Isotropic ZnSe Shell Growth for Uniform-Shaped Green InP Quantum Dots With Tunable Size and Absorption

Indium phosphide (InP) quantum dots (QDs) are among the most promising heavy-metal-free emitters for next-generation displays, yet achieving isotropic growth of thick ZnSe shells remains challenging because of strain accumulation and facet-dependent surface energies. Here, we report a halide-mediated, stepwise ZnSe growth strategy that produces uniform, near-spherical green-emitting InP/ZnSe/ZnS QDs with precisely tunable shell thicknesses (1.75-5.5 nm) and final sizes up to 14 nm. The resulting QDs preserve near-unity photoluminescence quantum yields (PL QYs) up to a critical ZnSe thickness of ∼3.5 nm, beyond which accumulated compressive strain at the InP/ZnSe interface generates interfacial defects and reduces PL QY. Notably, ZnSe shell contributes significantly to optical absorption, with the molar absorption coefficient at 450 nm scaling nearly with shell volume and following a clear empirical relation. A series of differently sized QDs is further assessed as blue-to-green color converters, revealing a size-dependent balance between enhanced absorption and efficient light conversion.