Fig. 1: Slow hot electron relaxation in n-doped QDs.
a In a typical CdSe QD, an 1Pe hot electron relaxes on a sub-ps timescale through electron-to-hole energy transfer, breaking the otherwise expected phonon bottleneck. b In n-doped QDs, slow hot electron relaxation is expected due to the preoccupying 1Se electrons. For a QD doped with one 1Se electron (left), there is a 50% probability that the 1Pe electron would relax slowly due to a Pauli spin blockade; for a QD doped with two 1Se electrons (middle), relaxation of the 1Pe electron is completely blocked due to state-filling; alternatively, a preoccupying 1Se electron can be excited into the 1Pe level (right), which would be followed by slow relaxation because the phonon bottleneck cannot be bypassed for lack of a valence band hole.
