Analysis of the Influence of Current on the Optical Parameters of Power White LEDs
In the 21st century, with the continuous advancement of semiconductor technology and packaging technology, the long-term use of semiconductor light sources for indication and display is developing in the field of forward illumination. The emerging semiconductor lighting products represented by power white LEDs are expected to have potential in the lighting market. A common way to obtain white LEDs is to apply a layer of yellow phosphor (YAG: Ce3+) on the surface of the blue LED chip . Compared with ordinary LEDs, power LEDs have larger chip sizes and require larger driving currents to emit brighter light, but with more heat generated, the optical electrical parameters and stability of the power white LEDs are stabilized. Sex has an impact.
At present, the measurement method of LED optical parameters is still under discussion at home and abroad. LED is an electroluminescent device. When electrons and holes are combined with radiation, energy is emitted in the form of photons, so the injected current is LED-emitting. Optical properties have a direct impact.
1, the impact on color coordinates
Now the LED's illuminating color is more and more abundant. The color coordinate parameter of the LED is one of the important physical parameters of the LED. As the injection current increases, the color coordinate of the device illuminates to a certain extent, as shown in Figure 1.
Figure 1 Color coordinates change with current
2, the impact on color temperature
When an absolute black body is heated, the color of the emitted light is close to the color of the light source being tested, and the temperature of the black body is called the correlated color temperature of the light source. In the currently most commonly used scheme for realizing white light, when there are more yellow phosphors coated, the blue light spectrum in the emitted white light spectrum is less, the color temperature of the device is lower; when the yellow phosphor is less, the white light spectrum is emitted. There are many blue light components and a high color temperature.
Figure 2 Correlation between correlated color temperature and forward current
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