Πλοήγηση ανά Συγγραφέας "Stoumpos, Konstantinos"

Τώρα δείχνει 1 - 2 of 2
  • Μικρογραφία εικόνας
    Τεκμήριο
    Lattice dynamics of hybrid halide perovskite single crystals by dielectric spectroscopy
    (ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-04-02) Gkikas, Ioannis; Γκίκας, Ιωάννης; Lappas, Alexandros; Stoumpos, Konstantinos; Λάππας, Αλέξανδρος; Στούμπος, Κωνσταντίνος
    Halide perovskites AMX3 (A+ = Cs, CH3NH3 or HC(NH2)2 , M2+ = Pb, Sn or Ge and X- = Cl, Br or I), are amongst the leading emerging materials in the past decade towards optoelectronic and environmental remediation applications, including devices such as solar cells, light-emitting diodes, hard radiation detectors and photocatalytic modules. What makes these semiconductor materials so attractive for optoelectronic devices is their superb absorption across the visible and near-infrared region (Eg = 1.1-3.0 eV) and their high charge-carrier mobility and long charge-carrier diffusion lengths. An important research branch of halide perovskites focuses in the understanding of the underlying physicochemical origins of these fascinating properties, which is currently lacking. Such understanding will be beneficial not only from the fundamental science perspective but also crucial for the rational enhancement of the optoelectronic performance. In this work, mm-sized single-crystals of hybrid halide perovskites were grown (MAPbCl3 and MAPbBr3) and studied. Structurally and spectroscopically using a custom made set up, with capabilities to investigate the lattice dynamic of the crystalline material, and correlate the phase transition transformation to the dielectric properties. Also, relaxation time mechanisms were studied compering different models and proving the optional as the Havriliak-Negami. Calculated the relaxation time and the exponents of the fitting model, providing information of the dipole behavior.
  • Μικρογραφία εικόνας
    Τεκμήριο
    Noble metal halide crystals
    (ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-04-02) Michailidis-Barakat, Alaelddin; Μιχαηλίδης-Μπαρακάτ, Αλαελντίν; Stoumpos, Konstantinos; Στούμπος, Κωνσταντίνος
    Halide Perovskites have attracted significant attention in the field of materials science due to their potential in optoelectronic applications, as they behave as high-performance semiconductors with interesting properties, such as defect tolerance that enables them to act as photo-active layers in solar cell thin-film devices. The aim of the exploratory research project examined in this Thesis, is the synthesis and characterization of inorganic halide crystal semiconductors through wet synthesis and characterization of their structural, optical and electrical properties. Our findings revealed the existence of a new series of quaternary perovskites in the A-M-M’-X system (A is an alkali metal, M is a group 10 metal M’ is a group 11 metal and X is a halogen), with the observed compounds presenting close characteristics to that of typical halide perovskites such as CsPbBr3. The combination of groups 10/11 metals provides a fertile ground for the discovery of new structure-type archetypes divided in several families of composition- and property-tunable compounds. Among the new compounds synthesized, a hitherto unknown perovskite structure was obtained in the form of the vacancy-ordered quadruple perovskite Cs4Au2Pd□X12 (□ denotes an ordered vacancy) crystallizing in a 4x4x4 body-centered cubic space group. The crystal structure for all the compounds were determined via singlecrystal X-ray diffraction which, where necessary, were complemented by elemental analyses (SEM/EDS) and oxidation number sensitive spectroscopy (XPS). The materials were further characterized thermochemically to establish thermal stability, while their optical spectra (0.8eV > Eg > 2.0 eV) and electrical resistivity (ρ ∼ 108Ωcm) were recorded to establish their semiconducting nature. Our research provides new insights into the halide perovskite compositional space and assesses the fundamental properties of these new inorganic and hybrid halide perovskite-like crystals towards further optoelectronic applications