the relative high device operation voltage, a stable electroluminescence spectrum was
successfully confirmed (Fig. 5.4b). This coincides with the observed steady-state
fluorescence spectrum [21]. However, the gradual decrease of fluorescence intensity
was seen with increasing the operation time due to the oxidation of Ca electrode.
Anyway, we can summarize that [7]Hl-NAIQx is stable enough for OLED operation
because of no spectral change during operation.
5.2.2 [5]Carbohelicene Derivatives for CPL
In association with the above section, [5]carbohelicene (i.e., a shorter carbohelicene
relative to [7]carbohelicene) derivatives were similarly examined. These brief summaries are discussed here. A [5]carbohelicene derivative having electronwithdrawing maleimide, i.e., maleimide-substituted [5]carbohelicene (HeliIm), was
designed and synthesized to investigate the photophysical behaviors and circularly
polarized luminescence (CPL) as shown in Fig. 5.5a [44]. The fluorescence quantum
yield of HeliIm (Φ FL ¼ 0.37) significantly improved as compared to the reference
Fig. 5.4 (a) Current–
luminance–voltage (J–L–V )
characteristics and (b) an
electroluminescence
(EL) spectrum of
ITO/PEDOT:PSS/PFO: [7]
Hl-NAIQx-(95:5)/Ca/Al)
(Reprinted with permission
from Ref. [21]. Copyright
2015 American Chemical
Society)
5 Structural Control of Fluorescent Helicates for Improved Circularly Polarized. . .
105
successfully confirmed (Fig. 5.4b). This coincides with the observed steady-state
fluorescence spectrum [21]. However, the gradual decrease of fluorescence intensity
was seen with increasing the operation time due to the oxidation of Ca electrode.
Anyway, we can summarize that [7]Hl-NAIQx is stable enough for OLED operation
because of no spectral change during operation.
5.2.2 [5]Carbohelicene Derivatives for CPL
In association with the above section, [5]carbohelicene (i.e., a shorter carbohelicene
relative to [7]carbohelicene) derivatives were similarly examined. These brief summaries are discussed here. A [5]carbohelicene derivative having electronwithdrawing maleimide, i.e., maleimide-substituted [5]carbohelicene (HeliIm), was
designed and synthesized to investigate the photophysical behaviors and circularly
polarized luminescence (CPL) as shown in Fig. 5.5a [44]. The fluorescence quantum
yield of HeliIm (Φ FL ¼ 0.37) significantly improved as compared to the reference
Fig. 5.4 (a) Current–
luminance–voltage (J–L–V )
characteristics and (b) an
electroluminescence
(EL) spectrum of
ITO/PEDOT:PSS/PFO: [7]
Hl-NAIQx-(95:5)/Ca/Al)
(Reprinted with permission
from Ref. [21]. Copyright
2015 American Chemical
Society)
5 Structural Control of Fluorescent Helicates for Improved Circularly Polarized. . .
105