The essence of the white LED we use at present is a Fluval led light. Its basic characteristics are the same as ordinary Fluval light. Its performance indicators are much worse than our expectations. It cannot be deified. Fluval led light should step down from the altar. The conceptual fusion of LED and Fluval led grow light has caused huge losses to my country’s lighting industry, and this phenomenon cannot continue. Real white LED still has a long way to go, don’t be impetuous.
The pursuit of high-efficiency, energy-saving, green and environmentally friendly electric light sources with good display are the persistent goal of the scientific and technological circles. Since the 1960s, LED has developed rapidly in an amazing era, especially after entering the 21st century, the development of LED has made more encouraging achievements. LED displays unparalleled superiority compared with other electric light sources in display screens, signal lights, liquid crystal backlights and the replacement of other low-power light sources. However, in the current development of white color high-power LED, the basic attributes between ordinary LEDs and white color LED are mixed, and the advantages of ordinary LEDs are mistakenly transferred to white color LED, mistakenly thinking that the service life of white color LEDs, The luminous efficiency can be the same as that of ordinary LEDs. It has overestimated its luminous efficiency and deified its function in the field of electric light sources. It seems that as long as the use of LEDs is high-tech, LEDs can solve a lighting problem; projects that use LEDs can get the government Projects that don’t use LEDs will not be able to get government support; ignoring that white LEDs are the basic essence of Fluval led light. Below we briefly introduce the light-emitting mechanism of the current white color LED (Fluval led light).
Principle of white light LED luminescence
Figure 1 The light-emitting mechanism of a white LED (Fluval led light)
It can be seen from Figure 1 that the white color LED (Fluval led light) is white light emitted by the phosphor around the blue PN junction. Usually, the Fluval lights are excited by the ultraviolet light in the tube to emit light. They are completely the same in the light-emitting principle, such as As shown in Figure 2, the difference is that the filament of the ordinary Fluval light is replaced by a blue PN junction. Figure 3(c) indicates how it works. In addition, there are Fluval led lights that generate white light by exciting phosphors by ultraviolet LEDs, as shown in Figure 3(b).
Luminous principle of ordinary Fluval light
Figure 2 The luminous principle of ordinary Fluval led grow light
The luminous principle of LEDs is quite different from that of the incandescent light and gas-discharge light we currently use. The spontaneous luminescence of LED is caused by the recombination of electrons and holes. The electroluminescence mechanism of this LED PN junction determines that it emits monochromatic light, and it is impossible to produce white light with continuous spectrum lines. It is impossible for only LEDs to produce more than two kinds of high-brightness monochromatic light. If the LED is required to generate white light, it is only possible to first let the LED emit blue light, and then use phosphors to indirectly generate a broadband spectrum to synthesize white light.
The luminous efficiency of white LED light
The process of converting a certain form of energy into light energy is a quantum conversion process that obeys the law of conservation of energy. The quantum efficiency, quantum extraction rate and the energy spectrum of the radiated photons in the luminescence process determine the light efficiency of the process. The more quantum conversion processes a white light source goes through when it is operating, the greater the energy loss, and the light efficiency will inevitably decrease.
Although the quantum conversion efficiency of the carrier recombination process when the LED emits light is very high. However, it is necessary to use phosphors for the second quantum conversion to be converted into a white light LED, so the quantum efficiency and quantum extraction rate are greatly reduced, which limits the improvement of the light efficiency of the white light LED.
Although all kinds of Fluval light including high-frequency electrodeless Fluval light are low-pressure discharge light, they use mercury resonance radiation to convert electrical energy into radiant energy with high efficiency. However, since this resonance spectrum is in the ultraviolet region, Fluval powder must be used for the second Sub-quantum conversion can be turned into visible light, and the second-quantum conversion efficiency is only 46%, and phosphor absorption reduces the quantum extraction rate, so the continuous secondary quantum conversion process limits the light efficiency of the Fluval light to 90-100 lm/ About W, it is difficult to exceed 120 lm/W according to the current structure and materials.
Improve LED luminous efficiency
It is also worth noting that the luminous center of the conventional light source is in the center of the light, and the light radiation is evenly distributed in the 4π solid angle, consistent with the irradiation space, and the quantum extraction rate is close to 100%. LED is a flat solid light source, only outward (2π solid angle or less) photons can be emitted, so 50% of the inward radiation photons of conventional LEDs mostly disappear inside the chip to generate heat, and the quantum extraction rate is very low; The output window is a multi-layered different solid medium, the particle density is very large, the absorption coefficient of photons is large when propagating in it, and the reflection at the interface of different medium layers also reduces the quantum extraction rate. These characteristics of the current structure of the LED cannot be changed, so the improvement of the light efficiency is limited. Don’t imagine that the luminous efficiency of white LEDs can be increased to more than 140lm/W, unless it is a single-color yellow LED or another brand-new LED structure. For example, if a three-level (red, green, and blue) LED can be developed, There are more than three different donor or acceptor energy levels in the n-type semiconductor or p-type semiconductor of the LED. When the carriers recombine, they directly generate a proper proportion of red, green, and blue photons, thus directly emitting white light. The second quantum conversion process of omitting the phosphor can greatly improve the light efficiency of the LED. However, the characteristics of LED unilateral light emission cannot be changed, and the factor that limits the significant improvement of light efficiency can only be reduced, and cannot be completely eliminated.
Structure of health spectrum
It is very necessary to reduce the blue light component in the white light LED spectrum, although this will reduce its light effect, too much blue light can easily cause visual fatigue and damage the visual film. Until this point is improved, it is difficult to enter the home on a large scale to compete with compact Fluval light.
From any angle, the highest luminous efficiency of the current white LED (Fluval led light) of this structure can never exceed 140lm/W. According to tests, the maximum total photon conversion efficiency of currently commercially available white light LEDs (Fluval led light) is about 15-25%, and the luminous efficiency is about 45-80 lm/W. The actual luminous efficiency is usually 60 lm/W during stable operation. Below W. The report that the light efficiency of white LED (Fluval led light) has reached 160lm/W or 200lm/W is unreliable. Perhaps their test has gone wrong. As for the prediction of 400lm/W, it is absurd for white LED (Fluval led light). The yellow LED with a central emission wavelength of 555 is also too high.
In the future, true white LEDs should be white LEDs that encapsulate red, green, blue, or more color LED chips to produce white light. It will eliminate the conversion process of phosphor’s secondary light emission and increase the luminous efficiency by 15%. Above, the efficiency can reach 150-160Lm/W, while reducing the harmful blue light; the problem of light decay and chip heating has been improved. There are still many technical bottlenecks in this true white LED, and it will take a long time to solve these technical problems. . Figure 3(a) indicates this method.
Function of phosphor
Figure 3 The method of producing white Fluval led grow light
Since the light-emitting mechanism of the Fluval led light is the emission of phosphor, its luminous efficiency and light decay characteristics are restricted by the phosphor, and the result must be similar to that of the Fluval light. Figure 4 is a comparison chart of the decay of Fluval led light and ordinary Fluval light. It can be seen that there is not much difference between Fluval led light and ordinary Fluval light. Figure 5 is a comparison of the decay of LEDs of different colors and Fluval led light, so it can be seen that Fluval led light no longer have many of the advantages of LEDs.
Figure 4 Comparison of decay of Fluval led grow light and ordinary fluorescent
Figure 5 Comparison of light decay between Fluval led grow light of different colors and LED Fluval light
The filament of the ordinary Fluval light is replaced by the blue PN junction. The LED Fluval light has many advantages that the ordinary Fluval light does not have:
1: If the heat dissipation problem is solved well, Since the Fluval led light has no filament, the service life of the Fluval led light is much longer than that of the ordinary Fluval light.
2: It can be switched on and off frequently.
3: Low-power white light and high-efficiency lighting can be achieved. (The efficiency of ordinary electric light sources is not high at low power)
1: The essence of the white LED we currently use is a Fluval led light. Its basic characteristics are the same as ordinary Fluval light. Its performance indicators are much worse than our expectations. It cannot be deified. Fluval led light should step down from the altar.
2: The conceptual fusion of LEDs and Fluval led light has caused huge losses to my country’s lighting industry, and this phenomenon cannot continue.
3: Real white LED still has a long way to go, don’t be impetuous.