Impact of metastable defect structures on carrier recombination in semiconductors

Presentation given to the 3D Materials Lab group in the Colorado School of Mines, led by Prashun Gorai https://www.prashungorai.org/, focused on our recent publication Impact of metastable defect structures on carrier recombination in semiconductors (https://doi.org/10.1039/D2FD00043A)

Also discussed are our recent papers:
https://pubs.acs.org/doi/abs/10.1021/acsenergylett.1c00380
https://www.sciencedirect.com/science/article/pii/S2590238521002733

For other research articles and updates, check out my website at:
https://seankavanagh.com/

Transcript

1. Impact of metastable defect structures on carrier recombination in semiconductors Seán R. Kavanagh Colorado School of Mines, 15th Apr 2022 Profs: Aron Walsh (Imperial) & David Scanlon (UCL) sean.kavanagh.19@ucl.ac.uk e- / h+ Dq D*q Dq±1
2. Impact of metastable defect structures on carrier recombination in semiconductors Seán R. Kavanagh Colorado School of Mines, 15th Apr 2022 Profs: Aron Walsh (Imperial) & David Scanlon (UCL) sean.kavanagh.19@ucl.ac.uk e- / h+ Dq D*q Dq±1
3. A Little Bit About Me • Undergraduate: Nanoscience, Physics & Chemistry of Advanced Materials at Trinity College Dublin, Ireland. • PhD: Modelling Solid-State Photovoltaic Materials, with an emphasis on defects and disorder, at Imperial College London & University College London. • 🥾🏔🏃🏋🏂🎥🍻☕🍕🍱🕺
4. Defects: Flash Introduction 4 𝐺 = 𝐻 − 𝑇𝑆 𝑐! = 𝑔exp −Δ𝐻 𝑘" 𝑇
5. Motivation 5
6. Example: VCd 0 in CdTe I. Mosquera-Lois and S. R. Kavanagh, Matter, 2021, 4, 2602–2605.
7. Motivation 7 I. Mosquera-Lois and S. R. Kavanagh, Matter, 2021, 4, 2602–2605.
8. Defect Dynamics • Alkauskas et al., Role of Excited States in SRH Recombination in Wide-Band-Gap Semiconductors, Phys. Rev. B, 2016. (LED Efficiency in GaN) • L.W. Wang, S.H. Wei et al., Non-Radiative Carrier Recombination Enhanced by Two- Level Process, Scientific Reports, 2016. (Solar Efficiency in CdTe; TeCd ) • Guo et al., Nonradiative Carrier Recombination Enhanced by Vacancy Defects in Ionic II-VI Semiconductors, Phys. Rev. Applied, 2021. (Vse in ZnSe) S. R. Kavanagh, Aron Walsh and D. O. Scanlon, Rapid Recombination by Cadmium Vacancies in CdTe, ACS Energy Lett. 2021, 6, 4, 1392–1398
9. Potential Structural Transitions Degenerate Minima: Thermal Excitation: Thermal Relaxation: Photo Excitation: E Q e- / h+ e- / h+ e- / h+
10. 10 a. Graph network of potential recombination pathways b. Standard electron-hole recombination c. Capture into metastable, relax, capture back d. Excite to metastable, capture, capture e. Excite, capture, relax, capture
12. Case Study: Tei in CdTe 12
13. 13 Case Study: Tei in CdTe
14. 14 Upper Orange Middle Blue Lower Orange e– h+
15. 15 h+ capture e– capture h+ capture e– capture h+ capture e– capture h+ capture e– capture Upper Orange Middle Blue Lower Orange e– h+
17. CdTe: Tei Recombination Kinetics 17
18. Conclusions Defect dynamics can be crucial for understanding their impact on device performance. -> Demonstrated by Tei , where metastability catalyses a 4-step recombination cycle. Metastable defect structures potentially more important to non-radiative recombination than currently understood, particularly with: - Emerging ionic-covalent inorganic materials - Highly mobile defects Thanks to MPIE for the ‘Max Planck Travel Award’! Kavanagh, S. R.; Scanlon, D. O.; Walsh, A.; Freysoldt, C. Faraday Discuss. 2022. https://doi.org/10.1039/D2FD00043A.