Nanoparticle based direct solar absorption is a promising technology for future solar thermal systems. Having so many individual studies on different nanomaterials for solar energy harness, a comprehensive comparison of photothermal conversion characteristics of various nanofluids at the same experimental conditions is much needed. The photothermal conversion performance of six commonly used nanomaterials in direct absorption solar collectors (DASC) was investigated under a focused simulated solar flux. The contribution of sensible heating and latent heat of vaporization of the nanofluids was revealed in context of their photothermal performance. The results show that all the nanofluids have higher solar energy absorption than the base fluid and silver nanofluid turned out to be the best amongst all due its strong plasmonic resonance nature. A 99.7% enhancement in the photothermal conversion efficiency of silver was achieved within the experimental domain. A simulation model was proposed to state the temperature difference between the surface of the nanoparticle and the surrounding fluid under lower solar flux.