Surface Morphology Control of Strongly Confined CsPbBr₃ PQDs

Highly confined perovskite quantum dots (PQDs) have gained significant attention for their promising use in optoelectronic devices and as quantum light sources. Synthetically, there have been significant advances reported in literature regarding the regulation of PQD sizes and morphology. However, due to lack of chemical stability of PQDs in the strongly confined region (< 5 nm), simultaneous regulation of PQD sizes and surface morphology for strongly confined PQDs has been underexplored. Here we propose that by utilizing ligands that have a stronger affinity for binding along a specific crystal facet of the PQDs, will result in selective binding to that facet that during growth, thus stabilizing the facet and yielding a desired surface morphology for the synthesized PQDs. Dicationic quaternary ammonium ligands with the linking carbon chain length tuned to match that of inter Cs⁺ distance of the (100) and (110) facets of the PQD result in particle morphologies exposing the (100) and (110) facet selectively. By introducing these dicationic quaternary ammonium ligands into a thermodynamic equilibrium controlled synthesis, CsPbBr₃ PQDs < 5 nm with controlled morphologies have been synthesized. Our work offers a route to studying facet dependent optical properties of PQDs in the strongly confined region.