Five aspects of the impact of temperature on the LED display
LED display has great development prospects due to its advantages of energy saving, environmental protection and long life. But the temperature is very important to the LED display, the effect of temperature on the LED display: LED display related to life and luminous efficiency, color and the like. So the right temperature is critical to the LED display. The effect of temperature on the LED display has the following five points: First, the temperature is too high will lead to the complete destruction of the LED display (1) The operating temperature of the LED display exceeds the carrying temperature of the chip, which will cause the luminous efficiency of the LED display to decrease rapidly, causing obvious light decay and causing damage; (2) The LED display is mostly encapsulated in transparent epoxy resin. If the junction temperature exceeds the solid phase transition temperature (usually 125 °C), the packaging material will change to rubber and the thermal expansion coefficient will rise sharply, resulting in open and invalid LED display. . Second, the temperature rise will shorten the life of the LED display The life of an LED display is characterized by its light decay, that is, the time is long, and the brightness is getting lower and lower until it is finally extinguished. The time at which the LED display's luminous flux decays by 30 is usually defined as its lifetime. The causes of the LED display's light decay are as follows: (1) The defects existing in the LED display chip material will rapidly proliferate and multiply at higher temperatures until invading the light-emitting area, forming a large number of non-radiative composite centers, which seriously reduce the luminous efficiency of the LED display. In addition, under high temperature conditions, micro-defects in the material and fast-expanding impurities from the interface and the electric board will also be introduced into the light-emitting area, forming a large number of deep levels, which will also accelerate the light decay of the LED display device. (2) When high temperature, the transparent epoxy resin will be denatured and yellow, which will affect its light transmission performance. The higher the working temperature, the faster the process will proceed, which is another major cause of LED display light decay. (3) The light decay of phosphors is also a major cause of the light fade of LED displays, because the phosphors are very attenuated at high temperatures. Therefore, high temperature is the main source of LED display light decay and shortening the life of LED display. The light decay of different brands of LED displays is different. Usually LED display manufacturers will give a set of standard light decay curves. The LED display luminous flux attenuation caused by high temperature is unrecoverable, and the LED display does not have the luminous flux before the unrecoverable light attenuation, which is called the "initial luminous flux" of the LED display. Third, the temperature rise will reduce the luminous efficiency of the LED display The reasons why temperature affects the LED display efficiency include the following: (1) As the temperature rises, the concentration of electrons and holes increases, the band gap decreases, and the electron mobility decreases. (2) When the temperature rises, the probability of recombination of electrons and holes in the potential well is reduced, resulting in non-radiative recombination (heat generation), thereby reducing the internal quantum efficiency of the LED display. (3) The temperature rise causes the blue light peak of the chip to shift toward the long wave direction, so that the emission wavelength of the chip and the excitation wavelength of the phosphor do not match, which also causes the external light extraction efficiency of the white LED display to be lowered. (4) As the temperature rises, the quantum efficiency of the phosphor decreases, the light emission decreases, and the external light extraction efficiency of the LED display panel decreases. (5) The performance of silica gel is greatly affected by the ambient temperature. As the temperature rises, the thermal stress inside the silica gel increases, causing the refractive index of the silica gel to decrease, thereby affecting the light effect of the LED display. Fourth, the effect of temperature on the LED display wavelength (light color) The wavelength of the LED display can generally be divided into a peak wavelength and a dominant wavelength. The peak wavelength is the wavelength at which the light intensity is the largest, and the dominant wavelength can be determined by the X, Y chromaticity coordinates, reflecting the color perceived by the human eye. Obviously, the change in the wavelength of the LED display caused by the junction temperature will directly cause the human eye to feel differently about the color of the LED display. For an LED display device, the forbidden band width of the luminescent material directly determines the wavelength or color of the device's illumination. As the temperature rises, the forbidden band width of the material will decrease, resulting in a longer wavelength of the device and a red shift in color. 5. Excessive temperature will limit the maximum injection current of the LED display. The above points are the introduction of the influence of temperature on the LED display. It is known from the above that the effect of temperature rise on the LED display is very large. 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