Tech Wood | Explain the causes of LED junction temperature in detail
"LED junction temperature" is not so familiar to most of the people, but even people in the LED industry are not so clear! 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 extraction efficiency is the main reason for the increase of LED junction temperature. At present, the advanced material growth and component manufacturing process can convert most of the input electrical energy of the LED into light radiation energy. However, compared with the surrounding medium, the LED chip material has a much larger refractive index, resulting in an extremely large amount of energy generated inside the chip. Part of the photons (>90%) cannot flow out of the interface smoothly, but produce total reflection at the interface between the chip and the medium, return to the inside of the chip, and are finally absorbed by the chip material or substrate through multiple internal reflections, and change in the form of lattice vibration. heat up, causing the junction temperature to rise.
2. Since the P-N junction cannot be extremely perfect, the injection efficiency of the component will not reach 100%. That is to say, when the LED is working, in addition to the injection of charges (holes) from the P region to the N region, the N region will also Charges (electrons) are injected into the P region. Under normal circumstances, the latter type of charge injection will not produce photoelectric effect, but will be consumed in the form of heat. Even if the useful part is injected with charges, it will not all turn into light, and some will eventually become heat in combination with impurities or defects in the junction region.
3. Poor electrode structure of components, materials of the window layer substrate or junction area, and conductive silver glue all have certain resistance values. These resistances are stacked on each other to form the series resistance of LED components. When the current flows through the P-N junction, it also flows through these resistors, resulting in Joule heating, resulting in an increase in chip temperature or junction temperature.
The above are the main reasons for the LED junction temperature, and of course others are not excluded. Of course, we can't understand the chemical or physical phenomena among them, but in the near future, with the continuous progress of science and technology, we can better To explain the phenomenon, science will use its magic to solve our doubts one by one!
