Hot-injection synthesis of monodispersed Cu2ZnSn(SxSe1−x)4 nanocrystals: tunable composition and optical properties

Abstract

In this study, we demonstrate that Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals with a tunable bandgap could be synthesized by a ''hot-injection'' protocol. In this protocol, metal stearates dissolved in oleylamine were injected into a hot solution of anion precursors in 1-octadecene (ODE) at a given reaction temperature. ODE, which is a low-cost, low-hazard, and air-stable liquid, was used as the solvent. Oleylamine was chosen as both the reagent to activate the precursors and as the capping agent for the nanocrystals. The composition of the Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals could be adjusted across the x range from 0 to 1 by varying the S/Se reactant ratio. The lattice parameters (a and c) measured from X-ray diffraction patterns decreased linearly with increasing Se content. This trend was consistent with Vegard's law, which confirmed the formation of homogeneous Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals. The A 1 symmetry modes of the Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals seen by Raman spectroscopy gradually shifted with decreasing x (S content) to the lower frequency side and completely disappeared when x ¼ 0. The absorption spectra of the Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals revealed that the bandgaps of the nanocrystals could be adjusted over the range 1.0-1.5 eV by decreasing the S content. The relatively small value for the bowing parameter indicated that the synthesized Cu 2 ZnSn(S x Se 1Àx ) 4 nanocrystals had good miscibility.

Voltammetry investigation on copper zinc tin sulphide /selenide (CZTSxSe1-x) alloy nanocrystals: Estimation of composition dependent band edge parameters

“…The CZTS sample (x ¼1) shows typical bands at 291 cm À 1 , 337.5 cm À 1 and 368 cm À 1 . These are attributed to the kesterite phase of CZTS [40][41][42]. In case of CZTSe (x ¼ 0), the bands observed at 165 cm À 1 , 189 cm À 1 and 235 cm À 1 are again attributed to the kesterite phase of CZTSe [40,41].…”

Electronic structure and photocatalytic activity of wurtzite Cu–Ga–S nanocrystals and their Zn substitution

“…45 The peak in Figure 2d, located at 161.7 eV, can be assigned to the S 2p binding energy with a valence of S 2− . Because copper, gallium, and zinc share the lattice sites in the wurtzite structure, the relative compositions of wurtzite Cu−Ga−S and Zn-substituted Cu−Ga−S ternary nanocrystals can widely vary.…”

“…42,43 Based on the results, it can be concluded that the Cu−Ga−S nanocrystals are composed of metastable defected wurtzite rather than formation of the thermodynamically preferred chalcopyrite phase. 45,46 In fact, 1-dodecanethiol and oleylamine are strong coordinating ligands and can bind to the surface of Cu−Ga−S nanocrystals and consequently decrease the surface energy for stabilizing the metastable wurtzite phase. [43][44][45][46] Such a 'ligand effect' as a structure-directing agent has been observed also in experimental studies of wurtzite CuInS 2 nanocrystal synthesis.…”

“…45,46 In fact, 1-dodecanethiol and oleylamine are strong coordinating ligands and can bind to the surface of Cu−Ga−S nanocrystals and consequently decrease the surface energy for stabilizing the metastable wurtzite phase. [43][44][45][46] Such a 'ligand effect' as a structure-directing agent has been observed also in experimental studies of wurtzite CuInS 2 nanocrystal synthesis. To prove the necessity of 1-dodecanethiol in the synthesis as a capping ligand and sulfur source, CuGa 5 S 8 was prepared employing solid sulfur dissolved in oleylamine as a sulfur source instead of 1-dodecanethiol under the same condition.…”

Improved size-tunable synthesis of monodisperse NiO nanoparticles

“…Zhang et al [18] found that CdS NCs were controllably synthesized by adjusting reaction conditions through a hot-injection method. Ou et al [19] reported hot-injection method for synthesizing Cu 2 ZnSn(S X Se 1-X ) 4 nanocrystals. This paper describes an optimized reaction system for preparing size-tunable NiO nanoparticles with high-level of monodispersity [20].…”