If you must lower the current of LEDs because of heat, the result is inconsistency in the luminosity and chromaticity of an LED display. High temperatures also dramatically shorten the life span of the LEDs. As the temperature increases, the amount of current sent through the LEDs must be regulated, which decreases the luminosity of the LEDs. Conversely, if the ambient temperature is lower, the luminosity of the LEDs will be higher. Keep in mind that ambient temperature does not necessarily refer to the temperature of the air.
Manufacturers build LED displays with black screens for maximum contrast.
By keeping the LEDs cool, enough current can pass through them to maintain optimum brightness of the screen without risking the life of the individual LEDs. CCDL's VLSI chips of 304 pins, the world largest and most powerful driver.