How does the energy of light emitted by each LED change with temperature? Which of the observed changes (color, Amax, voltage) are reversible (meaning the observed changes go back to their original state once the conditions are changed back to their original state)? What changes in wavelength emitted AND brightness took place upon cooling the LEDs below room temp? What similarities AND differences are in the changes you observed when comparing different LED compositions?
Solution
For a diode the conductivity increases with temperature . So the energy of light emitted will increase as temperature is increased .
Among the observable changes , only voltage is not reversible . Because its an external property . And remaining changes are dependent only on conditions .
When temperature is cooled down below room temperature , the band width or the gap between bands is reduced . So the brightness and the wavelength are accordingly decreased .
Similarities observed are , conducting mechanism is same with any composition . The difference is only the conductance . After doping the conductance is increased .
.
How does the energy of light emitted by each LED change with temperatu.docx
1. How does the energy of light emitted by each LED change with temperature? Which of the
observed changes (color, Amax, voltage) are reversible (meaning the observed changes go back
to their original state once the conditions are changed back to their original state)? What changes
in wavelength emitted AND brightness took place upon cooling the LEDs below room temp?
What similarities AND differences are in the changes you observed when comparing different
LED compositions?
Solution
For a diode the conductivity increases with temperature . So the energy of light emitted will
increase as temperature is increased .
Among the observable changes , only voltage is not reversible . Because its an external property .
And remaining changes are dependent only on conditions .
When temperature is cooled down below room temperature , the band width or the gap between
bands is reduced . So the brightness and the wavelength are accordingly decreased .
Similarities observed are , conducting mechanism is same with any composition . The difference
is only the conductance . After doping the conductance is increased .
