Synthesis Of Environment Friendly Core/Shell And Doped Semiconductor Quantumdots And Their WLEDs Utilization

The evolution of environment-friendly, long PL lifetime and high luminous efficiency QDs with broadband emission spectra is greatly desirable for use as color converters in solid-state lighting. Synthesis and characterization of environment-friendly core/shell and doped semiconductor quantum dots have been the focus of this work due to their fascinating properties for different application such as white light emitting diodes,biological imaging and others. These core/shell and doped quantum dots were synthesized by using environment friendly precursors. This makes the quantum dots relevance for practical real world industrial applications.In here primarily, quaternary CuInZnS (CIZS) and CIZS/ZnS QDs were synthesized by using commercially available,low toxic precursors CuI,In(Ac)3 and Zn(Ac)2, via a facile two-step process based on one-pot route, which is a flexible and an efficient method. The coating of ZnS shell would lead to improving the optical properties of the quantum dots. The results show that the absorption peak of CIZS/ZnS core/shell QDs exhibits blue-shifting, and the PL emission wavelength move to a higher energyas compared to the core CIZS QDs. The prepared core/shell CIZS/ZnS QDs also exhibit an increase in PL emission spectra intensity. The time-resolved spectra illustrate that the calculated average PL decay lifetime for CIZS QDs is 257.3 ns, but the CIZS/ZnS core/shell QDs is prolonged to 411.6 ns by the efficient surface passivation of ZnS shell. The CIZS/ZnS QDs with yellow emission were used to compose white light emitting diodes (WLED) on blue LED chip. The WLED had a Ra of 80, Tc of 4793 K, and CIE coordinates of (0.346, 0.321) under 20 mA current,and had a bright warm white emission, which indicated the promising potential of the CIZS/ZnS QDs in the optoelectronics.Secondly, Mn doped CIZS and CIZS/ZnS QDs were synthesized simply through adding Mn(Ac)2, and varying the reaction time from the above synthesis route. The resulting d-dotes show the effective incorporation of Mn2+ ions into CIZS host lattice and a high crystallinity, a longer PL decay lifetime and redshifted PL emission spectra peak, as compared to the corresponding pure quantum dots mentioned above. Hence,the core/shell Mn: CIZS/ZnS QDs have bright yellow emission of the PL emission peaks of 580 nm and high PL decay lifetime of 6281.4 ns, and the core Mn: CIZS PL emission peaks at 654 nm and PL decay lifetime of 2525.6 ns, respectively.Finally, the manganese doped zinc selenide quantum dots (Mn: ZnSe d-dots) were synthesized by means of highly reactive Se-octadencene suspension precursor, which have high monodisperse, excellent optical quality, and pure dopant emission, The experimental results reveal that the as-prepared Mn: ZnSe d-dots with zinc-blende structure have an average size about 3.9 nm and the calculated lattice distance is 0.32 nm at (2 0 0) lattice plane. And also shows the optical/absorption and PL spectra band are red shifted as the size of the nanocrystal increase. Additionally, geometrical structures of (ZnSe)n, n= 3x, (x = 1 - 4) and (MnxZn2xSe3x), (x = 1 - 4) clusters were calculated using density functional theory (DFT). The optical/absorption spectra,Raman spectra, HOMO-LUMO gap energy, and binding energy of each cluster were calculated. The calculated results show when the manganese atoms were doped in ZnSe clusters red shift of the optical/absorption spectra band is observed, and the HOMO-LUMO gap energy value is decreased.In general, this work will open lots of opportunities for synthesis environment friendly core/shell and doped semiconductors quantum dots for WLEDs applications.