Electronic structures of organic molecular materials for organic electroluminescent devices studied by ultraviolet photoemission spectroscopy

Electronic structures of evaporated films of five organic light-emitting and carrier-injecting materials for organic electroluminescent devices were studied by ultraviolet photoemission spectroscopy. The compounds examined were (i) light-emitting materials tris(8-hydroxyquinolino) aluminum (Alq3) and 1,2,3,4,5-pentaphenylcyclopentadiene, (ii) a hole-injecting material N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine, and (iii) electron-injecting materials N,N′-diphenyl-1,4,5,8-naphthyletracarboxyldiimide and 1,3,5-tris(5-phenyl-1,3,4-oxadiazol-2-yl)benzene. The spectral features corresponding to the top parts of the valence states, which dominate the electric properties of the materials, were assigned by the comparison with the simulated density of states obtained from PM3 molecular orbital calculations. Using these calculations, the evolution of the electronic structure of each molecule from those of constituent parts was discussed. The characters of the unoccupied states obtained by t...

[1]  N. Sato,et al.  UV photoemission spectroscopic studies on molecular aggregation of triphenylamines dispersed in polycarbonate thin films , 1992 .

[2]  S. Tokito,et al.  Energy structures of triphenylamine oligomers , 1997 .

[3]  Edgar Heilbronner,et al.  Das HMO-Modell und seine Anwendung , 1968 .

[4]  A. Epstein,et al.  Photoemission studies of TCNQ compounds , 1974 .

[5]  Yuji Hamada,et al.  Organic Electroluminescent Devices with 8-Hydroxyquinoline Derivative-Metal Complexes as an Emitter , 1993 .

[6]  J. Stewart.  Optimization of parameters for semiempirical methods II. Applications , 1989 .

[7]  K. Seki.  Ionization Energies of Free Molecules and Molecular Solids , 1989 .

[8]  Donal D. C. Bradley,et al.  Conjugated polymer electroluminescence , 1993 .

[9]  Y. Ouchi,et al.  Uv Photoemission Study of 8-Hydroxyquinoline Aluminum (ALQ3) / Metal Interfaces , 1996 .

[10]  Y. Ouchi,et al.  Ultraviolet photoelectron spectroscopy of poly(pyridine‐2,5‐diyl), poly(2,2′‐bipyridine‐5,5′‐diyl), and their K‐doped states , 1995 .

[11]  Neal R Armstrong,et al.  Electronic states of vapor deposited electron and hole transport agents and luminescent materials for light‐emitting diodes , 1995 .

[12]  K. Seki,et al.  Ultraviolet photoelectron spectra of tetrahalogeno-p-benzoquinones and hexahalogenobenzenes in the solid state , 1981 .

[13]  K. Seki,et al.  Energy level alignment at organic/metal interfaces studied by UV photoemission , 1997 .

[14]  A. Miura,et al.  Molecular design for nonpolymeric organic dye glasses with thermal stability : relations between thermodynamic parameters and amorphous properties , 1993 .

[15]  T. Hambley,et al.  Crystal and molecular structures of pentaphenylcyclopentadiene and of an isomer, 4,8-diphenyltribenzo[b,f,i]tricyclo[6.2.1.01.5]undecane, the product of a novel metal-assisted photoreaction , 1992 .

[16]  Takehiko Mori,et al.  A plane-grating monochromator for 2 eV ≤ hv ≤ 150 eV , 1986 .

[17]  Photoemission of Some Organic Donor–Acceptor Complexes , 1968 .

[18]  J. Stewart.  Optimization of parameters for semiempirical methods I. Method , 1989 .

[19]  Chihaya Adachi,et al.  Molecular design of hole transport materials for obtaining high durability in organic electroluminescent diodes , 1995 .

[20]  K. Yoshino,et al.  Enhancement of Electroluminescence Intensity from Dye-Doped Poly(3-Alkylthiophene) Light Emitting Diode with Different Alkyl-Side-Chain Length , 1996 .

[21]  P. Strohriegl,et al.  Efficient synthesis of starburst oxadiazole compounds , 1996 .

[22]  K. Seki,et al.  UV photoelectron spectroscopic study of the photopolymerization of long-chain diacetylene monocarboxylic acid in Langmuir—Blodgett films , 1987 .

[23]  L. Ley,et al.  Photoemission in Solids I , 1978 .

[24]  C. Tang,et al.  Organic Electroluminescent Diodes , 1987 .

[25]  R. L. Elsenbaumer,et al.  Handbook of conducting polymers , 1986 .