Temperature and aging

As with all semiconductors, the properties of an LED are temperature-dependent. Typical changes occur mainly in the luminosity, the wavelength of the emitted light and the conducting voltage.

  1. Luminous flux
    An increasing temperature in the LED chip leads to a reduction in the luminous flux.
  2. Wavelength λ
    An increasing temperature in the LED chip leads to an increase in the wavelength (the extent depends on the semiconducting material)
  3. Conducting voltage UD
    An increasing temperature in the LED chip leads to a reduction in the conducting voltage (2 mV/°C). In contrast, the conducting voltage increases at low temperatures. A reduction in the conducting voltage leads to an increase in the current. As the current increases, the temperature of the LED chip continues to rise. This leads to a further drop in the conducting voltage.

LED circuits must be sufficiently dimensioned or cooled to prevent temperature-related changes in the current from causing damage or shortening of service life.

With falling temperatures, the current would be reduced by the increasing conducting voltage. This could lead to the required luminosity not being achieved.

The aging of LEDs is approximately exponential. The speed of aging depends on the respective semiconducting material and the operating conditions (temperature, current). If LEDs are operated at the usage limits (maximum forward voltage, maximum forward current, maximum operating temperature), the service life of the LED is shortened. The aging of LEDs is reflected in the reduction of luminosity and a change in the color temperature.