Phenanthrene is an aromatic hydrocarbon with three fused benzene rings that has high thermal stability and good hole transport properties. They can be substituted with various functional groups to tailor their electronic and optical properties for specific applications. Phenanthrene is often used as a core structure in the synthesis of small molecule semiconductors due to its stable aromatic skeleton and excellent charge transport properties. In OLEDs, they are used as hole transport materials, while in OPVs, they can be used as electron donating elements. Their diverse chemical properties and characteristics make them suitable for a variety of organic electronic devices, including OLEDs, OPVs, and OFETs.