| Organic light-emitting diodes (OLEDs) have attracted considerable attention owing to their potential applications in large-area full-color flat-panel displays. Since the breakthrough by Kodak in 1987, great progresses have been made in the field of electroluminescence, both in scientific research and practical application. The promising technologies are continuously developing and the novel materials are endlessly designed, synthesized and improved in order to fulfill the requirements of the application.The small organic molecules are easy to crystallize and their film-forming ability is not good. By dispersing small organic molecular into the polymer matrix, the crystallization and aggregation of small organic molecules could also be controlled effectively, which can prohibit fluorescene quenching resulting from strong intermolecularπ-πinteraction. At the same time, because polymers are commonly good hole-transporting materials, the hole-mobility could be improved by inducing polymer, which can enhance the efficiency of light-emitting diodes. Moreover, the luminance and efficiency of light-emitting device could be further improved by energy transfer or the forming of the electromer of polymeric hosts doped with organic small molecular. The application of polymeric hosts doped with small organic molecules is also an important method in the field of organic light-emitting device.Here we focused on the photoluminescent and electroluminescent properties of novel molecular materials blended in PVK. The energy transfer and the luminescent properties of four novel intramolecular charge-transfer donor-π-acceptor (D-π-A) molecules (CKD,TKD,PKD,NKD) doped in PVK were investigated by analyzing UV-vis absorption spectra, photoluminescent excitation (PLE) spectra and photoluminescent (PL) spectra. The electroluminescence (EL) properties of the blend system were investigated by fabricating the devices ITO/PEDOT/PVK:D-π-A X wt.-%/Alq3/Al. The results demonstrate that the band gap of D-π-A molecules can be adjusted by changing the donor moieties of D-π-A molecule. Meanwhile the fluorescence quantum efficiency varies significantly with the stereostructure of donor moieties of D-π-A molecules. Both the PL and EL spectra show that the energy transfer between PVK and D-π-A molecules occurs effectively. The emissive performance of the blend system could be improved by changing the dopant ratio of PVK and D-π-A molecules. The power efficiency of the device is up to 1.75cd/A at 729.1cd m-2, when the ratio of the dopant concentration between PVK and TKD is 6.0wt.-%. A white organic light-emitting diode (WOLED) was fabricated with the emitting layer of doping PVK and fluorene-centerd ethynylene-linked carbazole oligomers(L-Z-251) and Alq3 as the electron transport layer. The structure is ITO/PEDOT/ PVK :L-Z-251(1:1)/Alq3/Al. Because of the emission from the electroplex of PVK: L-Z-251 and the excimer of L-Z-251, the whole device emitted good white light. The results show, when the blending ratio was 1:1, the white light is pure with CIE coordinates of (0.32, 0.34) for single layer device and (0.30, 0.33) for bi-layer device. For the bi-layer device, the maximum of brightness is 401.9cd/m2 and the maximum of current efficiency is 0.10cd/A.
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