A system includes a display. The display includes an array of LEDs covered by a transparent material. The array of LEDs includes a plurality of first, second, third, and fourth LEDs respectively configured to emit red, green, blue, and violet light. The red, green, and blue light from the first, second, and third LEDs is visible to human eye. Violet light from the fourth LEDs is invisible to human eye. The system includes a photocatalytic coating disposed on the transparent material. The photocatalytic coating includes a photo-catalyst responsive to ultraviolet radiation present in sunlight and to the violet light emitted by the fourth LEDs in the array of LEDs. The system includes a controller configured to selectively turn on the fourth LEDs to activate the photo-catalyst in the photocatalytic coating disposed on the transparent material.