Fabrication of high color rendering index white LED using Cd-free wavelength tunable Zn doped CuInS_2 nanocrystals

Abstract

Highly luminescent Cd-free Zn doped CuInS(2) nanocrystals (ZCIS NCs) were synthesized, and their properties were evaluated using X-ray diffraction, Raman, UV, and photoluminescence. The crystal structure of the ZCIS NCs was similar to the zinc blende, and the lattice constant decreased with increasing Zn concentration. By incorporation of Zn, the emission wavelength was tuned from 536 to 637 nm with concomitant enhancement of the quantum yield up to 45%. A white light emitting diodes, integrating dual ZCIS NCs (λ(em) = 567, and 617 nm) and a 460 nm InGaN LED, exhibited a high color rendering index of 84.1 with a warm color temperature of 4256.2K. The CIE-1931 chromaticity coordinates were slightly shifted from (0.3626, 0.3378) at 20 mA to (0.3480, 0.3206) at 50 mA.

Full‐visible spectrum emitting Zn–In–S:Cu/ZnS nanocrystals based on varying Cu concentrations and its application in white LEDs

“…Figure A,B reveal the UV/vis absorption and emission spectra of undoped and Cu‐doped Zn–In–S NCs synthesized by a conventional hot injection method under the same reaction condition. Both Zn–In–S NCs and Zn–In–S:Cu d‐NCs show poorly resolved excitonic absorption feature, which is characteristic for ternary and quaternary alloyed semiconductor nanocrystals, coming from the irregular composition distribution among different NCs and/or intra‐bandgap states . However, the introduction of 10% Cu into Zn–In–S NCs markedly increased the absorption between 370 nm and 500 nm, which enables them to match well with the near UV‐blue InGaN LED chips.…”

Cadmium- and zinc-alloyed Cu–In–S nanocrystals and their optical properties

“…Although CIS is a good material for near-infrared quantum dots (QDs) and photovoltaic devices, applications of CIS NCs have likely been hindered by their limited quality. A number of ongoing research efforts are focused on improving CIS NC quality (Bao et al 2011; Chung et al 2012; Deng et al 2012; Feng et al 2011; Li et al 2011; Li et al 2009; Wang et al 2010; Wang et al 2012; Xie et al 2009; Zhong et al 2008; Zhang et al 2011a; Zhang et al 2011b). …”

“…Several laboratories have reported Zn-CIS NCs with tunable band gaps covering the whole visible spectrum. Green-to-red visible and near infrared QDs based on Zn-CIS have been developed (Zhang et al 2011a; Chung et al 2012; Feng et al 2011; Zhang et al 2011b). Cd alloyed CIS NCs, as an important class of materials for solar cells and photocatalysis, also demonstrate a capacity for band gap/size/structure tuning (Wang et al 2010).…”

Characterization of surface modified ZnCuInS2 nanocrystals and its application to white light-emitting diodes

“…However, the high toxicity of cadmium limits the application of II-VI compound NCs. Therefore, nontoxic multinary semiconductor compounds, such as CuInS 2 (CIS), CuInSe 2 , AgInS 2 , and ZnCuInS 2 (ZCIS) were considered as promising alternatives to II-VI compound NCs; in particular, CIS and ZCIS can emit a similar color range to that of CdSe [7].…”