A light-emitting diode (LED) (10) includes a chip body (103), an encapsulation can (105) surrounding the chip body, and a base (106) supporting the encapsulation can and the chip body thereon. Numerous diffusion structures (1050) are provided on the encapsulation can, and the encapsulation can is made of a piezoelectric material for widening radiation angles of light beams emitted from the chip body. With the diffusion structures and the piezoelectric encapsulation can, light beams from the chip body are diffused and attain wider radiation angles. A backlight system (900) includes a light guide plate (20), and a number of the above-described LEDs disposed adjacent to the light guide plate. Light beams having wide radiation angles are emitted from the LEDs and enter the light guide plate. This enables a light emitting surface of the light guide plate to have highly uniform brightness.