Structure and properties of multibranched isophorone-based materials for organic light-emitting diodes

We designed and synthesized a three-branched isophorone-based compound, 4,4′,4′′-tri[2-(3-dicyanomethylene-5,5-dimethylcyclohex-1-enyl)vinyl]triphenylamine, as well as its one- and two-branched analogues. Their photophysical, electrochemical and electroluminescent characters showed a regular change with increasing branches. Density functional theory was employed to study their electron density distribution. Using the dyes as light-emitting layers without doping, organic light-emitting diodes showed appropriate red emission at λmax = 647–670 nm and a maximum brightness of 1801 cd m−2. Moreover, the results shows that the device using the single-branched material as a pure emitting layer has higher efficiency and lower turn-on voltage than using multi-branched materials.