Synthesis of phosphors by wet-chemical reaction method and their application to electroluminescence device

Abstract

In this thesis, various sized phosphor materials were synthesized using wet-chemical reaction method. At first, ZnS-based nanocrystals (NCs) were synthesized using chemical co-precipitation method and investigated its luminescence properties. To enhanced photoluminescence of the synthesized ZnS-based NCs passivation was attempted by using polyacrylic acid (PAA). Furthermore, novel white-emitting ZnS-based NCs were synthesized successfully by doping co-activators such as, Cu and Mn ions and it was found that the white emission of the ZnS:Cu,Cl,Mn NCs can be controlled by energy transfer from Cu to Mn2+ ion. The chemical co-precipitation synthesis method can be controlled the concentration of co-activators in ZnS host lattice easily compared to solid-state reaction method. The synthesized powder typed-ZnS NCs were used as emitting layer for EL device and their electroluminescence properties was investigated. For the extension of wet-chemical synthesis method to synthesis of oxide-based phosphor materials for white LED application, in this thesis, a novel various color-emitting Na2-xAl2-xSixO4:Eu2+ (0 ≤ x ≤ 1) phosphors and yellow-emitting Na3K(Si1-xAlx)8O16±δ:Eu2+ (0.44 ≤ x ≤ 0.60) phosphor were synthesized by using sol-gel method based on the hydrolysis of tetraorthosilicate (TEOS). In our experiment, it was very difficult to synthesize the complicated composition of phosphors such as Na2-xAl2-xSixO4:Eu2+, Na3K(Si1-xAlx)8O16±δ:Eu2+ phosphors through conven-tional solid-state reaction method; however, the Na2-xAl2-xSixO4:Eu2+, Na3K(Si1-xAlx)8O16±δ:Eu2+ phosphors was successfully synthesized by using wet chemical reaction method. The white LEDs combining near-UV LEDs with these phosphors were fabricated and their luminescent properties were investigated.

In chapter 3, Color changeable ZnS based-NCs with various co-activator, such as Cu, Cl, Mn, Fe, were synthesized by solution reaction method successfully. The synthesized ZnS based-NCs showed ~ 3 nm of crystall...