Predominated Thermodynamically Controlled Reactions for Suppressing Cross Nucleations in Formation of Multinary Substituted Tetrahedrite Nanocrystals

Precursor-Mediated Colloidal Synthesis of Compositionally Tunable Cu-Sb-M-S (M = Zn, Co, and Ni) Nanocrystals and Their Transport Properties

The solution-based colloidal synthesis of multinary semiconductor compositions has allowed the design of new inorganic materials impacting a large variety of applications. Yet there are certain compositions that have remained elusive-particularly quaternary structures of transition metal-based (e.g., Co, Zn, Ni, Fe, Mn, and Cr) copper antimony chalcogenides. These are widely sought for tuning the electrical and thermal conductivity as a function of the size, composition, and crystal phase. In this work, a facile hot injection approach for the synthesis of three different tetrahedrite-substituted nanocrystals (NCs) (Cu₁₀Zn₂Sb₄S₁₃, Cu₁₀Co₂Sb₄S₁₃, and Cu₁₀Ni_1.5Sb₄S₁₃) and their growth mechanisms are investigated. We reveal that the interplay between the Zn, Ni, and Co precursors on the basis of thiophilicity is key to obtaining pure phase NCs with controlled size and shape. While all of the synthesized crystal phases display outstanding low thermal conductivity, the Cu_10.5Sb₄Ni_1.5S₁₃ system shows the most enhanced electrical conductivity compared to Cu₁₀Zn₂Sb₄S₁₃ and Cu₁₀Co₂Sb₄S₁₃. This study highlights an effective synthesis strategy for the growth of complex quaternary nanocrystals and their high potential for application in thermoelectrics.

Equilibriums in Formation of Lead Halide Perovskite Nanocrystals

Physical insights related to ion equilibrium involved in the synthesis of lead halide perovskite nanocrystals remain key parameters for regulating the phase stability and luminescence intensity of these emerging materials. These have been extensively studied since the development of these nanocrystals, and different reaction processes controlling the formation of CsPbX₃ nanocrystals are largely understood. However, growth kinetics related to the formation of these nanocrystals have not been established yet. Hence, more fundamental understanding of the formation processes of these nanocrystals is urgently required. Keeping these in mind and emphasizing the most widely studied nanocrystals of CsPbBr₃, different equilibrium processes involved in their synthesis for phase and composition variations are summarized and discussed in this Perspective. In addition, implementations of these findings for shape modulations by growth are discussed, and several new directions of research for understanding more fundamental insights are also presented.

Scalable synthesis of Cu-Sb-S phases from reactive melts of metal xanthates and effect of cationic manipulation on structural and optical properties

We report a simple, economical and low temperature route for phase-pure synthesis of two distinct phases of Cu–Sb–S, chalcostibite (CuSbS₂) and tetrahedrite (Cu₁₂Sb₄S₁₃) nanostructures. Both compounds were prepared by the decomposition of a mixture of bis(O-ethylxanthato)copper(II) and tris(O-ethylxanthato)antimony(III), without the use of solvent or capping ligands. By tuning the molar ratio of copper and antimony xanthates, single-phases of either chalcostibite or tetrahedrite were obtained. The tetrahedrite phase exists in a cubic structure, where the Cu and Sb atoms are present in different coordination environments, and tuning of band gap  energy was investigated by the incorporation of multivalent cationic dopants, i.e. by the formation of Zn-doped tetrahedrites Cu_12−xZn_xSb₄S₁₃ (x = 0.25, 0.5, 0.75, 1, 1.2 and 1.5) and the Bi-doped tetrahedrites Cu₁₂Sb_4−xBi_xS₁₃ (x = 0.08, 0.15, 0.25, 0.32, 0.4 and 0.5). Powder  X-ray diffraction (p-XRD) confirms single-phase of cubic tetrahedrite structures for both of the doped series. The only exception was for Cu₁₂Sb_4−xBi_xS₁₃ with x = 0.5, which showed a secondary phase, implying that this value is above the solubility limit of Bi in Cu₁₂Sb₄S₁₃ (12%). A linear increase in the lattice parameter a in both Zn- and Bi-doped tetrahedrite samples was observed with increasing dopant concentration. The estimated elemental compositions from EDX data are in line with the stoichiometric ratio expected for the compounds formed. The morphologies of samples were investigated using SEM and TEM, revealing the formation of smaller particle sizes upon  incorporation of  Zn. Incorporation of Zn or Bi into Cu₁₂Sb₄S₁₃ led to an increase in band gap energy. The estimated band gap energies of Cu_12−xZn_xSb₄S₁₃ films ranges from 1.49 to 1.6 eV, while the band gaps of Cu₁₂Sb_4−xBi_xS₁₃ films increases from 1.49 to 1.72 eV with increasing x.

Multinary copper-based chalcogenide nanocrystal systems from the perspective of device applications

Multinary chalcogenide semiconductor nanocrystals are a unique class of materials as they offer flexibility in composition, structure, and morphology for controlled band gap and optical properties. They offer a vast selection of materials for energy conversion, storage, and harvesting applications. Among the multinary chalcogenides, Cu-based compounds are the most attractive in terms of sustainability as many of them consist of earth-abundant elements. There has been immense progress in the field of Cu-based chalcogenides for device applications in the recent years. This paper reviews the state of the art synthetic strategies and application of multinary Cu-chalcogenide nanocrystals in photovoltaics, photocatalysis, light emitting diodes, supercapacitors, and luminescent solar concentrators. This includes the synthesis of ternary, quaternary, and quinary Cu-chalcogenide nanocrystals. The review also highlights some emerging experimental and computational characterization approaches for multinary Cu-chalcogenide semiconductor nanocrystals. It discusses the use of different multinary Cu-chalcogenide compounds, achievements in device performance, and the recent progress made with multinary Cu-chalcogenide nanocrystals in various energy conversion and energy storage devices. The review concludes with an outlook on some emerging and future device applications for multinary Cu-chalcogenides, such as scalable luminescent solar concentrators and wearable biomedical electronics.