Investigation on photometric and photoluminescent properties of Mn2+-doped ZnS quantum dots

Abstract

ZnS and Mn2+-doped ZnS quantum dots (ZnS QDs, ZnS:Mn2+QDs) are prepared by the co-precipitation route at 80oC in basic aqueous solutions. X-ray diffraction (XRD), photoluminescence (PL), photoluminescence excitation (PLE) spectroscopy, and photometric analysis were employed to characterize the samples. The ZnS QDs and ZnS:Mn2+QDs have a zinc-blende structure and a sphere in shape with average particle sizes of about 20 nm. The XRD and PLE analysis results indicate that the Mn2+ ions have been successfully doped into the Zn2+ ion position in the ZnS host lattice. The blue emission peak observed at about 430 nm is due to the ZnS host lattice, and the PL peak that appeared at about 540 nm is due to the energy transfer from the ZnS host lattice to the Mn2+ impurity. The overlap between the ZnS:Mn2+ QDs spectral power and the human eye sensitivity spectra is significantly enhanced with the efficient energy transfer process. The scotopic/photopic (S/P) ratios are proportional to the color correlated temperature (CCT) values. The CIE (x, y) chromaticity coordinates of ZnS QDs and ZnS:Mn2+QDs were also calculated from the tristimulus values X, Y, Z. Photometric and chromatic parameters of ZnS:Mn2+ QDs with VTGA = 1.5 ml are LER = 331 (lm/Wotp), S/P = 1.54, CCT = 4494 K, CRI = 64, CQS = 64 and CIE (x, y) = (0.38; 0.50). Thus, the ZnS:Mn2+ QDs are suitable for developing tune color components in white thin film electroluminescent (TFEL) devices and light-emitting diodes (LEDs) for solid-state lighting applications..