It is required to trim the wavelength of the emitted light from light emitting diodes. Can this be accomplished by varying the operating temperature of the diode or by any other means?
The light emitting diodes are made of direct energy gap semiconductors. These materials are mostly three five compounds such as GaAs. On forward biasing the LED excess electron hole pairs are stored in the diode. These excess electron hole pairs recombine with each others producing photons of light which are emitted to outside of the diode. The emitted light intensity is proportional to the excess charges which in turn increases linearly with the diode current.
Concerning the spectrum of the emitted light, it is concentrated in and around a specific wavelength defined by the energy gap Eg such that: Eg= hC/ Lambda. With h the the Planck s constant, C the speed of light and Lambda the wavelength of the emitted light. By increasing the temperature, the band gap energy decreases and the emitted wavelength increases. It follows that the peak wavelength shifts to longer wavelength and therefore this shift called the red shift.
So, from the principle point of view, one can tune Lambda by varying the temperature of the LED.
To complete the picture, unfortunately, increasing the temperature of the diode results in decreasing its emitted light intensity. Therefore trimming the wavelength by decreasing the temperature is beneficial since it leads to increasing the emitted light for the same diode current. For increasing the temperature the opposite is true.
As a practical consideration one would choose a LED having slightly larger wavelength than required and then cool the diode down to adjust the emitted light wavelength. For more information please refer to the link:
https://www.google.com.eg/#q=temperature+dependence+of+wavelength+of+the+emitted+light+from+LEDs&start=10
Thank you Bipul for your comment. You proved that the faithful efforts are never lost.
Yes, I agree on this point. LED technology should be developed in such a way as to reduce the temperature of glowing LEDs, because part of the energy is consumed for the production of thermal energy. If it were possible to reduce the temperature increase of LEDs several times, then energy savings would be obtained. You should also improve LED bulbs in such a way that they emit more light at a specific energy consumption, so that the heat energy is converted into light. Then LED bulbs would become even more energy-efficient. In addition, the length of the emitted light waves should be modified so that the artificial, bluish-white, cold and unfavorable to human eyesight is turned into a warm, yellowish-white, close to natural, human-friendly shade of white. The improvement of LED technology is necessary in connection with the need to develop an energy saving economy.
Best wishes
Dariusz Prokopowicz
Abdelhalim abdelnaby Zekry You are spot on in your explanations of the behavior of LED wavelength with temperature.
- Badges
- Science topic
- Similar topics
- Computer Communications (Networks)
- Simulators