Radiative recombination dynamics in tetrapod-shaped CdTe nanocrystals: Evidence for a photoinduced screening of the internal electric field

We study the radiative recombination processes in CdTe tetrapod nanocrystals at 10 K. Two intrinsic emission bands, namely the ground state (GS) and the excited state (EX), decay with three time constants, due to a power dependent Auger-like recombination process (tens of picoseconds), to the intrinsic emission of the two states (hundreds of picoseconds) and to emission from defect states (a few nanoseconds). The existence of an internal electric field originating from the e-h separation induced by the peculiar symmetry of the GS is demonstrated by a dynamical shift of the GS emission energy that is correlated to the EX population. (C) 2008 American Institute of Physics.