As the sun sets, the light-emitting diode (LED) street lights gradually light up; in the crowded bus compartment after get off work, people play with their smartphones; on the bustling streets, colorful LED signs Glitteringly. These scenes may seem trivial to us, but have you ever thought that before 1990, LEDs were only used as indicator lights. Due to a revolutionary invention in 1993, the LED field entered a new era, and soon, white LEDs also came out.

LED first originated in 1961. Texas Instruments developed an LED synthesized with indium gallium phosphide material, and its emission wavelength range is near-infrared. In 1962, the red light-emitting diode developed by Qiqi Company was not widely used because of its poor conversion efficiency and its emission wavelength was far from the visible light range, and was only used as an indicator light. In 1991, the green light-emitting diodes developed by HP Company of the United States and Toshiba Company of Japan could not be combined into a white light source by using the principle of three colors due to the lack of blue LEDs.