Response of Semiconductor
Nanocrystals to Extremely
Energetic Excitation
- Publication date
- Publisher
Abstract
Using a combination of transient photoluminescence and
transient
cathodoluminescence (trCL) we, for the first time, identify and quantify
the distribution of electronic excitations in colloidal semiconductor
nanocrystals (NCs) under high-energy excitation. Specifically, we
compare the temporally and spectrally resolved radiative recombination
produced following excitation with 3.1 eV, subpicosecond photon pulses,
or with ionizing radiation in the form of 20 keV picosecond electron
pulses. Using this approach, we derive excitation branching ratios
produced in the scenario of energetic excitation of NCs typical of
X-ray, neutron, or gamma-ray detectors. Resultant trCL spectra and
dynamics for CdSe NCs indicate that all observable emission can be
attributed to recombination between states within the quantum-confined
nanostructure with particularly significant yields of trions and multiexcitons
produced by carrier multiplication. Our observations offer direct
insight into the transduction of atomic excitation into quantum-confined
states within NCs, explain that the root cause of poor performance
in previous scintillation studies arises from efficient nonradiative
Auger recombination, and suggest routes for improved detector materials