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RISS 인기검색어
- 검색키워드
- 저자 : Maheshwaran Athithan (검색결과 4 건)
- 무료
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박호열,Maheshwaran Athithan,진성호 한국정보디스플레이학회 2020 Journal of information display Vol.21 No.4
The new efficient green heteroleptic phosphorescent Ir(III) complex [5-methyl-8-trifluoromethyl- 5H-benzo(c)(1,5)naphthyridin-6-one](3-(2-ethoxyethoxypyraznate))iridium(III) (Ir-prz) was designed and synthesized with a high photoluminescence quantum yield (PLQY). In addition, the solubilizing group 2-ethoxyethanol (EO2-) was attached to the ancillary ligand via a tandem reaction. Their thermal, photophysical, electrochemical, and electroluminescent (EL) properties were fully investigated. The solution-processed green PHOLED using Ir-prz as dopant and 4,4'-bis(N-carbazolyl)-1,1'- biphenyl as host achieved a maximum external quantum efficiency of 8.94% and a maximum current efficiency of 16.50 cd A−1, with a maximum luminescence of 18,638 cd m−2.
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Sarada, Ganguri,Maheshwaran, Athithan,Cho, Woosum,Lee, Taegyun,Han, Si Hyun,Lee, Jun Yeob,Jin, Sung-Ho Elsevier 2018 Dyes and pigments Vol.150 No.-
<P><B>Abstract</B></P> <P>Pure blue phosphorescence with high quantum yield is crucial, yet highly challenging to achieve, for the successful application of phosphorescent organic light-emitting diodes (PhOLEDs) in display and lighting technologies. This study presents the design of three meridional tris-cyclometalated Ir(III) complexes (Ir1, Ir2 and Ir3) by introducing diphenylphosphine oxide (Ph<SUB>2</SUB>P = O) and/or fluorine (-F) group(s) on <I>N</I>-heterocyclic carbene (NHC) ligands (3-phenyl-3<I>H</I>-imidazo[4,5-<I>b</I>]pyridine or 1-phenyl-1<I>H</I>-imidazole) with the aim of achieving pure blue phosphorescence. Particularly, the introduction of –F on the NHC ligand greatly enhances the triplet (T<SUB>1</SUB>) energy and photoluminescence (PL) intensity of the Ir(III) complex (Ir3). Consequently, Ir3 exhibits ‘pure’ blue phosphorescence with high quantum yield (95%) and short triplet lifetimes (τ), the latter being beneficial for high radiative decay rates. Moreover, the Ir3 emitter shows pure blue Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.08), especially the ‘pure’ blue CIE <I>y</I> coordinate, in the PhOLEDs. However, Ir1 shows a maximum external quantum efficiency (EQE) of 8.6% at higher dopant concentration (20 wt%) with CIE coordinates of (0.16, 0.12).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three <I>N-</I>heterocyclic carbene based Ir(III) complexes were synthesized. </LI> <LI> Investigated the functionalization with diphenylphosphine oxide or fluorine. </LI> <LI> Achieved pure ‘blue’ coordinates (0.16, 0.08) for Ir3. </LI> <LI> The triplet energies of the phosphors are increased by the functionalization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Cho, Woosum,Sarada, Ganguri,Maheshwaran, Athithan,Gal, Yeong-Soon,Nam, Yeonsig,Yong Lee, Jin,Jin, Sung-Ho The Royal Society of Chemistry 2017 Journal of materials chemistry. C, Materials for o Vol.5 No.38
<▼1><P>Linking the hole transporting/electron transporting functional moieties to the Ir(iii) complex is a key strategy to improve performance of PhOLEDs.</P></▼1><▼2><P>A heteroleptic deep-red iridium(iii) complex, TPQIr-HT, based on thiophene-phenylquinoline (TPQ), and orange Ir(iii) complexes, <I>m</I>-CF3DPQIr-HT and <I>m</I>-CF3DPQIr-ET based on diphenylquinoline (DPQ), are designed by attaching a carbazole-based hole transporting (HT) group and an oxadiazole (OXD)-based electron transporting (ET) group to the parent Ir(iii) complexes, TPQIr and <I>m</I>-CF3DPQIr. The Ir(iii) complexes TPQIr-HT show a deep-red emission peak at 612 nm, similar to that of TPQIr, whereas <I>m</I>-CF3DPQIr-HT and <I>m</I>-CF3DPQIr-ET show an orange emission peak at 567 ± 1 nm, which is similar to that of <I>m</I>-CF3DPQIr. The newly functionalized Ir(iii) complexes show improved device performance compared to the Ir(iii) complexes, TPQIr and <I>m</I>-CF3DPQIr, without the additional functional groups. The phosphorescent organic light-emitting diodes (PhOLEDs) fabricated using a deep-red Ir(iii) complex, TPQIr-ET, achieved a maximum external quantum efficiency (EQE) of 17.47% using GraHIL as the hole injection layer (HIL). Similarly, the orange Ir(iii) complex, <I>m</I>-CF3DPQIr-HT, achieved a maximum EQE of 21.61%.</P></▼2>
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Reddy, Saripally Sudhaker,Sree, Vijaya Gopalan,Park, Ho-Yeol,Maheshwaran, Athithan,Song, Myungkwan,Jin, Sung-Ho Elsevier 2017 Dyes and pigments Vol.145 No.-
<P><B>Abstract</B></P> <P>A rational design strategy is proposed for synthesis of a new deep-blue emitter/dopant (denoted as TPA-3FA) based on triphenylamine (TPA) as the core with the addition of diethylfluorene/acridine analogues to frame a star-shaped material for solution processable high performance OLEDs. The photophysical, thermal, electrochemical, electronic, and hole transporting properties of TPA-3FA are examined. Most importantly, this rational design strategy of introducing diethylfluorene between TPA and acridine imparts high rigidity and non-planarity, which in turn completely suppress intermolecular interactions, and thus yields a strong narrow deep-blue fluorescence with a high quantum yield. Moreover, a solution processed non-doped device with TPA-3FA as an emitter exhibits excellent device performance with a maximum external quantum efficiency (EQE) of 4.43%, CIE (<I>x</I>,<I>y</I>) coordinates of (0.153, 0.045) and good device stability. The device performance was significantly improved with an EQE of 6.11% and CIE (<I>x</I>,<I>y</I>) coordinates of (0.156, 0.049) after doping into a host. The same device when processed in a halogen-free solvent exhibited an impressive EL performance (EQE: 5.72%; CIE (0.157, 0.046)).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rationally designed and synthesized an efficient deep-blue fluorescent emitter for solution processed OLEDs. </LI> <LI> A nondoped device exhibits an excellent device performance with an EQE of 4.43% and CIE (<I>x</I>,<I>y</I>) value of (0.153,0.045). </LI> <LI> Doped device performance is dramatically improved EQE of 6.11%; CIE (<I>x</I>,<I>y</I>):(0.156, 0.049). </LI> <LI> In a halogen-free solvent-processed device is also showed EQE of over 5.7% with a small CIE <I>y</I> value. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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