Answer / anil

cut in voltage of LED is higher bcoz LEDs are made up of
GaAs or GaAsP which has more threshold voltage.....

LEds are not used in rectifiers bcoz firstly they have more
cut in voltage so it creates a problem while rectifying low
voltages....and
secondly the PIV rating of LED is less than a typical Si
diode....so LED can get damaged during the negative portion
of the AC voltage....

Answer / raikwar rajesh kumar

The cut in voltage f LED is higher then diode because the
LED are a very important use of diodes in that they are the
most commonly used indicators.
All diodes emit radiation when a electron meets a
hole and falls into a lower energy state. The released
photon is dependant on the band gap. So, for particular
band gaps this released enery is chromatic.

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