Structural diversity and electronic properties of Cu2SnX3(X=S, Se): A fir

Abstract

The ternary semiconductors Cu2SnX3 (X=S, Se) are found frequently as secondary phases in synthesized Cu2ZnSnS4 and Cu2ZnSnSe4 samples, but previous reports on their crystal structures and electronic band gaps are conflicting. Here we report their structural and electronic properties as calculated using a first-principles approach. We find that: (i) the diverse range of crystal structures such as the monoclinic, cubic and tetragonal phases can all be derived from the zinc-blende structure with tetrahedral coordination. (ii) The energy stability of different structures is determined primarily by the local cation coordination around anions, which can be explained by a generalized valence octet rule. Structures with only Cu3Sn and Cu2Sn2 clusters around the anions have low and nearly degenerate energies, which makes Cu and Sn partially disordered in the cation sublattice. (iii) The direct band gaps of the low energy compounds Cu2SnS3 and Cu2SnSe3 should be in the range of 0.8-0.9 eV and 0.4 eV respectively, and are weakly dependent on the long-range structural order. A direct analogy is drawn with the ordered vacancy compounds found in the Cu(In, Ga)Se2 (CIGS) solar cell absorbers.

Silver-Doped Cu2SnS3Absorber Layers for Solar Cells Application

“…CTS consists of two motifs, Cu 2 Sn 2 and Cu 3 Sn 1 , periodically arranged and tetrahedrally bound to sulfur atoms [10]. Long range order of the motifs leads to the monoclinic structure and disorder to the cubic structure [11].…”

Microstructure of Cu2S nanoprecipitates and its effect on electrical and thermal properties in thermoelectric Cu2Zn0.2Sn0.8S3 ceramics

“…19,20 In fact, it is difficult to obtain pure phase in the Cu-Zn-Sn-S system, because the crystalline phases, including CuS, Cu 2-x S, Cu 2 S, ZnS, SnS, SnS 2 and Cu 3 SnS 4 , have similar lattice structures and formation energies as CTS and CZTS. And it is also very difficult to investigate these impurity phases by conventional X-ray diffraction (XRD) 21 and Raman techniques 22 due to the high similarity of crystal structures and local structures, especially when these structures or phases are reduced to nanometer scale. Though high-resolution transmission electron microscopy (HRTEM) techniques have tremendous advantages on the characterization of these nanostructures in the Cu-Zn-Sn-S system, detailed HRTEM investigations of the Cu-Zn-Sn-S materials were rarely reported.…”

Структурные, оптические и электрические свойства тонких пленок Cu-=SUB=-2-=/SUB=-SnS-=SUB=-3-=/SUB=-, полученных золь-гель-методом

“…Ширина запрещенной зоны экс-периментально получаемых тонких пленок CTS, отве-чающая прямым оптическим переходам, расположена в приемлемом для фотопреобразователей диапазоне: E g = 0.95−1.35 eV [1]. Материалу свойствен высокий коэффициент поглощения α > 10 6 m −1 [2,3], что спо-собствует полному поглощению света в тонких слоях ∼ 1−2 nm.…”