%0 Journal Article
%A Kim, Yejin
%A Park, Sunghee
%A Lee, Young Hoon
%A Jung, Jaehoon
%A Yoo, Seunghyup
%A Lee, Min Hyung
%D 2016
%T Homoleptic Tris-Cyclometalated Iridium Complexes with
Substituted o‑Carboranes: Green Phosphorescent
Emitters for Highly Efficient Solution-Processed Organic Light-Emitting
Diodes
%U https://acs.figshare.com/articles/journal_contribution/Homoleptic_Tris_Cyclometalated_Iridium_Complexes_with_Substituted_i_o_i_Carboranes_Green_Phosphorescent_Emitters_for_Highly_Efficient_Solution_Processed_Organic_Light_Emitting_Diodes/2086645
%R 10.1021/acs.inorgchem.5b02444.s001
%2 https://acs.figshare.com/ndownloader/files/3719860
%K steric
%K ligand
%K lm
%K 3 c dopant
%K phosphorescence quantum efficiency
%K wt
%K phosphorescence quantum efficiencies
%K ppy
%K CB
%K 3 c
%K vs
%K nm
%K complex
%K performance
%K device
%K Ir
%K PL quantum yields
%X Homoleptic
tris-cyclometalated
iridium complexes, fac-Ir[5-(2-RCB)ppy]3 (3a–3c; CB = o-carboran-1-yl; ppy = 2-phenylpyridinato-C2,N; R = H (3a), Me (3b), iBu
(3c)) with 2-R-substituted o-carboranes
at the 5-position of the ppy ligand, were prepared
and characterized. X-ray diffraction analysis of 3a and 3c revealed that the three C^N ligands adopt a fac-arrangement around the Ir atom and that the carboranyl C–C
bond distance increases with increasing steric effects of the 2-R
substituent. The phosphorescence wavelengths of the complexes were
apparently blue-shifted by ca. 20 nm (λem = 487–493
nm) compared to that of the parent fac-Ir(ppy)3 (4; λem = 508 nm). In particular, 3a–3c were highly emissive in toluene,
and the phosphorescence quantum efficiencies of 3a and 3b (ΦPL = 0.95–0.98) were comparable
to that of 4. Solution-processed electroluminescent devices
incorporating 3a–3c as emitters displayed
green light with high performance, and devices based on the 3c dopant showed the highest performance. In particular, the
devices based on 3c exhibited performance more than double
of that of the device based on 4 in terms of current
efficiency (29.6 cd/A for 3c vs 15.8 cd/A for 4 at 4 wt % Ir and 1000 cd/m2), power efficiency (11.0
lm/W for 3c vs 6.3 lm/W for 4), and external
quantum efficiency (10.2% for 3c vs 4.7% for 4) over a wide range of luminance. The higher PL quantum yields of
doped host films with 3c than those with 4 at high dopant concentrations above 8 wt % suggested that along
with high phosphorescence quantum efficiency, the steric bulkiness
of the 2-iBu-substituted o-carborane in 3c plays a crucial role in improving device
performance.
%I ACS Publications