Led displays have great potential due to their energy saving, environmental protection, and long life. But the temperature is very important for the led display, the temperature of the led display: relates to the led display life, light efficiency, color and so on. So the right temperature is very important for the led display.
The effect of temperature on the led display has the following five points:
One, the temperature is too high will lead to the complete destruction of 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 rapidly decrease, resulting in significant light failure and causing damage.
(2) The LED display is mostly made of transparent epoxy resin. If the junction temperature exceeds the solid phase transition temperature (usually 125°C), the encapsulating material will change to a rubbery shape and the coefficient of thermal expansion will escalate, causing the LED display to open and fail. .
Second, the temperature will shorten the life of the led display
The life of the led display is its light decay, that is, the time is long, and the brightness is getting lower and lower until it finally goes out. Usually defines the LED display light flux decay time 30 for its life.
The reason that led to the led display light fades usually has the following aspects:
(1) Defects in the LED display screen chip material will rapidly proliferate and multiply at a high temperature until they invade the light emitting area, forming a large number of non-radiative recombination centers, and seriously reducing the luminous efficiency of the LED display. In addition, under high temperature conditions, the micro-defects in the material and the fast-spreading impurities from the interface and the plate will also be introduced into the light-emitting region to form a large number of deep levels, which will also accelerate the light decay of the LED display device.
(2) At high temperatures, the transparent epoxy resin will degenerate and yellow, affecting its light transmission performance. The higher the operating temperature, the faster the process will proceed. This is another major reason for the decline of the LED display.
(3) The light decay of the phosphor is also a major factor affecting the light fade of the LED display, because the attenuation of the phosphor at high temperatures is very serious.
Therefore, the high temperature is the cause of led display failure, shortening the main source of led display life.
Different brands of LED display light decline is different, usually led display manufacturers will give a set of standard light decay curve. LED display luminous flux attenuation caused by high temperature is irreversible, led display screen does not occur before the irreversible light attenuation of light flux, called the led display "initial luminous flux."
Third, the temperature will reduce the luminous efficiency of the led display
The effects of temperature on the efficacy of LED display include the following aspects:
(1) As the temperature increases, the concentration of electrons and holes increases, the band gap decreases, and the electron mobility decreases.
(2) When the temperature rises, the probability of radiative 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) Temperature rise causes the blue light wave peak of the chip to shift toward the long wave direction, which makes the emission wavelength of the chip and the excitation wavelength of the phosphor unmatched, and also causes the reduction of the external light extraction efficiency of the white light led display screen.
(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 screen 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, resulting in a decrease in the refractive index of the silica gel, thereby affecting the light efficiency of the led display.
Fourth, the temperature on the LED display light wavelength (light color)
The luminous wavelength of the led display can generally be divided into the peak wavelength and the dominant wavelength. The peak wavelength is the wavelength with the largest light intensity, and the dominant wavelength can be determined by the X, Y color coordinates, reflecting the color perceived by human eyes. Obviously, the change in the light emitting wavelength of the led display caused by the junction temperature will directly cause the human eye to feel differently about the light color of the led display. For a led display device, the bandgap value of the light emitting region material directly determines the wavelength or color of the device's light emission. As the temperature rises, the bandgap of the material will decrease, resulting in longer device emission wavelengths and red-shifted colors.
Fifth, the temperature is too high will limit the maximum input current of the led display
The above points are the introduction of the effect of temperature on the LED display. It is learned from the above introduction that the effect of temperature increase on the LED display is very large. So the right and proper temperature is the focus of the led display.
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