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Cs3bi2br9 Perovskite Variant Quantum Dots:Synthesis,Optical Properties And White Light-emitting Diode ?WLED? Application

Posted on:2020-06-01Degree:MasterType:Thesis
Country:ChinaCandidate:Y YangFull Text:PDF
GTID:2428330590958287Subject:Electronic Science and Technology
Abstract/Summary:PDF Full Text Request
Quantum dots?QDs?,possessing various favorable properties such as narrow-band emission and tunable band gap,show broad application prospects in the fields of lighting and displaying,laser,etc.Compared with tranditional II-VI compounds,the recently emerging lead halide perovskite not only demonstrates comparable photoluminescence quantum yield?PLQY,>90%?,narrower full width at half-maximum?FWHM,12-35 nm?and wider color gamut?140%NTSC?,but also exhibits an emission wavelength covering the whole visible spectrum?400-700 nm?through controlling the halide compositions.These excellent features make lead halide perovskite as the next generation candidates for future light emitters and vivid display.However,the severe toxicity of lead and stability problem can be a great hindrance toward commercial applications.Therefore,the development of low-toxic and stable lead free perovskite materials is highly desirable in this field.In this paper,all inorganic bismuth-based perovskite with similar electronic configuration to Pb,low structural dimension and good stability were selected,and the optical properties of Cs3Bi2Br9 QDs were systematically studied.Before the exploration of Cs3Bi2Br9 QDs,the basic properties of the material were preliminarily studied by growing Cs3Bi2Br9 single crystals.Following the deep study of the bulk material,Cs3Bi2Br9 QDs with benign photoluminescence were synthesized by ligand-assisted reprecipitation?LARP?method,and extended to light-emitting diodes?LED?applicaiton.The main works were summarized as follows:?1?Study on the growth and basic properties of Cs3Bi2Br9 single crystal.The Cs3Bi2Br9 single crystals with millimeter size were grown by temperature-lowering crystallization method.X-ray diffraction?XRD?and thermogravimetry-differential thermal analysis?TG-DSC?characterization revealed that Cs3Bi2Br9 held two-dimensional layered structure and good thermal stability.Transmission spectroscopy,photoluminescence spectroscopy?PL?and temperature-dependent fluorescence?TDPL?characterization showed that Cs3Bi2Br9 is a direct bandgap material with energy gap of2.61 eV,and the emission peak and activation energy of Cs3Bi2Br9 single crystal was 473nm and 77.9 meV.?2?Synthesis of Cs3Bi2Br9 QDs and study of their optical properties.Cs3Bi2Br9 QDs were synthesized by using ethanol as anti-solvent in LARP strategy.After optimizing the reaction conditions,Cs3Bi2Br9 QDs with emission wavelength of 410 nm,FWHM of 48nm and PLQY of 19.4%were achieved.Subsequently,the exciton recombination dynamics in quantum dots were characterized.It was found that the quantum dots had higher activation energy?210.7 meV?than the bulk materials,which makes them have shorter PL lifetime and higher PL intensity.In addition,the presence of surface defects is one of the important reasons for the low PLQY of QDs.?3?The stability of Cs3Bi2Br9 QDs and their application of LEDs.The photostability and water stability of Cs3Bi2Br9 QDs were also investigated in this research.The results showed that Cs3Bi2Br9 QDs exhibit good photostability and excellent water stability.The hypothesis of self-passivation from the water-induced BiOBr was subsequently proposed and verified.Cs3Bi2Br9 QDs/silica composite was obtained by one-pot synthesis dut to its outstanding performance in water.A lead-free perovskite white LED was fabricated by simply combining Cs3Bi2Br9 QDs/silica composite with Y3Al5O12?YAG?phosphor on GaN chip.
Keywords/Search Tags:Quantum dots, Lead free perovskite, Cs3Bi2Br9, Photoluminescence, Stability
PDF Full Text Request
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