"LED junction temperature" is not so familiar to most people, but even for people in the LED industry, it is not so familiar! Now we come to a detailed explanation. When the LED is working, the following conditions can cause the junction temperature to rise to varying degrees.
1. After many practices, it has been proved that the limitation of light extraction efficiency is the main reason for the increase of LED junction temperature. At present, advanced material growth and component manufacturing processes can convert most of the input electrical energy of the LED into light radiation energy. However, the material of the LED chip has a much larger refractive index than the surrounding medium, resulting in a large amount of energy generated inside the chip. Part of the photons (>90%) cannot smoothly overflow the interface, and total reflection occurs at the interface between the chip and the medium, returns to the inside of the chip and is finally absorbed by the chip material or substrate through multiple internal reflections, and becomes a form of lattice vibration. Heat causes 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, in addition to the charge (holes) injected from the P area to the N area when the LED is working, the N area will also Injecting charge (electrons) into the P area, under normal circumstances, the latter type of charge injection will not produce a photoelectric effect, but is consumed in the form of heat. Even if the useful part of the injected charge, it will not all become light, and some of it will become heat when combined with impurities or defects in the junction area.
3. The electrode structure of the component is not good, the material of the window layer substrate or junction area and the conductive silver glue all have a certain resistance value, and these resistances add to each other to form the series resistance of the LED component. When current flows through the P-N junction, it will also flow through these resistors, thereby generating Joule heat, causing the chip temperature or junction temperature to rise.
The above are the main reasons for the LED junction temperature. Of course, others are not excluded. Of course, we still can’t understand the chemical or physical phenomena, but in the near future, with the continuous advancement of science and technology, we can better To explain the phenomenon, science will use its magic to solve our doubts one by one!
