1. The principles of UV LED light-emitting
PN junction terminal voltage of a certain potential barrier, when to add positive bias voltage drop time base, P and N the majority carrier diffusion to the other party. Due to the electron mobility is much bigger than hole mobility, so there will be a large number of electronic spreading P area, constitute of P area of minority carrier injection. These electrons and valence with hole composite, composite when the energy in the form of light energy to release out. This is the principle of PN junction glow.
2. UVLED luminous efficiency
Commonly referred to as the external quantum efficiency, component as components of the internal quantum efficiency and the product of the removal efficiency. So-called internal quantum efficiency of the component, in fact, the component itself electro-optic conversion efficiency, mainly with the characteristics of the component itself (such as a band of component materials, defects and impurities), base composition and crystal structure of components, etc. While component extraction efficiency refers to the components inside of photons, after component itself, absorption, refraction, reflection after the actual number of photons on the outside of the component can be measured. Factors on extraction efficiency, therefore, including the components of the absorption material itself, component geometry structure, components and packaging materials of refractive index difference and the scattering characteristics of components, etc. And components of the internal quantum efficiency and the extraction efficiency of the product, are the components of the luminous effect, also is the component of the external quantum efficiency. Early component development focused on improving its internal quantum efficiency, by improving the barrier is the main method of crystal quality and change of crystal structure, that is not easy to convert electrical energy into heat energy, and thus improve the luminous efficiency of UVLED indirectly, thereby can obtain 70% internal quantum efficiency, the theory of but the internal quantum efficiency is almost close to the theoretical limit. Under such conditions, improve the internal quantum efficiency of component alone is unlikely to increase the total quantity of light component, thus improve the extraction efficiency of component becomes the important research subject. Method now is that the change of grain appearance - TIP structure, surface roughening technology.
3. Electrical characteristics of UVLED
Current control device, UI curve of load characteristic similar PN junction, which is to the voltage of the tiny changes can lead to great changes of the forward current (index level), reverse leakage current is very small, there are reverse breakdown voltage. In use of actual, should be choose. Smaller UVLED forward voltage with the temperature increasing, and has a negative temperature coefficient. UVLED consumed power, one part is converted into light energy, this is what we need. The rest is converted into heat energy, make the junction temperature rise high. Can be said to send out heat (power).
4. Optical properties of UVLED
UVLED provides a half of width at maximum monochromatic light, as a result of the semiconductor energy gap decreases with temperature rise, therefore its emission peak wavelength with the temperature rising and growth, namely the spectrum redshift, temperature coefficient is + 2 ~ 3 a /.UVLED luminescence brightness L with forward current. Current increases, the shining brightness also increase approximation.Luminescence brightness also is associated with environment temperature, environment temperature is high, composite efficiency drops, luminous intensity decreased.
5. The thermal characteristics
Small electrical flow, LED temperature rise is not obvious. If the environment temperature is higher, UVLED main wavelength redshift, brightness will decline, luminescence uniformity, consistency. Especially the rise of temperature of the lattice, large screen more significant influence on the reliability and stability of the LED. So heat dissipation design is key.
6. The lifetime of UVLED
UVLED long hours to work can light failure caused by aging, especially for high-power UVLED, light failure problem is more serious. In measuring UVLED life, only to the damage of the lamp as UVLED life by the end of the is not enough, should be specified by the percentage of light attenuation to the UVLED LED the life of, say 35%, so it makes more sense.
7. The packaging of high-power UVLED
Main consideration heat and light. Cooling, with the copper base hot line, again to connect to the aluminum radiator, grain size and connection with tin welding as hot line, this way of cooling effect is good, high cost performance. The aspect of light, by adopting the technology of flip chip, and reflective surface reflected in bottom and side waste energy, so that we can get more out of the light.