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All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Optimization of Annealing for WZ-Phase Removal and Densification in Sb-Doped CdSexTe1-x Solar Cells

The impact of high temperature annealing (HTA) treatments on the performance of Sb-doped CdSeTe solar cells containing a CdSe0.25Te0.75/CdTe front stack and a vapor transport (VT) deposited CdTe:Sb absorber was studied. The HTA treatment of the thermally evaporated CdSe0.25Te0.75/CdTe front stack converts the mixed-phase film into a single zinc blende structure through recrystallization of the photo-inactive wurtzite phase. Subsequently, HTA treatment of the full device stack after vapor transport deposition of CdTe:Sb absorber promotes Se-Te intermixing, reduces voids, densifies the full stack and enhances CdTe:Sb grain growth. Comprehensive characterizations revealed that the combined HTA treatments significantly improved film crystallinity, removed the WZ phase in the front stack, enhanced full-stack densification, reduced defect densities, and enhanced carrier dynamics. With HTA treatments, the open-circuit voltage (VOC) of CdSeTe:Sb devices increased from ~ 400 mV to >= 600 mV, and when combined with optimized CdCl2 treatment, VOC reached 849 mV. The net carrier concentrations (NA-ND) of representative devices were NA-ND = 1.5 x 10^15, 1.1 x 10^15, and 3.5 x 10^14 cm-3 for the no-HTA, moderate-HTA, and optimized high-VOC conditions, respectively. Since the highest VOC corresponds to the lowest apparent NA-ND, , which is similar to a Cu-doped-only CdSeTe solar cell (NA-ND ~= 2 x 10^14 cm-3), the data indicate that improved device performance does not result from increased electrically active Sb; instead, it points to structural improvement as the dominant effect of HTA. The findings demonstrate the potential of HTA treatments to improve the structural and electrical properties of CdSeXTe1-X solar cells.

14 SOLAR ENERGY↗
DOE OSTI2020

Materials Data on NaNd3 by Materials Project

NaNd3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Na is bonded to twelve equivalent Nd atoms to form NaNd12 cuboctahedra that share corners with twelve equivalent NaNd12 cuboctahedra, edges with twenty-four equivalent NdNa4Nd8 cuboctahedra, faces with six equivalent NaNd12 cuboctahedra, and faces with twelve equivalent NdNa4Nd8 cuboctahedra. All Na–Nd bond lengths are 3.66 Å. Nd is bonded to four equivalent Na and eight equivalent Nd atoms to form NdNa4Nd8 cuboctahedra that share corners with twelve equivalent NdNa4Nd8 cuboctahedra, edges with eight equivalent NaNd12 cuboctahedra, edges with sixteen equivalent NdNa4Nd8 cuboctahedra, faces with four equivalent NaNd12 cuboctahedra, and faces with fourteen equivalent NdNa4Nd8 cuboctahedra. All Nd–Nd bond lengths are 3.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3Nd by Materials Project

Na3Nd is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Na sites. In the first Na site, Na is bonded to eight Na and four equivalent Nd atoms to form distorted NaNa8Nd4 cuboctahedra that share corners with four equivalent NdNa12 cuboctahedra, corners with fourteen NaNa8Nd4 cuboctahedra, edges with six equivalent NdNa12 cuboctahedra, edges with twelve NaNa8Nd4 cuboctahedra, faces with four equivalent NdNa12 cuboctahedra, and faces with sixteen NaNa8Nd4 cuboctahedra. There are a spread of Na–Na bond distances ranging from 3.57–3.81 Å. There are two shorter (3.67 Å) and two longer (3.69 Å) Na–Nd bond lengths. In the second Na site, Na is bonded to eight Na and four equivalent Nd atoms to form distorted NaNa8Nd4 cuboctahedra that share corners with four equivalent NdNa12 cuboctahedra, corners with fourteen NaNa8Nd4 cuboctahedra, edges with six equivalent NdNa12 cuboctahedra, edges with twelve NaNa8Nd4 cuboctahedra, faces with four equivalent NdNa12 cuboctahedra, and faces with sixteen NaNa8Nd4 cuboctahedra. Both Na–Na bond lengths are 3.59 Å. There are two shorter (3.67 Å) and two longer (3.69 Å) Na–Nd bond lengths. In the third Na site, Na is bonded to eight Na and four equivalent Nd atoms to form distorted NaNa8Nd4 cuboctahedra that share corners with four equivalent NdNa12 cuboctahedra, corners with fourteen NaNa8Nd4 cuboctahedra, edges with six equivalent NdNa12 cuboctahedra, edges with twelve NaNa8Nd4 cuboctahedra, faces with four equivalent NdNa12 cuboctahedra, and faces with sixteen NaNa8Nd4 cuboctahedra. There are a spread of Na–Na bond distances ranging from 3.57–3.81 Å. There are two shorter (3.67 Å) and two longer (3.69 Å) Na–Nd bond lengths. Nd is bonded to twelve Na atoms to form NdNa12 cuboctahedra that share corners with six equivalent NdNa12 cuboctahedra, corners with twelve NaNa8Nd4 cuboctahedra, edges with eighteen NaNa8Nd4 cuboctahedra, faces with eight equivalent NdNa12 cuboctahedra, and faces with twelve NaNa8Nd4 cuboctahedra.

36 MATERIALS SCIENCE↗