Stimulated Emission from Stable Multiexciton-Polaron States in Fully Inorganic Perovskite Quantum Wells

Isabella Wagner^a, Kai Chen^c^,^d, Justin Hodgkiss^a^,^d, Zeger Hens^b, Pieter Geiregat^b

^aSchool of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

^bPhysics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Belgium, Krijgslaan 281 - S3, Ghent, Belgium

^cRobinson Research Institute, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

^dMacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand., PO Box 600, Wellington, New Zealand

^eThe Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, PO Box 56, Dunedin, New Zealand

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2021 (NFM21)

#PerNC21. Perovskites II: Synthesis, Characterization, and Properties of Colloidal

Online, Spain, 2021 October 18th - 22nd

Organizers: Maksym Kovalenko, Ivan Infante and Lea Nienhaus

Contributed talk, Pieter Geiregat, presentation 158
DOI: https://doi.org/10.29363/nanoge.nfm.2021.158
Publication date: 23rd September 2021

Solution processable semiconducting perovskites hold great promise for demanding applications involving light emission, such as printable lasers or quantum light sources. A case example is that of fully inorganic CsPbBr3quantum wells (CQWs) which display high quantum yield at room temperature. Less studied than their organic-inorganic counterparts, these CQWs sustain high single exciton binding energies and luminescence quantum yields, yet little is known on the nature of the exciton and multi-excitons states required for advanced applications. Here, we show that charge carriers in fully inorganic 2D perovskites exist as stable exciton - polarons, a complex between a charge neutral exciton and a lattice deformation. Next, we show that these unique species can fuse together to form a hereto unexplored bi-exciton polaron state, i.e. a two-particle complex bound by attractive Coulomb attraction whilst simultaneously being strongly coupled to the lattice. Finally, we show that net stimulated emission occurs through radiative recombination from this unique bi-exciton polaron state to a single free exciton polaron, showing the stability of the newly found species. Consequences of the polaronic character are identified as a low threshold for stimulated emission but with limited optical gain coefficients, both of which we can fully reproduce using a thermodynamic gain model. As such, our results provide a general framework to understand and predict the behavior of not only single, but also multi-exciton polaron states in perovskite materials.

Acknowledgements:

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