Contribution to the Understanding of the Optoelectronic Properties of New Low-Gap Organic Materials for Organic Electronics

My thesis work was conducted jointly at the Laboratory of Physical Chemistry of Materials (LR01ES19, FSM) and at the University of Messina, Italy, as part of a co-tutelle agreement. The thesis aims to extend the understanding of the relationships between the structure and physical properties of fluorescent, low-gap organic materials through molecular modeling based on Density Functional Theory (DFT). The first part of this thesis focuses on validating the structural and optical properties (UV-Vis and photoluminescence) of small sulfur-containing chromophore organic molecules derived from nitrobenzofurazans (NBDs). This theoretical approach enabled a fundamental understanding of non-covalent intramolecular interactions and the control of charge transfer within these molecular structures. Comparing the simulation results with experimental data from the literature has provided a solid foundation for evaluating the reliability of the theoretical modeling approaches used, including the choice of method, functional, and basis sets. The second part of the thesis involves the design and modeling of new π-conjugated organic systems with a push-pull architecture, featuring modified phenylene motifs as electron donors and NBD-based units as electron acceptors. The third and fourth parts focus on designing new NBD-based materials that act as both electron donors and acceptors, acting as Non-Fullerene Acceptors, for integration into organic solar cells (OSCs). The modeling results revealed exceptional behavior and unique characteristics of these materials, demonstrating their excellent properties for both solar energy conversion (with power conversion efficiencies ranging from 7.1% to 10.5%) and nonlinear optics. These findings open new avenues for advancements in organic electronics, highlighting the potential of NBD derivatives for high-performance applications.