"LED junction temperature" is not so familiar to most people, but even for the LED industry, it is not so obvious! Now let's explain in detail. When the LED is working, the following conditions can cause the junction temperature to rise to varying degrees.

1. After many times of practice, it has been proved that the limitation of light output efficiency is the main reason for the rise of LED junction temperature. At present, advanced material growth and component manufacturing processes can convert most of the input energy of LEDs into light radiant energy. However, because the LED chip material has a much larger refractive index than the surrounding medium, it causes great Part of the photons (> 90%) cannot smoothly overflow the interface, and total reflection is generated at the interface between the chip and the medium, which returns to the inside of the chip and is absorbed by the chip material or substrate through multiple internal reflections and becomes in the form of lattice vibration Heat causes the junction temperature to rise.

2. Since the PN junction cannot be extremely perfect, the injection efficiency of the device will not reach 100%, that is to say, in addition to the injection of charge (holes) from the P region to the N region during LED operation, the N region will also Injecting electric charge (electrons) into the P area. In general, the latter type of electric charge does not produce a photoelectric effect, but is consumed in the form of heat. Even if the useful part is injected with charge, it will not all become light, and a part of it will be combined with impurities or defects in the junction area, and will eventually become heat.

3. The defective electrode structure of the element, the material of the window layer substrate or the junction area, and the conductive silver paste all have a certain resistance value, and these resistances add to each other to form the series resistance of the LED element. When the current flows through the PN junction, it will also flow through these resistors, resulting in Joule heat, causing the chip temperature or junction temperature to increase.

The above is the main reason for the LED junction temperature. Of course, it does not rule out others. Of course, we cannot understand the chemical or physical phenomena, but in the near future, with the continuous progress of science and technology, we can better Explain the phenomenon, and science will use its magic to solve our doubts one by one!