Poster presented at the 2022 ETH Zürich Defects Workshop.
Paper here: https://doi.org/10.1039/D2FD00043A
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
For other research articles and updates, check out my website at:
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
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:
(Left) Charge capture
surfaces (PESs) for all
(Right Upper) Resulting
charge capture cross-
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).