Why don t ordinary diodes emit light? 100

The diode is forward conducted, and the current flows from the p-region to the n-region, which is equivalent to the electron flowing from the n-region to the p-region. The energy levels of electrons in the two regions of the pn junction are different, and the energy level in the n region is higher than that in the p region. Therefore, the process of current flowing from the p-region to the n-region when the diode is turned on is the process of continuously flowing electrons from the n-region to the p-region.

Since the energy level of the p-region is lower than that of the n-region, the process of continuous flow of electrons from the n-region to the p-region can be said to be the process of electrons falling from the n-region to the p-region. When electrons are continuously falling from the n-region to the p-region, the excess energy is released. There are no more than two ways to release energy, one is to release heat energy and the other is to release light energy.

Due to the material characteristics of the PN junction, the excess energy of the electrons is dissipated as heat energy when a forward current flows through an ordinary diode, so it does not emit light.

LED, that is, when the light-emitting diode flows through the forward current, the excess energy of the electrons is dissipated as light energy, so it emits light. By changing the LED material, you can change the frequency of the light waves, i.e., the color.

This theory of energy level change can not only explain the phenomenon that LED can emit light when it flows through the forward current, but also can explain the fact that it cannot emit light when it flows through the reverse current. Because when the LED flows through the reverse current, it is the electrons that are continuously lifted from the low energy level to the high energy level, and it needs to continuously absorb the energy, rather than release the energy, so it cannot emit light or generate heat.

By the way, the semiconductor cooler is based on the continuous reduction of electrons from high energy level to low energy level under the action of power supply, and constantly releases energy to form a hot end; It is continuously lifted from the low energy level to the high energy level by the power supply, and continuously absorbs energy to form a cold end and refrigerate.

The statement that the electron and hole recombination energy released in the traditional modular electron book to explain the working principle of LED cannot explain the fact that ordinary diodes cannot emit light, nor can it explain the fact that the reverse current of LED cannot emit light.

Therefore, the statement that the energy released by electrons and holes is not true and therefore false.

Light-emitting diodes emit light.

There are many reasons why it doesn't shine, but let's take a look at what's wrong with the immortal line.

First, the multimeter selects the diode gear.

When observing, the long legs are positive. When measuring with a meter, if the watch has a reading, the end measured by the red watch pen is the positive pole of the diode, and the light-emitting diode will emit light;

If there are no readings, the pen is reversed and measured again, and if there is no indication on both measurements, the LED is damaged.

If not, test again. If there is no indication for both measurements, the Zener diode is damaged. If there is a reading, it is normal.

Summary. There are three reasons why LEDs don't light up. 1) The voltage applied to the LED is lower than the on-voltage of the LED.

2) The positive and negative poles of the power supply added to the light-emitting diode are reversed. 3) The voltage applied to the light-emitting diode is too large, which burns out the light-emitting diode.

There are three reasons why LEDs don't count brighter quickly. 1) The voltage applied to the LED is lower than the on-voltage of the LED. 2) The positive and negative poles of the power supply added to the light-emitting diode are connected to the first and negative electrodes.

3) The voltage applied to the light-emitting diode is too large, which burns out the round photodiode.

I'm still a little confused, can you be more detailed?

The above three reasons are that the light-emitting diode does not light up.

The reason why a diode emits light is that when an electric current is injected into it, the charge carriers composed of electrons and holes combine in the central region of the junction and reunite, releasing energy, which in turn excites other luminous substances, causing the surface of the diode to emit light.

There is a p-n junction between the p region and the n region in the diode structure, the proton content of the material in the p region is higher than that of the electrons, and the electronic content of the material in the n region is higher than that of the protons.

It should be noted that the luminous efficiency of the diode is low, only part of the electrical energy will be converted into light energy, and most of it will be converted into heat energy, so in practical applications, in order to improve the efficiency of the luminous bond deficit, special materials and structural equipment need to be used.

The operating voltage is very low (some are only a few volts); The working current is very small (some can emit light only a few tenths of a milliampere); Good impact and seismic resistance, high reliability and long life; The intensity of the luminous light can be easily modulated by modulating the strength of the passing current.

Because of these characteristics, light-emitting diodes are used as light sources in some optoelectronic control devices and as signal displays in many electronic devices. The core of the tube is made into strips, and 7 strips of light-emitting tubes are used to form a 7-segment semiconductor digital tube, each of which can display 0 9, 10 Arabic numerals and some letters such as a, b, c, d, e, f (must be case-sensitive).

<> 1. Why does the light-emitting diode seep out and emit light?

Under the action of electricity, the energy of electrons inside it is excited and displayed in a low or high state, and these electrons will gradually change from high energy back to low energy. According to the principle of conservation of energy, some excess energy will be released by light, so it will also be seen that the diode emits light. Diode light is formed gradually when electrons transition, and the holes in the valence band of electrons gradually converge.

In the process of use, the energy will manifest itself in the state of light.

Second, how to choose high-quality LED lights.

When choosing LED lights, you should take a look at the packaging and trademark of LED lights. On the outer packaging of a good LED light, there will be a clear logo. Then we can take out a wet paper towel and wipe down the logo to see if it will be wiped off.

If it can be wiped off, it means that this LED light is of inferior quality, and it cannot be purchased at this time.

Be sure to buy a trademark that can't be erased, so that it can prove that this LED light is qualified and regular.

And when choosing LED lights, you should take a look at how the LED lights look. If the appearance is smooth and there are no flaws, it means that this LED light is good. Moreover, this good LED lamp shell is made of flame-retardant materials, which can be fireproof.

Inferior lamps are easy to deform, easy to burn, and the effect of energy saving is particularly poor.

When choosing an LED light, we can take a look at how well it dissipates heat. If the heat dissipation effect of the LED light is poor, it is best not to buy it. Because this kind of LED light will be damaged after not being used for a long time.

If the sound is particularly obvious when the LED light is used, then the LED light is also of inferior quality. It proves that the power supply quality is particularly poor, so it cannot be purchased and used.

Lights make the world colorful. In life, you can see various colors of light-emitting diodes everywhere, and these light-emitting diodes are very beautiful. Some colors are green, some are red, and some are blue, which is dazzling and dazzling.

In addition to this, there are diode lights that are invisible infrared and ultraviolet light. So why do light-emitting diodes emit light?

Before knowing this problem, you need to understand the principle of electroluminescence, which is very helpful to understand how diodes emit light. The role of the electric field is to excite electrons to transition from a low-energy state to a high-energy state, and these electrons will in turn return from the high-energy state to the low-energy state. According to the conservation theorem of energy, the remaining excess energy is released in the form of light, which is what we see as diodes emitting light.

Therefore, the luminescence of the diode is formed by the electronic transition. The electrons recombine with the holes in the valence band, and in the process, the energy is presented in the form of light. Let's introduce how diodes exhibit different colors:

Anyone who has studied physics knows that there is a wavelength for every type of light, the red light-emitting diode wavelength is about 650 to 700 nm, the orange light-emitting diode wavelength is about 610 to 630 nm, the yellow light-emitting diode wavelength is about 585 nm, and the green light-emitting diode wavelength is about 555 to 570nm. The wavelength of the luminescence depends on the junction width of the material pn, according to the junction width of pn, the diode can present different colors of light, and the more common colors in life are green, red, yellow and blue.