Rubrene (5,6,11,12-tetraphenyltetracene) is the organic compound with the formula . It is a red colored polycyclic aromatic hydrocarbon. Because of its distinctive optical and electrical properties, rubrene has been extensively studied. It has been used as a sensitiser in chemoluminescence and as a yellow light source in lightsticks.[1]
As an organic semiconductor, the major application of rubrene is in organic light-emitting diodes (OLEDs) and organic field-effect transistors, which are the core elements of flexible displays. Single-crystal transistors can be prepared using crystalline rubrene, which is grown in a modified zone furnace on a temperature gradient. This technique, known as physical vapor transport, was introduced in 1998.[2] [3]
Rubrene holds the distinction of being the organic semiconductor with the highest carrier mobility, reaching 40 cm2/(V·s) for holes. This value was measured in OFETs prepared by peeling a thin layer of single-crystalline rubrene and transferring to a Si/SiO2 substrate.[4]
Several polymorphs of rubrene are known. Crystals grown from vapor in vacuum can be monoclinic,[5] triclinic,[6] and orthorhombic motifs.[7] Orthorhombic crystals (space group Bbam) are obtained in a closed system in a two-zone furnace at ambient pressure.[8]
Rubrene is prepared by treating 1,1,3-Triphenyl-2-propyn-1-ol with thionyl chloride.[9]
The resulting chloroallene undergoes dimerization and dehydrochlorination to give rubrene.[10]
Rubrene, like other polycyclic aromatic molecules, undergoes redox reactions in solution. It oxidizes and reduces reversibly at 0.95 V and −1.37 V, respectively vs SCE. When the cation and anion are co-generated in an electrochemical cell, they can combine with annihilation of their charges, but producing an excited rubrene molecule that emits at 540 nm. This phenomenon is called electrochemiluminescence.[11]