Colloidal semiconductor quantum dots (QDs) are frequently called ''artificial atoms'', and are undoubtedly one of the prominent light sources. In a colloidal QD, the electronic motion is confined in all spatial directions to give a discrete energy level. Hence, the precise size control of the QDs leads to highly efficient light emission with a narrow full width at half maximum (FWHM). As well as visible-light sources, light emitters in the ultraviolet (UV) region have recently been attracting research attention owing to their potential optics applications, including compact UV lasers, laser diodes, convenient light sources suitable for white-light illumination and biomedical tagging, and photodetectors. [1] For example, the shortening of the emission wavelength means that the light is focused more sharply, thus leading to its application in highdensity information storage devices such as optical and magnetic discs. A near-UV laser is also suitable for medical care of heat-labile areas in the human body, for example the cornea, because, unlike IR light, such a short wavelength does not produce heat radiation. However, current rapid developments of these devices have been entirely focused on enhancing the solid-state emitters. Unlike such semiconductor compounds, soft materials, for example organic phosphor molecules, provide many advantages: mechanical flexibility, light weight, excellent processability, compactness, and cost
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