Luminous principle of LED lamp

LED lamp is an electroluminescent semiconductor material chip, cured to the bracket with silver glue or white glue, and then connected to the chip and circuit board with silver wire or gold wire, and sealed with epoxy resin around to protect the internal core wire. Finally, the shell is installed, so the anti-seismic performance of LED lamp is good.

1. Lamp bead structure

One of the most important light emitting structures of LED (light emitting diode) lamps is the mung bean sized beads in the lamp. Although its volume is very small, its function is not small. After magnifying the structure of LED lamp beads, we will find a sesame sized chip.

The structure of the wafer is extremely complex, which is divided into several layers: the top layer is called p-type semiconductor layer, the middle layer is light-emitting layer, and the bottom layer is called n-type semiconductor layer.

So, how does LED light come out?

2. Luminescent principle

From a physical point of view: when the current passes through the chip, the electrons in the n-type semiconductor and the holes in the p-type semiconductor collide violently in the light-emitting layer to produce photons, which emit energy in the form of photons (that is, the light we see).

light-emitting diode

LED is also known as light-emitting diode, it is very small and fragile, not convenient for direct use. So the designer added a protective shell for it and sealed it inside, so as to form an easy-to-use LED lamp bead.

After many LED lamp beads are put together, a variety of LED lamps can be formed.

3. LED lights of different colors

Semiconductors of different materials will produce different colors of light, such as red light, green light, blue light and so on. However, so far, no semiconductor material can emit white light.

But how do we usually use white LED beads?

4. Generation of white LED lamp

Here we need to mention a Nobel Prize winner - Dr. Nakamura Shuji. He invented blue LED, which also laid a foundation for white LED. Based on this important contribution, he was awarded the Nobel Prize in physics in 2014.

As for how blue LED turns into white LED, the biggest reason is that there is a layer of phosphor in the chip.

In this picture, not only the n-type semiconductor layer, p-type semiconductor layer and light emitting layer mentioned above appear, but also a "phosphor coating" is added.

The basic principle of luminescence has not changed much: between two layers of semiconductors, electrons and holes collide and recombine and produce blue photons in the luminescent layer.

Part of the blue light will be emitted directly through the fluorescent coating; The rest hits the fluorescent coating and interacts with it to produce yellow photons. Blue and yellow photons work together to produce white light.

The above picture shows the spectral curve of an LED: it can be seen that the peak of blue light is at 450 nm, while the lower peak value is the peak of yellow light produced by the absorption of blue light by the fluorescent powder.

If the proportion of blue light is a little more, white light with high color temperature will be produced; On the contrary, if the yellow light is a little more, white light with lower color temperature will be generated.