Roshini Jayabalan

Colloidal quantum dots (QDs) are promising for light‐emitting applications, but their synthesis under ambient conditions remains challenging. Here we present a rapid, room‐temperature (RT) method that produces highly stable QDs within minutes using the zwitterionic ligand 2‐ammonioethyl 2‐octyl‐1‐dodecyl phosphate (OD‐PEA). The strong binding of OD‐PEA enables precise size control and effective passivation, yielding blue‐emitting QDs () with narrow linewidths () and high photoluminescence quantum yields (up to 86 %). The QDs retain their optical quality for months in air and offer tunable emission from blue–cyan through ligand concentration, and from ultraviolet to deep red via halide exchange. A proof‐of‐concept perovskite light‐emitting diode (PeLED) fabricated from these QDs exhibits appreciable electroluminescence (EL) at with a low turn‐on voltage. This work establishes a simple and scalable strategy for producing stable, strongly confined perovskite QDs, advancing their potential for next‐generation optoelectronic and photonic technologies.

Lead halide perovskite nanocrystals (NCs) are promising materials for light-emitting diodes (LEDs) due to their wavelength tunability, narrow emission line width, and high photoluminescence quantum yield. Oftentimes, these devices suffer from charge carrier imbalance and reduced charge injection because as-synthesized NCs are covered by long aliphatic ligands. Here, we show a ligand exchange to small electron-withdrawing or electron-donating cinnamate ligands. We probe the influences of the ligands’ dipole moment on hole injection by photoluminescence spectroelectrochemistry (PL SEC). We find that hole injection into NCs covered by electron-withdrawing ligands is facilitated and that these NCs exhibit a superior LED performance. Our results emphasize the importance of kinetic hinderance for charge carrier injection into NC films, a feature that is more accurately derived by SEC compared to other techniques like photoelectron spectroscopy.

The study of lead halide perovskite nanocrystal based light‐emitting diodes (LEDs) has advanced significantly, with notable improvements in stability and optical properties. However, optimizing charge carrier injection and transport remains a challenge. Efficient electroluminescence requires a balanced transport of both holes and electrons within the emitting material. Here, cubic CsPbBr₃ nanocrystals passivated with oleylamine and oleic acid are investigated, comparing them to ligand‐exchanged nanocrystals with didodecyldimethylammonium bromide (DDABr). Nuclear magnetic resonance spectroscopy and transmission electron microscopy confirm successful ligand exchange, revealing reduced ligand coverage in DDABr‐treated nanocrystals. Photoelectron spectroscopy, spectroelectrochemistry, and single‐carrier devices indicate improved hole injection in DDABr‐capped nanocrystals. Density functional theory calculations further reveal the influence of ligand type and coverage on energy levels, with oleic acid introducing localized states in native nanocrystals. Additionally, incorporation of a polar electron transport layer enhances LED performance by over an order of magnitude in DDABr‐capped nanocrystals, driven by improved charge balance arising from the spontaneous orientation polarization of the electron transport layer. These findings highlight the critical role of ligand selection, passivation degree, and charge transport control by the adjacent organic transport layers in optimizing LED efficiency.