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Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3

Publication ,  Journal Article
Chang, ET; Koknat, G; McKeown Wessler, GC; Yao, Y; Blum, V; Mitzi, DB
Published in: Chemistry of Materials
January 24, 2023

Recently, bournonite (CuPbSbS3) has been identified as a potential ferroelectric photovoltaic (PV) material with a 1.3 eV band gap, which falls in an appropriate range for single-junction PV devices. Progress in applying bournonite has yielded several studies reporting successful thin-film processing, the most recent of which demonstrated a 2.65% power conversion efficiency for a bournonite-based PV device. In an effort to explore bournonite band gap engineering for PV and other prospective applications (e.g., thermoelectric, spintronic), we here consider the solid-state synthesis of selenium-alloyed bournonite, CuPbSb(S1−xSex)3, across the full range of x (0.0 ≤ x ≤ 1.0) and report phase purity for 0.0 ≤ x ≤ 0.5. We characterize the crystal structure and band gap of the samples using X-ray diffraction and diffuse reflectance spectroscopy, determining a band gap decrease for single-phase samples from 1.25 eV at x = 0.0 to 1.06 eV at x = 0.5. Formation energies determined using dispersion-corrected hybrid density functional theory (DFT) support experimental findings and are consistent with the stability (instability) of the x = 0.5 (x = 1.0) structure relative to starting materials. The computed band structures show a decreasing trend in the band gap with increasing x, again consistent with experiment, with the states at the conduction (valence) band minima (maxima) being principally derived from Pb (S/Se) states. Spin texture analysis and detailed comparison of spin splitting parameters show that Se alloying modifies the band gap while maintaining Rashba spin splitting character within the electronic structure. Rashba splitting is most pronounced for the conduction band minimum along the Γ−X path in the Brillouin zone. Energy separation between spin states is maintained at ΔE ∼0.2 eV for the various Se contents, with σz as the spin direction. A smaller spin splitting occurs along Γ−Z (decreasing value with increasing x), with σx as the spin direction.

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Published In

Chemistry of Materials

DOI

EISSN

1520-5002

ISSN

0897-4756

Publication Date

January 24, 2023

Volume

35

Issue

2

Start / End Page

595 / 608

Related Subject Headings

  • Materials
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences
 

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Chang, E. T., Koknat, G., McKeown Wessler, G. C., Yao, Y., Blum, V., & Mitzi, D. B. (2023). Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3. Chemistry of Materials, 35(2), 595–608. https://doi.org/10.1021/ACS.CHEMMATER.2C03109
Chang, E. T., G. Koknat, G. C. McKeown Wessler, Y. Yao, V. Blum, and D. B. Mitzi. “Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3.” Chemistry of Materials 35, no. 2 (January 24, 2023): 595–608. https://doi.org/10.1021/ACS.CHEMMATER.2C03109.
Chang ET, Koknat G, McKeown Wessler GC, Yao Y, Blum V, Mitzi DB. Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3. Chemistry of Materials. 2023 Jan 24;35(2):595–608.
Chang, E. T., et al. “Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3.” Chemistry of Materials, vol. 35, no. 2, Jan. 2023, pp. 595–608. Scopus, doi:10.1021/ACS.CHEMMATER.2C03109.
Chang ET, Koknat G, McKeown Wessler GC, Yao Y, Blum V, Mitzi DB. Phase Stability, Band Gap Tuning, and Rashba Splitting in Selenium-Alloyed Bournonite: CuPbSb(S1−xSex)3. Chemistry of Materials. 2023 Jan 24;35(2):595–608.
Journal cover image

Published In

Chemistry of Materials

DOI

EISSN

1520-5002

ISSN

0897-4756

Publication Date

January 24, 2023

Volume

35

Issue

2

Start / End Page

595 / 608

Related Subject Headings

  • Materials
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences