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DOE OSTI2020

Materials Data on Cs5As5Se9 by Materials Project

Cs5As5Se9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.71–4.21 Å. In the second Cs1+ site, Cs1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.66–4.11 Å. In the third Cs1+ site, Cs1+ is bonded in a 6-coordinate geometry to five Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.78–3.94 Å. There are three inequivalent As+2.60+ sites. In the first As+2.60+ site, As+2.60+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.35 Å) and two longer (2.48 Å) As–Se bond lengths. In the second As+2.60+ site, As+2.60+ is bonded in a water-like geometry to two Se2- atoms. There are one shorter (2.36 Å) and one longer (2.46 Å) As–Se bond lengths. In the third As+2.60+ site, As+2.60+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.33–2.50 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to three Cs1+ and two As+2.60+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to three Cs1+ and two As+2.60+ atoms. In the third Se2- site, Se2- is bonded in a 1-coordinate geometry to five Cs1+ and one As+2.60+ atom. In the fourth Se2- site, Se2- is bonded in a 1-coordinate geometry to four Cs1+ and one As+2.60+ atom. In the fifth Se2- site, Se2- is bonded in a 1-coordinate geometry to four Cs1+ and one As+2.60+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2Fe(SeO)2 by Materials Project

La2Fe(SeO)2 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are four inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 4-coordinate geometry to four Se2- and four O2- atoms. There are a spread of La–Se bond distances ranging from 3.22–3.53 Å. There are a spread of La–O bond distances ranging from 2.38–2.48 Å. In the second La3+ site, La3+ is bonded in a 4-coordinate geometry to four Se2- and four O2- atoms. There are a spread of La–Se bond distances ranging from 3.22–3.48 Å. There are a spread of La–O bond distances ranging from 2.39–2.45 Å. In the third La3+ site, La3+ is bonded in a 3-coordinate geometry to five Se2- and three O2- atoms. There are a spread of La–Se bond distances ranging from 3.10–3.46 Å. There are one shorter (2.35 Å) and two longer (2.40 Å) La–O bond lengths. In the fourth La3+ site, La3+ is bonded in a 3-coordinate geometry to five Se2- and three O2- atoms. There are a spread of La–Se bond distances ranging from 3.14–3.33 Å. There are a spread of La–O bond distances ranging from 2.33–2.40 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded in a distorted linear geometry to four Se2- and two O2- atoms. There are a spread of Fe–Se bond distances ranging from 2.87–2.96 Å. There is one shorter (1.97 Å) and one longer (1.98 Å) Fe–O bond length. In the second Fe2+ site, Fe2+ is bonded to four Se2- atoms to form corner-sharing FeSe4 tetrahedra. There are a spread of Fe–Se bond distances ranging from 2.53–2.62 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to six La3+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to two La3+ and four Fe2+ atoms. In the third Se2- site, Se2- is bonded in a 1-coordinate geometry to four La3+ and three Fe2+ atoms. In the fourth Se2- site, Se2- is bonded in a 1-coordinate geometry to six La3+ and one Fe2+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to three La3+ and one Fe2+ atom to form OLa3Fe tetrahedra that share corners with four OLa3Fe tetrahedra and edges with two equivalent OLa4 tetrahedra. In the second O2- site, O2- is bonded to three La3+ and one Fe2+ atom to form OLa3Fe tetrahedra that share corners with four OLa3Fe tetrahedra and edges with two equivalent OLa4 tetrahedra. In the third O2- site, O2- is bonded to four La3+ atoms to form a mixture of corner and edge-sharing OLa4 tetrahedra. In the fourth O2- site, O2- is bonded to four La3+ atoms to form a mixture of corner and edge-sharing OLa4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsLu7Se11 by Materials Project

CsLu7Se11 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Cs1+ is bonded in a 11-coordinate geometry to eleven Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.67–4.19 Å. There are five inequivalent Lu3+ sites. In the first Lu3+ site, Lu3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing LuSe6 octahedra. The corner-sharing octahedra tilt angles range from 5–7°. There are a spread of Lu–Se bond distances ranging from 2.78–2.84 Å. In the second Lu3+ site, Lu3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing LuSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–55°. There are a spread of Lu–Se bond distances ranging from 2.73–2.91 Å. In the third Lu3+ site, Lu3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing LuSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–55°. There are a spread of Lu–Se bond distances ranging from 2.73–2.94 Å. In the fourth Lu3+ site, Lu3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing LuSe6 octahedra. The corner-sharing octahedral tilt angles are 7°. There are a spread of Lu–Se bond distances ranging from 2.78–2.86 Å. In the fifth Lu3+ site, Lu3+ is bonded to six Se2- atoms to form a mixture of corner, edge, and face-sharing LuSe6 octahedra. The corner-sharing octahedra tilt angles range from 5–52°. There are a spread of Lu–Se bond distances ranging from 2.72–2.86 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Cs1+ and four Lu3+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to one Cs1+ and three Lu3+ atoms. In the third Se2- site, Se2- is bonded to five Lu3+ atoms to form edge-sharing SeLu5 square pyramids. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to one Cs1+ and four Lu3+ atoms. In the fifth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Lu3+ atoms. In the sixth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Cs1+ and four Lu3+ atoms. In the seventh Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Cs1+ and three Lu3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo2RuSe4 by Materials Project

Mo2RuSe4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Mo3+ sites. In the first Mo3+ site, Mo3+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with two MoSe5 square pyramids, corners with two RuSe5 square pyramids, edges with two RuSe5 square pyramids, and edges with three MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.54–2.68 Å. In the second Mo3+ site, Mo3+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one RuSe5 square pyramid, corners with three MoSe5 square pyramids, edges with two RuSe5 square pyramids, and edges with three MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.54–2.68 Å. In the third Mo3+ site, Mo3+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one RuSe5 square pyramid, corners with three MoSe5 square pyramids, edges with two RuSe5 square pyramids, and edges with three MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.67 Å. In the fourth Mo3+ site, Mo3+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with two MoSe5 square pyramids, corners with two RuSe5 square pyramids, edges with two RuSe5 square pyramids, and edges with three MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.69 Å. There are two inequivalent Ru2+ sites. In the first Ru2+ site, Ru2+ is bonded to five Se2- atoms to form RuSe5 square pyramids that share a cornercorner with one RuSe5 square pyramid, corners with three MoSe5 square pyramids, an edgeedge with one RuSe5 square pyramid, and edges with four MoSe5 square pyramids. There are a spread of Ru–Se bond distances ranging from 2.48–2.66 Å. In the second Ru2+ site, Ru2+ is bonded to five Se2- atoms to form RuSe5 square pyramids that share a cornercorner with one RuSe5 square pyramid, corners with three MoSe5 square pyramids, an edgeedge with one RuSe5 square pyramid, and edges with four MoSe5 square pyramids. There are a spread of Ru–Se bond distances ranging from 2.48–2.67 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to one Mo3+ and two Ru2+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to three Mo3+ and one Ru2+ atom. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two Mo3+ and two Ru2+ atoms. In the fifth Se2- site, Se2- is bonded in a 4-coordinate geometry to three Mo3+ and one Ru2+ atom. In the sixth Se2- site, Se2- is bonded in a 4-coordinate geometry to three Mo3+ and one Ru2+ atom. In the seventh Se2- site, Se2- is bonded in a 4-coordinate geometry to three Mo3+ and one Ru2+ atom. In the eighth Se2- site, Se2- is bonded in a 4-coordinate geometry to two Mo3+ and two Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(ScSe2)2 by Materials Project

Mg(ScSe2)2 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one ScSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with four ScSe7 pentagonal bipyramids, an edgeedge with one MgSe6 octahedra, edges with four ScSe6 octahedra, and edges with three ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 15–56°. There are a spread of Mg–Se bond distances ranging from 2.66–2.80 Å. In the second Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one ScSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with four ScSe7 pentagonal bipyramids, an edgeedge with one MgSe6 octahedra, edges with four ScSe6 octahedra, and edges with three ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 15–56°. There are a spread of Mg–Se bond distances ranging from 2.68–2.75 Å. There are four inequivalent Sc3+ sites. In the first Sc3+ site, Sc3+ is bonded to six Se2- atoms to form ScSe6 octahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent ScSe6 octahedra, corners with four ScSe7 pentagonal bipyramids, an edgeedge with one ScSe6 octahedra, edges with four MgSe6 octahedra, and edges with three ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 13–56°. There are a spread of Sc–Se bond distances ranging from 2.69–2.75 Å. In the second Sc3+ site, Sc3+ is bonded to six Se2- atoms to form ScSe6 octahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent ScSe6 octahedra, corners with four ScSe7 pentagonal bipyramids, an edgeedge with one ScSe6 octahedra, edges with four MgSe6 octahedra, and edges with three ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 13–56°. There are a spread of Sc–Se bond distances ranging from 2.68–2.79 Å. In the third Sc3+ site, Sc3+ is bonded to seven Se2- atoms to form distorted ScSe7 pentagonal bipyramids that share corners with four MgSe6 octahedra, corners with four ScSe6 octahedra, edges with three MgSe6 octahedra, edges with three ScSe6 octahedra, and faces with two equivalent ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 18–67°. There are a spread of Sc–Se bond distances ranging from 2.71–2.99 Å. In the fourth Sc3+ site, Sc3+ is bonded to seven Se2- atoms to form distorted ScSe7 pentagonal bipyramids that share corners with four MgSe6 octahedra, corners with four ScSe6 octahedra, edges with three MgSe6 octahedra, edges with three ScSe6 octahedra, and faces with two equivalent ScSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 19–66°. There are a spread of Sc–Se bond distances ranging from 2.72–3.00 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two Mg2+ and three Sc3+ atoms to form distorted SeMg2Sc3 trigonal bipyramids that share corners with two equivalent SeMg2Sc3 square pyramids, corners with three equivalent SeMgSc3 tetrahedra, corners with two equivalent SeMg2Sc3 trigonal bipyramids, edges with three SeMg2Sc3 square pyramids, and edges with five SeMg2Sc3 trigonal bipyramids. In the second Se2- site, Se2- is bonded to two Mg2+ and three Sc3+ atoms to form distorted SeMg2Sc3 trigonal bipyramids that share corners with six SeMg2Sc3 square pyramids, corners with two equivalent SeMgSc3 tetrahedra, corners with two equivalent SeMg2Sc3 trigonal bipyramids, an edgeedge with one SeMg2Sc3 square pyramid, an edgeedge with one SeMgSc3 tetrahedra, and edges with five SeMg2Sc3 trigonal bipyramids. In the third Se2- site, Se2- is bonded to one Mg2+ and three Sc3+ atoms to form distorted SeMgSc3 tetrahedra that share corners with two SeMg2Sc3 square pyramids, corners with ten SeMg2Sc3 trigonal bipyramids, edges with two SeMg2Sc3 square pyramids, and edges with two SeMgSc4 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Sc3+ atoms. In the fifth Se2- site, Se2- is bonded to two Mg2+ and three Sc3+ atoms to form distorted SeMg2Sc3 square pyramids that share a cornercorner with one SeMgSc3 tetrahedra, corners with eight SeMg2Sc3 trigonal bipyramids, edges with two equivalent SeMg2Sc3 square pyramids, an edgeedge with one SeMgSc3 tetrahedra, and edges with four SeMg2Sc3 trigonal bipyramids. In the sixth Se2- site, Se2- is bonded to two Mg2+ and three Sc3+ atoms to form distorted SeMg2Sc3 square pyramids that share a cornercorner with one SeMgSc3 tetrahedra, corners with eight SeMg2Sc3 trigonal bipyramids, edges with two equivalent SeMg2Sc3 square pyramids, an edgeedge with one SeMgSc3 tetrahedra, and edges with four SeMg2Sc3 trigonal bipyramids. In the seventh Se2- site, Se2- is bonded to one Mg2+ and four Sc3+ atoms to form distorted SeMgSc4 trigonal bipyramids that share corners with two equivalent SeMg2Sc3 square pyramids, corners with two equivalent SeMgSc3 tetrahedra, corners with two equivalent SeMgSc4 trigonal bipyramids, edges with three SeMg2Sc3 square pyramids, an edgeedge with one SeMgSc3 tetrahedra, and edges with five SeMg2Sc3 trigonal bipyramids. In the eighth Se2- site, Se2- is bonded to one Mg2+ and four Sc3+ atoms to form distorted SeMgSc4 trigonal bipyramids that share corners with six SeMg2Sc3 square pyramids, corners with three equivalent SeMgSc3 tetrahedra, corners with two equivalent SeMgSc4 trigonal bipyramids, an edgeedge with one SeMg2Sc3 square pyramid, and edges with five SeMg2Sc3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2(TaSe2)3 by Materials Project

K3(TaSe2)4K(TaSe2)2 crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of one K(TaSe2)2 sheet oriented in the (0, 0, 1) direction and one K3(TaSe2)4 sheet oriented in the (0, 0, 1) direction. In the K(TaSe2)2 sheet, K1+ is bonded in a 12-coordinate geometry to six equivalent Se2- atoms. All K–Se bond lengths are 3.21 Å. Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.64 Å) Ta–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 38°. In the second Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Ta+3.33+ atoms. In the K3(TaSe2)4 sheet, there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 12-coordinate geometry to six Se2- atoms. There are three shorter (3.20 Å) and three longer (3.22 Å) K–Se bond lengths. In the second K1+ site, K1+ is bonded in a 12-coordinate geometry to six equivalent Se2- atoms. All K–Se bond lengths are 3.22 Å. There are two inequivalent Ta+3.33+ sites. In the first Ta+3.33+ site, Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.64 Å) Ta–Se bond lengths. In the second Ta+3.33+ site, Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.63 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Ta+3.33+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three equivalent K1+ and three equivalent Ta+3.33+ atoms. In the third Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 37°. In the fourth Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 37°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo3(SeS)2 by Materials Project

Mo3(SeS)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Mo+2.67+ sites. In the first Mo+2.67+ site, Mo+2.67+ is bonded to three Se2- and two S2- atoms to form a mixture of corner and edge-sharing MoSe3S2 square pyramids. All Mo–Se bond lengths are 2.56 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Mo–S bond lengths. In the second Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. Both Mo–Se bond lengths are 2.57 Å. There are a spread of Mo–S bond distances ranging from 2.43–2.45 Å. In the third Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. There are one shorter (2.54 Å) and one longer (2.55 Å) Mo–Se bond lengths. There are one shorter (2.44 Å) and two longer (2.45 Å) Mo–S bond lengths. In the fourth Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form MoSe2S3 square pyramids that share corners with four MoSe2S3 square pyramids and edges with five MoSe3S2 square pyramids. There are one shorter (2.57 Å) and one longer (2.61 Å) Mo–Se bond lengths. There are two shorter (2.45 Å) and one longer (2.50 Å) Mo–S bond lengths. In the fifth Mo+2.67+ site, Mo+2.67+ is bonded to three Se2- and two S2- atoms to form a mixture of corner and edge-sharing MoSe3S2 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.61 Å. There are one shorter (2.42 Å) and one longer (2.50 Å) Mo–S bond lengths. In the sixth Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. There are one shorter (2.56 Å) and one longer (2.57 Å) Mo–Se bond lengths. There are a spread of Mo–S bond distances ranging from 2.44–2.46 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo+2.67+ atoms. In the fourth Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo+2.67+ atoms. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the third S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the fourth S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Selenium Migration and Local Structures in Cu‐Doped CdSeTe Solar Cells after Aging

Selenium grading plays a critical role in state-of-the-art Cadmium Telluride photovoltaic cells by enhancing long-wavelength absorption and extending minority carrier lifetimes —key to enabling the current performance record of 23.08%. However, very little is understood about selenium motion. In this study, a comprehensive, multimodal, and multiscale approach is employed to investigate Se migration and local structural changes in copper (Cu)-doped CdSeTe solar cells subjected to accelerated stress. X-ray fluorescence (XRF) microscopy shows unexpected levels of Se diffusion after 500 h under heat (75°C) and light (0.8 suns, 80 mW/cm 2 ), suggesting the coexistence of fast and slow diffusion channels even at low temperatures, with unexpectedly low activation energies (<0.85 eV). X-ray Absorption Near Edge Structure (XANES) analysis indicates a preferential migration of Se atoms to anionic lattice sites and a reduction in Se-Cl co-passivation at Te-terminated dislocation cores. Furthermore, these findings point to a reconfiguration of Se local environments and highlight the potential role of extended structural defects in enabling Se transport at low temperatures. Additionally, XANES results suggest that the presence of metallic Cu across the absorber layer may contribute to back-contact degradation and reduced hole density in both fresh and aged devices.

14 SOLAR ENERGY↗
DOE OSTI2021

Engineering integration in elementary science classrooms: Effects of disciplinary language scaffolds on English learners' content learning and engineering identity

Abstract Background Limited research examines the effects of integrated science and engineering (SE) instruction emphasizing disciplinary literacy and language activities on engineering identity and content understanding. Far fewer studies target English learners (ELs). Purpose The impact of an SE intervention on the development of science, engineering, and technology knowledge as well as engineering identity was examined. To address ELs' learning needs, the curricular design was built on a validated SE model by integrating (1) developmental, (2) language scaffolds, and (3) culturally based accommodations. Design/Method Separate analysis of variance examined the effects of the intervention on science, engineering, and technology knowledge as well as engineering identity. The relationship among engineering identity and content outcomes was also examined. ELs from kindergarten to second grade classrooms were randomly assigned to the integrated SE group or control group. Results Integrated SE instruction significantly increased ELs' science, engineering, and technology knowledge as well as a substantially developed engineering identity. Overall, ELs' engineering identity is associated with an increase in science, engineering, and technology content knowledge. However, second grade girls' identity development was not associated with learning measures. These correlations suggest the context of the engineering activity may have reinforced gendered stereotypes and reduced the effects for girls' engineering attitudes. Conclusions Integrated SE instruction emphasizing disciplinary literacy and cultural accommodations increases early elementary ELs' learning and engineering identity. Future studies should examine the unique effects of language scaffolds and cultural modifications on student learning and the impact of gender stereotypes on girls' engineering attitudes.

Aguirre‐Muñoz, Zenaida↗
DOE OSTI2025

Monocrystalline CdSeTe/MgCdTe Double‐Heterostructure Solar Cells

This article reports monocrystalline CdSeTe/MgCdTe double‐heterostructure (DH) solar cells with varying Se compositions in the absorber layers that are grown on InSb substrates by using molecular beam epitaxy. The Se composition in the samples studied is determined to be 4%–11% through high‐resolution X‐ray diffraction (XRD) and photoluminescence measurements. Increased Se incorporation induces higher defect density attributed to increased lattice mismatch, and mixed‐phase formation due to the small difference in formation energies between the wurtzite and zinc blende phases of CdSe, which causes stacking faults and grain boundaries. Devices are fabricated by directly depositing an n‐type indium tin oxide (ITO) layer on the CdSeTe/MgCdTe DHs followed by Ag metal contacts. Reduced bandgap is observed in solar cells with increased Se composition. The devices with an absorber containing 4% Se exhibit an average open‐circuit voltage ( V OC ) of 0.925 V, a short‐circuit current density ( J SC ) of 23.4 mA/cm 2 , a fill factor ( FF ) of 0.650 and an efficiency of 14.1% without anti‐reflection coating. Absorbers with higher Se compositions result in poor device performance, mainly attributed to high defect density in the materials.

Ju, Zheng [Center for Photonics Innovation Arizona↗
DOE OSTI2023

Behavior of selenium and arsenic in $\mathrm{HCl}$ and $\mathrm{HNO}$ 3 on $\mathrm{TRU, TEVA, DGA,}$ and $\mathrm{Pb}$ extraction chromatography resins

The uptake behavior of 73 As and 75 Se was studied in HCl and HNO 3 -H 2 O 2 solutions on commercial extraction chromatography resins (TEVA, TRU, DGA, and Pb resin). There was no uptake of 73 As or 75 Se from HNO 3 media. From HCl, there was 75 Se uptake at high concentrations on all the resins and no uptake of 73 As. Separations of 75 Se and 73 As on these resins have high yields and high radiopurity for 73 As, but limited recovery of 75 Se. TRU and TEVA resin may have potential for use in isotope generators as 75 Se can be retained for at least 26 days with repeated elutions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Solvent-free and low temperature synthesis of chalcogenide Na superionic conductors for solid-state batteries

Sodium chalcogenide ionic conductors are attractive candidates as solid electrolytes (SEs) in solid-state Na metal batteries. They show the advantages of high ionic conductivity of 10 –4 –10 –2 S cm –1 at room temperature and great chemical stability in air. However, simple, efficient, and scalable approaches for the synthesis of chalcogenide solid electrolytes (SEs) are required. In this work, we report a solvent-free mixing to form dry intermediate products, which are subjected to different treatments (electron-beam assisted method or low temperature heating (≤150 °C)) to produce pure phase of Na 3 SbS 4-y Se y (0 ≤ y < 2) chalcogenides. Heavy Se-doping in Na 3 SbS 4 results in the tetragonal-to-cubic phase transition as well as a significant change of Sb-S bonding in Raman spectra. Among all chalcogenide SEs, Na 3 SbS 3 Se showed the highest ionic conductivity of 3.75 × 10 –4 S cm –1 at room temperature, 47% higher than that of pristine Na 3 SbS 4 . Moreover, the Se-dopant also enhanced the electrochemical stability towards Na metal in solid-state batteries. The solid-state Na||FeS 2 battery with Na 3 SbS 3 Se SE displayed long-term cycling ability up to 1,000 cycles within the voltage window of 1.0–2.7 V and retained a specific capacity of 105 mAh g –1 after 600 cycles. As a result, this technique promotes the practical applications of chalcogenide SEs in solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Steam explosion pretreatment coupling high-temperature short-time sterilization facilitating cellulose degradation and sporulation-regulatory gene expression in high-solid fermentation

Steam explosion coupling high-temperature short-time sterilization (SE-HTST) was exploited to modify cellulosic biomass medium properties and promote high-solid fermentation (HSF). Biomass characterization analysis showed that SE-HTST enlarged microstructural pores and cavities in solid media, providing more effective space for microbial growth. Meanwhile, SE-HTST helped to release glucose from the cellulose with 35.8 ± 4.5, 20.0 ± 2.3, and 12.3 ± 5.7 mg glucose/g dry medium at 24, 48, and 72 h of fermentation, which were 3.1, 2.3, and 1.5 times higher than that in medium from conventional thermal sterilization (CTS), respectively. SE-HTST increased the viable cell and spore number of Bacillus subtilis by 1.8 and 1.6 times at 72 h of fermentation compared to CTS. Moreover, the expressions of master transcriptional gene spo0A and the early sigma factors of sigF and sigE genes gradually increased in the SE-HTST medium, showing enhanced sporulation in HSF. Therefore, SE-HTST is an effective strategy for facilitating cellulose degradation, improving glucose nutrients in biomass medium, and promoting sporulation-regulatory gene expression during high-solid fermentation, which enhances the production of microbial ecological agents using B. subtilis significantly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Homologous Alkali Metal Copper Rare-Earth Chalcogenides A 2 Cu 2 n Ln 4 Q 7+ n ( n = 1, 2, 3)

Twenty-seven new members of the A 2 Cu 2n Ln 4 Q 7+n (A = Cs, Rb; Ln = La-Nd, Sm, Gd-Yb; Q = S, Se) homologous series were synthesized in one of three structural types (indicated by n = 1, 2, 3). All the compounds contained 3D frameworks with alkali-metal-containing tunnels. For each increment in n, one Cu 2 Q was added, which was incorporated into the framework as an edge-sharing tetrahedron by replacing a square planar chalcogenide site. High-throughput DFT calculations predicted many of the phases to be thermodynamically stable. These predictions were compared with the synthesis results for the phases formed in each composition space. In the syntheses, heavier lanthanides showed a preference to start forming the n = 3 ACu 3 Ln 2 Q 5 , which is consistent with the predictions. RbCuNd 2 Se 4 and RbCuTb 2 Se 4 were found to be thermally stable under vacuum at temperatures up to 1000 °C. Optical measurements revealed band gaps of 1.55(5) and 1.62(5) eV for CsCuCe 2 Se 4 and RbCuTb 2 Se 4 , respectively, and a work function of 4.83(5) eV for CsCuPr 2 Se 4 . Additionally, some n = 3 ACu 3 Ln 2 Qs compounds exhibit a negative phonon mode because of a copper atom coordination, which may distort to a trigonal planar geometry at sufficiently low temperatures. The dynamic instabilities and the predicted distortion in the copper tetrahedra for the n = 3 ACu 3 Ln 2 Q 5 compounds were found to have a linear relationship with the atomic number of the lanthanides and the electronegativity of the lanthanides. In conclusion, the A 2 Cu 2 n Ln 4 Q 7+n compounds can potentially find application as high-temperature thermoelectric materials and other semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Improved Accuracy in Semi-Experimental Structure Determination by Resolving Problems Associated with Rotation of Principal Inertial Axes of Isotopologues: Structures of 1,3-Oxazole ( c -C 3 H 3 NO)

The rotational spectrum of the normal isotopologue of 1,3-oxazole (c-C 3 H 3 NO) was observed from 43 to 750 GHz. Over 3900 transitions for the ground vibrational state are measured, assigned, and least-squares fit to sextic centrifugally distorted-rotor Hamiltonians. The measured frequencies and resulting spectroscopic constants from this extended spectral range, combined with previous measurements of the nuclear quadrupole coupling constants, will facilitate astronomical searches for oxazole across the majority of the range of modern radiotelescopes. Spectra for a set of 30 oxazole isotopologues, which include multiple isotopic substitutions of each atom, are used to determine the first semi-experimental equilibrium ($r$$^{SE}_{e}$) structure and semi-experimental substitution structure ($r$$^{SE}_{e}$), each using CCSD(T) computed values for the vibration–rotation interaction and electron-mass corrections. The large number of isotopologues, including 21 isotopologues observed for the first time, and the redundant substitutions of each atom provide sufficient spectroscopic information to determine the $r$$^{SE}_{e}$ structure with the expected high level of accuracy and precision (0.0001 or 0.0002 Å in bond distances and 0.013 to 0.025° in bond angles). In the course of this study, we analyzed a known issue for some $r$$^{SE}_{e}$ structure determinations of near-oblate asymmetric tops in which inclusion of individual isotopologues degrades the structure determination. We demonstrate that this problem primarily arises from the difference in the values of the computed vibration–rotation interaction corrections as evaluated at the computed re geometry vs the $r$$^{SE}_{e}$ geometry of the “real” molecule. Our solution to this problem substantially improves the $r$$^{SE}_{e}$ structure of oxazole and likely can be generalized to many other molecules.

Chemical structure↗
DOE OSTI2025

Minimization of Cathode|Solid-Electrolyte Interfacial Delamination through the Application of Interphase Layers

Next-generation lithium-ion batteries are expected to use solid electrolytes (SEs) to enable higher energy density and extreme fast-charge capabilities. One major mode of degradation at the cathode|SE interface is delamination between the cathode active materials and SEs, which leads to performance decay. Experimental observations indicate that implementation of interphase layers can minimize the cathode|SE delamination induced capacity fade. A multiscale computational methodology is developed here to investigate the applicability of boron substituted lithium carbonate (Li 2+x B x C 1–x O 3 , x = 0.5, or LBCO) to minimize the delamination at the cathode|SE interface. Atomistic simulations indicate that the fracture energies at both the cathode|LBCO and LBCO|SE interfaces are higher than those at the cathode|SE interface, which reduces the extent of delamination. Mesoscale simulations indicate that, apart from increasing the fracture energy, decreasing the evolution of strain energy by lowering the elastic modulus of the interphase layer can also minimize the extent of delamination at the cathode|SE interface. However, the adoption of an interphase layer with high ionic conductivity is necessary to minimize the ohmic losses during operation at higher current densities. This study provides guidance on selecting interphase layers with specific properties and thicknesses to minimize both interfacial delamination and impedance growth.

LBCO↗
DOE OSTI2023

Functional Predictor Variables for the Leaching Potential of Arsenic and Selenium from Coal Fly Ash

The release of leachates from intact coal ash impoundments is a concern due to the enrichment and mobilization of toxic elements such as arsenic (As) and selenium (Se). This study aims to explore the intrinsic properties of coal fly ash that correlate with the relative leachability of As and Se. We performed leaching experiments with 52 fly ash samples collected from 15 different U.S. power plants and representing coal feedstocks from the three major domestic regions. We assessed the mobilization potential of As and Se in fly ash based on standardized leaching protocols and performed multivariate and lasso regression analyses to explore correlations of leachable As and Se contents with characteristics such as major element contents, loss on ignition, and pH. The results of regression models indicated that major elements (Fe, Ca, and Al) for a wide range of fly ashes can serve as predictor variables for the leaching potential of As but not for Se. LOI and pH were not important predictive variables in the models. Both regression approaches resulted in relatively strong fits for leachable As (correlation coefficient R 2 = 0.78 for both models) compared to models for leachable Se (R 2 = 0.49). Overall, these results suggest that correlation models combined with on-site elemental analysis with portable analyzers may enable a screening method for leachable As in coal ash.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2023

Non-Markovian Hole Excess Noise in Avalanche Amorphous Selenium Thin Films

Enhancing the signal-to-noise ratio in avalanche photodiodes by utilizing impact ionization gain requires materials exhibiting low excess noise factors. Amorphous selenium (a-Se) as a wide bandgap at ~2.1 eV, a solid-state avalanche layer, demonstrates single-carrier hole impact ionization gain and manifests ultralow thermal generation rates. A comprehensive study of the history dependent and non-Markovian nature of hot hole transport in a-Se was modeled using a Monte Carlo (MC) random walk of single hole free flights, interrupted by instantaneous phonon, disorder, hole–dipole, and impact-ionization scattering interactions. The hole excess noise factors were simulated for 0.1–15 μm a-Se thin-films as a function of mean avalanche gain. The hole excess noise factors in a-Se decreases with an increase in electric field, impact ionization gain, and device thickness. The history dependent nature of branching of holes is explained using a Gaussian avalanche threshold distance distribution and the dead space distance, which increases determinism in the stochastic impact ionization process. An ultralow non-Markovian excess noise factor of ~1 was simulated for 100 nm a-Se thin films corresponding to avalanche gains of 1000. Future detector designs can utilize the nonlocal/non-Markovian nature of the hole avalanche in a-Se, to enable a true solid-state photomultiplier with noiseless gain.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗