A backlight unit including a light source formed to provide primary light; a quantum dot phosphor excited by the primary light provided from the light source to emit secondary light having a wavelength different from a wavelength of the primary light and disposed to be spaced apart from the light source; an optical agent absorbing light having a specific wavelength from the primary light provided by the light source and the secondary light emitted from the quantum dot phosphor; and a matrix configured to support the quantum dot phosphor and the optical agent. Further, the quantum dot phosphor and the optical agent are randomly mixed in the matrix; and the quantum dot phosphor, the optical agent, and the matrix form a composite.