Shell Engineering of ITO Nanocrystals via Seed-Mediated Growth and Precursor Crowding for Broadband Visible- to-Infrared Absorption

Seed-mediated growth strategies provide a powerful platform for constructing complex nanocrystal architectures by enabling controlled shell deposition on preformed cores. Here, we report a modular synthesis of multicomponent metal oxide nanocrystals featuring compositionally modulated core–shell architectures. Specifically, indium tin oxide (ITO) nanocrystals are engineered through sequential shelling combined with tunable precursor crowding─a strategy analogous to molecular crowding─that reinforces the local precursor concentration near the nanocrystal surface. This environment promotes diffusion-limited growth and enables anisotropic shell formation along with controlled incorporation of otherwise inaccessible transition metal dopants. Undoped shells transform from quasi-spherical to faceted cuboidal morphologies via directional crystallization, while codoping with Fe and Ni disrupts anisotropic growth and introduces visible-light absorption. Unlike conventional doping strategies, our approach yields broadband-active oxide nanocrystals with spatially controlled composition. These findings establish a versatile class of functional oxide heterostructures with tunable visible-to-NIR absorption.