Comparison of improved operating parameters of five different wavelength LEDs for significantly brighter illumination

Although light-emitting diodes exhibit much higher efficiencies and greatly reduced power consumption compared to incandescent light sources, the use of LEDs in lighting applications is limited by their smaller size and subsequently lower light output. However, it has been found that these parameters can be increased significantly by cooling the diodes to cryogenic temperatures. This may make their use feasible for several applications requiring more efficient and brighter illumination for much less cost. In this paper, we compare the temperature-dependent behavior of five commercially available LEDs of different wavelengths down to liquid nitrogen temperatures. It was found that three AlInGaP diodes (red, yellow, and green) demonstrated significant operating improvements. The performance of InGaN-based blue LEDs declined at low temperatures, and because most white LEDs are simply blue LEDs coated with YAG, these exhibited similar behavior. However, the three AlInGaP LEDs demonstrated at least an order of magnitude improvement in illuminance, absolute intensity, and maximum operating current. The green LEDs showed the largest improvement factors, while the yellow LEDs produced the brightest illumination at low temperatures. The emissions of all five LEDs shifted to shorter wavelengths at low temperatures. This is significant in terms of lighting applications since the low-temperature AlInGaP diodes emitted more visible spectra.