What is the cause of the LED junction temperature?

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

First, after many practices have proved that the limitation of light extraction 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 electrical energy of the LED into optical radiant energy. However, since the LED chip material has a much larger refractive index than the surrounding medium, most of the photons generated inside the chip are generated. (>90%) can not smoothly overflow the interface, and the total reflection on the chip and media interface, return to the inside of the chip and through the internal reflections, eventually absorbed by the chip material or substrate, and become hot in the form of lattice vibration, Causes the junction temperature to rise.

Second, because the P-N junction can not be very complete, the injection efficiency of the component will not reach 100%, that is to say, in the operation of the LED, in addition to the P zone to inject charge (hole) into the N zone, the N zone will also Injecting a charge (electron) into the P region, in general, the latter type of charge injection does not produce a photoelectric effect, but is consumed in the form of heat. Even if the useful part of the injected charge does not become all of the light, some of it combines with the impurities or defects of the junction and eventually becomes hot.

Third, the electrode structure of the defective component, the material of the window layer substrate or the junction region, and the conductive silver paste have a certain resistance value, and these resistors are mutually added to form a series resistance of the LED element. When a current flows through the P-N junction, these resistors also flow through, causing Joule heat, which causes an increase in chip temperature or junction temperature.

The above is the main reason for the LED junction temperature. Of course, the other is not excluded. Of course, the chemical or physical phenomena in this are not yet understandable, but in the near future, with the continuous advancement of technology, we can be better. Explain the phenomenon, science will solve our doubts one by one!