A quantum dot/quantum well light emitting diode (LED) is provided with a LED at one side of a substrate, and a second light emitting layer and a third light emitting layer at the other side of the substrate. When a proper forward bias is applied to the LED to emit a first light by the first light emitting layer, the first light is used to excite the second light emitting layer and the third light emitting layer to generate the second light output and the third light output of different colors respectively. Then, the light output of a desired color can be generated by mixing the first light, the second light and the third light.