As we all know, light color of LED can be determined by materials used in n-type region and p-type region, and light intensity is determined by the number of carriers within LED Street Light. Carriers’ number is not fixed in diodes. Temperature can exert a significant influence on it. With the increase of temperature, the intrinsic excitation effect will be enhanced. More electron-hole pairs will be generated in n-type region and p-type region respectively. This additional electron-hole pairs will change the width of LED PN junction as well as internal current.
Apply a forward bias voltage on LED High Bay, a certain amount of heat will be generated. Thus more electron-hole pairs will be created during this process. This intrinsic excitation can happen within p-type region, n-type region and space charge region.
Intrinsic excitation within p-type region: electrons created by intrinsic excitation combine with holes provided by the positive potential connected to the other side of p-type section, leading the reduction of PN junction. This kind of combination can generate heat energy.
Intrinsic excitation within LED PN junction: if an electron-hole pair is generated within PN junction, the electron will be impelled into p-type section due to external electric field. This electron will combine with a hole provide by the positive potential. Since this kind of combination cannot provide enough potential energy to generate visible light but infrared rays. Some parts of these infrared rays are absorbed by LED and consequently converted into heat energy, the other parts radiated into the air. Scientists also name this type of combination as invalid combination.
From the analysis of above two intrinsic excitations, a part of holes provided by power supply will be combined by electrons created by intrinsic excitations. These holes cannot pass PN junction. Similarly, a part of electrons provided by power supply cannot pass PN junction due to intrinsic excitations. Intrinsic excitation within LED PN junction is the chief culprit for this invalid combination. Thus, only a part of carriers provide by power supply can pass though PN junction containing enough potential energy (reach the band gap) to emit visible lights.
However, if the working temperature is higher than a certain threshold value, optical quenching phenomenon will be caused. Except for invalid combination caused by intrinsic excitations within LED PN junction and LED Panel, tunnel effect is another factor. When carriers concentration is too high, the Fermi level of p-type region can reach up to or even exceed the Fermi level of n-type region. So electrons have no need to pass PN junction and reach to p-type region directly. The energy released by the combination of electrons and holes will be lower than the band gad, leading to the optical quenching phenomenon.