E. Gondek et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 610–613
613
method at the B3LYP/6-31+G(d,p) level of theory. The absorption
and fluorescence processes appear to be weakly dependent on the
position of side methyl radicals exhibiting the first absorption band
(000 transition) in the region of 386–401 nm and the fluorescence
band (000 transition) in the range of 412–425 nm. The quantum-
chemical analysis based on DFT/TDDFT/PCM with B3LYP xc-poten-
tial quite accurately predicts the excitation energies. The
absorption–emission cycle is accompanied by relatively small
Stokes shift (17–40 nm) what may be an evidence that the solute
relaxation in the excited state is indeed weak for all the DPP dyes.
We demonstrate also the OLEDs being constructed according to
the scheme with the polymer PVK layer doped by DPP fluorescence
emitters. All the devices exhibit deep blue electroluminescence with
the emission maximum being rather weakly dependent on the type
of the fluorescent dopant. Based on the electroluminescence spectra
the emission color is characterized by the color coordinates accord-
ing to the CIE(1931) standard. The obtained results show that a ser-
ies of newly synthesized DPP dyes may be considered as perspective
blue fluorescent emitters for electroluminescent applications.
Fig. 3. Luminance-voltage characteristics of the electroluminescence devices with
OLED structure ITO/PEDOT:PSS/PVK:DPP/Ca/Al (DPP ꢃ DPP1-DPP4). The insert
shows schematically the configuration of OLED.
Acknowledgement
The DFT/TDDFT calculations have been carried out in Wrocław
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Evidently, the designed OLEDs emit light of deep blue color, the
most deeper blue emission exhibits DPP1 dye.
Conclusion
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