Novel organic compounds for solar energy conversion: applications in photoelectrochemical cells for Hydrogen production and solar thermal energy storage

This thesis reports the design, synthesis, and characterization of novel organic materials for solar energy conversion and storage applications. The first part focuses on the development of two donor–acceptor–π–acceptor (D–A–π–A) organic dyes based on a benzothiadiazole–dithienosilole (BTD–DTS) core for use as anodic sensitizers in dye-sensitized photoelectrochemical cells (DS-PECs) aimed at molecular hydrogen production. The dyes, featuring a common cyanoacrylic acid anchoring group and donor moieties with different hydrophilic properties, were preliminarily investigated by density functional theory (DFT) calculations, which confirmed suitable electronic structures and energy-level alignment for photoelectrochemical applications. Following their synthesis through a concise route involving a microwave-assisted Stille–Migita cross-coupling reaction, the compounds were fully characterized and employed to sensitize nanocrystalline TiO2 and SnO2 photoanodes. Their performance in DS-PEC devices was evaluated in terms of photocurrent generation, hydrogen evolution, and operational stability under different experimental conditions. The final part of the thesis presents a research project conducted during a six-month stay at the laboratory of Prof. Kasper Moth-Poulsen at the Universitat Politècnica de Catalunya (UPC), Barcelona, focused on the development of anthracene-based molecular solar thermal (MOST) energy storage systems. Novel ortho-dianthrylbenzene derivatives bearing electron-donating methoxy substituents at the 10-position of the anthracene units were synthesized and fully characterized. Preliminary photochemical studies were performed to investigate their photoswitching behavior, reversibility, and photostability, as well as the influence of direct anthracene substitution on photodimerization and energy storage properties. The results provide useful insights for the future design of improved MOST materials and contribute to the broader development of molecular systems for sustainable solar energy utilization.