Researchers from SET have identified three mechanisms that may trigger a drop in UV LEDs (below 250 nm)—the decrease in external quantum efficiency at higher current densities—that is, self-heating, load discharge (from quantum wells to blocking layers or P-type cap layer) and Auger composite.
The SET researchers concluded that comparing the continuous wave and pulse output of a strip device with different "H-pixel" and different drive currents, one can conclude that self-heating is a cause of decline. They found that the drop is not only dependent on current density, but also on the total injected current that produces Joule heat. In addition, the efficiency of the UV LEDs (pulses of 500 ns and 200 ns, 20 kHz) decreases as the current increases.
Another possible factor is the load leakage due to weak void injection, where blue shifting at high pump currents means faster inter-band filling and subsequent electron spillage into the wider bandgap material. There is also the Auger compound, which is also considered to be one of the reasons for the decline. They are considering the characterization of devices at temperatures that are not available, which may be useful for understanding more about Auger's complex effects.
In the research, the wavelength of the ultraviolet LED is between 245 and 247 nm, and the continuous wave output has a power of 2 mW. (LEDC MH compilation)
The bulbs are installed inside of a vehicle. There are many different types of interior bulb. Interior lights for indoor lighting are usually installed in the center of the car interior. It's better to light up the car interior evenly. In addition, the light switch (SW) should be operated on both front and rear seats at the time of layout. SW generally has ON, OFF, and door linkage 3 locations. In order to reduce the thickness of the lamp, 5-10w bulb bulbs are usually used. To meet the illumination requirement of capacious indoor, the power of the bulb that uses is commonly 8~30W. The original reading light in the car is designed to read the map. In order to drive the driver, read the light and light up to the point, only on the required part. The rear reading lamp is the rear seat special reading light, with a larger point light illumination. Be careful not to give the driver and other passengers a sense of vertigo. The light can be connected to the door and switch. When the door is open, the lamp is mounted on the door to illuminate the foot part of the room and the outside foot. In order to give the signal to the back of the car, the installation position should be considered. The lamp has no special switch, but is connected with the door.
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