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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on SnO2 by Materials Project

SnO2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are nine inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one SnO4 tetrahedra, corners with two equivalent SnO4 trigonal pyramids, and edges with four SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.05–2.30 Å. In the second Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one SnO4 trigonal pyramid and edges with five SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.03–2.33 Å. In the third Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one SnO4 tetrahedra, corners with two equivalent SnO4 trigonal pyramids, and edges with four equivalent SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.05–2.29 Å. In the fourth Sn4+ site, Sn4+ is bonded to six O2- atoms to form edge-sharing SnO6 octahedra. There are three shorter (2.06 Å) and three longer (2.19 Å) Sn–O bond lengths. In the fifth Sn4+ site, Sn4+ is bonded to four O2- atoms to form corner-sharing SnO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 58–68°. There are three shorter (2.05 Å) and one longer (2.10 Å) Sn–O bond lengths. In the sixth Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with two equivalent SnO4 tetrahedra and edges with five SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.10–2.17 Å. In the seventh Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one SnO4 trigonal pyramid and edges with five SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.04–2.34 Å. In the eighth Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with two equivalent SnO4 tetrahedra and edges with five SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.10–2.17 Å. In the ninth Sn4+ site, Sn4+ is bonded to four O2- atoms to form corner-sharing SnO4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–60°. There are a spread of Sn–O bond distances ranging from 2.01–2.03 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two Sn4+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to three Sn4+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the fourth O2- site, O2- is bonded in a water-like geometry to two Sn4+ atoms. In the fifth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Sn4+ atoms. In the sixth O2- site, O2- is bonded in a distorted T-shaped geometry to three Sn4+ atoms. In the seventh O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Sn4+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to four Sn4+ atoms. In the ninth O2- site, O2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Sn4+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Sn4+ atoms. In the twelfth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Sn4+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted T-shaped geometry to three Sn4+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to four Sn4+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Sn4+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Sn4+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Sn4+ atoms. In the eighteenth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Sn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

SnO2 Buffer Layers for High Efficiency CdSeTe/CdTe Devices

SnO2 buffer layers of different thickness were deposited onto TEC 15 Fluorine doped tin oxide coated glass substrates using rf magnetron sputtering. The buffer layers were then incorporated into Cu-doped CdSeTe/CdTe devices using a range of CdCl 2 activation treatments and CuCl2 annealing temperatures to determine the effects of buffer layer thickness on device performance. Results show that all devices fabricated with thinner buffer layers resulted in much better J - V characteristics than their thicker counterparts. This was mainly due to a reduced open-circuit voltage (Voc) when using thicker buffer layers. The best device produced a conversion efficiency of 16.59%, fill factor of 71.62%, Jsc of 28.44 mA/cm 2 and Voc of 814.23 mV.

buffer layers↗
DOE OSTI2020

Materials Data on Ti(SnO2)2 by Materials Project

Sn2TiO4 crystallizes in the tetragonal P4_2/mbc space group. The structure is three-dimensional. Ti4+ is bonded to six O2- atoms to form edge-sharing TiO6 octahedra. There is two shorter (1.99 Å) and four longer (2.00 Å) Ti–O bond length. Sn2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.12 Å) and one longer (2.24 Å) Sn–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Ti4+ and two equivalent Sn2+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ti4+ and one Sn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SnO2)4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(SnO2)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SnO2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(SnO2)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al(SnO2)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2022

Physical and Flow Properties of Glass Forming Chemicals (V2O5, SnO, SnO2, Cr2O3, FeCr2O4, and ZrSiO4) and Mixtures

For a sustainable nuclear waste vitrification process at the Hanford Tank Waste Treatment and Immobilization Plant (WTP), proper selection and consistent supply of glass-forming chemicals (GFCs) are crucial. Establishing rigorous acceptance criteria for the characterization of GFCs will be required to operate the vitrification facility and to mitigate any processing issues or failures. Low-activity wastes (LAW) are blended with GFCs to form slurry melter feeds and vitrified in a melter. To enhance properties of waste glasses, new chemicals are being introduced to the current GFC mixture (Vienna et al. 2016; Muller et al. 2017, 2019). In this study, three new GFCs were evaluated for enhanced LAW glass formulations: chromium oxide (Cr 2 O 3 ), vanadium oxide (V 2 O 5 ), and stannic oxide (SnO 2 ). These three oxide components are included in enhanced waste glass (EWG) formulations and GFCs with the appropriate physical and flow properties are needed. As a starting point, single metal oxide GFCs: Cr 2 O 3 , V 2 O 5 , and SnO 2 were sourced and tested. To characterize these new individual GFCs and mixtures of GFCs, the industrial bulk characterization consultant, Jenike and Johanson, was employed to measure physical and flow properties of individual GFCs and their mixtures. Pacific Northwest National Laboratory (PNNL) also measured several selected physical properties for data evaluation as a quality assurance step. In addition, PNNL measured physical and rheological properties of slurry melter feeds containing those GFCs. Subsequent data analyses and verification were conducted. The purpose of this report is to assess the applicability of these GFCs for LAW vitrification based on their properties. This report will help understand measured data and evaluate new GFCs for use. Moreover, this report may give useful insights to help troubleshoot any GFC and melter feed transport and mixing issues that arise during processing, leading to a successful cleanup mission at WTP.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Generalized Ellipsometry Measurements of Crystalline Thin Film and Bulk Tin Oxide

Here, several bulk and thin-film crystals of SnO2 are grown and examined using generalized ellipsometry techniques. The bulk samples are grown using the chemical vapor transport technique and thin films of SnO2 are grown using the pulsed laser deposition technique. The bulk samples are examined using the two-modulator generalized ellipsometry microscope (2-MGEM) at normal incidence and the spectroscopic two-modulator generalized ellipsometer (2-MGE). The spectroscopic optical functions of tin oxide are then obtained using the 2-MGE from 1.46 to 6.2 eV. The material is highly birefringent, and the ordinary bandgap is less than the extraordinary band edge. 2-MGE measurements are also made on thin-film samples of crystalline tin oxide grown on sapphire and rutile, showing no cross polarization. Because of the complicated morphology of the tin oxide films grown on sapphire, the ellipsometry data are simulated using the Tauc–Lorentz model. Films grown on rutile had the optic axis perpendicular to the sample surface, but the film is strained, resulting in a more complicated ellipsometric spectrum. These films are modeled using the air/surface roughness/tin oxide/interface/rutile model, where the roughness and interface are modeled using the incomplete Beta function.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Computational Insights into Phase Equilibria Between Wide-Gap Semiconductors and Contact Materials

Novel wide-band-gap semiconductors are needed for next-generation power electronics, but there is a gap between a promising material and a functional device. Finding stable (metal) contacts is one of the major challenges that is currently dealt with mainly via trial and error. Herein, we computationally investigate the thermochemistry and phase coexistence at the junction between three wide-gap semiconductors, ..beta..-Ga2O3, GeO2, and GaN, and possible contact materials. The pool of possible contacts includes 47 elemental metals and a set of 4 common, n-type transparent conducting oxides (ZnO, TiO2, SnO2, and In2O3). We use first-principles thermodynamics to model the Gibbs free energies of chemical reactions as a function of gas pressure (pO2/pN2) and equilibrium temperature. We deduce whether a semiconductor/contact interface will be stable at relevant conditions or a chemical reaction between them is to be expected, possibly influencing the long-term reliability and performance of devices. We generally find that most elemental metals tend to oxidize or nitridize and form various interface oxide/nitride layers. Exceptions include select late- and post-transition metals and, in the case of GaN, also the alkali metals, which are predicted to exhibit stable coexistence, although in many cases at relatively low gas partial pressures. Similar is true for the transparent conducting oxides, for which, in most cases, we predict a preference toward forming ternary oxides when in contact with ..beta..-Ga2O3 and GeO2. The only exception is SnO2, which we find to form stable contacts with both oxides. Finally, we show how the same approach can be used to predict gas partial pressure vs temperature phase diagrams to help direct synthesis of ternary compounds. We believe these results provide a valuable guidance in selecting contact materials to wide-gap semiconductors and suitable growth conditions.

contact materials↗
DOE OSTI2021

Reducing sputter induced stress and damage for efficient perovskite/silicon tandem solar cells

Reducing damages caused by sputtering of transparent conductive oxide (TCO) electrodes is critical in achieving highly efficient and stable perovskite/silicon tandem solar cells. Here we study the sputter caused damage to bathocuproine (BCP), which is widely used in highly efficient p-i-n structure single junction perovskite solar cells. While BCP buffer layer protects the underneath layers from damage, itself can be damaged by sputtering of TCOs at a wide range of target-substrate distances, supported by molecular dynamic simulation. More intriguingly, it is observed that TCO easily peeled off after sputtering when the sputtering target is close to substrate. This is ascribed to formation of stress during cooling down process after sputtering due to different thermal expansion coefficients of the layers. Our studies explain why tin oxide (SnO2) made by atomic layer deposition can replace BCP for a much better tandem device performance. SnO2 has high affinity with sputtered TCO electrode to suppress peeling-off issue and has higher bond energy to resist sputter induced damage, thus it allows a wider window of target-substrate distances than BCP during TCO sputtering. Ultimately, we demonstrate an efficient perovskite/silicon monolithic tandem solar cell with efficiency of 26.0% to illustrate the beneficial effects of reduced stress and damage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Advances in SnO 2 for Efficient and Stable n-i-p Perovskite Solar Cells

Perovskite solar cells (PSCs) based on the regular n-i-p device architecture have reached above 25% certified efficiency with continuously reported improvements in recent years. A key common factor for these recent breakthroughs is the development of SnO 2 as an effective electron transport layer in these devices. In this review, we discuss the key advances in SnO 2 development, including various deposition approaches and surface treatment strategies, to enhance the bulk and interface properties of SnO 2 for highly efficient and stable n-i-p PSCs. We also discuss the general materials chemistry associated with SnO 2 along with the corresponding materials challenges and improvement strategies, focusing on defects, intrinsic properties, and impact on device characteristics. Finally, we highlight some SnO2 implementations related to scalable processes and flexible devices, and we also provide our perspective on the future development of efficient and stable large-scale perovskite solar modules.

14 SOLAR ENERGY↗