A light emitting diode (LED) with higher illumination efficiency is revealed. The LED includes a LED chip and an optical layer arranged on the bottom of the LED chip. The optical layer is a light-guiding layer, a light reflective layer or an energy-conversion layer that increases light emitting efficiency of the LED. Furthermore, a rough layer is disposed between the LED chip and the optical layer so as to increase surface area of the LED chip. Thus light emitted from the LED chip enters the optical layer more easily and the illumination efficiency of the LED is increased.