% and 38%, respectively compared to the classic layout of the PVT system.