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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 is Rutile structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent F1- atoms to form a mixture of corner and edge-sharing MgF6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two shorter (2.01 Å) and four longer (2.02 Å) Mg–F bond lengths. F1- is bonded in a distorted trigonal planar geometry to three equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent F1- atoms to form corner-sharing MgF6 octahedra. The corner-sharing octahedral tilt angles are 60°. All Mg–F bond lengths are 2.05 Å. F1- is bonded in a trigonal planar geometry to three equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Mg2+ is bonded to five F1- atoms to form a mixture of edge and corner-sharing MgF5 trigonal bipyramids. There is two shorter (1.88 Å) and three longer (2.01 Å) Mg–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted T-shaped geometry to three equivalent Mg2+ atoms. In the second F1- site, F1- is bonded in a linear geometry to two equivalent Mg2+ atoms. In the third F1- site, F1- is bonded in a linear geometry to two equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 is Hydrophilite structured and crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent F1- atoms to form a mixture of edge and corner-sharing MgF6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two shorter (2.02 Å) and four longer (2.03 Å) Mg–F bond lengths. F1- is bonded in a distorted trigonal planar geometry to three equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 is Cotunnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded in a 7-coordinate geometry to seven F1- atoms. There are a spread of Mg–F bond distances ranging from 2.02–2.23 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal non-coplanar geometry to three equivalent Mg2+ atoms. In the second F1- site, F1- is bonded to four equivalent Mg2+ atoms to form a mixture of corner and edge-sharing FMg4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgF2 by Materials Project

MgF2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Mg2+ is bonded to five F1- atoms to form a mixture of distorted edge and corner-sharing MgF5 trigonal bipyramids. There are a spread of Mg–F bond distances ranging from 1.89–2.03 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted T-shaped geometry to three equivalent Mg2+ atoms. In the second F1- site, F1- is bonded in a linear geometry to two equivalent Mg2+ atoms. In the third F1- site, F1- is bonded in a linear geometry to two equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Over 11% Efficient Eco-Friendly Kesterite Solar Cell: Effects of S-Enriched Surface of Cu2ZnSn(S,Se)4 Absorber and Band Gap Controlled (Zn,Sn)O Buffer

For high efficiency kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cell, CdS thin film was usually used as a buffer layer. However, due to the toxicity of Cd and pollution problems involved from the solution-based chemical bath deposition, eco-friendly high efficiency CZTSSe solar cell with Cd-free buffer is necessary. As an Cd-free buffer layer, we investigated (Zn,Sn)O (ZTO) film deposited by sputtering method. In order to achieve high power conversion efficiency, we controlled energy band gaps of CZTSSe absorber as well as ZTO buffer, which was required to optimize conduction band offset (CBO) between the absorber and the buffer and to increase open circuit voltage (Voc) and fill factor (FF). The CBO was optimized by controlling the band gap of ZTO. By varying the Sn/(Zn + Sn) ratio and its deposition temperature, band gap of ZTO was successfully adjusted. Experimental and computational calculation results showed that solar cell performance was strongly affected by the CBO between absorber and buffer. Besides CBO matching, larger band gap of ZTO improved short circuit current density (Jsc) with enhanced external quantum efficiency value in blue photon spectrum range. As an additional way to improve power conversion efficiency of solar cell, band graded CZTSSe absorber was developed by using spray-based two-step process. The sprayed CZTSSe film was engineered to have S-enriched surface, which makes surface band gap widened and surface passivated, and resultantly increases Voc, Jsc and fill factor (FF). By controlling band gaps of both CZTSSe absorber and ZTO buffer, we obtained 11.22% environment-friendly CZTSSe solar cell without MgF2 anti-reflection coating.

(Zn↗
DOE OSTI2020

Materials Data on MgAlF5 by Materials Project

MgF2AlF3 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two AlF3 ribbons oriented in the (1, 0, 0) direction and two MgF2 ribbons oriented in the (1, 0, 0) direction. In each AlF3 ribbon, Al3+ is bonded in a square co-planar geometry to four F1- atoms. There is two shorter (1.67 Å) and two longer (1.70 Å) Al–F bond length. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the second F1- site, F1- is bonded in a single-bond geometry to one Al3+ atom. In each MgF2 ribbon, Mg2+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent F1- atoms. All Mg–F bond lengths are 2.08 Å. F1- is bonded in a water-like geometry to two equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photonic near infrared heater

A multilayer photonic stack comprising a lower plurality of alternating layers comprising at least A and B and an upper plurality of alternating layers comprising at least C and D, layer A comprises at least one of Al, Au, W, Ag, Ni, Ti, Pt, and Cr, layer B comprises at least one of Al2O3, AlN, MgO, SiO2, TiO2, Si3N4, MgF2, Ta2O5, SiC, Si, Ge, and Indium Tin Oxide (ITO), and layers C and D comprise at least one of Al2O3, AlN, MgO, SiO2, TiO2, Si3N4, MgF2, Ta2O5, SiC, Si, Ge, and Indium Tin Oxide (ITO).

Prasher, Ravi Shankar↗
DOE OSTI2022

Semiconductor-dielectric-metal solar absorbers with high spectral selectivity

An ideal solar thermal absorber has a sharp transition between high and low absorptance at the wavelength where the blackbody emissive power begins to exceed the solar irradiance. However, most real selective absorbers have a fairly broad transition, leading to both solar absorption and thermal emission losses. Here, we model, fabricate, and characterize a highly selective semiconductor-dielectric-metal (Ga0.46In0.54As - MgF2 - Ag) solar absorber with an extremely sharp transition from high to low absorptance. The thin semiconductor serves as a selective filter, absorbing photons with wavelengths shorter than the bandgap and transmitting those with longer wavelengths. The highly reflective dielectric-metal rear mirror allows the structure to have very low emittance for longer wavelengths. These characteristics provide the absorber with a measured solar absorptance >91% below the bandgap wavelength and infrared emittance <5% at 100 degrees C above the bandgap wavelength. This transition wavelength can be tuned by modifying the semiconductor composition, and modeling indicates that the absorber's optical properties should be stable at high temperatures, making the structure a good candidate for unconcentrated to highly concentrated solar thermal energy conversion.

14 SOLAR ENERGY↗