High-resolution remote thermography using luminescent low-dimensional tin-halide perovskites

While metal-halide perovskites have recently revolutionized research in optoelectronics through a unique combination of performance and synthetic simplicity, their low-dimensional counterparts can further expand the field with hitherto unknown and practically useful optical functionalities. In this context, we present the strong temperature dependence of the photoluminescence (PL) lifetime of low-dimensional, perovskite-like tin-halides, and apply this property to thermal imaging with a high precision of 0.05 {\deg}C. The PL lifetimes are governed by the heat-assisted de-trapping of self-trapped excitons, and their values can be varied over several orders of magnitude by adjusting the temperature (up to 20 ns {\deg}C-1). Typically, this sensitive range spans up to one hundred centigrade, and it is both compound-specific and shown to be compositionally and structurally tunable from -100 to 110 {\deg} C going from [C(NH2)3]2SnBr4 to Cs4SnBr6 and (C4N2H14I)4SnI6. Finally, through the innovative implementation of cost-effective hardware for fluorescence lifetime imaging (FLI), based on time-of-flight (ToF) technology, these novel thermoluminophores have been used to record thermographic videos with high spatial and thermal resolution.Comment: 25 pages, 4 figure

Laser Patterning of High‐Mass‐Loading Graphite Anodes for High‐​Performance Li‐​Ion Batteries

Given the ongoing efforts to build Li-ion batteries with higher volumetric energy and power densities, the research on enhancing Li-ion transport within compressed high-mass-loading electrodes at fast cycling conditions is imperative. In this work, we show that the rate capability of graphite electrodes with high areal capacity of 4.5 mAh cm2 and density of 1.79 g cm3 (15% of porosity) can be considerably improved by laser patterning, namely by the fabrication of arrays of vertically aligned channels serving as diffusion paths for rapid Li-ion transport. Resultant laser patterned graphite electrodes delivered enhanced volumetric capacity as compared to that of non-patterned electrodes (450 vs. 396 mAh cm3 at C/2 rate). The reduction of the total steady-state concentration drop within the graphite electrodes after their patterning was also assessed

Reconfigurable halide perovskite nanocrystal memristors for neuromorphic computing

Many in-memory computing frameworks demand electronic devices with specific switching characteristics to achieve the desired level of computational complexity. Existing memristive devices cannot be reconfigured to meet the diverse volatile and non-volatile switching requirements, and hence rely on tailored material designs specific to the targeted application, limiting their universality. “Reconfigurable memristors” that combine both ionic diffusive and drift mechanisms could address these limitations, but they remain elusive. Here we present a reconfigurable halide perovskite nanocrystal memristor that achieves on-demand switching between diffusive/volatile and drift/non-volatile modes by controllable electrochemical reactions. Judicious selection of the perovskite nanocrystals and organic capping ligands enable state-of-the-art endurance performances in both modes – volatile (2 × 10$^{6}$ cycles) and non-volatile (5.6 × 10$^{3}$ cycles). We demonstrate the relevance of such proof-of-concept perovskite devices on a benchmark reservoir network with volatile recurrent and non-volatile readout layers based on 19,900 measurements across 25 dynamically-configured devices

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 difficult to resolve emitters with overlapping point-spread functions by standard dSTORM methods due to false localizations. A new workflow based on ellipticity filtering efficiently 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.ISSN:2195-107

Manganese(II) in Tetrahedral Halide Environment: Factors Governing Bright Green Luminescence

Finding narrow-band light emitters for the visible spectral region remains an immense challenge. Such phosphors are in great demand for solid-state lighting and display application. In this context, green luminescence from tetrahedrally coordinated Mn(II) is an attractive research direction. While the oxide–ligand environment had been studied for decades, much less systematic efforts have been undertaken with regard to halide coordination, especially in the form of fully inorganic halide matrixes. In this study, we synthesized a series of hybrid organic–inorganic Mn(II) halides as well as a range of fully inorganic Zn halide hosts (chlorides, bromides, iodides) doped with Mn(II). In the latter, tetrahedral coordination is attained via substitutional doping owing to the tetrahedral symmetry of Zn sites. We find that the choice of the halide as well as subtle details of the crystal structure profoundly govern the photoluminescence peak positions (500–550 nm range) and emission line widths (40–60 nm) as well as radiative lifetimes (shorter for iodides) through the altered ligand-field effects and degrees of spin–orbit coupling. The photoluminescence quantum yields were as high as 70–90%. The major hurdle for the practical use of these compounds lies in their low absorption coefficients in the blue spectral regions.ISSN:0897-475

Disphenoidal Zero-Dimensional Lead, Tin, and Germanium Halides: Highly Emissive Singlet and Triplet Self-Trapped Excitons and X-ray Scintillation

Low-dimensional metal halides have been researched as optoelectronic materials for the past two decades. Zero-dimensional halides of ns2 elements (Sn, Pb, Sb) have recently gained attention as highly efficient broadband light emitters. These compounds comprise discrete metal halide centers, isolated by bulky organic cations. Herein, we report isostructural halide complexes of Ge(II), Sn(II), and Pb(II) with a 1-butyl-1-methyl-piperidinium cation (Bmpip), featuring unusual disphenoidal coordination with a highly stereoactive lone pair. Spectrally broad, bright emission from highly localized excitons, with quantum efficiencies of up to 75%, is observed in blue to red spectral regions for bromides (for Pb, Sn, and Ge, respectively) and extends into the near-infrared for Bmpip2SnI4 (peak at 730 nm). In the case of Sn(II) and Ge(II), both singlet and triplet excitonic emission bands have been observed. Furthermore, Bmpip2SnBr4 and Bmpip2PbBr4 exhibit X-ray-excited luminescence (radioluminescence) with brightness being commensurate with that of a commercial inorganic X-ray scintillator (NaI:Tl).ISSN:0002-7863ISSN:1520-512

Single-pulse femtosecond laser fabrication of concave microlens- and micromirror arrays in chalcohalide glass

International audienceThe diffraction-limited piano-concave microlens- and micromirror arrays were produced in chalcohalide glass of 65GeS(2)-25Ga(2)S(3)-10CsCl composition transparent from similar to 0.5 to 11 mu m. Only a single 200 fs laser pulse with 800 nm central wavelength is required to form microlens, which after metal coating becomes a concave micromirror. This process can serve as a basis for flexible technology to fabricate regular microlens and micromirror arrays for optotelecom applications, its performance being limited only by repetition rate of the laser pulses (typically 1000 microlenses per second)

Colloidal CdSe Quantum Wells with Graded Shell Composition for Low-Threshold Amplified Spontaneous Emission and Highly Efficient Electroluminescence

ISSN:1936-0851ISSN:1936-086

Bright Blue and Green Luminescence of Sb(III) in Double Perovskite Cs2MInCl6 (M = Na, K) Matrices

The vast structural and compositional space of metal halides has recently become a major research focus for designing inexpensive and versatile light sources; in particular, for applications in displays, solid-state lighting, lasing, etc. Compounds with isolated ns2-metal halide centers often exhibit bright broadband emission that stems from self-trapped excitons (STEs). The Sb(III) halides are attractive STE emitters due to their low toxicity and oxidative stability; however, coupling these features with an appropriately robust, fully inorganic material containing Sb3+ in an octahedral halide environment has proven to be a challenge. Here, we investigate Sb3+ as a dopant in a solution-grown metal halide double perovskite (DP) matrix, namely Cs2MInCl6:xSb (M = Na, K, x = 0–100%). Cs2KInCl6 is found to crystallize in the tetragonal DP phase, unlike Cs2NaInCl6 that adopts the traditional cubic DP structure. This structural difference results in distinct emission colors, as Cs2NaInCl6:xSb and Cs2KInCl6:xSb compounds exhibit broadband blue and green emissions, respectively, with photoluminescence quantum yields (PLQYs) of up to 93%. Spectroscopic and computational investigations confirm that this efficient emission originates from Sb(III)-hosted STEs. These fully inorganic DP compounds demonstrate that Sb(III) can be incorporated as a bright emissive center for stable lighting applications.ISSN:0897-475

Pressure‐Induced Perovskite‐to‐non‐Perovskite Phase Transition in CsPbBr3

The expanding range of optoelectronic applications of lead‐halide perovskites requires their production in diverse forms (single crystals, thin‐ and thick‐films or even nanocrystals), motivating the development of diverse materials processing and deposition routes that are specifically suited for these structurally soft, low‐melting semiconductors. Pressure‐assisted deposition of compact pellets or thick‐films are gaining popularity, necessitating studies on the pressure effects on the atomic structure and properties of the resulting material. Herein we report the phase transformation in bulk polycrystalline cesium lead bromide from its three‐dimensional perovskite phase (γ‐CsPbBr3) into the one‐dimensional polymorph (δ‐CsPbBr3) upon application of hydrostatic pressure (0.35 GPa). δ‐CsPbBr3 is characterized by a wide bandgap of 2.9 eV and broadband yellow luminescence at 585 nm (2.1 eV) originating from self‐trapped excitons. The formation of δ‐CsPbBr3 was confirmed and characterized by Raman spectroscopy, 207Pb and 133Cs solid‐state nuclear magnetic resonance, X‐ray diffraction, absorption spectroscopy, and temperature‐dependent and time‐resolved photoluminescence spectroscopy. No such phase transition was observed in colloidal CsPbBr3 nanocrystals.ISSN:0018-019XISSN:1522-267