Periodic Reporting for period 4 - SCALE-HALO (Multiscale chemical engineering of functional metal halides)
Reporting period: 2023-12-01 to 2024-11-30
SCALE-HALO developed a holistic approach to novel highly luminescent materials comprising metal halides (MHs). The compositional and morphological space of metal halides (MHs) offers novel semiconductors and solid-state emitters. The project's key initial motivation and achievement was to demonstrate versatile photonic sources in modern appliances (e.g. displays and lighting) and as quantum light sources. Materials' design objectives have encompassed the chemical engineering of MHs at the atomic scale (e.g. new compounds), nanoscale (e.g. synthesis of nanostructures and their surface chemistry), and mesoscale (e.g. nanostructure superlattices and composites). Particularly, a range of novel main-group and transition-metal halides were synthesized and demonstrated as versatile light emitters with tunable spectral widths and emission peak wavelengths, Stokes shifts, radiative lifetimes, and quantum efficiencies. In parallel, besides discovering new chemically robust and nontoxic MH emitters, SCALE-HALO focused on precision morphological engineering (e.g. thin films, nanocrystals, composites, etc.), chiefly nanocrystals and their assemblies, embarking on the multiscale approach. The project returned new methods for the surface functionalization of structurally soft metal halide nanocrystals using synthetic zwitterionic ligands. This development was matched with the conception of the new synthesis methodology for highly monodisperse nanocrystals. The obtained NCs were assembled into long-range ordered superlattices with tunable collective light emission – superfluorescence. In parallel, highly comprehensive single-dot characterization has demonstrated that lead halide perovskite nanocrystals perform as ultrafast and coherent sources of single photons. SCALE-HALO had also contributed to the fundamental understanding of the structure-property relationship by nuclear magnetic resonance methods such as solid-state multinuclear NMR and nuclear quadrupolar resonance. The project showcased novel use of solid-state and ionic liquid-like metal halides, such as in remote thermometry and thermography, and fast neutron imaging. The project team had also demonstrated the first monolithically stacked vertical image sensor using perovskites as absorber materials.
WP1. Atomic-scale engineering of metal halides led to a number of novel, highly luminescent main-group metal halides. Their optical properties were rationalized, particularly temperature-dependent luminescence lifetimes, and thus their eventual utility as thermoluminophores or for solid-state lighting was demonstrated. In particular, novel phosphors based on Tin and Antimony halides for high-spatial-resolution thermography were shown. Most efforts focused on bright ionic liquids and crystals of novel main-group halides with bright photoluminescence, and also transition metal halides with narrow-band green luminescence.
WP2. Nanoscale and mesoscale engineering have focused on lead halide perovskites. New synthesis of lead halide perovskite nanocrystals with molecular-like nucleation and growth kinetics was demonstrated. Novel robust surface-capping ligand strategies were developed. A large library of synthetic phospholipids was developed as superb capping ligands for metal halide quantum dots. Another major systematic study was the co-assembly of highly luminescent perovskite nanocrystals with size- and shape-uniform nanocrystals of other functionalities (dielectric, magnetic). In these superlattices, the decisive factor was the cubic shape, leading to superlattice structures not commonly observed in the mixtures of spheres. These superlattices exhibit collective emission of light, known as superfluorescence, which was systematically investigated in relation to the superlattice structure.
WP3. This work-package focuses on solid-state NMR spectroscopy of metal halides. In particular, this project, for the first time, emphasized the great utility of lead and halide NMR and NQR for capturing the structure, structure dynamics, size- and surface-effects in lead-halide perovskite nanostructures.
WP4. This work package focused on showcasing new applications of metal halides in their diverse forms. Light-emitting diodes with the external quantum efficiencies of 14% were demonstrated using ligand-engineered lead halide perovskite nanocrystals. The first demonstration of a monolithic three-layer RGB image sensor was a culmination of the thin-film perovskite work. Various metal halides and perovskite nanocrystals were demonstrated as compelling scintillator materials for fast-neutron imaging. A novel application in thermography and thermometry was demonstrated as well.
WP2. Nanoscale and mesoscale engineering have focused on lead halide perovskites. New synthesis of lead halide perovskite nanocrystals with molecular-like nucleation and growth kinetics was demonstrated. Novel robust surface-capping ligand strategies were developed. A large library of synthetic phospholipids was developed as superb capping ligands for metal halide quantum dots. Another major systematic study was the co-assembly of highly luminescent perovskite nanocrystals with size- and shape-uniform nanocrystals of other functionalities (dielectric, magnetic). In these superlattices, the decisive factor was the cubic shape, leading to superlattice structures not commonly observed in the mixtures of spheres. These superlattices exhibit collective emission of light, known as superfluorescence, which was systematically investigated in relation to the superlattice structure.
WP3. This work-package focuses on solid-state NMR spectroscopy of metal halides. In particular, this project, for the first time, emphasized the great utility of lead and halide NMR and NQR for capturing the structure, structure dynamics, size- and surface-effects in lead-halide perovskite nanostructures.
WP4. This work package focused on showcasing new applications of metal halides in their diverse forms. Light-emitting diodes with the external quantum efficiencies of 14% were demonstrated using ligand-engineered lead halide perovskite nanocrystals. The first demonstration of a monolithic three-layer RGB image sensor was a culmination of the thin-film perovskite work. Various metal halides and perovskite nanocrystals were demonstrated as compelling scintillator materials for fast-neutron imaging. A novel application in thermography and thermometry was demonstrated as well.
SCALE-HALO advanced the frontiers in the multiscale chemical engineering of luminescent metal halides beyond the discovery of the new compounds and demonstrated a range of their novel applications. It thus focuses on novel surface chemistry approaches and self-assembly principles. Extensive is also the contribution to structural characterization methods by focusing on multinuclear magnetic nuclear resonance, including nuclear quadrupolar resonance, which was thus far underappreciated and seldom used for metal halides. For the first time, colloidal quantum dots were demonstrated to exhibit ultrafast coherent emission. The efforts on surface engineering of perovskite quantum dots translated into collaboration with industry on implementation of these novel emitters in display technologies.