yield (>90%) and clear circularly polarized phosphorescence, with dissymmetry
factors (|g PL |) of approximately 3.7 Â 10
À3 in solution and about 4.1 Â 10
À3 in doped
films. The CP-PHOLEDs with two enantiomers as emitters exhibited symmetric
CPEL signals with |g EL | of (1.1–1.6) Â 10
À3 and good device performances,
achieving a maximum brightness of 11,590 cd m
À2 , a maximum external quantum
efficiency up to 18.81%, which are the highest values among the reported
devices based on chiral phosphorescent Pt
II complexes. To suppress the effect
of reverse CPEL signal from the cathode reflection, the further implementation
of semi-transparent aluminum/silver cathode successfully boosted up the |g EL | by
over three times to 5.1 Â 10
À3 .
4.11 Conclusion
Since the first examples of helicenes displaying circularly polarized luminescence
described in the literature [13, 37], there has been a growing interest in CPL-active
helicenes and helicenoids, and the number of reported examples is growing
Table 4.14 Photophysical data of helicene-NHC iridium complexes
Compound
λ Abs
max a (nm)
λ Em (nm)
Φ (%)
Solvent (CPL)
10
3 g lum
Ref.
(P,Δ Ir )-(+)-77a
1
402
525
9
CH 2 Cl 2
+3.7
[49]
(P,Λ Ir )-(+)-77a
2
403
526
13
CH 2 Cl 2
+1.5
[49]
(Δ Ir )-(+)-78
390
498
29
CH 2 Cl 2
+0.9
[49]
(Δ Ir )-(+)-79
394
510
5
CH 2 Cl 2
+3.1
[72]
a Lowest-energy UV-vis band
Fig. 4.31 (a) CP-PLED based on blends between enantiopure 9 and 80. Adapted with permission
19 Copyright 2013, Wiley. (b) CP-PHOLED based on pure enantiopure cycloplatinahelicene 66a.
Adapted with permission [75]. Copyright 2016, American Chemical Society
92
J. Crassous
factors (|g PL |) of approximately 3.7 Â 10
À3 in solution and about 4.1 Â 10
À3 in doped
films. The CP-PHOLEDs with two enantiomers as emitters exhibited symmetric
CPEL signals with |g EL | of (1.1–1.6) Â 10
À3 and good device performances,
achieving a maximum brightness of 11,590 cd m
À2 , a maximum external quantum
efficiency up to 18.81%, which are the highest values among the reported
devices based on chiral phosphorescent Pt
II complexes. To suppress the effect
of reverse CPEL signal from the cathode reflection, the further implementation
of semi-transparent aluminum/silver cathode successfully boosted up the |g EL | by
over three times to 5.1 Â 10
À3 .
4.11 Conclusion
Since the first examples of helicenes displaying circularly polarized luminescence
described in the literature [13, 37], there has been a growing interest in CPL-active
helicenes and helicenoids, and the number of reported examples is growing
Table 4.14 Photophysical data of helicene-NHC iridium complexes
Compound
λ Abs
max a (nm)
λ Em (nm)
Φ (%)
Solvent (CPL)
10
3 g lum
Ref.
(P,Δ Ir )-(+)-77a
1
402
525
9
CH 2 Cl 2
+3.7
[49]
(P,Λ Ir )-(+)-77a
2
403
526
13
CH 2 Cl 2
+1.5
[49]
(Δ Ir )-(+)-78
390
498
29
CH 2 Cl 2
+0.9
[49]
(Δ Ir )-(+)-79
394
510
5
CH 2 Cl 2
+3.1
[72]
a Lowest-energy UV-vis band
Fig. 4.31 (a) CP-PLED based on blends between enantiopure 9 and 80. Adapted with permission
19 Copyright 2013, Wiley. (b) CP-PHOLED based on pure enantiopure cycloplatinahelicene 66a.
Adapted with permission [75]. Copyright 2016, American Chemical Society
92
J. Crassous