Molecular Alignment of Homoleptic Iridium Phosphors in Organic Light?Emitting Diodes

The orientation of facial (fac) tris-cyclometalated iridium complexes in doped films prepared by vacuum deposition is investigated altering the physical shape and electronic asymmetry molecular structure. Angle-dependent photoluminescence spectroscopy Fourier-plane imaging microscopy show that roughly spherical fac-tris(2-phenylpyridyl)iridium (Ir(ppy)3) isotropic, whereas are oblate spheroids, fac-tris(mesityl-2-phenyl-1H-imidazole)iridium (Ir(mi)3) fac-tris((3,5-dimethyl-[1,1?-biphenyl]-4-yl)-2-phenyl-1H-imidazole)iridium (Ir(mip)3), have a net horizontal alignment their transition dipole moments. Optical anisotropy factors 0.26 0.15, respectively, obtained from latter when into tris(4-(9H-carbazol-9-yl)phenyl)amine host thin films. attributed to favorable van der Waals interaction between Ir material. Trifluoromethyl groups substituted on one polar face Ir(ppy)3 Ir(mi)3 introduce chemical asymmetries molecules at expense shapes. with these derivatives lower relative parent complexes, indicating fluorinated patches reinforce during deposition. High efficiencies organic light emitting diodes using dopants attributed, part, improved outcoupling electroluminescence brought about alignment.