Preparation Of Polymer Nanoparticles And A Primary Study On Light-emitting Diodes

Preparation and the size-dependence of organic nanoparticles are not investigated as well as those of inorganic quantum dots by far. In this thesis, using a low molecular weight polymer TPA-PPV and a high molecular weight polymer PVK as the model compounds, a series of highly monodisperse nanoparticles with controlled size and shape had been prepared by reprecipitation method and a new method respectively. Further ,their optical size-dependent properties were studied by means of UV-visible absorption and photoluminescence spectra. Also, PVK nanoparticles self-assembled in line and array were studied. At last, polymer nanoparticles used in novel nano-optoelectronic devices were explored. The optical size effects exhibited by polymer nanoparticles maybe proved useful in the future luminescence applications, and in the study of the fundamental process connecting both of these more conventional classes of materials.1. TPA-PPV (M_W of 3000-4000 g/mol) is a good kind of polymeric light-emitting diodes (PLEDS) material and has a high photoluminescent (PL) quantum yield, we prepared a series of TPA-PPV nanoparticles with diameters ranging from 20 to 100 nm by reprecipitation method. It was found that UV-visible absorption and photoluminescence spectra of the TPA-PPV nanoparticles all exhibit blue-shift respectively at about 400nm and 500nm with decreasing nanoparticles size. The mechanism of size effects is discussed and the results show that the nanoparticals have great potential in novel nano-optoelectronic devices.2. Highly monodisperse, chemical pure, PVK ( M_w of 1.1× 10~6 g/mol) nanospheres with a range of sphere sizes from 120 to 1000 nm were fabricated through a novel method. It is found that at the same concentration the finally prepared PVK nanosphere sizes decrease from 400 to 160 nm when the temperature increase from 278 to 328 K, which are completely opposite to the reprecipitation method and miniemulsions process. The Uv-visible absorption of the PVK nanospheres displays size-dependent effect, that is, the absorption peaks evolve to the low-energy side withincrease in spheres size. The mechanisms were researched in the PVK nanospheres self-assemble process.3. Fabricated polymer light-emitting diodes(PLED) using TPA-PPV thin film as luminescent materials, and fabricated polymer nanoparticles light-emitting diodes using TPA-PPV nanoparticles film as luminescent materials. The devices structure are ITO/TPA-PPV (38 nm)/ TNSC25 nm)/ Alq3(30 nm)/Al and ITO/PDAC/TPA-PPV nanoparticles film/BCP (20 nm) /Akfc (30 nm) /Al respectively. The devices performance were studied and invalidation of the devices were explained.