Layered (Bi1-xInx) 2 Te3 -In2 Te3 (x = 0.075) composites of pronounced anisotropy in structure and thermoelectric properties were produced by zone melting and subsequent coherent precipitation of In2 Te3 from a (Bi1-xInx) 2 Te3 (x > 0.075) matrix. Employing solid state phase transformation, the Bi2 Te3 /In2 Te3 interface density was tuned by modifying the driving force for In2 Te3 precipitation. The structure-property relationship in this strongly anisotropic material is characterized thoroughly and systematically for the first time. Unexpectedly, with increasing Bi2 Te3 /In2 Te3 interface density, an increase in electrical conductivity and a decrease in the absolute Seebeck coefficient were found. This is likely to be due to electron accumulation layers at the Bi2 Te3 /In2 Te3 interfaces and the interplay of bipolar transport in Bi2 Te3. Significantly improved thermoelectric properties of Bi2 Te3 -In2 Te3 composites as compared to the single phase (Bi1-xInx) 2 Te3 solid solution are obtained. © The Author(s) 2017.

Cu2ZnSnSe4 thin-films for photovoltaic applications are investigated using combined atom probe tomography and ab initio density functional theory. The atom probe studies reveal nano-sized grains of Cu2Zn5SnSe8 and Cu2Zn6SnSe9 composition, which cannot be assigned to any known phase reported in the literature. Both phases are considered to be metastable, as density functional theory calculations yield positive energy differences with respect to the decomposition into Cu2ZnSnSe4 and ZnSe. Among the conceivable crystal structures for both phases, a distorted zinc-blende structure shows the lowest energy, which is a few tens of meV below the energy of a wurtzite structure. A band gap of 1.1 eV is calculated for both the Cu2Zn5SnSe8 and Cu2Zn6SnSe9 phases. Possible effects of these phases on solar cell performance are discussed. © 2015 AIP Publishing LLC.