CsPbBr Superstructures with Circularly Polarized Photolumines-Cence Obtained by the Self-Assembly and Annealing of Nanoclusters.

We report a two-step approach to fabricate CsPbBr superstructures with strongly circularly polarized photoluminescence by self-assembly of nanoclusters on a substrate, followed by their annealing. In the first step, the nanoclusters self-assemble upon solvent evaporation, a process that forms mesoscopic superstructures whose geometrical arrangement at the μm-scale confers them optical chirality. In the second step, mild annealing of such superstructures induces the coalescence of the nanoclusters, accompanied by a continuous red shift of the photoluminescence up to 530 nm, with preservation of the μm-scale wires bundles and the chiral properties of the sample (g=0.

Breaking the Boundaries of the Goldschmidt Tolerance Factor with Ethylammonium Lead Iodide Perovskite Nanocrystals.

We report the synthesis of ethylammonium lead iodide (EAPbI) colloidal nanocrystals as another member of the lead halide perovskites family. The insertion of an unusually large -cation (274 pm in diameter) in the perovskite structure, hitherto considered unlikely due to the unfavorable Goldschmidt tolerance factor, results in a significantly larger lattice parameter compared to the Cs-, methylammonium- and formamidinium-based lead halide perovskite homologues. As a consequence, EAPbI nanocrystals are highly unstable, evolving to a nonperovskite δ-EAPbI polymorph within 1 day.

Size-Dependent Multiexciton Dynamics Governs Scintillation From Perovskite Quantum Dots.

The recent emergence of quantum-confined nanomaterials in the field of radiation detection, in particular lead halide perovskite nanocrystals, offers scalability and performance advantages over conventional materials. This development raises fundamental questions about the mechanism of scintillation itself at the nanoscale and the role of particle size, arguably the most defining parameter of quantum dots. Understanding this is crucial for the design and optimization of future nanotechnology scintillators.

Cooling-Induced Order-Disorder Phase Transition in CsPbBr Nanocrystal Superlattices.

Perovskite nanocrystal superlattices are being actively studied after reports have emerged on collective excitonic properties at cryogenic temperatures, where energetic disorder is minimized due to the frozen lattice vibrations. However, an important issue related to structural disorder of superlattices at low temperatures has received little attention to date. In this work, it is shown that CsPbBr nanocrystal superlattices undergo a reversible order-disorder transition upon cooling to 90 K.

Additive-Driven Enhancement of Crystallization: Strategies and Prospects for Boosting Photoluminescence Quantum Yields in Halide Perovskite Films for Light-Emitting Diodes.

Halide perovskite light-emitting diodes (PeLEDs) hold great potential for applications in displays and lighting. To enhance the external quantum efficiency (EQE) of PeLEDs, it is crucial to boost the photoluminescence quantum yield (PLQY) of the perovskite films. The use of additives has emerged as a powerful chemical strategy to control the crystallization process in solution-processed perovskite films.