CuInS2/ZnS quantum dots (CIS/ZnS QDs) have wide full width at half maximum (FWHM) due to the emission mechanism caused by point defect. This property make CIS/ZnS QD suitable for application in solid-state lighting (SSL). However, it was mentioned in the literature that white light-emitting diode (WLED) using CIS/ZnS QDs as the conversion material has low color rendering (CRI is less than 70), and one of the methods to increase the color rendering is increasing the range of the emission spectrum. CIS QDs belong to the point defects emission mechanism, and non-stoichiometric chemical substitution can create a large number of point defects. Therefore, in this study, CIS/ZnS QDs were first prepared by traditional thermal injection method, and (ZnCuIn)S2 (ZCIS) QDs were prepared by adding Zn2+, Cu+ and In3+ ions at the same time. The results show that the emission wavelengths, relative quantum yield (QY), FWHM and surface morphology of CIS/ZnS QDs are 535 nm, 83 % and 72 nm and tetrahedron, respectively. On the other hand, those are 540 nm, 32 %, 118 nm and spherical shape for ZCIS QDs. Moreover, the diffraction peaks are between chalcopyrite and zinc blende structure meaning that the samples have alloyed structure. The CIE coordinates and color rendering index (CRI) of CIS/ZnS-based WLED are (0.35, 0.31) and 68. The CRI can be improved from 68 to 90 for ZCIS-based WLED. From the above results, it is known that ZCIS QDs with a FWHM up to 118 nm can be prepared by non-stoichiometric chemical substitution diffusion method. The wide FWHM shows positive effect to increase CRI value of ZCIS-based WLED and this advantage helps ZCIS QDs to be more widely used in solid-state lighting applications.
Cesium lead halide perovskite quantum dots (PQD) have potential for development in display backlights due to its high color purity, high luminous efficiency, wavelength tunability, and easily production. However, its poor stability is the biggest obstacle in practical application. In this study, we use post-treated by controlling the ratios between PQD and ligands (oleylamine and oleic acid are mixed in a volume ratio of 1:1) solution to improve quantum yield (QY). The result shows that the emission wavelength and QY of as-prepared CsPbBr3 QDs is 514 nm and 84 %, respectively. It was found that the QY of QDs increases with increasing the concentrations of ligands. The relative QY of the post-treated PQDs can be increased from 84 to 212 %, which depends on the ligand concentrations. After aging for one month, the QY of the as-prepared PQD reduces from 84 to 73 %, while no obviously QY decay can be observed for post-treated samples. The results show that post treatment by adding a ligand can improve QY and stability of PQDs effectively.