Energy transfer mechanisms in CdSe/CdS nanorod heterostructures.
Ngiam, Song Wee.
Date of Issue2010
School of Physical and Mathematical Sciences
A series of time-resolved transient absorption spectroscopy experiments were performed on ensembles of CdSe/CdS dot/rod nano-hetero-structures dispersed in toluene. The resulting decay dynamics were quantified via data fitting of the differential transmission of probe laser pulses to multi-exponential decay functions. The lifetimes extracted from the data fit indicates the timescales over which the recombination processes within the system of study occur. A plausible model was proposed in order to account for the various trends in lifetimes with increasing laser pump fluences. The model also identified the specific state transitions for which current literature enfolds as ”Auger processes”, and alludes the observed suppression of such non-radiative recombinations with increasing rod lengths, to that of a decrease in the effective overlap, in the wavefunction of a donor electron in the sulphur vacancy states, with that of the empty states above the conduction band-edge. A proof-of-concept which showed that the suppressed Auger processes can lead to lasing in such ensembles of nanocrystallites upon alignment and concentration, was also demonstrated through the realization of amplified spontaneous emission.
Final Year Project (FYP)