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The Effect of High Temperature on the LED Display

2019-04-27 www.myddisplay.com

Summer is coming soon, Shenzhen has entered the high temperature link. For large LED screen users, we must pay attention to the temperature change of the large LED screen, because the high temperature has the following four effects on the LED display:


1. If the temperature is too high, the LED display will be destroyed.


(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) LED display screens are mostly encapsulated in transparent epoxy resin. If the junction temperature exceeds the solid phase transition temperature (usually 125 °C), the package material will change to rubber and the coefficient of thermal expansion will rise sharply, resulting in failure of the LED display.


2. the temperature rise will shorten the life of the LED display


The life of an LED display is manifested by its light decay. That is, the time is long, and the brightness is getting lower and lower until it is finally extinguished.


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. 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.


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3. the temperature rise will reduce the luminous rate of the LED display


The reasons why temperature affects the LED display efficacy 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 decreases, 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 does not match the excitation wavelength of the phosphor, and the external light extraction efficiency of the white LED display screen is also 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 increases, 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.


4. the effect of temperature on the LED display wavelength (light color)


The LED display wavelength is generally divided into a peak wavelength and a dominant wavelength. The peak wavelength is the wavelength with the highest light intensity, and the dominant wavelength can be determined by the X, Y chromaticity coordinates, reflecting the color perceived by the human eye. Obviously, the change of the wavelength of the LED display caused by the junction temperature will directly cause the human eye to feel different colors 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. 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.


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