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Rational Design of Charge‐Neutral, Near‐Infrared‐Emitting Osmium(II) Complexes and OLED Fabrication
Author(s) -
Lee TsangChi,
Hung JuiYi,
Chi Yun,
Cheng YiMing,
Lee GeneHsiang,
Chou PiTai,
Chen ChungChia,
Chang ChihHao,
Wu ChungChih
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900233
Subject(s) - materials science , electroluminescence , oled , phosphor , optoelectronics , exciton , phosphorescence , excited state , photochemistry , fluorescence , optics , nanotechnology , atomic physics , chemistry , physics , layer (electronics) , quantum mechanics
A new series of charge neutral Os(II) isoquinolyl triazolate complexes ( 1 – 4 ) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis ‐arranged complexes 2 – 4 , the trans derivative 1 , which shows a planar arrangement of chromophoric N ‐substituted chelates, offers the most effective extended π ‐delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692–805 nm in degassed CH 2 Cl 2 at room temperature. Near‐infrared (NIR)‐emitting electroluminescent devices employing 6 wt % of 1 (or 4 ) doped in Alq 3 host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814 nm. Forward radiant emittance reaches as high as 65.02 µW cm −2 , and a peak EQE of ∼1.5% with devices employing Alq 3 , TPBi and/or TAZ as electron‐transporting/exciton‐blocking layers. Upon switching to phosphor 4 , the electroluminescence blue shifts to 718 nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (μW cm −2 ) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton‐blocking material. The OLEDs characterized represent the only NIR‐emitting devices fabricated using charge‐neutral and volatile Os(II) phosphors via thermal vacuum deposition.