1. What is the effect of small separation on the electron transport?
Small separation favours efficient charge transport (in the plane of the quantum-dot layer as well as in the injection direction), butalso leads to more rapid exciton dissociation13.
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2. What are the contributions in "Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control" ?
Here, by tuning the distance between adjacent PbS quantum dots, the authors fabricate thin-film quantumdot light-emitting diodes that operate at infrared wavelengths with radiances ( 6. 4 W sr m ) eight times higher and external quantum efficiencies ( 2. 0 % ) two times higher than the highest values previously reported.. The crucial development the authors report here is the ability to dramatically enhance the quantum efficiency of exciton recombination by tuning the distance between the PbS quantum dots in the active layer of an LED.. By fabricating devices with optimal linker length as well as high-performance carrier-injection layers, the authors demonstrate infrared quantum-dot LEDs with an eightfold increase in radiance and twofold increase in EQE compared with previous best devices.. Lead-salt quantum dots are well established as efficient emitters in the near-infrared, and in this work the authors focus on PbS quantum dots because their absolute energy levels14 are most appropriate ( Fig. 1b ).. The authors fabricated the electron-injecting layers using colloidal ZnO nanoparticles for several reasons.. By varying the size of the quantum dots, the authors can tune the emission wavelengths between 800 and 1,850 nm.. In particular, the development of high-power, efficient and low-cost infrared LEDs will further progress in applications such as night vision, optical communications and sensing.
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3. What is the effect of the ZnO nanoparticles on the quantum dots?
To couple the quantum dots within the active layer, the long-chain oleate ligands were displaced by bifunctional linker molecules of controlled length.
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4. What is the role of the carrier in the quantum-dot layer?
As well as overcoming the challenge of achieving efficient inter-dot charge transfer, which is common to both devices, an LED must also balance charge injection against efficient radiative recombination within the quantum-dot layer.
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