@article{15726, abstract = {{The behavior of alkali atom point defects in polycrystalline CuInSe2 is studied. In this work, three grain boundary models, one coherent twin boundary and two twin boundaries with dislocation cores, are considered. Total energy calculations show that all alkali metals tend to segregate at the grain boundaries. In addition, the segregation of alkali atoms is more pronounced at the grain boundaries with the dislocation cores. The diffusion of alkali metals along and near grain boundaries is studied as well. The results show that the diffusion of alkali atoms in the grain boundary models is faster than within the bulk. In addition, the ion exchange between Na and Rb atoms at the grain boundaries leads to the Rb enrichment at the grain boundaries and the increase of the Na concentration in the bulk. While the effects of Na and Rb point defects on the electronic structure of the grain boundary with the anion-core dislocation are similar, Rb atoms passivate the grain boundary with the cation-core dislocation more effectively than Na. This can explain the further improvement of the solar cell performance after the RbF-postdeposition treatment.}}, author = {{Chugh, Manjusha and Kühne, Thomas and Mirhosseini, S. Hossein}}, issn = {{1944-8244}}, journal = {{ACS Applied Materials & Interfaces}}, pages = {{14821--14829}}, title = {{{Diffusion of Alkali Metals in Polycrystalline CuInSe2 and Their Role in the Passivation of Grain Boundaries}}}, doi = {{10.1021/acsami.9b02158}}, year = {{2019}}, } @article{15725, abstract = {{Adaptive kinetic Monte Carlo simulation (aKMC) is employed to study the dynamics and the diffusion of point defects in the CuInSe2 lattice. The aKMC results show that lighter alkali atoms can diffuse into the CuInSe2 grains, whereas the diffusion of heavier alkali atoms is limited to the Cu-poor region of the absorber. The key difference between the diffusion of lighter and heavier alkali elements is the energy barrier of the ion exchange between alkali interstitial atoms and Cu. For lighter alkali atoms like Na, the interstitial diffusion and the ion-exchange mechanism have comparable energy barriers. Therefore, Na interstitial atoms can diffuse into the grains and replace Cu atoms in the CuInSe2 lattice. In contrast to Na, the ion-exchange mechanism occurs spontaneously for heavier alkali atoms like Rb and the further diffusion of these atoms depends on the availability of Cu vacancies. The outdiffusion of alkali substitutional atoms from the grains results in the formation of Cu vacancies which in turn increases the hole concentration in the absorber. In this respect, Na is more efficient than Rb due to the higher concentration of Na substitutional defects in the CuInSe2 grains.}}, author = {{Kormath Madam Raghupathy, Ramya and Kühne, Thomas and Henkelman, Graeme and Mirhosseini, Hossein}}, issn = {{2513-0390}}, journal = {{Advanced Theory and Simulations}}, title = {{{Alkali Atoms Diffusion Mechanism in CuInSe 2 Explained by Kinetic Monte Carlo Simulations}}}, doi = {{10.1002/adts.201900036}}, year = {{2019}}, } @article{13209, abstract = {{We performed ab initio calculations to study oxygen and hydrogen point defects in the CuInSe2 (CISe) solar-cell material. We found that H interstitial defects (when one H atom is surrounded by four Se atoms) and HCu (when a H atom is replacing a Cu atom) are the most stable defects. Whereas these H substitutional defects remain neutral, H interstitial defects act as donor defects and are detrimental to the cell performance. The incorporation of H2 into the CISe lattice, on the other hand, is harmless to the p-type conductivity. Oxygen atoms tend to either substitute Se atoms in the CISe lattice or form interstitial defects, though the formation of substitutional defects is more favorable. All oxygen point defects have high formation energies, which results in a low concentration of these defects in CISe. However, the presence of oxygen in the system leads to the formation of secondary phases such as In2O3 and InCuO2. In addition to the point defects, we studied the adsorption of H2O molecules on a defect-free surface and a surface with a (2VCu + InCu) defect using the ab initio thermodynamics technique. Our results indicate that the dissociative water adsorption on the CISe surface is energetically unfavorable. Furthermore, in order to obtain a water-free surface, the surface with defects has to be calcined at a higher temperature compared to the defect-free surface.}}, author = {{Sahoo, Sudhir and Kormath Madam Raghupathy, Ramya and Kühne, Thomas and Mirhosseini, Hossein}}, journal = {{J. Phys. Chem. C}}, number = {{37}}, pages = {{21202--21209}}, title = {{{Theoretical Investigation of Interaction of CuInSe2 Absorber Material with Oxygen, Hydrogen, and Water}}}, doi = {{10.1021/acs.jpcc.8b06709}}, volume = {{122}}, year = {{2018}}, } @article{13210, abstract = {{In this work, we investigated ternary chalcogenide semiconductors to identify promising p-type transparent conducting materials (TCMs). High-throughput calculations were employed to find the compounds that satisfies our screening criteria. Our screening strategy was based on the size of band gaps, the values of hole effective masses, and p-type dopability. Our search led to the identification of seven promising compounds (IrSbS, Ba2GeSe4, Ba2SiSe4, Ba(BSe3)2, VCu3S4, NbCu3Se4, and CuBS2) as potential TCM candidates. In addition, branch point energy and optical absorption spectra calculations support our findings. Our results open a new direction for the design and development of p-type TCMs.}}, author = {{Kormath Madam Raghupathy, Ramya and Wiebeler, Hendrik and Kühne, Thomas and Felser, Claudia and Mirhosseini, Hossein}}, journal = {{Chemistry of Materials}}, number = {{19}}, pages = {{6794--6800}}, publisher = {{American Chemical Society}}, title = {{{Database screening of ternary chalcogenides for p-type transparent conductors}}}, doi = {{10.1021/acs.chemmater.8b02719}}, volume = {{30}}, year = {{2018}}, } @article{13208, abstract = {{In this work, high-throughput ab initio calculations are employed to identify the most promising chalcogenide-based semiconductors for p-type transparent conducting materials (TCMs). A large computational data set is investigated by data mining. Binary semiconductors with large band gaps (Eg) and anions that are less electronegative than oxygen are considered. The roles of intrinsic defects and extrinsic dopants are investigated to probe the p-type performance of these semiconductors. Nine novel p-type non-oxide TCMs that have a low hole effective mass, good optical transparency, and hole dopability are proposed (ZnS, ZnSe, ZnTe, MgS, MgTe, GaSe, GaTe, Al2Se3, and BeTe). This study also focuses on a material engineering approach to modulate the electronic properties as a function of the layer thickness and external stress.}}, author = {{Kormath Madam Raghupathy, Ramya and Kühne, Thomas and Felser, Claudia and Mirhosseini, Hossein}}, journal = {{Journal of Materials Chemistry C}}, number = {{3}}, pages = {{541--549}}, publisher = {{Royal Society of Chemistry}}, title = {{{Rational design of transparent p-type conducting non-oxide materials from high-throughput calculations}}}, doi = {{https://doi.org/10.1039/C7TC05311H }}, volume = {{6}}, year = {{2018}}, } @article{15727, author = {{Kodalle, Tim and Kormath Madam Raghupathy, Ramya and Bertram, Tobias and Maticiuc, Natalia and Yetkin, Hasan A. and Gunder, René and Schlatmann, Rutger and Kühne, Thomas and Kaufmann, Christian A. and Mirhosseini, S. Hossein}}, issn = {{1862-6254}}, journal = {{physica status solidi (RRL) – Rapid Research Letters}}, title = {{{Properties of Co‐Evaporated RbInSe 2 Thin Films}}}, doi = {{10.1002/pssr.201800564}}, year = {{2018}}, } @article{19842, abstract = {{Non-trivial electronic properties of silver telluride and other chalcogenides, such as the presence of a topological insulator state, electronic topological transitions, metallization, and the possible emergence of superconductivity under pressure have attracted attention in recent years. In this work, we studied the electronic properties of silver selenide (Ag2Se). We performed direct current electrical resistivity measurements, in situ Raman spectroscopy, and synchrotron x-ray diffraction accompanied by ab initio calculations to explore pressure-induced changes to the atomic and electronic structure of Ag2Se. The temperature dependence of the electrical resistivity was measured up to 30 GPa in the 4–300 K temperature interval. Resistivity data showed an unusual increase in the thermal energy gap of phase I, which is a semiconductor under ambient conditions. Recently, a similar effect was reported for the 3D topological insulator Bi2Se3. Raman spectroscopy studies revealed lattice instability in phase I indicated by the softening of observed vibrational modes with pressure. Our hybrid functional band structure calculations predicted that phase I of Ag2Se would be a narrow band gap semiconductor, in accordance with experimental results. At a pressure of ~7.5 GPa, Ag2Se underwent a structural transition to phase II with an orthorhombic Pnma structure. The temperature dependence of the resistivity of Ag2Se phase II demonstrated its metallic character. Ag2Se phase III, which is stable above 16.5 GPa, is also metallic according to the resistivity data. No indication of the superconducting transition is found above 4 K in the studied pressure range.}}, author = {{Naumov, P and Barkalov, O and Mirhosseini, Hossein and Felser, C and A Medvedev, S}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{38}}, pages = {{385801}}, publisher = {{{IOP} Publishing}}, title = {{{Atomic and electronic structures evolution of the narrow band gap semiconductor Ag2Se under high pressure}}}, doi = {{10.1088/0953-8984/28/38/385801}}, volume = {{28}}, year = {{2016}}, } @article{15731, author = {{Thonig, Danny and Rauch, Tomáš and Mirhosseini, Hossein and Henk, Jürgen and Mertig, Ingrid and Wortelen, Henry and Engelkamp, Bernd and Schmidt, Anke B. and Donath, Markus}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, title = {{{Existence of topological nontrivial surface states in strained transition metals: W, Ta, Mo, and Nb}}}, doi = {{10.1103/physrevb.94.155132}}, year = {{2016}}, } @article{15732, author = {{Mirhosseini, Hossein and Kiss, Janos and Roma, Guido and Felser, Claudia}}, issn = {{0040-6090}}, journal = {{Thin Solid Films}}, pages = {{143--147}}, title = {{{Reducing the Schottky barrier height at the MoSe2/Mo(110) interface in thin-film solar cells: Insights from first-principles calculations}}}, doi = {{10.1016/j.tsf.2016.03.053}}, year = {{2016}}, } @article{15733, author = {{Miyamoto, K. and Wortelen, H. and Mirhosseini, Hossein and Okuda, T. and Kimura, A. and Iwasawa, H. and Shimada, K. and Henk, J. and Donath, M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, title = {{{Orbital-symmetry-selective spin characterization of Dirac-cone-like state on W(110)}}}, doi = {{10.1103/physrevb.93.161403}}, year = {{2016}}, } @article{15734, author = {{Ghorbani, Elaheh and Kiss, Janos and Mirhosseini, Hossein and Schmidt, Markus and Windeln, Johannes and Kühne, Thomas and Felser, Claudia}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{2064--2069}}, title = {{{Insights into Intrinsic Defects and the Incorporation of Na and K in the Cu2ZnSnSe4 Thin-Film Solar Cell Material from Hybrid-Functional Calculations}}}, doi = {{10.1021/acs.jpcc.5b11022}}, year = {{2016}}, } @article{15736, author = {{Ghorbani, Elaheh and Kiss, Janos and Mirhosseini, Hossein and Roma, Guido and Schmidt, Markus and Windeln, Johannes and Kühne, Thomas and Felser, Claudia}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{25197--25203}}, title = {{{Hybrid-Functional Calculations on the Incorporation of Na and K Impurities into the CuInSe2 and CuIn5Se8 Solar-Cell Materials}}}, doi = {{10.1021/acs.jpcc.5b07639}}, year = {{2015}}, }