Synthesis of Colloidal Inorganic Nanocrystals for Broadband Light Harvesting in Organic/Inorganic Hybrid Systems

• Génesis Arroyo-Santana, Chemistry, University of Puerto Rico - Rio Piedras Campus

• Emil Hernández-Pagán, Chemistry, University of Delaware

A significant portion of solar energy remains underutilized due to the limited spectral absorption range of conventional materials. To address this limitation, photon-conversion mechanisms have emerged as a promising strategy, enabling more efficient energy harvesting for practical applications. Among the most widely studied approaches are upconversion (UC) and downconversion (DC), where UC allows for the absorption of low-energy photons and emission of higher-energy photons, while DC does the opposite. Nanocrystals have demonstrated high potential for photon conversion due to their size-tunable optical properties. Despite these advances, challenges remain in the efficient utilization of these nanocrystals. In this context, this project focuses on the synthesis and characterization of lanthanide-and chalcogenide-doped inorganic nanocrystals for subsequent integration with organic polymer brushes within hybrid systems. Chalcogenide nanocrystals enable downconversion through quantum confinement effects, while lanthanide-based nanocrystals facilitate upconversion due to their long-lived excited states. The experimental work focused on synthesizing NaYF₄ and CdS-ZnS-core-shell nanocrystals using hot-injection methods under controlled temperature and an inert nitrogen atmosphere to ensure precise nucleation and growth. Shell formation was achieved via the successive ionic layer adsorption and reaction (SILAR) method to control ZnS shell thickness. The resulting materials were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, UV-Vis absorption, and photoluminescence spectroscopy to evaluate their structural and optical properties. Moreover, the integration of the polymer brushes with the nanocrystals is expected to enable efficient communication between the inorganic and organic components, improving the overall optical performance of the material. Future studies involve integrating SiO₂ shells into nanocrystals and optimizing the interface between nanocrystals and polymer brushes to enhance energy transfer efficiency.