28 August 2017 Luminescence and transient lifetime studies for energy transfer of PbS QD films
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Quantum confined semiconductor materials in colloidal form have drawn great attention in scientific communities due to the size-tunability, which controls their optical properties. PbS quantum dots (QDs) are exciting candidates for quantum optics, particularly due to the control of the QD sizes during the synthetic process enabling the realization of precisely tunable emission properties in the near-infrared region. Differently sized pairs of PbS QDs were deposited onto glass substrates to form thin films using supercritical CO2 (sc-CO2) deposition and solvent deposition methods (SDM). The fluorescence and photoluminescence (PL) spectra obtained from these closely packed films prepared by the sc-CO2 method reveal effective Förster resonance energy transfer (FRET) between two different sized dots, while the films composed of three different QD sizes show an even more effective FRET from the smallest to the largest ones. Energy transfer can be observed more directly by temporally resolved PL decay of mixed dots. By means of transient lifetime measurements, a mixed PbS film with 3.1 and 4.7 nm QDs was studied for FRET by time correlated single photon counting. The PL peak of the 3.1 nm QDs is quenched with respect to the emission of the 4.7 nm QDs and decays faster, and the best fit for the lifetime (decay constant)-1 is a biexponential decay mode. The long wavelength decay (4.7 nm QDs) is best fit by a mono-exponential equation. More theoretical and experimental work is required for a thorough understanding of the radiative lifetimes of PbS QDs in mixed QD systems.
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Joanna S. Wang, Joanna S. Wang, Bruno Ullrich, Bruno Ullrich, Chandriker K. Dass, Chandriker K. Dass, Anirban Das, Anirban Das, Chien M. Wai, Chien M. Wai, Gail J. Brown, Gail J. Brown, Joshua R. Hendrickson, Joshua R. Hendrickson, } "Luminescence and transient lifetime studies for energy transfer of PbS QD films", Proc. SPIE 10344, Nanophotonic Materials XIV, 103440R (28 August 2017); doi: 10.1117/12.2272734; https://doi.org/10.1117/12.2272734

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