Highly efficient green-1ight-emitting diodes (LEDs) based on CdSe@ZnS quantum dots (QDs) with a chemical-composition gradient are demonstrated. Through the moderate control of QD coverage in multilayered devices, excellent device performance has been achieved. The color-saturated green-light emission (see figure for Commission Internationale de I'Eclairage (CIE) co-ordinates) is mainly from the QD layers (more than 99% of total emission).