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Photoluminescence (PL) properties of semiconductor quantum dots (QDs) may be significantly improved by forming hybrid structures with plasmonic nanoparticles (PNPs). In general, three main effects can be observed when QDs are placed near PNPs – a local enhancement of excitation, acceleration of radiative recombination rate (Purcell effect), and acceleration of nonradiative relaxation rate due to the metal-induced energy transfer. All these effects lead to an increase in PL quantum yield (QY), excitonic (EX) and biexcitonic (BX) states and to the strong reduction of PL lifetime. In this study, we investigated the EX and BX PL parameters of single QDs in the vicinity of PNPs at different overlapping between the excitation wavelength, QDs PL, and PNPs extinction spectra. Here, we have fabricated thin films of QDs separated from the environment by the polymer spacer, and placed PNPs atop of these structures under the continuous observation of optical parameter of the same single QD. We have found that the excitation may be strongly increased in the case of a strong spectral overlap between excitation band and PNPs extinction. Nevertheless, the EX QY is strongly reduced by the energy transfer. In the case of strong spectral overlap between QDs PL and PNPs extinction, the radiative rate is increased, which leads to an increase of both EX and BX QYs and to a near-unity BX-to-EX QY ratio. Finally, we managed to combine these two effects in one material with a synergistically increased PL intensity, ultrashort PL lifetime, and levelling of EX and BX QY.
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