Excitonic and Biexcitonic Transitions in Spherical Halide Perovskite Quantum Dots

Anja Barfüßer^a, Sebastian Rieger^a, Amrita Dey^a, Ahmet Tosun^a, Quinten A. Akkerman^a, Tushar Debnath^a, Jochen Feldmann^a

^aChair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-University Munich, Germany

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2024 Conference (MATSUS24)

#PeroQuant24 - Halide perovskites for quantum technologies

Barcelona, Spain, 2024 March 4th - 8th

Organizers: Simon Boehme, Sascha Feldmann and Maksym Kovalenko

Oral, Anja Barfüßer, presentation 304
DOI: https://doi.org/10.29363/nanoge.matsus.2024.304
Publication date: 18th December 2023

In recent years, lead halide perovskite (LHP) quantum dots (QDs) have attracted much attention for their unique optical properties. In contrast to conventional III-V and II-VI semiconductors with a rather complex valence band structure, LHPs are free of band degeneracies around the band gap. This reduces the complexity of their optical spectra around the band gap. Furthermore, the rather small effective electron and hole mass in LHPs generates a light exciton, which leads to significant confinement energies. The resulting well-separated energy levels simplify the assignment of electronic transitions, making LHP QDs an ideal model system to study quantum confinement effects.

We discuss highly monodisperse [1] spherical-like LHP QDs with diameters in the range of the exciton Bohr diameter, which feature a multitude of distinct resonances in their absorption spectra. By employing a simplified analysis within the envelope function approximation [2], we are able to assign the absorption resonances to center-of-mass motion confined excitons. Femtosecond transient absorption measurements on these QDs reveal bleaching of the exciton levels as well as a series of induced absorption features which we attribute to biexcitonic transitions [3]. In the context of light emitting devices, the emission and lasing properties of confined systems are of special interest. We therefore use our well-defined excitonic QDs to study their optical gain and amplified spontaneous emission characteristics. Our work shows the first insight into confined excitons in LHP QDs and provides a better understanding of their linear and nonlinear absorption and emission spectra as well as their polarization-dependent properties.

References:

[1] Akkerman, Q. A.; Nguyen, Tan P. T.; Boehme, S. C.; Montanarella, F.; Dirin, D. N.; Wechsler, P. et al., Controlling the nucleation and growth kinetics of lead halide perovskite quantum dots, Science 2022, 377, 6613, 1406–1412

[2] Gaponenko, S. V., Optical properties of semiconductor nanocrystals, Cambridge University Press 1998, Cambridge studies in modern optics, 23

[3] Barfüßer, A.; Rieger, S.; Dey, A.; Tosun, A.; Akkerman, Q. A.; Debnath, T.; Feldmann, J., Confined Excitons in Spherical-Like Halide Perovskite Quantum Dots, Nano Lett. 2022, 22, 22, 8810–8817

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