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Study On Performance Enhancement Of Quantum Dot Opoelectronic Device By Surface Modification

Posted on:2021-07-16Degree:MasterType:Thesis
Country:ChinaCandidate:Y J ChenFull Text:PDF
GTID:2518306560452254Subject:Electronic Science and Technology
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Quantum dots(QDs)as semiconductor nanocrystals have unique photoelectric properties and show broad application prospects in the field of lighting and display.With the deepening study,surface chemistry has become an important field in the research of QDs.Reasonable control of the QDs surface not only benefit the growth control,but also play a key role in the optical performance of QDs as well as QDs-based optoelectronic devices.This article focuses on the surface modification to optimize the light emitting performance and stability of QDs and light emitting diode(LED)devices.The research contents include “trioctylphosphine(TOP)-mediated surface ligands passivation of PbS QDs for near-Infrared LED application” and “efficient and stable CdSe/CdS/Zn S quantum rods-in-matrix assembly(QRAs)inorganic packaging for white LED application”.1.For organic surface ligand passivation: Infrared lead QDs suffer fast degradation due to the easy oxidation of surface chalcogen atoms.Here,a surface modification strategy is developed to improve air stability of PbS QDs by targeted passivation of surface S atoms.The improvement mechanism follows a trioctylphosphine-mediated surface reaction route.The modified PbS QDs exhibit a Pb-rich surface passivated by lead carboxylate,which effectively protects surface S atoms against oxidation.Surface analysis reveals that the reaction only affects surface S atoms,regardless of the original ligands on the surface Pb.The modified PbS QDs withstand long-time exposure to air without obvious fluorescence quenching and shift of emission peak.Moreover,the modified PbS QDs show high compatibility with polymers,and the stability of the QDs is further improved after being embedded in a matrix such as silicone and polymethyl methacrylate(PMMA).Studies have shown that the modified PbS quantum dots have high stability in LEDs.The LEDs display a slight degradation of only 1.5% after continuous operating in air for 250 h.The research shows a promising potential for the modified PbS QDs in optoelectronic applications.2.For inorganic encapsulation and assembly: CdSe/CdS core-shell quantum rods(QRs)can alleviate the problem of self-absorption of CdSe QDs,but QRs usually present relative low quantum efficiency and stability.Here,efficient and stable CdSe/CdS/Zn S QRAs by growing and embedding CdSe/CdS QRs in Zn S matrices were reported.Structural characterizations show that the CdSe/CdS QRs were packaged and interconnected by Zn S in the QRAs structure.The stable Zn S package renders CdSe/CdS QRAs high quantum efficiency up to 85%.The QRAs also present high photo-and thermal-stability and could preserve 93% of the initial efficiency at 100 ?.The QRAs film present a light degradation of only 2% under continuous excitation for 100 hours.The research shows white light-emitting diodes(WLEDs)were fabricated by encapsulating the QRAs powder as red phosphor on top of blue Ga N chip.The WLED shows high optical performance and light quality.
Keywords/Search Tags:quantum dots, surface modification, near-infrared, stability, light emitting diodes
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