Structural studies of magnesium nitride fluorides by powder neutron diffraction

Newly predicted halide perovskites Mg3AB3 (A = N, Bi; B = F, Br, I) for next-generation photovoltaic applications: a first-principles study

The research examines the exceptional physical characteristics of Mg3AB3 (A = N, Bi; B = F, Br, I) perovskite compounds through density functional theory to assess their feasibility for photovoltaic applications. Mechanical characterization further supports their stability where out of all the compounds, Mg3BiI3 demonstrates high ductility, while Mg3NF3 and Mg3BiBr3 possess a brittle nature. The calculated elastic constants and anisotropy factors also substantiate their mechanical stability, while there is an observed declining trend in Debye temperature with increase in atomic number. From the electronic point of view, Mg3NF3 can be considered as a wide-bandgap insulator with the bandgap of 6.789 eV, whereas Mg3BiBr3 and Mg3BiI3 can be classified as semiconductors suitable for photovoltaic applications bandgaps of 1.626 eV and 0.867 eV, respectively. The optical characteristics of such materials are excellent and pronounced by high absorption coefficients, low reflectivity, and good dielectrics, which are very important in the collection of solar energy. Among them, Mg3BiBr3 and Mg3BiI3 possess high light absorption coefficient, moderate reflectivity, and good electrical conductivity, indicating that they are quite suitable for applying the photoelectric conversion materials for solar cells. In addition, thermal analysis shows that Mg3NF3 is a good heat sink material, Mg3BiBr3 and Mg3BiI3 are favorable for thermal barrier coating materials. Due to their high absorption coefficients, low reflectance and suitable conductivity, both Mg3BiBr3 and Mg3BiI3 could be regarded as the most appropriate materials for the creation of the next generation of photovoltaic converters.

Investigation of novel all-inorganic perovskites Ba3PX3 (X = F, Cl, Br, I) with efficiency above 29

Lead-free inorganic halide perovskites, specifically Ba3PX3 (X = Cl, F, I, Br) have gained attention in green photovoltaics due to their remarkable mechanical, optical, structural, and electronic properties. Using first-principles calculations, we investigated the mechanical, electronic, and optical characteristics of Ba3PX3, revealing direct band gaps at the Γ-symmetry point, assessed with the PBE and HSE functionals. The charge distribution analysis shows strong ionic bonding between Ba and halides and covalent bonding between P and halides. The perovskites exhibit desirable optical properties, including high absorption in the visible-UV range, making them ideal for optoelectronic devices. Furthermore, SCAPS-1D simulations on Ba3PF3, Ba3PCl3, Ba3PBr3, and Ba3PI3-based solar cells with the SnS2 ETL layer revealed power conversion efficiencies of 23.15%, 16.13%, 21.63%, and 29.89%, respectively. Consequently, the Ba3PI3 compound shows significant potential as an absorber in solar cells based on the SnS2 ETL layer in the near future.

Designing antiperovskite derivatives via atomic-position splitting for photovoltaic applications

Due to the success of halide perovskites in the photovoltaic field, halide perovskite-derived semiconductors have also been widely studied for optoelectronic applications. However, the photovoltaic performance of these perovskite derivatives still lags significantly behind their perovskite counterparts, mainly due to deficiencies at the B-site or X-site of the derivatives, which disrupt the connectivity of the key [BX6] octahedra units. Herein, we developed a class of antiperovskite-derived materials with the formula , achieved by splitting the A anion, originally at the corner site of the cubic antiperovskite structure, into three edge-centered sites. This structural transformation maintains the three-dimensional octahedral framework. The thermodynamic stability, dynamical stability, and band gaps of 80 compounds were calculated using first-principles calculations. Based on criteria including stability and electronic properties, we identified 9 promising antiperovskite derivatives for further evaluation of their photovoltaic performance. Notably, the calculated theoretical maximum efficiencies of Ba3BiI3, Ba3SbI3, and Ba3BiBr3 all exceed 24.5%, which is comparable to that of CH3NH3PbI3 solar cells. Interpretable machine learning analysis was further carried out to identify critical physical descriptors influencing thermodynamic stability and band gap. Our work provides a novel approach for designing high performance perovskite-type structure-inspired semiconductors with potential for optoelectronic applications.

Investigating the effects of hydrostatic pressure on the physical properties of cubic Sr3BCl3 (B = As, Sb) for improved optoelectronic applications: A DFT study

This article explores changes in the structural, electronic, elastic, and optical properties of the novel cubic Sr3BCl3 (B = As, Sb) with increasing pressure. This research aims to decrease the electronic band gap of Sr3BCl3 (B = As, Sb) by applying pressure, with the objective of enhancing the optical properties and evaluating the potential of these compounds for use in optoelectronic applications. It has been revealed that both the lattice parameter and cell volume exhibit a declining pattern as pressure increases. At ambient pressure, analysis of the band structure revealed that both Sr3AsCl3 and Sr3SbCl3 are direct band gap semiconductors. With increasing pressure up to 25 GPa the electronic band gap of Sr3AsCl3 (Sr3SbCl3) reduces from 1.70 (1.72) eV to 0.35 (0.10) eV. However, applying hydrostatic pressure enables the attainment of optimal bandgaps for Sr3AsCl3 and Sr3SbCl3, offering theoretical backing for the adjustment of Sr3BCl3 (B = As, Sb) perovskite's bandgaps. The electron and hole effective masses in this perovskite exhibit a gradual decrease as pressure rises from 0 to 25 GPa, promoting the conductivity of both electrons and holes. The elastic properties are calculated using the Thermo-PW tool, revealing that they are anisotropic, ductile, mechanically stable, and resistant to plastic deformation. Importantly, these mechanical properties of both compounds are significantly enhanced under pressure. Optical properties, including the absorption and extinction coefficients, dielectric function, refractive index, reflectivity, and loss function, were calculated within the 0-20 eV range under different pressure conditions. The calculated optical properties highlight the versatility and suitability of Sr3AsCl3 and Sr3SbCl3 perovskites for pressure-tunable optoelectronic devices.

Computational Screening of Promising Deep-Ultraviolet Light Emitters

Deep-ultraviolet (DUV) light sources are technologically highly important, but DUV light-emitting materials are extremely rare; AlN and its alloys are the only materials known so far, significantly limiting the chemical and structural spaces for materials design. Here, we perform a high-throughput computational search for DUV light emitters based on a set of carefully designed screening criteria relating to the sophisticated electronic structure. In this way, we successfully identify 5 promising material candidates that exhibit comparable or higher radiative recombination coefficients than AlN, including BeGeN2, Mg3NF3, KCaBr3, KHS, and RbHS. Further, we unveil the unique features in the atomic and electronic structures of DUV light emitters and elucidate the fundamental genetic reasons why DUV light emitters are extremely rare. Our study not only guides the design and synthesis of efficient DUV light emitters but also establishes the genetic nature of ultrawide-band-gap semiconductors in general.

A novel investigation of pressure-induced semiconducting to metallic transition of lead free novel Ba3SbI3 perovskite with exceptional optoelectronic properties

The structural, electronic, mechanical, and optical characteristics of barium-based halide perovskite Ba3SbI3 under the influence of pressures ranging from 0 to 10 GPa have been analyzed using first-principles calculations for the first time. The new perovskite Ba3SbI3 material was shown to be a direct band gap semiconductor at 0 GPa, but the band gap diminished when the applied pressure increased from 0 to 10 GPa. So the Ba3SbI3 material undergoes a transition from semiconductor to metallic due to high pressure at 10 GPa. The Ba3SbI3 material also exhibits an increase in optical absorption and conductivity with applied pressure due to the change in band gap, which is more suitable for solar absorbers, surgical instruments, and optoelectronic devices. The charge density maps confirm the presence of both ionic and covalent bonding characteristics. Exploration into the mechanical characteristics indicates that the Ba3SbI3 perovskite is mechanically stable. Additionally, the Ba3SbI3 compound becomes strongly anisotropic at high pressure. The insightful results of our simulations will all be helpful for the experimental structure of a new effective Ba3SbI3-based inorganic perovskite solar cell in the near future.

Development of Mixed-Anion Photocatalysts with Wide Visible-Light Absorption Bands for Solar Water Splitting

Rapid fossil-fuel consumption, severe environmental concerns, and growing energy demands call for the exploitation of environmentally friendly, recyclable, new energy sources. Fuel-producing artificial systems that directly convert solar energy into fuels by mimicking natural photosynthesis are expected to achieve this goal. Among them, the conversion of solar energy into hydrogen energy through the photocatalytic water-splitting process over a particulate semiconductor is one of the most promising routes due to advantages such as simplicity, cheapness, and ease of large-scale production. Abundant metal oxide photocatalysts have been developed in the last century, but most are only active under UV-light irradiation. To harvest a much wider range of the solar spectrum, the development of photocatalysts with wide visible-light absorption bands has become increasingly popular this century. Herein, a brief overview of materials developed for promising solar water splitting, with an emphasis on a mixed-anion structure and wide visible-light absorption bands, is presented, with some basic information on the principles, approaches, and research progress on the photocatalytic water-splitting reaction with particulate semiconductors. Typical progress on research into one- and two-step (Z-scheme) overall water-splitting systems by utilizing mixed-anion photocatalysts is highlighted, together with research strategies and modification methods.