Structure-Property Relationships in Luminescent Alkali Metal Halide Hybrid Perovskites
Abstract: This dissertation examines the relationships between composition, structure, and luminescence in lead-free alkali metal hybrid halides by analyzing the roles of halide anions, alkali metal cations, and organoammonium cations.
A study of halide ion substitution in piperazinium-based 3D perovskites shows that, among the compounds studied, only the iodide equivalent exhibits intense broadband emission. Spectroscopic and compositional analyses point to an emission mechanism associated with defects linked to the presence of excess iodine species.
The substitution of alkali metal cations made it possible to change the dimensionality of the inorganic lattice from 3D to 1D and to obtain broad-band emissions in the 540–644 nm range.
The choice of specific organic cations, such as morpholinium, allows the crystallization of various inorganic alkali metal halide networks emitting around 578–600 nm. Chiral organic cations also lead to non-centrosymmetric crystals of the space group P2 1 2 1 2 1 , exhibiting broadband photoluminescence and second-harmonic generation. Together, these results highlight the influence of hydrogen bonding on structural and optical properties.
Overall, this thesis demonstrates that adjusting the composition is an effective strategy for controlling structural dimensionality, defect-associated excited states, and broad-band luminescence in lead-free alkali metal hybrid halides.
Keywords: Hybrid materials, perovskite-type alkali metal halides, photoluminescence, dimensionality
Copper iodide-based materials with luminescent mechanochromic properties for the development of shock/stress sensors
Abstract: Luminescent stimulus-responsive materials are receiving increasing attention due to their switchable optical properties in response to external stimuli, which lead to a variety of potential applications such as stress detection, optical recording, and information storage. Among these materials, luminescent mechanochromic materials are characterized by a change in their luminescence properties in response to external mechanical forces, such as grinding. Materials based on transition metals—particularly those based on copper(I) halide—are of interest due to their wide structural diversity, their broad range of photophysical properties, and their economic and environmental advantages stemming from the low cost and limited toxicity of copper.
In this context, this thesis focuses on the study of new luminescent mechanochromic materials based on copper(I) iodide. New materials have been synthesized, and their structure and optical properties have been characterized. Particular attention has been paid to understanding the relationships between the structure and the optical properties of these compounds. The materials have also been processed by incorporating them into polymer matrices, for example, to develop potential applications.
Keywords: Hybrid materials, Copper(I) iodide, Optical properties, Luminescence mechanochromism, Luminescence thermochromism
