| In recent years,inorganic halide perovskite materials have developed rapidly and show great application prospects in solar cells,light emitting diodes,lasers,photodetectors and other fields.At present,the research of inorganic halide perovskites still faces the problems:the crystal structure is easily destroyed when the inorganic halide perovskite contacts directiy with a polar solvent(such as water,ethanol,etc.);and the inorganic halide perovskite has poor light stability,with the extension of ultraviolet or blue light irradiation time,the luminescent performance gradually deteriorates.How to improve its luminous stability under the action of light and polar solvents has become a key issue for all inorganic perovskite materials.In order to solve the above problems,this paper uses natural hollow fibers as a template to Cs4PbBr6 nanosheets are grown in situ in the inner wall of the fiber,and with the changes of precursor composition,a series of luminescent fibers with adjustable emission wavelength could be obtained.The hydrophobic nature of the fiber can protect the Cs4PbBr6 nanosheets,thus greatly improve the stability of the perovskite.Next,we developed a method to directly grow perovskite Cs4PbBr6 microcrystals on the outer wall of the fiber,and successfully produced a white LED with an excellent performance.The research work is divided into the following three parts:1.Under vacuum assistance,the precursor solution is uniformly filled in the hollow Calotropis gigantea fiber and volatilized at a certain temperature,and a growth center is formed on the inner wall of the fiber.Using it as a "nucleus","crystallization" on the substrate,perovskite Cs4PbBr6 luminescent fibers are successfully prepared by in situ growth of Cs4PbBr6 nanosheets.The effects of temperature,vacuum,and vacuum operation time on the synthetic luminescent fibers were investigated in detail.The results indicate that the as-obtained luminescent fiber showed the best luminous effect at a growth temperature of 60℃,vacuum of 13 Pa and a vacuuming for 3 h,and the fluorescence quantum yield was 41.5%.The luminous intensity of the luminescent fibers remained basically unchanged after being left in the air for 30 days,which greatly improved the stability of the Cs4PbBr6 nanosheets in the air.2.Based on the above experiments,the halogens in the precursor were simply changed to successfully prepare perovskite Cs4PbX6 luminescent fibers(blue,green,red)with different colors.The stability of luminescent fibers in water,ethanol,air,and artificial sweat was investigated in detail.The results showed that after direct water and ethanl washing the luminescence intensity of the fibers not much fiber change.Even after 50 h of direct immersion of luminescent fibers in the artificial sweat,the fluorescence intensity only decreased to 38.7%of the initial fluorescence intensity.The addition of hydrophobic fibers successfully isolated the direct contact between the perovskite nanosheets and air and polar solvents,as well as prevented the air and polar solvents from eroding the perovskite,thus achieving the stable presence of perovskite nanosheets in air,water and artificial sweat.3.Using the Calotropis gigantea fiber as a template to grow the inorganic halide perovskite,micron-sized Cs4PbBr6 crystals were obtained with the fluorescence quantum yield of 31.5%.The prepared perovskite microcrystals as green phosphors and mixing with blue phosphor(BaMgAl10O17:Eu2+)and red phosphor(CaAlSiN3:Eu2+)for LED packaging,and white LEDs with good performance were successfully produced.The CIE color coordinates is(0.32,0.35)which is very close to the ideal of CIE for pure white emission(0.33,0.33).The correlated color temperature(CCT)is 6040 K and the color rendering index(CRI)is 83.5 with a working current of 40 mA. |
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