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.
