White Emitting ZnS Nanocrystals: Synthesis and Spectrum Characterization

Spherical organic-bonded ZnS nanocrystals with 4.0± 0.2 nm in diameter are synthesized by a liquid-solid-solution method. The photoluminescence spectrum of sample (S^2-/Zn²⁺ =1.0) shows a strong white emission with a peak at 490 nm and ~ 170 nm full widths at half maximum. By Gauss fitting, the white emission is attributed to the overlap of a blue emission and a green-yellow emission, originating from electronic transitions from internal S^2- vacancies level to valence band and to the internal Zn²⁺ vacancy level, respectively. After sealingZnS nanocrystals onto InGaN chips, the device shows CIE coordinates of (0.29,0.30), which indicates their potential applications for white light emitting diodes.