A simple sonication-assisted chemical synthesis method for nano-PCM synthesis as well as thermal evaluation has been presented by Liu et al in 2019.
Article Preparation and Characterization of New Nano-particle Mixed ...
Furthermore, you can find a clear, updated overview on nanofluids and PCM enhanced PV/T technology in the following book by Dr Hussein Kazem from Sohar University.
Book Photovoltaic/Thermal (PV/T) Systems: Principles, Design, and...
See section 3.5 titled "PCM and Nano-PCM-Based PV/T Systems" and the references provided.