Utilizing Solvent Repulsion between Dimethylformamide and Isopropanol to Manipulate Sn Distribution for Bifacial CuZnSn(S,Se) Solar Cells.

Rationalizing the role of chemical interactions in the precursor solutions on the structure, morphology, and performance of thin-film CuZnSn(S,Se) (CZTSSe) is key for the development of bifacial and other photovoltaic (PV) device architectures designed by scalable solution-based methods. In this study, we uncover the impact of dimethylformamide (DMF) and isopropanol (IPA) solvent mixtures on cation complexation and rheology of the precursor solution, as well as the corresponding morphology, composition, and PV performance of CZTSSe thin-film grown on fluorine-doped tin oxide (FTO). We find that increasing the proportion of IPA leads to a nonlinear increase in dynamic viscosity due to the strong repulsion between DMF and IPA, which is characterized by an interaction cohesion parameter of 3.

Enhanced Electron Emission Performance and Air-Surface Stability in ScO-Terminated Diamond for Thermionic Energy Converters.

Diamond with negative electron affinity (NEA) and low work function surfaces are suggested as a suitable material for electron-generation applications in vacuum, in particular, as the emitter electrode in thermionic energy converters. Such NEA surfaces can be fabricated by evaporating and then annealing submonolayers of a suitable metal in vacuo onto bare or oxidized diamond. Among the metals studied, scandium termination of bare diamond (100) and (111) surfaces is recently reported to give the largest NEA values reported to date for a metal-diamond system, as well as being thermally stable to 900 °C.

Versatile Method for Preparing Two-Dimensional Metal Dihalides.

Ever since the ground-breaking isolation of graphene, numerous two-dimensional (2D) materials have emerged with 2D metal dihalides gaining significant attention due to their intriguing electrical and magnetic properties. In this study, we introduce an innovative approach anhydrous solvent-induced recrystallization of bulk powders to obtain crystals of metal dihalides (MX, with M = Cu, Ni, Co and X = Br, Cl, I), which can be exfoliated to 2D flakes. We demonstrate the effectiveness of our method using CuBr as an example, which forms large layered crystals.

Ge-doping of CZTS nanocrystals and CZTSSe solar absorber films.

CuZnSn(S,Se) (CZTSSe) is a promising material for thin-film photovoltaics, however, the open-circuit voltage () deficit of CZTSSe prevents the device performance from exceeding 13% conversion efficiency. CZTSSe is a heavily compensated material that is rich in point defects and prone to the formation of secondary phases. The landscape of these defects is complex and some mitigation is possible by employing non-stoichiometric conditions.

Correlating Thermionic Emission with Specific Surface Reconstructions in a <100> Hydrogenated Single-Crystal Diamond.

Thermionic emission relies on the low work function and negative electron affinity of the, often functionalized, surface of the emitting material. However, there is little understanding of the interplay between thermionic emission and temperature-driven dynamic surface transformation processes as these are not represented on the traditional Richardson-Dushman equation for thermionic emission. Here, we show a new model for thermionic emission that can reproduce the effect of dynamic surface changes on the electron emission and correlate the components of the thermionic emission with specific surface reconstruction phases on the surface of the emitter.

Characterisation of thermionic emission current with a laser-heated system.

Thermionic emitting materials are relevant for several technological applications like electron guns, X-ray sources, or thermionic energy converters. As new materials and surface functionalisations that enable thermionic emission are developed, it is essential to be able to test them in a repeatable and reliable manner. Here, we present a CO laser-heated system for thermionic tests that can be used to test the thermionic emission current of different materials regardless of the optical properties or form factor.

Anodization study of epitaxial graphene: insights on the oxygen evolution reaction of graphitic materials.

The photoemission electron microscopy and x-ray photoemission spectroscopy were utilized for the study of anodized epitaxial graphene (EG) on silicon carbide as a fundamental aspect of the oxygen evolution reaction on graphitic materials. The high-resolution analysis of surface morphology and composition quantified the material transformation during the anodization. We investigated the surface with lateral resolution <150 nm, revealing significant transformations on the EG and the role of multilayer edges in increasing the film capacitance.

Mapping Shunting Paths at the Surface of CuZnSn(S,Se) Films via Energy-Filtered Photoemission Microscopy.

The performance of CuZnSn(S,Se) thin-film solar cells, commonly referred to as kesterite or CZTSSe, is limited by open-circuit voltage (V) values less than 60% of the maximum theoretical limit. In the present study, we employ energy-filtered photoemission microscopy to visualize nanoscale shunting paths in solution-processed CZTSSe films, which limit the V of cells to approximately 400 mV. These studies unveil areas of local effective work function (LEWF) narrowly distributed around 4.

A theoretical study of substitutional boron-nitrogen clusters in diamond.

Substitutional clusters of multiple light element dopants are a promising route to the elusive shallow donor in diamond. To understand the behaviour of co-dopants, this report presents an extensive first principles study of possible clusters of boron and nitrogen. We use periodic hybrid density functional calculations to predict the geometry, stability and electronic excitation energies of a range of clusters containing up to five N and/or B atoms.

A Perspective on the Application of Spatially Resolved ARPES for 2D Materials.

In this paper, a perspective on the application of Spatially- and Angle-Resolved PhotoEmission Spectroscopy (ARPES) for the study of two-dimensional (2D) materials is presented. ARPES allows the direct measurement of the electronic band structure of materials generating extremely useful insights into their electronic properties. The possibility to apply this technique to 2D materials is of paramount importance because these ultrathin layers are considered fundamental for future electronic, photonic and spintronic devices.

Imaging the Predicted Isomerism of Oligo(aniline)s: A Scanning Tunneling Microscopy Study.

The self-assembly of two emeraldine base tetra(aniline) derivatives is investigated using scanning tunneling microscopy. A combination of the scanning tunneling microscopy data and calculations reveals the presence of predicted cis/trans isomerism in this oxidation state. This isomerism is shown to hinder self-assembly into ordered structures, and provides indications as to why the properties of these materials, and their parent polymer, polyaniline, remain unfulfilled.

Electrochemical properties of two dimensional assemblies of insulating diamond particles.

The electrochemical properties of two-dimensional assemblies of 500 nm type Ib diamond particles are investigated as a function of their surface oxidation state. High Pressure High Temperature particles are sequentially exposed to a hot strong acid bath and to H(2) plasma in order to generate oxygen (ODP) and hydrogen surface terminations (HDP). Changes in the surface composition following the chemical treatments are confirmed by FTIR.

Experimental and modeling studies of B atom number density distributions in hot filament activated B2H6/H2 and B2H6/CH4/H2 gas mixtures.

Experimental and modeling studies of the gas-phase chemistry occurring in dilute, hot filament (HF) activated B2H6/H2 and B2H6/CH4/H2 gas mixtures are reported. Spatially resolved relative number densities of B (and H) atoms have been measured by resonance enhanced multiphoton ionization methods, as a function of process conditions (e.g.