Low Temperature Solution-Phase Deposition of SnS Thin Films

The solution-phase deposition of inorganic semiconductors is a promising, scalable method for the manufacture of thin film photovoltaics. Deposition of photovoltaic materials from molecular or colloidal inks offers the possibility of inexpensive, rapid, high-throughput thin film fabrication through processes such as spray coating. For example, CdTe, Cu(In,Ga)(S,Se)_2 (CIGS), and CH_3NH_3Pb(Cl,I)_3 perovskite-based thin film solar cells have been previously deposited using solution-based processes. Inks have also recently been developed for the solution deposition of Cu_2ZnSn(S,Se)_4 (CZTS) and FeS_2 (iron pyrite) absorber layers for thin film solar applications, in order to provide sustainable alternatives to materials that contain environmentally harmful heavy metals (e.g., Cd, Pb) and/or scarce elements (e.g., Te, In)

Influence of rotational distortions on Li⁺- and Na⁺- intercalation in anti-NASICON Fe₂(MoO₄)₃

Anti-NASICON Fe₂(MoO₄)₃ (<i>P</i>2₁/<i>c</i>) shows significant structural and electrochemical differences in the intercalation of Li⁺ and Na⁺ ions. To understand the origin of this behavior, we have used a combination of in situ X-ray and high-resolution neutron diffraction, total scattering, electrochemical measurements, density functional theory calculations, and symmetry-mode analysis. We find that for Li⁺-intercalation, which proceeds via a two-phase monoclinic-to-orthorhombic (<i>Pbcn</i>) phase transition, the host lattice undergoes a concerted rotation of rigid polyhedral subunits driven by strong interactions with the Li⁺ ions, leading to an ordered lithium arrangement. Na⁺-intercalation, which proceeds via a two-stage solid solution insertion into the monoclinic structure, similarly produces rotations of the lattice polyhedral subunits. However, using a combination of total neutron scattering data and density functional theory calculations, we find that while these rotational distortions upon Na⁺-intercalation are fundamentally the same as for Li⁺-intercalation, they result in a far less coherent final structure, with this difference attributed to the substantial difference between the ionic radii of the two alkali metals

Surface functionalization of surfactant-free particles : a strategy to tailor the properties of nanocomposites for enhanced thermoelectric performance

Altres ajuts: MCS acknowledge MINECO Juan de la Cierva Incorporation fellowship (JdlCI 2019) and Severo Ochoa. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. This study was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and Generalitat de Catalunya.The broad implementation of thermoelectricity requires high-performance and low-cost materials. One possibility is employing surfactant-free solution synthesis to produce nanopowders. We propose the strategy of functionalizing "naked" particles' surface by inorganic molecules to control the nanostructure and, consequently, thermoelectric performance. In particular, we use bismuth thiolates to functionalize surfactant-free SnTe particles' surfaces. Upon thermal processing, bismuth thiolates decomposition renders SnTe-BiS nanocomposites with synergistic functions: 1) carrier concentration optimization by Bi doping; 2) Seebeck coefficient enhancement and bipolar effect suppression by energy filtering; and 3) lattice thermal conductivity reduction by small grain domains, grain boundaries and nanostructuration. Overall, the SnTe-BiS nanocomposites exhibit peak z T up to 1.3 at 873 K and an average z T of ≈0.6 at 300-873 K, which is among the highest reported for solution-processed SnTe

Surface Termination of CsPbBr3 Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Cesium lead halide perovskite quantum dots (QDs) have gained significant attention as next-generation optoelectronic materials; however, their properties are highly dependent on their surface chemistry. The surfaces of cuboidal CsPbBr3 QDs have been intensively studied by both theoretical and experimental techniques, but fundamental questions still remain about the atomic termination of the QDs. The binding sites and modes of ligands at the surface remain unproven. Herein, we demonstrate that solid-state NMR spectroscopy allows the unambiguous assignments of organic surface ligands via 1H, 13C, and 31P NMR. Surface-selective 133Cs solid-state NMR spectra show the presence of an additional 133Cs NMR signal with a unique chemical shift that is attributed to Cs atoms terminating the surface of the particle and which are likely coordinated by carboxylate ligands. Dipolar dephasing curves that report on the distance between the surface ammonium ligands and Cs and Pb were recorded using double resonance 1H{133Cs} and 1H{207Pb} RESPDOR experiments. Model QD surface slabs with different possible surface terminations were generated from the CsPbBr3 crystal structure and theoretical RESPDOR dipolar dephasing curves considering all possible 1H-133Cs/207Pb spin pairs were then calculated. Comparison of the calculated and experimental RESPDOR curves indicates the particles are CsBr terminated (not PbBr2 terminated), with alkylammonium ligands situated within surface Cs vacancies, consistent with the surface-selective 133Cs NMR experiments. These results highlight the utility of high-resolution solid-state NMR spectroscopy for studying ligand binding and the surface structure of nanomaterials

Correction to Tunable Room-Temperature Synthesis of Coinage Metal Chalcogenide Nanocrystals from <i>N</i>‑Heterocyclic Carbene Synthons

Correction to Tunable Room-Temperature Synthesis of Coinage Metal Chalcogenide Nanocrystals from <i>N</i>‑Heterocyclic Carbene Synthon

Solution Deposited Cu₂BaSnS_4–<i>x</i>Se_<i>x</i> from a Thiol–Amine Solvent Mixture

Solution Deposited Cu₂BaSnS_4–<i>x</i>Se_<i>x</i> from a Thiol–Amine Solvent Mixtur

Structural Evolution of BaTiO₃ Nanocrystals Synthesized at Room Temperature

Sub-10 nm BaTiO₃ nanocrystals were synthesized at room temperature via the vapor diffusion sol–gel method, and their structural evolution during nucleation and growth stages was followed using a series of techniques that probe the atomic structure on different length and time scales. Special emphasis was placed on assessing the evolution of the local symmetry and structural coherence of the resulting nanocrystals, as these are the structural bases for cooperative properties such as ferroelectricity. Although the room-temperature crystal structure of the fully grown nanocrystals appears cubic to Rietveld analysis of synchrotron X-ray diffraction data, Raman spectroscopy and pair distribution function analysis demonstrate the presence of non-centrosymmetric regions arising from the off-centering of the titanium atoms. This finding demonstrates that accounting for diffuse scattering is critical when attempting the structural characterization of nanocrystals with X-ray diffraction. The local symmetry of acentric regions present in BaTiO₃ nanocrystals, particularly structural correlations within an individual unit cell <i>and</i> between two adjacent unit cells, is best described by a tetragonal <i>P</i>4<i>mm</i> space group. The orthorhombic <i>Amm</i>2 space group also provides an adequate description, suggesting both types of local symmetry can coexist at room temperature. The average magnitude of the local off-center displacements of the titanium atoms along the polar axis is comparable to that observed in bulk BaTiO₃, and their coherence length is on the order of 16 Å. The presence of local dipoles suggests that a large amount of macroscopic polarization can be achieved in nanocrystalline BaTiO₃ if the coherence of their ferroelectric coupling is further increased