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High‐Efficiency Electrophosphorescent Copolymers Containing Charged Iridium Complexes in the Side Chains
Author(s) -
Du Bin,
Wang Lei,
Wu HongBin,
Yang Wei,
Zhang Yong,
Liu RanSheng,
Sun MingLiang,
Peng Junbiao,
Cao Yong
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601811
Subject(s) - iridium , side chain , oxadiazole , quantum efficiency , electroluminescence , benzimidazole , materials science , oled , luminous efficacy , electrochemistry , cathode , pedot:pss , phosphorescence , polymer , photochemistry , chemistry , optoelectronics , fluorescence , layer (electronics) , nanotechnology , physics , optics , organic chemistry , electrode , catalysis , composite material
A convenient approach to novel charged Ir polymers for optoelectronic devices to achieve red emission was developed. 2‐(Pyridin‐2‐yl)benzimidazole units grafted into the side chains of macroligands (PFCz and PFP) served as ligands for the formation of charged Ir complex pendants with 1‐phenylisoquinoline (1‐piq). The charged Ir polymers (PFPIrPiq and PFCzIrPiq) showed exclusive Ir(1‐piq) 2 { N ‐[2‐(pyridin‐2‐yl)benzimidazole]hexyl} + BF 4 − (IrPiq) emission, with the peak at 595 nm. The best device performances were obtained from PFCzIrPiq4 with the device configuration of ITO/PEDOT:PSS/PFCzIrPiq4+PBD (30 wt %)/TPBI/Ba/Al (PBD: 5‐(4‐ tert ‐butylphenyl)‐2‐(biphenyl‐4‐yl)‐1,3,4‐oxadiazole; TPBI: 1,3,5‐tris‐(2‐ N ‐phenylbenzimidazolyl)benzene). A maximum external quantum efficiency (EQE) of 7.3 % and a luminous efficiency (LE) of 6.9 cd A −1 with a luminance of 138 cd m −2 were achieved at a current density of 1.9 mA cm −2 . The efficiencies remained as high as EQE=3.4 % and LE=3.3 cd A −1 with a luminance of 3770 cd m −2 at a current density of 115 mA cm −2 . The single‐layer devices based on charged Ir polymers also showed high efficiency with the high work‐function metal Ag as cathode. The maximum external quantum efficiencies of the devices were 0.64 % and 0.66 % for PFPIrPiq2 and PFPIrPiq10, respectively. A possible mechanism of an electrochemical cell associated with its electrochemical redox pathway for single‐layer devices has been proposed. The results showed that the charged Ir polymers are promising candidate materials for polymer optoelectronic devices.