Study On Luminescent Properties Of Organic MEH - PPV And Inorganic Nanocrystalline Composites

Organic light-emitting devices (OLEDs) are widely used in the field of illumination and flat panel display based on total solidification, wide spectrum, high brightness, wide viewing angle and other advantages. However, with the deep research of polymer luminescence property, there are many problems demanding prompt solution, for instance, how to further improve the luminous efficiency, reduce the driving voltage, optimize the light purity, enhance the device stability and extend device life.When compositing inorganic nano-crystals and organic polymer to prepare emitting layer, we can combine the good workability and easy modificability of polymer with high electron mobility and stable physical/chemical properties of inorganic materials to fabricate large area display with long life, high efficiency, high stability, low cost and good workability. It is also possible to realize the carriers’energy transfer of composite film by adjusting the grain diameter, doping ratio and driving voltage to control the wavelength.In our work, ZnO nanoparticles synthesized by using sol-gel method have monocrystal hexagonal wurtzite structure. Then organic-inorganic composite luminescent devices which have ITO/PEDOT:PSS/MEH-PPV:ZnO/Al/Ag sandwich structure were prepared by utilizing MEH-PPV doped with ZnO nanoparticles as emitting layer. Furthermore, we have also investigated the EL property of the devices. The experiment results indicated that the doping ZnO could effectively reduce electron injection barrier and balance two carriers to improve recombination efficiency and lower turn-on voltage. The doping ratio of ZnO had effect on the luminous efficiency and wavelength of the OLEDs. The highest luminous efficiency could be achieved when the doping ratio is up to 10%, and with the increase of doping proportion, the main peak of spectrum occurred obvious blue shift and the migration length is 18nm. Furthermore, the doping only affected the shift of the main peak located in 585nm.In this paper, then core-shell structure CdSe/ZnS QDs and MEH-PPV: CdSe/ZnS composite materials were prepared. We investigated the PL prope rty and the effect of CdSe/ZnS QDs on emission intensity and wavelength of composite devices. The experiment results indicated that composite mater ials have the main PL peak of MEH-PPV. However, it has apparent blue s hift in comparison with MEH-PPV, and the biggest shift can reach 25nm when doping ratio is 5:10. With the increase of doping ratio, the luminous intensity shows the trend of first increased and then decreased. The strong est intensity appears at the 3:10 doping ratio.