“…Due to their unique photoelectrical properties, such as high color purity, near unity photoluminescence quantum yield, large absorption cross section, and quasi-discrete energy levels, colloidal quantum dots (QDs) are emerging as an attractive class of luminescent materials for light-emitting diodes (referred to as QLEDs), laser diodes, and down-conversion layers. − In the last three decades, huge progress has been made regarding QLEDs as a potential alternative technology for display and lighting applications. − Various QD designs, such as alloying shell, gradient energy level engineering, and selenium throughout the core/shell, are reported to improve the performance of QLEDs. Benefiting from the advance of QD synthesis, the maximum external quantum efficiency of the red, green, and blue three-primary-color QLEDs has been over 20%, the theoretical limit value for planar devices without any light outcoupling technology.…”