Wide-bandgap and heavy-metal-free quantum dots for blue light-emitting diodes

Abstract Colloidal quantum dots (CQDs) are highly regarded for their outstanding photovoltaic characteristics, including excellent color purity, stability, high photoluminescence quantum yield (PLQY), narrow emission spectra, and ease of solution processing. Despite significant progress in quantum dot light-emitting diodes (QLEDs) technology since its inception in 1994, blue QLEDs still fall short in efficiency and lifespan compared to red and green versions. The toxicity concerns associated with Cd/Pb-based quantum dots (QDs) have spurred the development of heavy-metal-free alternatives, such as group Ⅱ−Ⅵ (e.g., ZnSe-based QDs), group Ⅲ−Ⅴ (e.g., InP, GaN QDs), and carbon dots (CDs). In this review, we discuss the key properties and development history of quantum dots (QDs), various synthesis approaches, the role of surface ligands, and important considerations in developing core/shell (C/S) structured QDs. Additionally, we provide an outlook on the challenges and future directions for blue QLEDs.