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Metastable Defect Structures and their Effect on Carrier Recombination (ETH Zürich Defects Workshop Poster 2022)

Metastable Defect Structures and their Effect on Carrier Recombination (ETH Zürich Defects Workshop Poster 2022)

Poster presented at the 2022 ETH Zürich Defects Workshop.

Paper here: https://doi.org/10.1039/D2FD00043A

Other references:
Recombination at V_Cd in CdTe (involving metastable states): https://pubs.acs.org/doi/abs/10.1021/acsenergylett.1c00380
Defect Structure Searching: https://arxiv.org/abs/2207.09862
Matter Preview of Defect Structure Searching: https://www.sciencedirect.com/science/article/pii/S2590238521002733
ShakeNBreak: https://shakenbreak.readthedocs.io/en/latest/

For other research articles and updates, check out my website at:

Seán R. Kavanagh

September 17, 2022

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  1. Seán R. Kavanagh, Aron Walsh, David O. Scanlon,
    Christoph Freysoldt; Faraday Discussions, 2022
    Impact of metastable defect structures on carrier recombination
    Scan me for the paper link and a YouTube talk on this work!
    Metastable defect structures
    affect defect concentrations and
    carrier recombination
    a. Graph network of possible recombination paths
    b. Standard, two-step (SRH) electron-hole recombination
    c. Charge capture into a metastable defect, relaxation, capture back
    d. Thermal/Photo-excitation to metastable defect, capture, capture
    e. Excitation, charge capture, relaxation, charge capture
    e- / h+
    Metastable defects can introduce several potential non-radiative recombination
    pathways, killing solar cell / LED / quantum computing performance.
    When can metastable defects impact recombination?
    Ø When energy relative to groundstate is less than the trap level: ∆E < ε(q/q±1)
    Should we expect metastable defects to be fast trap levels?
    Ø Based on conventional wisdom, if present, low-energy metastable states are likely
    to act as fast trapping / recombination centres (trap levels closer to band edges)
    Transition level positions;
    ground-state ε(q/q±1) &
    ground ↔ metastable
    defects ε(q/q∗±1) (left),
    also on a vertical energy
    level diagram (right).
    Capture into metastable
    states corresponds to
    transition levels closer to
    the band edge.
    Case Study: Tellurium Interstitials in CdTe (Tei
    ) The Result:
    h+ capture
    e– capture
    h+ capture
    e– capture
    h+ capture
    e– capture
    h+ capture
    e– capture
    (Left) Charge capture
    potential energy
    surfaces (PESs) for all
    possible Tei
    (+/0) levels.
    (Right Upper) Resulting
    charge capture cross-
    sections σn/p
    temperature T.
    (Right Lower)
    Schematic of electron-
    hole recombination at
    Tellurium interstitials in
    @Kavanagh_Sean_ [email protected]
    S.R. Kavanagh, D.O. Scanlon, A. Walsh, and C. Freysoldt, Faraday Discuss. (2022).
    A. Alkauskas, Q. Yan, and C.G. Van de Walle, Phys. Rev. B 90, 075202 (2014).
    A. Alkauskas, C.E. Dreyer, J.L. Lyons, and C.G. Van de Walle, Phys. Rev. B 93, 201304 (2016).
    I. Mosquera-Lois and S.R. Kavanagh, Matter 4, 2602 (2021).
    S.R. Kavanagh, A. Walsh, and D.O. Scanlon, ACS Energy Lett. 6, 1392 (2021).

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