New Ambipolar Blue Emitting Materials Based on Amino Coumarin Derivatives with High Efficiency for Organic Lightemitting Diodes

New blue emitting materials, 7-diphenylamino-4-methyl-coumarin (DPA-MC) and aminotri(4-methylcoumarin) (T-MC) including coumarin moiety were synthesized by Ullman reaction. Optical and electronic properties were examined by UV-Vis. Absorption spectrum, PL spectrum, and cyclic voltammetry. UV-Vis. spectra of DPA-MC and T-MC in a film state showed maximum absorption wavelengths of 382 nm and 399 nm, respectively. PL spectra of DPA-MC and T-MC show maximum emission wavelengths of 463 nm and 481 nm respectively. Non-doped OLED devices were fabricated by using the synthesized materials as an emitting material layer. DPA-MC compound showed highly efficient luminescence properties. EL spectrum of DPA-MC exhibited a maximum value of 463 nm and DPA-MC device provided luminescence efficiency of 3.83 cd/A, power efficiency of 2.46 lm/W, external quantum efficiency of 3.71% and CIE coordinates of (0.154, 0.190) at a current density of 10 mA/cm². In particular, Power efficiency increased by more than 1.6 times in DPA-MC (2.46 lm/W), which is higher than commercialized material, DPVBi (1.46 lm/W). High EL performance might come from ambipolar effects of a molecular structure.