Abstract
The broadband photoluminescence (PL) emissions from CdSe QDs and plasmon-coupled QDs were characterized with time-resolved and temperature-dependent spectroscopy for the application of solid-state white light. The origin of broad spectral emission includes the transitions from bandedge and surface-trapped states. The emission intensity enhancement of plasmon-coupled QDs with respect to that of bare QDs is attributable to the reduction of nonradiative decay and the local field enhancement with plasmon-exciton coupling through the Coulomb interaction. The temperature-dependent and time-resolved PL spectroscopy revealed the existence of selective contribution strength of both the local field enhancement and the reduction of nonradiative decay with plasmon-exciton coupling at different spectral regions.
Highlights
Semiconductor quantum dots (QDs) have been of great interest for optoelectronic and biomedical applications due to wide optical tunability, high color purity, and high luminescence efficiency [1,2,3,4,5]
Some possible radiative processes may include the bandedge transition between the lowest level of conduction band and the highest level of valence band, the bandedge to deep surface-trapped states, the surface-trapped to the valence band, and shallow surface-trapped state to deep surface-trapped state
The origin of broad spectral emission includes the transitions from the bandedge and surface-trapped states
Summary
Semiconductor quantum dots (QDs) have been of great interest for optoelectronic and biomedical applications due to wide optical tunability, high color purity, and high luminescence efficiency [1,2,3,4,5]. The fractional contribution and the spectral distribution of PL from bandedge transitions and surface-trapped states may be elucidated with time-resolved and temperature-dependent spectroscopy with/without plasmon-exciton coupling through the Coulomb interaction at multiple spectral regions. Another important factor for photonic applications is the quantum yield of the QDs which is enhanced when excitons are coupled with plasmons in metallic nanoparticles (NPs). Temperature-dependent spectroscopy further clarifies the PL enhancement mechanism for the plasmon-coupled CdSe QDs. The time-resolved spectroscopy yields the PL lifetimes and the fractional contributions of the bandedge transition and surface-trapped state transition to the PL in the presence of plasmonic NPs
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