Hidden Spontaneous Polarisation in the ns2-Cation Sn2SbS2I3 Chalcohalide Photovoltaic Absorber

Slides for my SMTG Group Meeting talk on 'Hidden Spontaneous Polarisation in the ns2-Cation Sn2SbS2I3 Chalcohalide Photovoltaic Absorber' in June 2021.

Open-access Materials Horizons paper at: https://doi.org/10.1039/D1MH00764E

YouTube talk on this work here:
https://www.youtube.com/watch?v=H8cvJfZq8S8&t=1s

Questions welcome!

Also find our open-access review on perovskite-inspired materials here: https://iopscience.iop.org/article/10.1088/1361-6528/abcf6d

Transcript

1. Hidden Spontaneous Polarisation in the Sn2 SbS2 I3 Chalcohalide Photovoltaic Absorber Seán Kavanagh, Christopher N. Savory, Aron Walsh, David O. Scanlon SMTG Group Meeting June 2021
2. Sn2 SbS2 I3 – ‘Perovskite-Inspired’ • Novel ns2-cation chalco-halide. • Mixed anions (and cations) allows mixed ionic-covalent character. • Strong dielectric screening? • Lattice polarity? • Defect Tolerance? • Nie et al. (Group of Sang Il Seok), demonstrated >4% efficiency in the first experimental device fabrication (Nov 2020). 1. R. Nie, K. S. Lee, M. Hu, M. J. Paik and S. I. Seok, Heteroleptic Tin-Antimony Sulfoiodide for Stable and Lead-free Solar Cells. 2020 Matter, S2590238520304471.
3. Sn2 SbS2 I3 – ‘Perovskite-Inspired’ Project Plan: Quick characterisation of bulk structural and electronic properties. • Structural Relaxation • Dielectric Properties • Electronic Structure • Optical Absorption • Efficiency Potential (SLME / Blank)
4. Sn2 SbS2 I3 – ‘Perovskite-Inspired’ Project Plan: Quick characterisation of bulk structural and electronic properties. • Structural Relaxation • Dielectric Properties • Electronic Structure • Optical Absorption • Efficiency Potential (SLME / Blank)
5. Sn2 SbS2 I3 – Structural Relaxation A. Ibanez, J.-C. Jumas, J. Olivier-Fourcade and E. Philippot, Journal of Solid State Chemistry, 1984, 55, 83–91.
6. Sn2 SbS2 I3 – Structural Relaxation Sn Sb S I Cmcm Cmc2 1 b c ΔE(Cmc21 /Cmcm) = -35.8 meV/atom (RPA w/ HSE06 orbitals)
7. Sn2 SbS2 I3 – Structural Relaxation Sn Sb S I Cmcm Cmc2 1 b c ΔE(Cmc21 /Cmcm) = -35.8 meV/atom (RPA w/ HSE06 orbitals)
8. Sn2 SbS2 I3 – Dynamic Stability Cmcm Cmc21
9. Sn2 SbS2 I3 – Structural Relaxation A. Ibanez, J.-C. Jumas, J. Olivier-Fourcade and E. Philippot, Journal of Solid State Chemistry, 1984, 55, 83–91.
10. Sn2 SbS2 I3 – Structural Relaxation
11. Sn2 SbS2 I3 – Structural Relaxation
12. Sn2 SbS2 I3 – Structural Relaxation
13. Sn2 SbS2 I3 – Structural Relaxation
14. Sn2 SbS2 I3 – Structural Relaxation
15. Sn2 SbS2 I3 – Structural Relaxation
16. Sn2 SbS2 I3 – Spontaneous Polarisation Cmcm ⟹ Cmc21 ΔP(Cmc21 /Cmcm) = 37 μC/cm2 (optB86b-vdW) c.f. BaTiO3 (∼27 μC/cm2), KNbO3 (∼30 μC/cm2), MAPbI3 (4.4 μC/cm2), SbSI (11 μC/cm2)
17. Sn2 SbS2 I3 – Molecular Dynamics ΔP = 37 μC/cm2
18. Molecular Dynamics: T= 300K
19. Molecular Dynamics: T= 500K
20. Sn2 SbS2 I3 – Electronic & Optical Properties Eg = 1.08 eV (HSE06 + SOC)
21. Electronic & Optical Properties: Cmcm
22. Electronic & Optical Properties: Cmcm
23. Electronic & Optical Properties: Cmc21
24. Electronic & Optical Properties: Cmc21
25. Sn2 SbS2 I3 – Electronic & Optical Properties
26. Sn2 SbS2 I3 – Potential Defect Tolerance Eg = 1.08 eV (HSE06 + SOC) - Small band gap - Anti-bonding character, high- energy VBM (Sn 5s2 – anion p) - Mixed ionic-covalent bonding: - Strong dielectric screening - Wide conduction & valence bands - Atomic-chain structure (⟹ benign grain boundaries?) PL lifetime >7 ns recorded by Nie et al. R. Nie, K. S. Lee, M. Hu, M. J. Paik and S. I. Seok, Heteroleptic Tin-Antimony Sulfoiodide for Stable and Lead-free Solar Cells. 2020 Matter, S2590238520304471.
27. Conclusions & Acknowledgements Spontaneous symmetry breaking and lattice polarization, hidden by macroscopic averaging, unveiled in Sn2 SbS2 I3 . o Potential benefits for charge separation and PV efficiency. Promising outlook for the application in high-efficiency solution- processed solar cells.