Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Disorder Tolerance? Impact of Cation Disorder in ABZ₂ Chalcogenides

Disorder Tolerance? Impact of Cation Disorder in ABZ₂ Chalcogenides

Slides from my talk 'Cation Disorder and Solar Cell Performance in ABZ₂ Chalcogenides (AgBiS₂ and NaBiS₂)' at MRS Spring 2023 in San Francisco.

YouTube video recording: https://youtu.be/h1vU2dmnJVw

Papers Discussed:
AgBiS₂: https://www.nature.com/articles/s41566-021-00950-4
NaBiS₂ (open-access): https://www.nature.com/articles/s41467-022-32669-3

Questions welcome! For other computational photovoltaics, defects and disorder talks, have a look at my YouTube channel!
https://www.youtube.com/SeanRKavanagh

If you're interested in this work, you can check out our recent review on these and other perovskite-inspired materials:
https://iopscience.iop.org/article/10.1088/1361-6528/abcf6d

For more info about me and my research articles see:
https://seankavanagh.com

Seán R. Kavanagh

May 02, 2023
Tweet

More Decks by Seán R. Kavanagh

Other Decks in Research

Transcript

  1. 1
    02/05/2023
    Cation Disorder and Solar Cell
    Performance in ABZ2
    Materials
    (NaBiS2
    & AgBiS2
    )
    Seán Kavanagh
    Profs: David O. Scanlon & Aron Walsh
    [email protected]
    (University College London & Imperial College London)

    View full-size slide

  2. 2
    02/05/2023
    Cation Disorder and Solar Cell
    Performance in ABZ2
    Materials
    (NaBiS2
    & AgBiS2
    )
    Seán Kavanagh
    Profs: David O. Scanlon & Aron Walsh
    [email protected]
    (University College London & Imperial College London)

    View full-size slide

  3. Heard about Perovskites?
    3
    Y.-T. Huang, S.R. Kavanagh, D.O. Scanlon, A. Walsh, and R.L.Z. Hoye, Nanotechnology 32, 132004 (2021)
    R.L.Z. Hoye et al. Chem Mater 29, 1964 (2017)
    ‘Perovskite-Inspired’
    Materials?

    View full-size slide

  4. Perovskite-Inspired Materials
    4
    AI
    2
    BIBIIIX6
    Cation
    Substitution
    AI
    3
    B2
    IIIX9
    AI
    2
    BIVX6
    • Stable & non-toxic ✅
    • Sub-optimal bandgaps for solar cells ❌
    • Bandgap tuning via alloying & doping ✅
    • Carrier trapping & localisation due to
    reduced electronic dimensionality ❌ ❌
    Cs2
    AgBiBr6
    & Cs2
    AgSbBr6
    :
    A. H. Slavney et al. J. Am. Chem. Soc. 2016, 138, 7, 2138–2141.
    Z. Li ‡ & S. R. Kavanagh‡ et al. J. Mater. Chem. A, 2020, 8, 21780.
    Cs3
    Bi2
    Br9
    :
    B.-B. Yu et al. J. Mater. Chem. A, 2019, 7, 8818–8825.
    C. J. Krajewska, S. R. Kavanagh et al. Chem. Sci., 2021,
    12, 14686.
    Cs2
    TiX6
    & Cs2
    SnX6
    :
    M. Chen et al. Joule, 2018,
    2, 558–570.
    S. R. Kavanagh et al. J. Phys.
    Chem. Lett., 2022, 13,
    10965–10975.
    AIBIIX3
    Perovskite Structure:

    View full-size slide

  5. 5
    ABZ2 – ‘Perovskite-Inspired’
    • AI,BIII = Metal cations, Z = Chalcogen (S, Se)
    • Rocksalt crystal structure (!"#
    3") with AI/BIII cation disorder
    • MX6
    octahedra -> Similar to perovskite motif
    • Close-packed and cation disorder:
    • (Pseudo-)Direct and low bandgaps
    • Lower effective masses1
    • Metal-chalcogen bonds: Stability ⬆
    • Nanocrystal solution synthesis
    AI/BIII
    Z
    1. Y.-T. Huang, S. R. Kavanagh, D. O. Scanlon, A. Walsh and R. L. Z. Hoye, Nanotechnology, 2021, 32, 132004

    View full-size slide

  6. Modelling Disorder – A Challenge for Theory
    Special Quasirandom Structures (SQS)
    g(r)
    supercell
    ≃ g(r)
    random
    • Snapshot of total disorder
    Structural Enumeration:
    • Generate all (440) symmetry-inequivalent cation
    arrangements within a 32-atom supercell.
    • Calculate structures, energies, optical & scattering
    properties
    • Correlate with PV performance
    6
    Total
    Disorder
    (!"#
    3"):
    Total Order (%#
    3"):

    View full-size slide

  7. Cation Disorder: Optical Properties (AgBiS2
    )
    (Hybrid DFT + SOC)


    Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235

    View full-size slide

  8. Cation Disorder:
    Control via Annealing
    Collaborators:
    Dr. Yongjie Wang, Dr. Ignasi
    Burgués-Ceballos, Prof.
    Gerasimos Konstantatos (ICFO)
    Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235

    View full-size slide

  9. Cation Disorder:
    Control via Annealing
    Collaborators:
    Dr. Yongjie Wang, Dr. Ignasi
    Burgués-Ceballos, Prof.
    Gerasimos Konstantatos (ICFO)
    Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235

    View full-size slide

  10. XRD
    Theory:
    Expt:
    XPS
    Theory:
    Expt:
    TEM
    Theory:
    Expt:
    2θ ⬆
    2θ ⬆
    EBi 5d

    EBi 5d

    a
    AgBiS₂

    a
    AgBiS₂

    Cation Disorder: Control via Annealing Collaborators:
    Dr. Yongjie Wang, Dr. Ignasi Burgués-Ceballos,
    Prof. Gerasimos Konstantatos (ICFO)
    Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235

    View full-size slide

  11. AgBiS2
    :
    • Highest absorption coefficient ⍺ of any
    currently-studied PV material
    • Highest efficiency of any Bismuth-based
    solar material
    BiSI BiI3
    Bi2
    S3
    MA3
    Bi2
    I9
    Cs3
    Bi2
    I9
    Cs2
    AgBiBr6
    AgBi2
    I7
    Ag2
    Bi2
    I9
    AgBiS2
    0
    2
    4
    6
    8
    10
    PV Efficiency (%)
    Bi-Based PV
    • Solar cells with record-breaking efficiencies η > 9%,
    using an ultrathin 30 nm absorber (previous η = 6%)
    • Control of atomic disorder facilitates major absorption
    enhancement, allowing high-efficiency ultrathin devices
    Collaborators:
    Dr. Yongjie Wang, Dr. Ignasi
    Burgués-Ceballos, Prof.
    Gerasimos Konstantatos (ICFO)
    Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235

    View full-size slide

  12. What about NaBiS2
    ?
    AI/BIII
    Z
    Strong absorption ➡ high potential efficiency in ultrathin cells
    Y.T. Huang‡ & S. R. Kavanagh‡ et al. Nature Communications 2022 13 (1), 1-13
    Collaborators:
    Y-T. Huang, Prof. R.L.Z. Hoye
    (Oxford) I. Levine, T. Unold (HZB), L.
    M. Herz, S. M. Stranks (Cambridge)

    View full-size slide

  13. In-gap states impede PV performance
    Y.-T. Huang, S. R. Kavanagh, D.O. Scanlon, A. Walsh,
    R.L.Z. Hoye, Nanotechnology 32, 132004 (2021)
    Collaborators:
    Y-T. Huang, Prof. R.L.Z. Hoye
    (Oxford) I. Levine, T. Unold (HZB), L.
    M. Herz, S. M. Stranks (Cambridge)
    ➡ Calculations reveal trap levels above VBM, at Na-rich pockets
    Y.T. Huang‡ & S. R. Kavanagh‡ et al. Nature Communications 2022 13 (1), 1-13

    View full-size slide

  14. What causes the localised states in NaBiS2?
    Na+ = Empty valence shell (s0), Ag+ = Filled shell (d10) -> ‘defect-tolerant’
    ➡ Spectator ion, flat non-bonding VBM ➡ Trap levels above VBM, at Na-rich pockets
    Na 3s
    Y.T. Huang‡ & S. R. Kavanagh‡ et al. Nature Communications 2022 13 (1), 1-13

    View full-size slide

  15. Cation Disorder in NaBiS2
    : Electronic Properties
    ➡ Trap levels above VBM
    ➡ Ultrafast carrier trapping (% ~ ps), followed by slow decay (% ~ μs),
    confirmed by pump-probe measurements
    ➡Record efficiency η = 0.6% (c.f. η > 9% for AgBiS2)
    "
    short
    = 34 ps
    "
    long
    ~ 6 μs
    Na 3s
    Y.T. Huang‡ & S. R. Kavanagh‡ et al. Nature Communications 2022 13 (1), 1-13

    View full-size slide

  16. What causes the localised states?
    Na+ = s0, Ag+ = d10s0 -> ‘defect-tolerant’
    ➡ Spectator ion, flat non-bonding VBM
    ➡ Trap levels above VBM, at Na-rich pockets
    ‘Defect tolerant’ electronic
    structure in lead halide perovskites
    Y.-T. Huang, S. R. Kavanagh, D. O. Scanlon, A. Walsh
    and R. L. Z. Hoye, Nanotechnology, 2021, 32, 132004
    R. E. Brandt et al, Chem. Mater., 2017, 29, 4667–4674.

    View full-size slide

  17. BiSI BiI3
    Bi2
    S3
    MA3
    Bi2
    I9
    Cs3
    Bi2
    I9
    Cs2
    AgBiBr6
    AgBi2
    I7
    Ag2
    Bi2
    I9
    AgBiS2
    0
    2
    4
    6
    8
    10
    PV Efficiency (%)
    Bi-Based PV
    - Top performing lead halide perovskites are mixed
    triple-cation, triple-anion compositions.
    - Best performing Bi-based PV material (by far) is
    disordered AgBiS2, despite being a relative newcomer.
    - Disorder tolerance?
    Is Disorder Always Bad?
    Na 3s
    Minimal localisation with disorder in
    Sn2
    SbS2
    I3
    – potential disorder tolerance?
    A. Nicolson, S. R. Kavanagh et al. ChemRxiv
    (Under Review at J. Am. Chem. Soc)
    Localisation

    View full-size slide

  18. NaBiS2: Y.T. Huang‡ & S. R. Kavanagh‡ et al. Nature Communications 2022 13 (1), 1-13
    AgBiS2: Y. Wang‡ & S. R. Kavanagh‡, I. Burgués-Ceballos; A. Walsh, D.O. Scanlon, G. Konstantatos Nature Photonics 2022 16, 235
    Key Takeaways & Acknowledgements
    Profs David O. Scanlon & Aron Walsh
    Disorder = Powerful tool for materials design
    Both the nature of the disorder and the underlying orbital
    chemistry are key considerations for disorder engineering!
    Collaborators:
    Dr. Y. Wang, Prof. G. Konstantatos
    (ICFO Barcelona, Spain)
    Y-T. Huang, Prof. R. L. Z. Hoye (Oxford), Dr.
    I. Levine, Prof. T. Unold (HZB), Prof L. Herz,
    Prof. S. M. Stranks (Cambridge)

    View full-size slide