Synthesis of a high-efficiency red phosphorescent emitter for organic light-emitting diodes

Yang, Cheng‐Hsien; Tai, Chia‐Cheng; Sun, I‐Wen

doi:10.1039/b313843g

Cited by 130 publications

(47 citation statements)

References 17 publications

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“…The photophysical properties of these phosphors can be tuned by varying the ligand [5] or its substituent groups and by the use of additional ancillary ligands.…”

Section: Introductionmentioning

confidence: 99%

Cationic Bis‐cyclometallated Iridium(III) Phenanthroline Complexes with Pendant Fluorenyl Substituents: Synthesis, Redox, Photophysical Properties and Light‐Emitting Cells

Zeng

Tavaslı

Perepichka

et al. 2008

Chemistry A European J

106

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We report the synthesis, characterisation, photophysical and electrochemical properties of a series of cationic cyclometallated Ir(III) complexes of general formula [Ir(ppy)(2)(phen)]PF(6) (ppy=2-phenylpyridine, phen=a substituted phenanthroline). A feature of these complexes is that the phen ligands are substituted with one or two 9,9-dihexylfluorenyl substituents to provide extended pi conjugation, for example, the 3-[2-(9,9-dihexylfluorenyl)]phenanthroline and 3,8-bis[2-(9,9-dihexylfluorenyl)]phenanthroline ligands afford complexes 6 and 9, respectively. A single-crystal X-ray diffraction study of a related complex 18 containing the 3,8-bis(4-iodophenyl)phenanthroline ligand, revealed an octahedral coordination of the Ir atom, in which the metallated C atoms of the ppy ligands occupy cis positions. The complexes 6 and 9 displayed reversible oxidation waves in cyclic voltammetric studies (E(ox)(1/2)=+1.18 and +1.20 V, respectively, versus Ag/Ag(+) in CH(2)Cl(2)) assigned to the metal-centred Ir(III)/Ir(IV) couple. The complexes exhibit strong absorption in the UV region in solution spectra, due to spin-allowed ligand-centred (LC) (1)pi-pi* transitions; moderately intense bands occur at approximately 360-390 nm which are red-shifted with increased ligand length. The photoluminescence spectra of all the complexes were characterised by a broad band at lambda(max) approximately 595 nm assigned to a combination of (3)MLCT and (3)pi-->pi* states. The long emission lifetimes (in the microsecond time-scale) are indicative of phosphorescence: the increased ligand conjugation length in complexes 9 and 17 leads to increased lifetimes for the complexes (tau=2.56 and 2.57 micros in MeCN, respectively) compared to monofluorenyl analogues 6 and 15 (tau=1.43 and 1.39 micros, respectively). DFT calculations of the geometries and electronic structures of complexes 6', 9' (for both singlet ground state (S(0)) and triplet first excited (T(1)) states) and 18 have been performed. In the singlet ground state (S(0)) HOMO orbitals in the complexes are spread between the Ir atom and benzene rings of the phenylpyridine ligand, whereas the LUMO is mainly located on the phenanthroline ligand. Analysis of orbital localisations for the first excited (T(1)) state have been performed and compared with spectroscopic data. Spin-coated light-emitting cells (LECs) have been fabricated with the device structures ITO/PEDOT:PSS/Ir complex/Al, or Ba capped with Al (ITO=indium tin oxide, PEDOT=poly(3,4-ethylenedioxythiophene), PSS=poly(styrene) sulfonate). A maximum brightness efficiency of 9 cd A(-1) has been attained at a bias of 9 V for 17 with a Ba/Al cathode. The devices operated in air with no reduction in efficiency after storage for one week in air.

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“…The photophysical properties of these phosphors can be tuned by varying the ligand [5] or its substituent groups and by the use of additional ancillary ligands.…”

Section: Introductionmentioning

confidence: 99%

Cationic Bis‐cyclometallated Iridium(III) Phenanthroline Complexes with Pendant Fluorenyl Substituents: Synthesis, Redox, Photophysical Properties and Light‐Emitting Cells

Zeng

Tavaslı

Perepichka

et al. 2008

Chemistry A European J

106

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“…Yang et al [160] developed Ir(m-piq) 2 (acac) by adding a methyl group on position 5 of 1-(phenyl)isoquioline, whose EL emission is around 623 nm. When the phenyl is replaced by a naphthyl ring, the Ir(1-niq) 2 (acac) or Ir(2-niq) 2 (acac) formed have emission peaks at 664 and 633 nm, respectively.…”

Section: Red Phosphorescent Materialsmentioning

confidence: 99%

Organic Semiconductor Electroluminescent Materials

2015

Lecture Notes in Chemistry

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This chapter reviews the important progress made on small molecule electroluminescent materials used in organic light-emitting diode (OLED). In many cases we describe not only the material structures but also the properties associated with these materials, such as energy level, absorption and photoluminescence (PL) peaks, PL quantum yield, exciton life time, and so on. The performances of related devices are covered as well if they are available.

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“…[29][30][31] According to the I-V curve characteristics of the above three different color (R-G-B) device systems, an increase in the dopant concentration led to a decreasing drive voltage. This phenomenon indicates that the charges may be injected directly to the dopant molecules at high doping concentrations; these moieties then serve as an additional channel to transport charges by hopping between the dopant sites, with TFTPA acting as an inert host matrix.…”

Section: Full Papermentioning

confidence: 99%

A Novel Fluorene‐Triphenylamine Hybrid That is a Highly Efficient Host Material for Blue‐, Green‐, and Red‐Light‐Emitting Electrophosphorescent Devices

Shih

Chien

et al. 2007

Adv Funct Materials

143

101

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TFTPA (tris[4‐(9‐phenylfluoren‐9‐yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9‐phenyl‐9‐fluorenyl peripheries, was effectively synthesized through a Friedel‐Crafts‐type substitution reaction. Owing to the presence of its sterically bulky 9‐phenyl‐9‐fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 °C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full‐color phosphorescence. The performance of TFTPA‐based devices is far superior to those of the corresponding mCP‐ or CBP‐based devices, particularly in blue‐ and red‐emitting electrophosphorescent device systems. The efficiency of the FIrpic‐based blue‐emitting device reached 12 % (26 cd A–1) and 18 lm W–1 at a practical brightness of 100 cd m–2; the Ir(piq)2acac‐based red‐emitting device exhibited an extremely low turn‐on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W–1) relative to those of reference devices based on the CBP host material.

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Synthesis of a high-efficiency red phosphorescent emitter for organic light-emitting diodes

Cited by 130 publications

References 17 publications

Cationic Bis‐cyclometallated Iridium(III) Phenanthroline Complexes with Pendant Fluorenyl Substituents: Synthesis, Redox, Photophysical Properties and Light‐Emitting Cells

Cationic Bis‐cyclometallated Iridium(III) Phenanthroline Complexes with Pendant Fluorenyl Substituents: Synthesis, Redox, Photophysical Properties and Light‐Emitting Cells

Organic Semiconductor Electroluminescent Materials

A Novel Fluorene‐Triphenylamine Hybrid That is a Highly Efficient Host Material for Blue‐, Green‐, and Red‐Light‐Emitting Electrophosphorescent Devices

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