How to produce LED
When a certain amount of voltage is applied to the conjoined crystals, the electrons are then forced to move across the area between the two crystals. Now, if the flow movement is right, electrons in the higher up crystal flow into the crystal that is lower and must have to begin orbiting at the lower level of energy.
As the electrons come down to a lower energy level, they emit light. What the naked eye sees as light, the frequency of light becomes determined by the difference in energy levels amongst the two crystals. By manifesting different types of crystals with varying kinds of energy levels, many colors can be created.
Crystals with seemingly similar levels of energy, make low-energy photons of red light or even infrared light. With a huge difference in energy levels, green light can be produced.
An even greater energy creation can create blue light.