What are the applications of light-emitting diodes?

　　 Light-emitting diode LED, short for light-emitting diode, is a type of semiconductor diode made from compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), and other elements, capable of converting electrical energy into light energy.

　　When electrons and holes recombine, they emit visible light, making LEDs suitable for use in light-emitting diodes. They serve as indicator lights in circuits and instruments, or can be configured to display text or numerical digits. Gallium arsenide diodes emit red light, gallium phosphide diodes emit green light, silicon carbide diodes emit yellow light, and gallium nitride diodes emit blue light. Based on their chemical properties, LEDs are further classified into organic light-emitting diodes (OLEDs) and inorganic light-emitting diodes (LEDs). The following section will introduce the applications of light-emitting diodes.

　　Applications of light-emitting diodes:

　　1. Light-emitting diodes used as LED displays

　　Since the mid-1980s, both monochrome and multicolor display screens have been introduced, initially in the form of text displays or animated displays. In the early 1990s, advances in computer technology and integrated circuit technology enabled the realization of video capabilities in LED displays, allowing direct playback of television images on screen. Particularly in the mid-1990s, the successful development and rapid mass production of ultra-high-brightness blue and green LEDs greatly expanded the applications of outdoor LED displays, with screen sizes ranging from 100 to 300 square meters. Today, LED displays are widely used in sports venues, public squares, conference halls, and even on streets and in shopping malls. The most renowned example is the full-color Nasdaq display in Times Square, New York, which measures 120 feet by 90 feet—equivalent to 1,005 square meters—and is composed of 19 million ultra-high-brightness blue, green, and red LEDs. Recently, there has also been significant development in information displays along highways and elevated roadways. The application of light-emitting diodes in this field has now reached a substantial scale, giving rise to an emerging industry with prospects for steady growth.

　　2. Light-emitting diodes used as traffic signals

　　LEDs have been used as the light source for navigation lights for many years, and current efforts are focused on further improving and refining this technology. In recent years, road traffic signal lights have made substantial progress, with rapid technological advancement and explosive growth in applications. China currently receives approximately 40,000 sets of orders annually, while California alone replaced 50,000 conventional-light-source signal units with LED traffic signals last year. Based on performance evaluations, the advantages of longer service life, energy savings, and virtually maintenance-free operation are clearly evident. At present, the peak emission wavelengths of LEDs used in traffic signals are 630 nm for red, 590 nm for yellow, and 505 nm for green. It is important to note that the drive current should not be too high; otherwise, the high ambient temperatures under summer sunlight can adversely affect the LED’s lifespan.

　　LED airport-specific signal lights, used at airports as marker lights, floodlights, and omnidirectional lights, have also been successfully developed and put into service, with widespread positive feedback on their performance. These lights feature proprietary intellectual property rights, have been granted two patents, exhibit excellent reliability, significantly reduce power consumption, require no maintenance, and can be widely deployed at various airports to replace decades-old conventional signal lights. Not only do they offer high brightness, but their superior color purity and vividness make signal recognition exceptionally clear and straightforward.

　　Railway signal lights, with their wide variety of models and specifications, have varying requirements for luminous intensity and beam angle. Research and development are currently being accelerated, with expectations that these technologies will be gradually perfected and progressively put into practical use. From a market perspective, this represents a substantial opportunity.

　　3. Light-emitting diodes used as automotive lights

　　Ultra-bright LEDs can be used for automotive brake lights, tail lights, and turn signals, as well as for instrument panel lighting and interior cabin lighting. They offer significant advantages over incandescent bulbs in terms of vibration resistance, energy efficiency, and long service life. When employed as brake lights, their response time is just 60 nanoseconds—much faster than the 140 milliseconds of incandescent bulbs—thereby increasing the safe following distance by 4 to 6 meters when driving on highways.

　　4. Light-emitting diodes used as backlights for LCD screens

　　LEDs, when used as backlights for LCD displays, can not only provide red, green, blue, and white illumination but also serve as color-changing backlights; many such products have already entered the production and application stages. Recently, the use of LED-based backlights in mobile phone LCD screens has elevated product quality and delivered excellent performance. For instance, a 15-inch (1 inch ≈ 2.5 cm) LCD screen equipped with a backlight composed of eight blue, twenty-four green, and thirty-two red Luxeon LEDs achieves a total output of 120 W, a luminous flux of 2,500 lm, and a brightness of 18,000 nits (candela per square meter). Backlights for 22-inch LCD panels have also been developed; these are only 6 mm thick, offer superior color mixing, and achieve a color-rendering index of over 80. Although large-scale backlight solutions are still under development, they hold significant potential.

　　5. Light-emitting diodes used as lighting fixtures

　　Due to Light-emitting diode The combination of increased brightness, reduced costs, long service life, energy efficiency, and simpler drive and control systems—coupled with the ability to not only flash but also change colors—has made ultra-high-brightness LEDs an ideal choice for creating monochromatic, multicolor, and even color-changing illuminated columns. When paired with other shaped, multi-colored lighting units, these LED columns deliver outstanding decorative effects for high-rise buildings, bridges, streets, plazas, and other landscape projects, producing a vibrant, starlit, and ever-shifting display of light. Many organizations are already manufacturing LED light columns exceeding 10,000 meters in length and incorporating tens of thousands of colored lights; this technology is now being gradually rolled out and is expected to evolve into a standalone industry.

　　6. Light-emitting diodes used as lighting sources

　　LED light sources used for illumination should be white light; the classification of white-light LEDs is shown in Table 3. Currently, several models of military-grade white-light LED luminaires have entered mass production. Owing to the absence of infrared radiation, which facilitates concealment, as well as their inherent advantages—such as vibration resistance, compatibility with battery power, solid-state construction, and portability—LEDs are poised for substantial development in the field of specialized lighting. In civilian applications, lawn lights and underground lights are already being manufactured on a large scale; LEDs are also employed for microscope field illumination, flashlights, surgical headlamps, museum and art-gallery lighting, and reading desk lamps. As luminous flux increases and costs decline, the range of applications will gradually expand, thereby facilitating the transition from specialized to general-purpose lighting.