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Studies On Stable And Efficient Perovskite Light-Emitting Diodes

Posted on:2021-03-31Degree:MasterType:Thesis
Country:ChinaCandidate:Y JinFull Text:PDF
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All-inorganic lead halide perovskite materials have become the research focus in optoelectronics due to their excellent properties,such as optical bandgap tunability,narrow spectrum and high photoluminescence quantum yield?PLQY?.Particularly,there are many amazing achievements have been obtained in light-emitting diodes?LEDs?.However,the properties of perovskite film-s still need to be improved,the optical instability of the LEDs has not been suppressed,and the optical physical mechanism of perovskite is also worth further studying.To resolve these problems,focusing on the application of inorganic perovskite in LEDs,this thesis conducted a series of detailed investigation on basic points including material engineering,process optimization and device physics.What's more,efficient and stable blue,green and red perovskite LEDs were successfully fabricated.And the crystal structure,growth orientation and morphology of perovskite films were evaluated by using scanning electron microscopy?SEM?,atomic force microscopy?AFM?,X-ray diffractometer?XRD?and two-dimensional grazing incidence X-ray diffraction?GIXRD?technology.The energy levels and optical characteristics of perovskite films were studied by fluorescence spectroscopy?PL?and ultraviolet-visible absorption spectroscopy?UV-vis?.Moreover,the two-dimensional phase distribution,carrier recombination and transportation in perovskite layer were analyzed by time-resolved fluorescence spectroscopy?TRPL?and transient absorption spectroscopy?TA?.Specifically,the research contents of this thesis are as follows:1.From the perspective of crystal growth kinetics,appropriate amount of sulfobetaine?SB3-10?was introduced into the perovskite precursor.The interaction between SB3-10 and Cs Pb Br3 was used to optimize the crystal growth process,reduce the average size of grains,and make the film surface be compact and smooth.Meanwhile,the residual SB3-10 molecules attached to the grain surface,resulting in reduced state density of surface defects,suppressed probability of carrier non-radiation recombination,and improved PLQY.With this strategy,the performance of green LEDs had been improved,the highest external quantum efficiency?EQE?rised from 0.35%to 2.3%.2.Following two-dimensional?2D?perovskite strategy,two ligands,benzeneethanamine,hydrobromide?PEABr?and N-?2-Bromoethyl?-1,3-propanediamine dihydrobromide?NPABr2?,were combined to form pure bromine blue-light perovskite films.The 2D phase distribution and carrier dynamics of the new kind of blue perovskite film were analyzed in details.Based on the synergistic effect of the two ligands,the fabricated blue LEDs showed better photoelectric performance with a maximum luminance of 1200 cd m-2,a highest EQE of 2.62%and a T50 lifetime of 8.8 min.More importantly,the device could maintain good photochromic stability under different driving voltages.3.A kind of bidentate ligand,namely L-phenylalanine?L-PHE?,was utilized to replace some parts of oleylamine?OLA?and oleic acid?OA?,to synthesize high quality Cs Pb I3 quantum dots.The fluorescence quantum yield?PLQY?of the optimized Cs Pb I3quantum dots was close to 100%due to reduction of defects.Their stabilities with high temperature or in atmospheric environment,had also been improved significantly.Combined with a reasonable device structure,the maximum EQE of red perovskite LEDs with stable EL spectra had been increased to 10.21%.
Keywords/Search Tags:perovskite, light-emitting diodes (LEDs), spectral stability, twodimensional structure, carrier dynamics, quantum dots
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