Emission process: When an external forward voltage is applied, an electric current passes through the IR LED, which excites the electrons within the semiconductor. When these electrons transition from a lower energy level to a higher energy level, they release energy, i.e., emit infrared light.
Reception process: When infrared light hits the light-sensitive area of the IR LED, the light-sensitive material absorbs the light energy and generates an electric charge. These charges are amplified and processed by circuits and can be read and decoded.