Selectively Controlled Orientational Order in Linear-Shaped Thermally Activated Delayed Fluorescent Dopants

The orientational order of a linear-shaped thermally activated delayed fluorescent dopant 10-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-10H-phenoxazine (PXZ-TRZ) was selectively controlled in a randomly oriented host matrix composed of 3,3-di(9H-carbazol-9-yl)biphenyl (mCBP) by varying the temperature during deposition of the thin films. Although the molecular orientation of mCBP was random at deposition temperatures ranging from 200 to 300 K (orientational disorder), PXZ-TRZ molecules oriented horizontal to the substrate in this temperature range (high orientational order). This indicates that the orientational order was dominated by the kinetic behavior of PXZ-TRZ at the film surface rather than by randomization caused by aggregation of PXZ-TRZ and mCBP molecules. Using an orientation-controlled 6 wt % PXZ-TRZ:mCBP film as an emitting layer, we fabricated organic light-emitting diodes (OLEDs). The horizontal orientation of the dopants enhanced the external electroluminescence quantum efficiency of the ...

[1]  C. Adachi,et al.  Real-time measurement of molecular orientational randomization dynamics during annealing treatments by in-situ ellipsometry , 2012 .

[2]  Ken-Tsung Wong,et al.  Tunable organic solid-state DFB laser utilizing molecular reorientation , 2007, SPIE Organic Photonics + Electronics.

[3]  Hans-Joachim Egelhaaf,et al.  Electronic spectra of self-organized oligothiophene films with “standing” and “lying” molecular units , 1996 .

[4]  Hans-Joachim Egelhaaf,et al.  Optical constants of highly oriented oligothiophene films and nanoparticles , 1999 .

[5]  Wolfgang Brütting,et al.  Determination of molecular dipole orientation in doped fluorescent organic thin films by photoluminescence measurements , 2010 .

[6]  Daisuke Yokoyama,et al.  Horizontal Orientation of Disk-like Hole Transport Molecules and Their Application for Organic Light-Emitting Diodes Requiring a Lower Driving Voltage , 2012 .

[7]  Stefan Nowy,et al.  Light extraction and optical loss mechanisms in organic light-emitting diodes: Influence of the emitter quantum efficiency , 2008 .

[8]  Akio Sakaguchi,et al.  Horizontal molecular orientation in vacuum-deposited organic amorphous films of hole and electron transport materials , 2008 .

[9]  Akio Sakaguchi,et al.  Horizontal orientation of linear-shaped organic molecules having bulky substituents in neat and doped vacuum-deposited amorphous films , 2009 .

[10]  Tobias D. Schmidt,et al.  Oriented phosphorescent emitters boost OLED efficiency , 2011 .

[11]  C. Stafford,et al.  Thickness dependence of the elastic modulus of tris(8-hydroxyquinolinato)aluminium , 2010 .

[12]  Tobin J Marks,et al.  Polymer Gate Dielectric Surface Viscoelasticity Modulates Pentacene Transistor Performance , 2007, Science.

[13]  D. Haarer,et al.  The polarized absorption spectroscopy as a novel method for determining the orientational order of poled nonlinear optical polymer films , 1994 .

[14]  B. Vogt,et al.  Thickness dependent modulus of vacuum deposited organic molecular glasses for organic electronics applications , 2011 .

[15]  Akio Sakaguchi,et al.  Enhancement of electron transport by horizontal molecular orientation of oxadiazole planar molecules in organic amorphous films , 2009 .

[16]  Z. Fakhraai,et al.  High-throughput ellipsometric characterization of vapor-deposited indomethacin glasses. , 2013, The journal of physical chemistry. B.

[17]  Daisuke Yokoyama,et al.  In situ real-time spectroscopic ellipsometry measurement for the investigation of molecular orientation in organic amorphous multilayer structures , 2010 .

[18]  M. Oh-e,et al.  Anisotropy in amorphous films of cross-shaped molecules with an accompanying effect on carrier mobility: Ellipsometric and sum-frequency vibrational spectroscopic studies , 2013 .

[19]  Y. Chien,et al.  Anisotropic optical properties and molecular orientation in vacuum-deposited ter(9,9-diarylfluorene)s thin films using spectroscopic ellipsometry , 2004 .

[20]  Xun He,et al.  Simple CBP isomers with high triplet energies for highly efficient blue electrophosphorescence , 2012 .

[21]  Joseph L. Keddie,et al.  Interface and surface effects on the glass-transition temperature in thin polymer films , 1994 .

[22]  Peter Strohriegl,et al.  Meta-linked CBP-derivatives as host materials for a blue iridium carbene complex , 2011 .

[23]  J. Kido,et al.  Dual efficiency enhancement by delayed fluorescence and dipole orientation in high-efficiency fluorescent organic light-emitting diodes , 2011 .

[24]  Akio Sakaguchi,et al.  Orientation Control of Linear‐Shaped Molecules in Vacuum‐Deposited Organic Amorphous Films and Its Effect on Carrier Mobilities , 2010 .

[25]  Richard H. Friend,et al.  Effect of metal films on the photoluminescence and electroluminescence of conjugated polymers , 1997 .

[26]  Joseph L. Keddie,et al.  Size-Dependent Depression of the Glass Transition Temperature in Polymer Films , 1994 .

[27]  C. Adachi,et al.  Horizontal Orientation of a Linear-Shaped Platinum(II) Complex in Organic Light-Emitting Diodes with a High Light Out-Coupling Efficiency , 2011 .

[28]  C. Adachi,et al.  Suppression of Efficiency Roll-Off Characteristics in Thermally Activated Delayed Fluorescence Based Organic Light-Emitting Diodes Using Randomly Oriented Host Molecules , 2013 .

[29]  Tobias D. Schmidt,et al.  Device efficiency of organic light‐emitting diodes: Progress by improved light outcoupling , 2013 .

[30]  C. Adachi,et al.  Dependence of the amplified spontaneous emission threshold in spirofluorene thin films on molecular orientation , 2011 .

[31]  Yukio Furukawa,et al.  Molecular Stacking Induced by Intermolecular C–H···N Hydrogen Bonds Leading to High Carrier Mobility in Vacuum‐Deposited Organic Films , 2011 .

[32]  Tobias D. Schmidt,et al.  Charge accumulation at organic semiconductor interfaces due to a permanent dipole moment and its orientational order in bilayer devices , 2012 .

[33]  Stefan Nowy,et al.  Efficiency analysis of organic light-emitting diodes based on optical simulation , 2009 .

[34]  Yuya Tanaka,et al.  Threshold voltage shift and formation of charge traps induced by light irradiation during the fabrication of organic light-emitting diodes , 2008 .

[35]  Atsushi Kawada,et al.  Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes , 2011 .

[36]  Jeanne L. McHale,et al.  ELECTRIC POLING OF 4-(DIMETHYLAMINO)-4'-NITROSTILBENE IN POLY(METHYL METHACRYLATE) STUDIED BY POLARIZED ABSORPTION SPECTROSCOPY , 1997 .

[37]  Daisuke Yokoyama,et al.  Thermally Activated Delayed Fluorescence from Sn4+–Porphyrin Complexes and Their Application to Organic Light Emitting Diodes — A Novel Mechanism for Electroluminescence , 2009, Advanced materials.

[38]  Tobin J Marks,et al.  Probing the surface glass transition temperature of polymer films via organic semiconductor growth mode, microstructure, and thin-film transistor response. , 2009, Journal of the American Chemical Society.

[39]  Ken-Tsung Wong,et al.  Influences of molecular orientations on stimulated emission characteristics of oligofluorene films , 2007 .

[40]  Stephen R. Forrest,et al.  Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques. , 1997, Chemical reviews.

[41]  C. Adachi,et al.  Reorganization of the molecular orientation at the organic/substrate interface in spirofluorene thin films , 2013 .

[42]  K. Eichhorn,et al.  Diindenoperylene derivatives: A model to investigate the path from molecular structure via morphology to solar cell performance , 2013 .

[43]  Wolfgang Brütting,et al.  Increased light outcoupling efficiency in dye-doped small molecule organic light-emitting diodes with horizontally oriented emitters , 2011 .

[44]  C. Adachi,et al.  Highly efficient organic light-emitting diodes by delayed fluorescence , 2013 .

[45]  Atsushi Kawada,et al.  Organic luminescent molecule with energetically equivalent singlet and triplet excited states for organic light-emitting diodes. , 2013, Physical review letters.

[46]  D. Yokoyama.  Molecular orientation in small-molecule organic light-emitting diodes , 2011 .