O-phenanthroline is a heterocyclic compound with a fused ring system consisting of a pyridine ring and two fused benzene rings, which has strong luminescence and electron transport properties. They can be functionalized with various substituents to tune their electronic and optical properties for specific applications. O-phenanthroline is often used as a luminescent material in OLEDs due to its high quantum yield and good color purity. In OPVs, they can act as electron transport elements to improve the efficiency of photovoltaic cells. Their unique structure and properties make them promising candidates for the development of high-performance organic electronic devices.