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Oliviero Cannelli, Nicola Colonna, Michele Puppin, Thomas C. Rossi, Dominik Kinschel, Ludmila M. D. Leroy, ..., Franziska Krieg, Simon C. Boehme, Maksym V. Kovalenko, Majed Chergui*, and Giulia F. Mancini*

Quantifying Photoinduced Polaronic Distortions in Inorganic Lead Halide Perovskite Nanocrystals

The development of next-generation perovskitebased optoelectronic devices relies critically on the understanding of the interaction between charge carriers and the polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that the Pb−Br framework flexibility plays a key role in their light-activated functionality, the corresponding local structural rearrangement has not yet been unambiguously identified. In this work, we demonstrate that the photoinduced lattice changes in the system are due to a specific polaronic distortion, associated with the activation of a longitudinal optical phonon mode at 18 meV by electron−phonon coupling, and we quantify the associated structural changes with atomic-level precision. Key to this achievement is the combination of timeresolved and temperature-dependent studies at Br K and Pb L3 X-ray absorption edges with refined ab initio simulations, which fully account for the screened core-hole final state effects on the X-ray absorption spectra. From the temporal kinetics, we show that carrier recombination reversibly unlocks the structural deformation at both Br and Pb sites. The comparison with the temperaturedependent XAS results rules out thermal effects as the primary source of distortion of the Pb−Br bonding motif during photoexcitation. Our work provides a comprehensive description of the CsPbBr3 perovskites’ photophysics, offering novel insights on the light-induced response of the system and its exceptional optoelectronic properties.

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Leon G. Feld, Yevhen Shynkarenko, Franziska Krieg, Gabriele Raino*, and Maksym V. Kovalenko*

Perovskite Quantum Dots for Super-Resolution Optical Microscopy: Where Strong Photoluminescence Blinking Matters

Blinking nanoscale emitters, typically single molecules, are employed in single-molecule localization microscopy (SMLM), such as direct stochastic optical reconstruction microscopy (dSTORM), to overcome Abbe’s diffraction limit, offering spatial resolution of few tens of nanometers. Colloidal quantum dots (QDs) feature high photostability, ultrahigh absorption cross-sections and brightness, as well as wide tunability of the emission properties, making them a compelling alternative to organic molecules. Here, CsPbBr3 nanocrystals, the latest addition to the QD family, are explored as probes in SMLM. Because of the strongly suppressed QD photoluminescence blinking (ON/OFF occurrence higher than 90%), it is diffcult to resolve emitters with overlapping point-spread functions by standard dSTORM methods due to false localizations. A new work-flow based on ellipticity filtering effciently identifies false localizations and allows the precise localization of QDs with subwavelength spatial resolution. Aided by Monte-Carlo simulations, the optimal QD blinking dynamics for dSTORM applications is identified, harnessing the benefits of higher QD absorption cross-section and the enhanced QD photostability to further expand the field of QD super-resolution microscopy toward sub-nanometer spatial resolution.

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Tan Nguyen, Claudine Katan, Jacky Even

The 6th Journées Perovskites Halogénées 2021 (JPH2021)

In the context of rising popularity of perovskites as the potential candidate for many future photovoltaic and lighting applications, the Journées Pérovskites Halogénées 2021 (JPH2021) gathered researchers working on these exciting materials across France. Chemists, physicists and engineers from many experimental and theory groups discussed the diverse and multidisciplinary aspects of the field including synthesis, structural and optical characterization of thin films and nanostructures (0D, 1D, 2D and 3D), etc. These are of crucial importance for the applications in photovoltaics, light detection and LED, thermoelectricity and many more. Three intense sessions were dedicated to the following exciting themes: Synthesis and fundamental properties, Characterization of materials and modelling, Devices and industrial aspects. Interested viewers can find more details from the conference website at https://jph2021.sciencesconf.org. Our current theoretical work under the workpackage WP2 of the European POLLOC project is devoted to the electronic and optical properties of the nanocrystal systems of single exciton and beyond. The contributed talk, which was given during the session “Characterization of materials and modelling” of JPH2021, focuses on the correlation origin of the exciton fine-structure as well as the biexciton/trion emission using many-body perturbation theory as well as the configuration interaction approach. This project was funded by the European Union’s Horizon 2020 program, through a FET Open research and innovation action under the grant agreement No 899141 (PoLLoC).

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