Enhanced photo-luminescence from highly interconnected porous QD/BCP nanocomposites formed via controlled spinodal decomposition

Abstract

In this thesis, highly interconnected porous QD/BCP nanocomposites was demonstrated in order to achieve enhancement of photo-luminescence. The QD/BCP nanocomposites with strong emission has the potential to be used in photo-luminescence devices of display application with simple and fast fabrication method. Block copolymer (PS-b-P4VP) forms highly inteconnected porous structure via the mechanism of spinodal decomposition during the evaporation of solution when dimethylformamide (DMF) and water exist together. Here, the composite film was fabricated by simple spin-casting with the humidity control. The porous QD/BCP nanocomposites effectively enhanced absorption of quantum dots inside block copolymer matrix by the multiple light scattering and trapping effect inside film, resulting in enhanced photo-luminescence. A one of current obstacles towards high-performance QD devices is reducing energy transfer nearby quantum dots, which is called Fluorescence Resonance Energy Transfer (FRET). The quantum dot was functionalized with hydroxyl ligand for the conjugation with BCP. The hydrogen bonding between hydroxyl ligand and nitrogen atom of P4VP block was successfully established. Consequentially, by the microphase separation properties of block copolymer, the dispersion of quantum dots was induced, which indicated reduced Fluorescence Resonance Energy Transfer (FRET) effect. With the synergetic effects of light scattering from porous structure and dispersion of quantum dots from conjugation effect, the 21-fold enhancement in photo-luminescence was achieved compared to reference quantum dot film.