Mechanistic Insights into the Growth and Surface Chemistry of III-V Colloidal Quantum Dots

Abstract

Colloidal III–V quantum dots (QDs) offer tunable optical properties essential for optoelectronics. However, their synthesis and integration remain constrained by complex growth pathways, surface oxidation, and defects. This thesis investigates the growth mechanisms and inorganic surface chemistry of InP and InSb QDs, establishing principles for controlled synthesis, ligand exchange, and surface passivation. First, using InP QDs as a model, we explore ligand exchange with Group III metal salts. We demonstrate that in polar solvents, metal halides, nitrates, and perchlorates form metal-solvent complex cations rather than bare metal ions. These complexes effectively passivate the InP surface following organic ligands removal, enabling highly stable colloidal dispersions in polar solvents for over six months. For InSb QDs, we reveal a unique formation mechanism: room-temperature precursor reduction yields zero-valent indium and antimony intermediate nanoparticles. At elevated temperatures, intermetallic diffusion forms highly monodisperse, size-tunable InSb QDs. Spectroscopic analysis identifies surface oxides as the primary source of a dominant non-radiative decay channel. To resolve these intrinsic surface limitations, we systematically decode the biphasic ligand exchange of InSb QDs. While metal chalcogenides and Group III halides provide compatible passivation, hydrolysis of strongly electrophilic halides promotes surface etching. Building on these insights, we introduce a post-synthetic surface fluorination strategy that eliminates native oxides, substantially enhancing photoluminescence. This thesis establishes design principles for the synthesis of high-quality nanocrystals with controlled size, composition, and surface functionality. The insights gained pave the way for the development of environmentally benign quantum dot inks for next-generation optoelectronic devices.