Halide NMR and NQR of bulk and nanocrystalline cesium lead-halide perovskites

Laura Piveteau^a^,^b^,^h, Marcel Aebli^a^,^b, Nuri Yazdani^e^,^f, Marthe Millen^a, Lukas Korosec^c^,ⁱ, Franziska Krieg^a^,^b, Bogdan M. Benin^a^,^b, Viktoriia Morad^a^,^b, Christophe Piveteau^c, Toni Shiroka^c^,^d, Aleix Comas-Vives^j^,^a, Christophe Copéret^a, Aaron M. Lindenberg^f^,^g, Vanessa Wood^e, René Verel^b, Maksym V. Kovalenko^a^,^b

^aDepartment of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, CH-8093, Switzerland

^bEmpa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Überlandstrasse 129, CH-8600, Switzerland

^cDepartment of Physics, ETH Zürich, Otto Stern Weg 1, CH-8093, Switzerland

^dPaul Scherrer Institute, Villigen PSI, CH-5232, Switzerland

^eDepartment of Information Technology and Electrical Engineering, ETH Zürich, CH-8092, Switzerland

^fDepartment of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States

^gInstitute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California, 94025, United States

^hCNRS, UPR 3079, CEMHTI, 45071 Orléans Cedex 02, France

ⁱDepartment of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211, Switzerland

^jDepartament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès 08193 Bellaterra, Catalonia, Spain

Proceedings of Atomic-level characterization of hybrid perovskites (HPATOM)

Online, Spain, 2021 January 26th - 28th

Organizers: Dominik Kubicki and Amita Ummadisingu

Invited Speaker, Laura Piveteau, presentation 011
Publication date: 14th January 2021

Lead-halide perovskite (LHP) nanocrystals (NCs) have emerged over the last years as attractive light emitters and are being increasingly investigated for their application in LEDs, LCD displays, and many more optoelectronic devices.¹ Their bright photoluminescence (PL) spans the entire visible spectral range and exhibits narrow emission line widths (<100 meV) as well as a very high quantum yields of up to 100%. Unlike in other semiconductor NCs, the luminescence in LHP NCs is not produced by quantum confinement. Instead, it is ascribed to the high defect-tolerance of the perovskite structure.² However, these emissive properties are absent in bulk LHPs, which raises the question of their origins in LHP NCs. Detailed characterization of the bulk and nanocrystalline forms of LHP materials remains challenging, inter alia because of the softness of the LHP structure, but it is essential for a better understanding of the structure-property relationship of these materials.

We used halide NMR and halide nuclear quadrupole resonance (NQR) spectroscopy to investigate the structure and dynamics of both bulk and nanocrystalline CsPbX₃ (X = Cl, Br, I) perovskites. We exploited the strong quadrupole couplings of the halide nuclei, which originate from the interaction between the large quadrupole moments of the halide nuclei and the local electric-field gradients. The latter are especially strong in LHPs, thus making the quadrupole interaction highly sensitive to subtle structural variations, both in time and space. The comparison of the NMR and NQR spectra of nanocrystalline and bulk materials revealed larger structural disorder and accelerated dynamics in NCs compared to bulk. This was corroborated by ab-initio molecular dynamics, pointing out the role of the surface in causing radial distribution of strain and disorder. Thus, halide NMR and NQR are some of the few characterization methods that can probe both the bulk and nancrystalline forms of LHPs and they may this way provide the structural and dynamical insights fundamental to a better understanding of the exceptional properties of these materials.

Kovalenko, M. V.; Protesescu, L.; Bodnarchuk, M. I. Propertiesand potential optoelectronic applications of lead halide perovskitenanocrystals. Science 2017, 358, 745−750

Akkerman, Q. A.; Rainò, G.; Kovalenko, M. V.; Manna, L.Genesis, Challenges and Opportunities for Colloidal Lead HalidePerovskite Nanocrystals. Nat. Mater. 2018, 17(5), 394−405.

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