Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE.

A family of new branched phosphine derivatives {Ph2N-(C6H4)n-}3P → E (E = O 1-3, n = 1-3; E = S 4-6, n = 1-3; E = Se 7-9, n = 1-3; E = AuC6F5 4-6, n = 1-3), which are the donor-acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λem = 403-483 nm in CH2Cl2 solution, λem = 400-469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge -(C6H4)n-. The pyramidal geometry of central R3P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer formation and fluorescence self-quenching. Hence, compounds 2, 3, 5, and 12 were used as emitters to fabricate nondoped and doped electroluminescent devices. The luminophore 2 (E = O, n = 2) demonstrates excellently balanced bipolar charge transport and good nondoped device performance with a maximum external quantum efficiency (EQEmax) of 3.3% at 250 cd/m(2) and Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.08). The doped device of 3 (E = O, n = 3) shows higher efficiency (EQEmax of 6.5, 6.0 at 100 cd/m(2)) and high color purity with CIE (0.15, 0.06) that matches the HDTV standard blue. The time-resolved electroluminescence measurement indicates that high efficiency of the device can be attributed to the triplet-triplet annihilation to enhance generation of singlet excitons.

[1]  Shi-jian Su,et al.  Study of Configuration Differentia and Highly Efficient, Deep‐Blue, Organic Light‐Emitting Diodes Based on Novel Naphtho[1,2‐d]imidazole Derivatives , 2015 .

[2]  Yong-ki Kim,et al.  Energy level alignment at a charge generation interface between 4,4'-bis(N-phenyl-1-naphthylamino)biphenyl and 1,4,5,8,9,11 -hexaazatriphenylene-hexacarbonitrile , 2009 .

[3]  T. Baumgartner,et al.  Dithieno[3,2-c:2',3'-e]-2,7-diketophosphepin: a unique building block for multifunctional π-conjugated materials. , 2013, Journal of the American Chemical Society.

[4]  Yun‐Hi Kim,et al.  A new N-fluorenyl carbazole host material: Synthesis, physical properties and applications for highly efficient phosphorescent organic light emitting diodes , 2011 .

[5]  Ken‐Tsung Wong,et al.  A new benzimidazole/carbazole hybrid bipolar material for highly efficient deep-blue electrofluorescence, yellow–green electrophosphorescence, and two-color-based white OLEDs , 2010 .

[6]  Fred Wudl,et al.  Light-Emitting Polymers , 2006 .

[7]  S. Tunik,et al.  Emission tuning in dinuclear gold complexes with diphosphanes containing alkyne and/or oligophenylene spacers. , 2012, Dalton transactions.

[8]  Fred Wudl,et al.  Tetrathiafulvalenes, oligoacenenes, and their buckminsterfullerene derivatives: the brick and mortar of organic electronics. , 2004, Chemical reviews.

[9]  Yuguang Ma,et al.  Efficient Deep Blue Electroluminescence with an External Quantum Efficiency of 6.8% and CIEy < 0.08 Based on a Phenanthroimidazole–Sulfone Hybrid Donor–Acceptor Molecule , 2015 .

[10]  C. Adachi,et al.  Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence , 2014, Nature Photonics.

[11]  C. Adachi,et al.  Design of efficient thermally activated delayed fluorescence materials for pure blue organic light emitting diodes. , 2012, Journal of the American Chemical Society.

[12]  T. Baumgartner Insights on the design and electron-acceptor properties of conjugated organophosphorus materials. , 2014, Accounts of chemical research.

[13]  A multifunctional phosphine oxide-diphenylamine hybrid compound as a high performance deep-blue fluorescent emitter and green phosphorescent host. , 2014, Chemical communications.

[14]  Antonio Facchetti,et al.  π-Conjugated Polymers for Organic Electronics and Photovoltaic Cell Applications† , 2011 .

[15]  T. Baumgartner Insights on the Design and Electron‐Acceptor Properties of Conjugated Organophosphorus Materials , 2014 .

[16]  H. Wendt,et al.  Der Vergleich der Spannungsreihen in verschiedenen Solventien , 1960 .

[17]  Arunandan Kumar,et al.  Phosphine oxide functionalized pyrenes as efficient blue light emitting multifunctional materials for organic light emitting diodes , 2015 .

[18]  Elevating the triplet energy levels of dibenzofuran-based ambipolar phosphine oxide hosts for ultralow-voltage-driven efficient blue electrophosphorescence: from D-A to D-π-A systems. , 2013, Chemistry.

[19]  S. Trasatti The absolute electrode potential: an explanatory note (Recommendations 1986) , 1986 .

[20]  Wei Jiang,et al.  Alcohol-soluble electron-transport small molecule for fully solution-processed multilayer white electrophosphorescent devices. , 2014, Organic letters.

[21]  T. Higashiyama,et al.  A red-emitting ratiometric fluorescent probe based on a benzophosphole P-oxide scaffold for the detection of intracellular sodium ions. , 2015, Chemical communications.

[22]  Highly efficient red organic light-emitting devices based on a fluorene-triphenylamine host doped with an Os(II) phosphor , 2008 .

[23]  Wolfgang Rettig,et al.  Structural changes accompanying intramolecular electron transfer: focus on twisted intramolecular charge-transfer states and structures. , 2003, Chemical reviews.

[24]  A. Brockhinke,et al.  Syntheses of rod-shaped fluorescent 1,3,2-benzodiazaboroles with phosphonium, and phosphane chalcogenide acceptor functions. , 2012, Dalton transactions.

[25]  K. Char,et al.  Highly Efficient Red Phosphorescent OLEDs based on Non‐Conjugated Silicon‐Cored Spirobifluorene Derivative Doped with Ir‐Complexes , 2009 .

[26]  Yuguang Ma,et al.  A Twisting Donor‐Acceptor Molecule with an Intercrossed Excited State for Highly Efficient, Deep‐Blue Electroluminescence , 2012 .

[27]  J. Qin,et al.  Nondoped deep-blue organic light-emitting diodes with color stability and very low efficiency roll-off: solution-processable small-molecule fluorophores by phosphine oxide linkage. , 2012, Chemistry.

[28]  Tukaram K. Hatwar,et al.  Triplet annihilation exceeding spin statistical limit in highly efficient fluorescent organic light-emitting diodes , 2009 .

[29]  Chunmiao Han,et al.  Convergent modulation of singlet and triplet excited states of phosphine-oxide hosts through the management of molecular structure and functional-group linkages for low-voltage-driven electrophosphorescence. , 2013, Chemistry.

[30]  Kenji Okumoto,et al.  Green fluorescent organic light-emitting device with external quantum efficiency of nearly 10% , 2006 .

[31]  Yongsheng Chen,et al.  A—D—A Small Molecules for Solution-Processed Organic Photovoltaic Cells , 2015 .

[32]  P. Thilagar,et al.  Recent Advances in Purely Organic Phosphorescent Materials , 2015 .

[33]  Xianbin Xu,et al.  Recent advances of the emitters for high performance deep-blue organic light-emitting diodes , 2015 .

[34]  H. Chae,et al.  Effect of hole transporting materials in phosphorescent white polymer light-emitting diodes , 2010 .

[35]  H. Aziz,et al.  Correlation Between Triplet–Triplet Annihilation and Electroluminescence Efficiency in Doped Fluorescent Organic Light‐Emitting Devices , 2010 .

[36]  T. Higashiyama,et al.  Inside Cover: Environment‐Sensitive Fluorescent Probe: A Benzophosphole Oxide with an Electron‐Donating Substituent (Angew. Chem. Int. Ed. 15/2015) , 2015 .

[37]  Jwo-Huei Jou,et al.  Approaches for fabricating high efficiency organic light emitting diodes , 2015 .

[38]  T. Baumgartner,et al.  Conjugated main-group polymers for optoelectronics , 2013 .

[39]  Chen-Han Chien,et al.  A Novel Fluorene‐Triphenylamine Hybrid That is a Highly Efficient Host Material for Blue‐, Green‐, and Red‐Light‐Emitting Electrophosphorescent Devices , 2007 .

[40]  J. Qin,et al.  Efficient Solution-Processed Deep-Blue Organic Light-Emitting Diodes Based on Multibranched Oligofluorenes with a Phosphine Oxide Center , 2013 .

[41]  Hok-Lai Wong,et al.  Tunable photochromism in the robust dithienylethene-containing phospholes: design, synthesis, characterization, electrochemistry, photophysics, and photochromic studies. , 2015, Chemistry.

[42]  F. Huang,et al.  Recent advances in water/alcohol-soluble π-conjugated materials: new materials and growing applications in solar cells. , 2013, Chemical Society reviews.

[43]  Rui Li,et al.  Thiazole-based metallophosphors of iridium with balanced carrier injection/transporting features and their two-colour WOLEDs fabricated by both vacuum deposition and solution processing-vacuum deposition hybrid strategy , 2012 .

[44]  J. Qin,et al.  Diarylmethylene-bridged triphenylamine derivatives encapsulated with fluorene: very high Tg host materials for efficient blue and green phosphorescent OLEDs , 2010 .

[45]  J. Qin,et al.  A fully diarylmethylene-bridged triphenylamine derivative as novel host for highly efficient green phosphorescent OLEDs. , 2009, Organic letters.

[46]  J. Kido,et al.  Bisanthracene‐Based Donor–Acceptor‐type Light‐Emitting Dopants: Highly Efficient Deep‐Blue Emission in Organic Light‐Emitting Devices , 2014 .

[47]  Chun‐Sing Lee,et al.  Carbazole/Sulfone Hybrid D-π-A-Structured Bipolar Fluorophores for High-Efficiency Blue-Violet Electroluminescence , 2013 .

[48]  Jiann T. Lin,et al.  Versatile, Benzimidazole/Amine‐Based Ambipolar Compounds for Electroluminescent Applications: Single‐Layer, Blue, Fluorescent OLEDs, Hosts for Single‐Layer, Phosphorescent OLEDs , 2009 .

[49]  S. Jeon,et al.  Fabrication and Efficiency Improvement of Soluble Blue Phosphorescent Organic Light‐Emitting Diodes Using a Multilayer Structure Based on an Alcohol‐Soluble Blue Phosphorescent Emitting Layer , 2010, Advanced materials.

[50]  F. Jäkle Advances in the synthesis of organoborane polymers for optical, electronic, and sensory applications. , 2010, Chemical reviews.

[51]  Yun Chi,et al.  New Dopant and Host Materials for Blue‐Light‐Emitting Phosphorescent Organic Electroluminescent Devices , 2005 .

[52]  Jihyeon Janel Lee,et al.  Synthesis and Electroluminescence Properties of Highly Efficient Blue Fluorescence Emitters Using Dual Core Chromophores , 2013 .

[53]  A. Arias,et al.  Materials and applications for large area electronics: solution-based approaches. , 2010, Chemical reviews.

[54]  Junji Kido,et al.  Highly Efficient Organic Blue‐and White‐Light‐Emitting Devices Having a Carrier‐ and Exciton‐Confining Structure for Reduced Efficiency Roll‐Off , 2008 .

[55]  Shui-Tong Lee,et al.  Transient electroluminescence of organic quantum-well light-emitting diodes , 2002 .

[56]  Junji Kido,et al.  3,3′‐Bicarbazole‐Based Host Materials for High‐Efficiency Blue Phosphorescent OLEDs with Extremely Low Driving Voltage , 2012, Advanced materials.

[57]  M. Wong,et al.  Synthesis and functional properties of strongly luminescent diphenylamino end-capped oligophenylenes. , 2004, The Journal of organic chemistry.