The fourth-generation automotive light sources are LED: LED is a semiconductor PN junction diodes, when a forward bias when imposed on the PN junction at both ends, so that PN junction system has been stimulated, carrier transition from the low-energy state to a high-energy state, when the in the high-energy state of instability in the carrier back to low-energy state complex, in accordance with the conservation of energy of the original
Li, excess energy will be released as photons, it is the principle of LED electroluminescence. It is not an object through the fever can heat up and glow, is a direct conversion of light energy, emission wavelength depends on the energy difference of carrier state and low energy states thatenergy difference.