Ligand-driven facet control of InAs-based quantum dots for enhanced near- and shortwave infrared emission†

Abstract

InAs-based quantum dots (QDs) are promising heavy-metal-free semiconductors for infrared emission technologies, offering tunable bandgaps via quantum confinement and excellent charge-carrier transport properties. Building on these advantages, we report the synthesis of QDs tailored for emission in the near-infrared (NIR) and short-wave infrared (SWIR) regions, emphasizing the critical role of capping ligands in controlling surface facet populations and nanocrystal morphology. Specifically, we demonstrate that the choice of ligand plays a critical role in determining the morphology and surface characteristics of InAs QDs. Using dioctylamine as a ligand results in InAs QDs with a spherical or tetrapod morphology, where nonpolar (110) facets are predominantly exposed on the surface. In contrast, oleic acid as a ligand promotes the formation of tetrahedral-shaped QDs with polar (111) crystalline planes being more prominently exposed. Using a one-pot synthesis approach, we successfully synthesized InAs/InZnP/ZnSe/ZnS core-multi-shell structures that effectively minimize interfacial defects. QDs with dioctylamine-capped core exhibit significantly higher photoluminescence quantum yield (PLQY) compared to those with oleic acid-capped cores. We achieved a PLQY of 39% at 1260 nm and 7.3% at 1420 nm with QDs using dioctylamine, representing efficiency values among the best reported in both the NIR and SWIR regions. Transient absorption (TA) spectroscopy reveals that dioctylamine-capped QDs exhibit reduced ground-state bleaching differences across excitation wavelengths compared to oleic acid-capped QDs, indicating significantly reduced interfacial trap states. These findings highlight the importance of ligand-driven facet control in the context of minimizing interfacial defect formation.