How does the emission wavelength and color of the LED change when the junction temperature rises？

The Change of Emission Wavelength and Color with LED Junction Temperature Rise
LED (Light Emitting Diode) is a semiconductor light-emitting device widely used in lighting, display, signal indication, and other fields. Its working principle is to utilize the energy released when electrons and holes recombine at the P-N semiconductor interface to produce photons, thereby emitting visible light. The change in the emission wavelength and color of the LED is mainly related to factors such as the recombination efficiency of electrons and holes, carrier concentration, and electric field intensity inside the LED when the junction temperature rises.
One, The Impact of LED Junction Temperature Rise on Emission Wavelength
When the junction temperature of the LED rises, the concentration of carriers inside it increases, and the recombination efficiency of electrons and holes will also increase accordingly. However, the increase in the recombination efficiency of electrons and holes is not unconditional, as it is limited by the recombination path, and the length and width of the recombination path are determined by the structure of the LED. When the junction temperature of the LED rises, the recombination path of electrons and holes will become longer, leading to a decrease in recombination efficiency. In addition, the increase in temperature will also cause the electric field intensity inside the LED to increase, making the recombination path of electrons and holes narrower, further reducing the recombination efficiency of electrons and holes. Therefore, when the junction temperature of the LED rises, the recombination efficiency of electrons and holes inside it will decrease, resulting in a change in the emission wavelength and color of the LED.
Two, The Impact of LED Junction Temperature Rise on Emission Color
When the junction temperature of the LED rises, the recombination efficiency of electrons and holes inside it decreases, leading to longer and narrower recombination paths for electrons and holes, thereby reducing the recombination efficiency of electrons and holes. This will cause the emission wavelength of the LED to shift towards the longer wavelength, that is, the color of the LED will turn red. This is because the emission wavelength of the LED is determined by the bandgap width of the semiconductor material, and the relationship between the bandgap width and temperature is Tanh(kT/h), where k is the Boltzmann constant and h is the Planck constant. Therefore, when the junction temperature of the LED rises, its emission wavelength will shift towards the longer wavelength, that is, the color of the LED will turn red.
Three, Conclusion
As the junction temperature of the LED rises, the recombination efficiency of electrons and holes inside it decreases, leading to longer and narrower recombination paths for electrons and holes, thereby reducing the recombination efficiency of electrons and holes. This will cause the emission wavelength of the LED to shift towards the longer wavelength, that is, the color of the LED will turn red. Therefore, the junction temperature of the LED has a significant impact on the emission wavelength and color of the LED. In practical applications, in order to ensure the stability and service life of the LED, it is necessary to control the junction temperature of the LED within an appropriate range.