Color and voltage of LEDs © Siemens Stiftung 2018 CC BY-SA 4.0 international

Color and voltage of LEDs

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The operating voltage of LEDs depends on the color. This is an indication of discrete energy levels and the photon character of light.

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2018-07-27
What color an LED emits depends on the energy level of the charge transition from the non-conduction band to the conduction band. Depending on the basic material (Si, GaAs, GaN etc.) and doping, as well as the internal resistance every LED has a typical operating voltage (voltage = potential = energy difference). Although this is modified by the design (internal resistance, etc.), in the final analysis it is determined by the discrete energy level of the charge transition between non-conduction and conduction band.

Information and ideas:
The abstract principle of the quantization of energy in the form of photons is demonstrated clearly in an extremely simple experiment with four LEDs and a power supply unit. Red LEDs light up at a voltage from about 1.5 volts, yellow from about 1.9 volts, green from about 2.3 volts and blue from about 3.3 volts.
Instructions for building a variable LED color mixer can be found in the experimentation instructions “Experiments – energy quantization with LEDs" on the media portal of the Siemens Stiftung.
Example
Physics; Technology
Grade 5 to 6; Grade 7 to 9; Grade 10 to 13
Middle/high school
Color Theory; Light; Semiconductor; Wave (physics)
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