In the charge carrier recombination mechanism, trap assisted recombination occurs which is non-radiative in nature. The lifetime is often interpreted as a trap state. Is this the lifetime where the excited electron moves from the conduction band to the trap state or the time after which the electron recombines with the holes? Also, once the electron is in trap state, will it always remain there, or we need some energy to de trap this electron? Can someone please clear this concept to me?