Laser‐Induced Size‐Focusing Synthesis of High‐Quality Colloidal Quantum Dots

Abstract Laser‐assisted chemical synthesis has emerged as a promising toolkit for producing unconventional nanomaterials otherwise not readily accessible. However, it remains challenging for the high‐precision laser‐assisted photoetching of colloidal quantum dots (QDs). Here, we report a laser‐assisted atom‐by‐atom photoetching process that post‐synthetically enables the state‐of‐the‐art colloidal CdSe QDs. By deciphering the surface chemistry and ultrafast excitonic dynamics, we provide an atomic‐level activation–coordination coupling mechanism in such exciton‐involved photochemical reactions. In situ spectroscopies further reveal the reaction kinetics as a four‐step size‐focusing process that is highly dependent on the laser wavelength. As such, by modulating the laser wavelength, which dictates the excitonic absorption threshold of final QDs, we are capable of retrosynthetically programming their sizes across a wide quantum‐confined regime, thereby achieving an ultrabroad color gamut. These findings offer a guideline for the laser‐assisted retrosynthesis of high‐quality quantum‐confined materials.