Using vacuum process, we fabricated Cu2ZnSnS4 solar cells with 8.4% efficiency, a number independently certified by an external, accredited laboratory. This is the highest efficiency reported for pure sulfide Cu2ZnSnS4 prepared by any method. Consistent with literature, the optimal composition is Cu-poor and Zn-rich despite the precipitation of secondary phases (e.g., ZnS). Despite a very thin absorber thickness (~600 nm), a reasonably good short-circuit current was obtained. Time-resolved photoluminescence measurements suggest a minority carrier-diffusion length on the order of several hundreds of nanometers and relatively good collection of photo-carriers across the entire absorber thickness. Copyright © 2011 John Wiley & Sons, Ltd.

Thin film solar cell with 8.4% power conversion efficiency using an earth‐abundant Cu2ZnSnS4 absorber

Premises of creation of Internet portal designed to provide access to participants of educational and scientific process for the joint creation, consolidation, concentration and rapid spreading of educational and scientific information resources in its own depository are considered. CMS-based portal content management systems’ potentiality is investigated. Architecture for Internet portal of MES of Ukraine’s information resources is offered.

Створення порталу інформаційно-довідкових ресурсів міністерства освіти і науки україни

Non-stoichiometry effect and disorder in Cu2ZnSnS4 thin films obtained by flash evaporation: Raman scattering investigation

Considerable efforts have been devoted to enhancing thermoelectric performance, by employing phonon scattering from nanostructural architecture, and material design using phonon-glass and electron-crystal concepts. The nanostructural approach helps to lower thermal conductivity but has limited effect on the power factor. Here, we demonstrate selective charge Anderson localization as a route to maximize the Seebeck coefficient while simultaneously preserving high electrical conductivity and lowering the lattice thermal conductivity. We confirm the viability of interface potential modification in an n-type Bi-doped PbTe/Ag2Te nanocomposite and the resulting enhancement in thermoelectric figure-of-merit ZT. The introduction of random potentials via Ag2Te nanoparticle distribution using extrinsic phase mixing was determined using scanning tunneling spectroscopy measurements. When the Ag2Te undergoes a structural phase transition (T > 420 K) from monoclinic β-Ag2Te to cubic α-Ag2Te, the band gap in the α-Ag2Te...

Synergetic Enhancement of Thermoelectric Performance by Selective Charge Anderson Localization–Delocalization Transition in n-Type Bi-Doped PbTe/Ag2Te Nanocomposite

Anderson (disorder-induced) localization, proposed more than half a century ago, has inspired numerous efforts to explore the absence of wave diffusions in disordered media. However, the proposed disorder-induced metal-insulator transition (MIT), associated with the nonpropagative electron waves, has hardly been observed in three-dimensional (3D) crystalline materials, let alone single crystals. We report the observation of an MIT in centimeter-size single crystals of Li x Fe7Se8 induced by lattice disorder. Both specific heat and infrared reflectance measurements reveal the presence of considerable electronic states in the vicinity of the Fermi level when the MIT occurs, suggesting that the transition is not due to Coulomb repulsion mechanism. The 3D variable range hopping regime evidenced by electrical transport measurements at low temperatures indicates the localized nature of the electronic states on the Fermi level. Quantitative analyses of carrier concentration, carrier mobility, and simulated density of states (DOS) fully support that Li x Fe7Se8 is an Anderson insulator. On the basis of these results, we provide a unified DOS picture to explain all the experimental results, and a schematic diagram for finding other potential Anderson insulators. This material will thus serve as a rich playground for both theoretical and experimental investigations on MITs and disorder-induced phenomena.

https://advances.sciencemag.org/content/advances/2/2/e1501283.full.pdf

Anderson localization of electrons in single crystals: LixFe7Se8

We report density-functional studies of the ${\text{Fe}}_{1\ensuremath{-}x}{\text{Cu}}_{x}\text{Se}$ alloy done using supercell and coherent-potential approximation methods. Magnetic behavior was investigated using the disordered local moment approach. We find that Cu occurs in a nominal ${d}^{10}$ configuration and is highly disruptive to the electronic structure of the Fe sheets. This would be consistent with a metal-insulator transition due to Anderson localization. We further find a strong crossover from a weak moment itinerant system to a local moment magnet at $x\ensuremath{\approx}0.12$. We associate this with the experimentally observed jump near this concentration. Our results are consistent with the characterization of this concentration-dependent jump as a transition to a spin glass.

Electronic structure localization and spin-state transition in Cu-substituted FeSe: Fe1-xCuxSe

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Electronic structure localization and spin-state transition in Cu-substituted FeSe: Fe1-xCuxSe