Doctoral Researchers
B 12: Simon Letzer
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E-Mail: simon.letzer@tu-dresden.de Since the beginning of my physics studies, I have been fascinated by phenomena that emerge at the nanoscale. Nanocrystals offer an exciting platform to investigate energy transfer, radiative processes, and exciton dynamics with a level of tunability unavailable in bulk materials. This interest grows further when working with nanocrystal light-emitting diodes, where the worlds of organic and inorganic electronics merge. In these devices, the underlying physics is truly governed by nanoscale processes – from charge injection and transport to interface engineering and recombination dynamics. |
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Supervisors
Mentor: Caroline Murawski
Co-mentor: Vladimir Lesnyak
For health-monitoring applications, the near-infrared (NIR) window of biological tissue between 650 nm and 1350 nm is attractive because of its high penetration depth. Ultra-thin devices on flexible substrates are ideal for real-time and imperceptive monitoring. In the visible range, this is usually achieved with organic light-emitting diodes, as they are efficient and mechanically flexible. However, their external quantum efficiency (EQE) drops below 5% for emission above 820 nm. [1]
Nanocrystal LEDs can bridge this gap. They offer near-unity photoluminescence quantum yields in solution, and the best reported EQE above 800 nm is around 20%. [2] Yet these top devices often rely on cadmium-, lead-, or arsenic-based nanocrystals, which are not suitable for biological use.
My project focuses on implementing non-toxic nanocrystals in LEDs. Achieving high efficiency requires a solid understanding of charge injection, transport, and photon outcoupling. To build this foundation, I will first reproduce devices based on CdHgSe/CdZnS core-shell nanoplatelets to learn the processing and characterization steps. [3] Because these materials are toxic, I will then replace them with safer alternatives such as CuInS₂/ZnS quantum dots, CuZnInSe/ZnS nanocrystals, and the CuFeS nanocrystals developed in project A8. [4,5]
The final devices will be optimized for sensing applications, with a focus on flexibility, robust encapsulation, and long operational stability.
Literature:
- [1] S. Ahadzadeh, S. Brebels, W. Maes, W. Deferme, Strategies for Advancing Near-Infrared Organic Light-Emitting Diodes: Innovations in Luminescent Materials, Device Architectures, Fabrication Methods, and Applications. Adv. Funct. Mater. 2025, 2419599.
- [2] Li B, Wang Y, Zhang J, Li Y, Li B, Lin Q, Sun R, Fan F, Zeng Z, Shen H, Ji B. Efficient and stable near-infrared InAs quantum dot light-emitting diodes. Nat Commun. 2025 Mar 12;16(1):2450.
- [3] A. Prudnikau, H. Roshan, F. Paulus, B. Martín-García, R. Hübner, H. Bahmani Jalali, M. De Franco, M. Prato, F. Di Stasio, V. Lesnyak, Efficient Near-Infrared Light-Emitting Diodes Based on CdHgSe Nanoplatelets. Adv. Funct. Mater. 2024, 34, 2310067.
- [4] Zhenyang Liu, Chaoqi Hao, Yingying Sun, Junyu Wang, Lacie Dube, Mingjun Chen, Wei Dang, Jinxiao Hu, Xu Li, and Ou Chen, Rigid CuInS2/ZnS Core/Shell Quantum Dots for High Performance Infrared Light-Emitting Diodes. Nano Letters 2024 24 (17), 5342-5350.
- [5] Avijit Saha, Morena Cervino, Hossein Roshan, René Hübner, Angelika Wrzesińska-Lashkova, Christine Steinbach, Yana Vaynzof, Francesco Di Stasio, Vladimir Lesnyak, RoHS-Compliant, Cu-Zn-In-Se-Based Core/Multi-shell Quantum Dots with Efficient and Tunable Short-Wave Infrared Emission. Adv. Funct. Mater. (2025): e17605.
| 10/2019-09/2022 |
Bachelor of Science Physics Universität Leipzig (Germany)
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| 10/2022-12/2024 |
Master of Science Physics Technische Universität Dresden (Germany)
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