Synthesis Of ZnSe Nanocrystals And Its Application In Organic Electroluminance Devices

ABSTRACT:In recent years, "nanoscience" has become a new and promising field for researchers. Because of its unique optical and electrical properties, come from the quantum size effect, semiconductor nanocrystals, or quantum dots, have great potential use in thin film devices, such as light-emitting diodes, solar cells, and bio-science. In this thesis, ZnSe nanocrystals and core-shell structure of ZnSe/ZnS nanocrystals were synthesized in aqueous solution. After that, they were doped into the emissive layer, respectively, with electroluminance performance of the devices detected, to study their use in of organic light-emitting devices.Here, water-phase ZnSe nanocrystals and ZnSe/ZnS core-shell nanocrystals were synthesized, respectively, by using mercaotoacetic acid as the stabilizers. Good cubic synthetic crystal of single-core and core-shell structure were confirmed by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-power transmission electron microscopy (TEM) technology. The fluorescence-emission and absorption properties of synthetic ZnSe nanocrystals were studied by varying the reaction environment during their synthesis procedure. The results demonstrated that with a longer reflowing time, the synthesic nanocrystal size would enlarge and both spectrum of photoluminescence (PL) spectra and absorption would be red-shift. When the optimum PH is about 10, the photoluminescence of the nanocrystalline defects weaken. The exepriment showed good stability of the synthesic ZnSe/ZnS nanocrystals.Subsequently, the synthetic ZnSe nanocrystals and the ZnSe/ZnS core-shell nanocrystals were respectively doped into the emissive layer MEH-PPV (poly [2-methoxy-5-(2'-ethylhexyloxy-p-phenylenevinylene)]) of organic light-emitting diaodes (OLEDs). In ZnSe OLEDs, both brightness and efficiency properties reached optimal when the quality ratio of MEH-PPV and ZnSe quantum dots was 1:1. A thin LiF layer was introduced to improve the OLED performance. In ZnSe/ZnS OLEDs, we found that with an increase driving voltage, the EL spectrum would be blue-shift.