Electron tunnelling in vertical van der Waals junctions for electroluminescent devices

The assembly of van der Waals heterostructures enables the creation of devices comprising materials with vastly different electronic band structures, overcoming the limitations of matching crystal structures. Sandwiching an insulator between two (semi-)metallic electrodes constitutes a blueprint for a rational design of tunnelling devices, where bidirectional injection of electrons and holes onto the radiative states leads to electroluminescent processes. The nature of the radiative states may be vastly different, including Wannier-Mott-like excitons in semiconductors [1,2], Frenkel excitons coupled to magnetization textures in ferromagnets [3,4], or intradefect transitions raising single photons [5-9]. The structure of the barrier can be complex, involving multiple materials with atomically precise thickness. Consequently, the efficiency of the electroluminescent processes is tunable across multiple orders of magnitude due to the competition between the tunnelling dynamics and the radiative lifetimes. Alternative tunnelling pathways are activated by distinct device architectures at the material level, governing their spectroscopic characteristics.

[1] K. Walczyk, G. Krasucki, K. Olkowska-Pucko, Z. Chen, T. Taniguchi, K. Watanabe, A. Babiński, M. Koperski, M. R. Molas, N. Zawadzka, Optical response of WSe2-based vertical tunneling junction, Solid State Communications 396, 115756 (2025).
[2] J. Zultak, S. J. Magorrian, M. Koperski, A. Garner, M. J. Hamer, E. Tóvári, K. S. Novoselov, A. A. Zhukov, Y. Zou, N. R. Wilson, S. J. Haigh, A. V. Kretinin, V. I Fal’ko, R. Gorbachev, Ultra-thin van der Waals crystals as semiconductor quantum wells, Nature Communications 11 (1), 125 (2020).
[3] M. Grzeszczyk, S. Acharya, D. Pashov, Z. Chen, K. Vaklinova, M. van Schilfgaarde, K. Watanabe, T. Taniguchi, K. S. Novoselov, M. I. Katsnelson, M. Koperski, Strongly Correlated Exciton‐Magnetization System for Optical Spin Pumping in CrBr3 and CrI3, Advanced Materials 35 (17), 2209513 (2023).
[4] S. Grebenchuk, C. McKeever, M. Grzeszczyk, Z. Chen, M. Šiškins, A. R. C. McCray, Y. Li, A. K. Petford‐Long, C. M. Phatak, D. Ruihuan, L. Zheng, K. S. Novoselov, E. J. G. Santos, M. Koperski, Topological spin textures in an insulating van der Waals ferromagnet, Advanced Materials 36 (24), 2311949 (2024).
[5] M. Grzeszczyk, K. Vaklinova, K. Watanabe, T. Taniguchi, K. S. Novoselov, M. Koperski, Electroluminescence from pure resonant states in hBN-based vertical tunneling junctions, Light: Science & Applications 13 (1), 155 (2024).
[6] J. Howarth, K. Vaklinova, M. Grzeszczyk, G. Baldi, L. Hague, M. Potemski, K. S. Novoselov, A. Kozikov, M. Koperski, PNAS 121 (23), e2401757121 (2024).
[7] Z. Qiu, K. Vaklinova, P. Huang, M. Grzeszczyk, K. Watanabe, T. Taniguchi, K. S. Novoselov, J. Lu, M. Koperski, Atomic and Electronic Structure of Defects in hBN: Enhancing Single-Defect Functionalities, ACS Nano 18 (35), 24035–24043 (2024).
[8] L. Loh, J. Wang, M. Grzeszczyk, M. Koperski, G. Eda, Towards quantum light-emitting devices based on van der Waals materials, Nature Reviews Electrical Engineering 1, 815–829 (2024).
[9] D. Litvinov, A. Wu, M. Barbosa, K. Vaklinova, M. Grzeszczyk, G. Baldi, M. Zhu, M. Koperski, Single photon sources and single electron transistors in two-dimensional materials, Materials Science and Engineering: R: Reports 163, 100928 (2025).