Electronic – Is the wavelength of the light emitted from an LED at its turn-on voltage greater than or less than the peak wavelength of the LED

ledvoltage

Ok, so I know that the intensity of the light given by an LED is the minimum it can be at the turn-on voltage, however I don't know if the wavelength of the light emitted from the LED at the turn-on voltage will be below the peak wavelength (the wavelength at which the intensity of the light of the LED is at its maximum) or above it. My reasoning comes from the picture below:enter image description here

The picture shows that for a specific colour of LED, for any intensity instead of the peak intensity there can be two wavelengths associated with it. For instance, for the blue LED, there will two values for wavelength for when the intensity is 20%. So, my question is: Is the wavelength of the light emitted from an LED at its turn-on voltage greater than or less than the peak wavelength of the LED?

Best Answer

The wavelength distribution will look like the graph, pretty much regardless of current at a given temperature. LEDs are not purely monochromatic.

However, as the die heats (and it will tend to heat more at higher current) the center of the spectrum will shift toward the red for all LEDs (longer wavelength).

From this OSRAM document, you can see a typical change of about +70pm/K die temperature.

enter image description here