It is a common observation that the photovoltaic (PV) panelshows a compromised performance when its temperature rises. To handle the performance reduction, most PV panels are equipped with a thermal absorber for removing the solar cells? excessive heatwith the help of a heat transfer fluid. The mentioned thermal absorber system is termed as PV thermal or simply PV/T. This study aims to experimentally investigate the effectsof a graphene nano-platelets (GNP) nanofluid, distilled water, and hybrid nanofluid (HyNF)as transfer fluids in PV/Tcollectors. A hybrid nanofluid comprises aluminum oxide (Al2O3) and GNP. An outdoor experimental setup was installed and tested under the climatic conditions in Karab?k (Turkey) to measure the inlet as well as outlet PV/Tfluid temperatures, ambient temperature with solar radiation, and surface temperatures of both PV/T collector and the PV panel. The mass percentage of the coolant fluids was 0.5% (by weight) and their flow rate was 0.5L/m. Resultsshow that the (GNP)nanofluid is the most effective fluid because it showed superior thermal efficiency among all the tested fluids. Adding a thermal unit to the PV/Tunit increased the overall energy efficiency by 48.4%, 52%, and 56.1% using distilled water, hybrid nanofluid, and graphene nanofluid, respectively.