Magic-Sized InP Clusters as Platforms for Core-Only Emitters with Narrow Linewidths

Colloidal quantum dots (QDs) excel at converting light or electricity into bright, tunable, color-pure luminescence, a property that promises a future of display technology that can reproduce the range of spectral hues discernable to humans. While several materials are disqualified due to hazardous substance restrictions, indium phosphide (InP) is energetically qualified and not RoHS restricted. Imparting synthetic control over the resultant photophysical properties of InP is an outstanding challenge, however. Our efforts have focused on developing the synthesis of atomically precise InP magic-sized clusters that show unique and distinct photophysical behavior from their larger QD counterparts. Importantly, these clusters demonstrate exceptionally narrow emission linewidths and long-term ambient stability, making them a promising platform for emissive materials. This is achieved by exchanging carboxylic acid ligands for phosphonic acids, employing reaction additives, and exploring post-synthetic atomistic surface modifications. Despite exhibiting exceptionally narrow ensemble linewidths, the as-synthesized clusters suffer from low photoluminescence quantum yield. Low brightness is remedied by including phosphine oxides in the synthesis, which affords highly monodisperse InP nuclei demonstrating improved photoluminescence intensity and lifetimes. Ongoing and future efforts are focused on exploring the formation, physical structure, and the role of ligands and extraneous additives on modulating the surface chemistry and resultant photophysical behavior of phosphonic acid-capped InP magic-sized clusters.