CN115942780A - Packaging structure for enhancing luminescent property of nanocrystal and preparation method thereof - Google Patents
Packaging structure for enhancing luminescent property of nanocrystal and preparation method thereof Download PDFInfo
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Abstract
The invention provides a packaging structure for enhancing the luminescent property of nanocrystals and a preparation method thereof. The nano resonant cavity is processed by taking the nano spheres as the auxiliary chemical template, and the preparation method is flexible, low in cost and large in scale. The specific structure and periodic pattern give the material unique light-substance interactions. By utilizing the flexibility of resonant cavity design to match the emission peaks of the nanocrystals in different wavebands, the intrinsic photoluminescence intensity is significantly enhanced based on the Purcell effect. The high molecular polymer encapsulation also effectively improves the stability of the nanocrystal.
Description
Technical Field
The invention relates to the field of preparation of optoelectronic materials, in particular to an encapsulation structure for enhancing the luminescent property of a nanocrystal and a preparation method thereof.
Background
Display technology has profoundly changed people's lifestyle and is widely recognized as an indispensable part of modern society (nat. Mater.2015,14,454 light sci. Appl.2018,7, 17168). Currently, the mainstream display technology in the market is mainly based on Liquid Crystal Display (LCD) and Organic Light Emitting Diode (OLED) display. Although LCDs are leading in terms of lifetime, cost, resolution density and peak brightness compared to OLED displays, the performance of wide color gamut and excellent color reproduction is also being tested as the demand for more realistic, low-energy image presentations also grows sharply (adv. Mater.2010,22, 3076). Currently, conventional commercial display backlights typically rely on blue LEDs and Ce: YAG yellow phosphors, which produce a yellow spectrum that is too broad to be converted to highly saturated RGB primaries (prog.mater.sci.2016, 84, 59). Or, a combination of green beta-Sialon and Eu 2+ And red K 2 SiF 6 :Mn 4+ (KSF) phosphors, although the red and green emission spectra are well separated, the green spectrum is rather broad and the red spectrum is not deep enough (appl. Phys.express 2009,2,022401 opt.express 2015,23, 28707).
Compared with conventional quantum dot materials such as CdSe and InP, all-inorganic perovskite nanocrystals (Pencs) (CsPbX) 3 (X = Cl, br or I)) is considered one of the most promising candidates for next generation backlit displays due to its excellent optical properties (such as color purity and tunable bandgap), ease of synthesis and high defect tolerance (chem. Eng.j.2022,433,133195; ACS Energy lett.2021,6,519; adv. Funct. Mater.2022,32, 2113010). However, the low luminous efficiency of the PenC film still remains a problem to be solved urgently in the commercialization process (chem.Eng.J.2020, 393,124767; nano Lett.2018,18, 1185). Although the nanopatterned thin film can improve its luminous efficiency, the realization of the process inevitably relies on Electron Beam Lithography (EBL) and poly-depositionTechniques such as Focused Ion Beam (FIB) face obstacles in terms of manufacturing area, cost and processing complexity (adv. Opt. Mate. 2021,9, 2001474). Furthermore, the instability of PeNC films is also a bottleneck for practical applications (soc. Rev.2019,48,310, adv. Mater.2019,31, 1804294). Various factors such as humidity, light, temperature and oxygen can lead to degradation of the nanocrystals and severe Photoluminescence (PL) quenching when PeNC is exposed to the external environment for a long time (adv. Funct. Mater.2021,31, 2008211).
Disclosure of Invention
The technical problem is as follows: in view of the above, the present invention provides an encapsulation structure for enhancing the luminescence property of nanocrystals and a method for preparing the same. The specific structure and periodic pattern endow the material with unique light-substance interaction, and have important influence on improving the photoelectric property of the device. It is worth mentioning that the manufacturing process of the nano resonant cavity avoids complex, time-consuming and expensive process flows, and lays a foundation for further commercialization outside a laboratory.
The technical scheme is as follows: the packaging structure for enhancing the luminescent property of the nanocrystals comprises a luminescent layer, a resonant cavity and a packaging layer which are sequentially arranged from inside to outside, wherein the luminescent layer at the innermost layer is the nanocrystals, the resonant cavity at the middle layer is composed of a plurality of mutually independent metal oxide cavities, the packaging layer at the outermost layer is a transparent high polymer, when the emission wavelength of the nanocrystals is matched with the resonant cavity, resonance is formed, the luminescence of a coupling system is remarkably enhanced, and the high polymer plays a role in protecting and stabilizing the nanocrystals.
Wherein the content of the first and second substances,
the resonant cavity is in a shape of a hemisphere, a cone, an inverted pyramid, a polygon or a barrel.
The nano crystal is any one or the combination of CdS, cdSe, cdTe, znSe, inP and InA traditional nano crystal and perovskite nano crystal.
The perovskite nanocrystal is of a general formula ABX 3 Wherein the A site cation comprises MA + (CH 3 NH 3 + )、FA + ([(NH 2 ) 2 CH] + ) And Cs + (ii) a The B site is mainly Pb 2+ Or using different metal ions Sr 2+ 、Zn 2+ 、Ni 2+ 、Mn 2+ 、Cd 2+ 、Sn 2+ 、Co 2+ 、Eu 3+ 、Er 3+ 、Yb 3+ 、Bi 3+ Partial or complete substitution of Pb 2+ ；X＝Cl、Br、I。
The preparation method of the packaging structure for enhancing the luminescent property of the nanocrystal specifically comprises the following steps:
step 1, assembling a two-dimensional dense nanosphere array on a substrate and carrying out dry etching treatment;
step 2, depositing metal oxide sol between the etched nano-sphere arrays, and forming a nano resonant cavity by removing the nano-spheres and crystallizing the metal oxide framework;
step 3, coating the mixture of the nano-crystal or the precursor liquid thereof and the high molecular polymer on a substrate containing a nano resonant cavity, and heating to promote the evaporation of the solvent and the growth of the nano-crystal;
and 4, stripping the substrate to obtain an independent nanocrystal composite film, namely the packaging structure for enhancing the luminescence performance of the nanocrystal.
The assembly of the two-dimensional dense nanosphere array is any one of a gravity self-assembly method, langmuir-Blodgett deposition, spin coating, electrophoretic deposition, a vertical deposition method or an MPI system by utilizing micro-propulsion injection.
The photoluminescence spectra of the nanocrystalline composite film respectively have wavelengths of 400-500nm, 500-600nm and 600-700nm, wherein,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 400-500nm, the selected nanospheres are as follows: polystyrene spheres with diameter of 300-370nm and concentration of 2.5-5 wt%;
when the photoluminescence spectrum of the nanocrystalline composite film is 500-600nm, the selected nanospheres are as follows: polystyrene spheres with a diameter of 370-450nm and a concentration of 2.5-5 wt%;
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 600-700nm, the selected nanospheres are as follows: polystyrene spheres with a diameter of 450-530nm and a concentration of 2.5-5 wt%.
The dry etching treatment is carried out by selecting an inductively coupled plasma etching machine to complete etching, selecting 100-150W of power, introducing oxygen and argon into the inductively coupled plasma etching machine, wherein the flow rate is 20-50sccm,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 400-500nm, the etching time is 5-9s,
the nano-crystalline composite film has a photoluminescence spectrum with a wavelength of 500-600nm and an etching time of 6-10s,
the etching time of the photoluminescence spectrum of the nanocrystalline composite film is 8-12s at the wavelength of 600-700 nm.
Removing the nanospheres, and dissolving the nanospheres by dry etching, high-temperature calcination or solution of any one of toluene, xylene, chloroform, dichloroethane, acetone, tetrahydrofuran and ethyl acetate.
The metal oxide is TiO 2 ,ZnO,VO 2 ,HfO 2 After removing the nanospheres and crystallizing the metal oxide framework, the formed nano resonant cavity can generate resonant peaks with resonant wavelengths of 400-500nm, 500-600nm and 600-700nm to match with the nano crystal or precursor liquid thereof with the photoluminescence spectrum of the nano crystal composite film of 400-500nm, 500-600nm and 600-700 nm.
Has the advantages that: as can be seen from the above description, the encapsulation structure and the preparation method for enhancing the light emitting performance of the nanocrystal provided in one or more embodiments of the present disclosure have several advantages:
1. the problem of a single nanoresonator resonance being too weak can be solved by using an array of multiple Mie scatterers, adjacent resonances will effectively enhance the intensity of the resonance mode. This enhancement will be further improved as the number of scatterers increases. It is worth mentioning that a nanoresonator prepared by adjusting the etched nanosphere diameter, the metal oxide layer thickness and the lattice size (i.e. the original nanosphere diameter) will significantly increase the resonance intensity, thereby affecting the transmission spectrum;
2. the nano-resonant cavity has the capability of capturing, limiting and enhancing the nano-scale optical field, and the combination of technologies such as Electron Beam Lithography (EBL) and Focused Ion Beam (FIB) is the most widespread strategy for manufacturing the nano-resonant cavity, and although these technologies can manufacture high-quality micro/nano structures, these methods may face the bottleneck of high cost and process design complexity when large-area production is involved; the method uses a more convenient chemical strategy for processing, and overcomes the obstacles of micro-nano structure preparation in time, cost and manufacturing area; the nanoresonators provide an excellent platform for enhancing and tuning the spontaneous emission of a nanoscale light source located in their vicinity, which is crucial for many possible applications of the resonator (e.g., quantum light sources or displays); the photoluminescence spectrum of the perovskite nanocrystalline film is strongly reshaped due to the embedding of the nano resonant cavity, and when the resonant cavity is resonated and tuned to the intrinsic emission peak of the perovskite nanocrystalline, the emission signal of the coupling system is obviously enhanced;
3. the perovskite nanocrystalline composite film has good stability, and the high molecular polymer enables the PenCs to be mutually separated, thereby preventing further close contact and regeneration; furthermore, the polymer matrix with compact molecular chains can passivate the perovskite surface and protect it from environmental influences;
4. the perovskite nanocrystalline composite film has excellent high luminescence and environmental stability, and has the characteristics of low cost and large-area manufacturing, so that the perovskite nanocrystalline composite film becomes an ideal candidate material for a color conversion layer in illumination and display application; the color gamut of the manufactured LCD backlight module can reach 122% of National Television Standard Committee (NTSC) standard and 180% of the color gamut of a traditional commercial screen; these results indicate that perovskite nanocrystalline thin films have great potential for photovoltaic applications.
Drawings
In order to more clearly illustrate one or more embodiments or prior art solutions of the present description, the drawings that are needed in the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the description below are only one or more embodiments of the present description, and that other drawings may be obtained by those skilled in the art without inventive effort from these drawings.
FIG. 1 is a scanning electron microscope image of a nano-resonator;
FIG. 2 shows the resonant peaks of the nano-resonator in example 2; wherein h, d and T respectively represent TiO 2 Thickness, etched nanosphere diameter and lattice period (initial nanosphere diameter) used to prepare the resonator;
FIG. 3 is a comparison of perovskite nanocrystalline thin films with and without embedded nanoresonators.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, the present disclosure will be described in further detail with reference to specific embodiments.
The invention relates to a packaging structure for enhancing the luminescence property of a nanocrystal, which is characterized in that a luminescent layer, a resonant cavity and a packaging layer are sequentially arranged from inside to outside, wherein the luminescent layer at the innermost layer is the nanocrystal, the resonant cavity at the middle layer is composed of a plurality of mutually independent metal oxide cavities, the packaging layer at the outermost layer is a transparent high polymer, when the emission wavelength of the nanocrystal is matched with the resonant cavity, resonance is formed, the luminescence of a coupling system is remarkably enhanced, and the high polymer plays a role in protecting and stabilizing the nanocrystal. The resonant cavity is in a shape of a hemisphere, a cone, an inverted pyramid, a polygon or a barrel. The nano crystal is any one or the combination of CdS, cdSe, cdTe, znSe, inP and InA traditional nano crystal and perovskite nano crystal. The perovskite nanocrystal is shown as a general formula ABX 3 Wherein the A site cation comprises MA + (CH 3 NH 3 + )、FA + ([(NH 2 ) 2 CH] + ) And Cs + (ii) a The B site is mainly Pb 2+ Or using different metal ions Sr 2+ 、Zn 2+ 、Ni 2+ 、Mn 2+ 、Cd 2+ 、Sn 2+ 、Co 2+ 、Eu 3+ 、Er 3+ 、Yb 3+ 、Bi 3+ Partial or complete substitution of Pb 2+ ；X＝Cl、Br、I。
Example 1
The method takes a nanosphere array as an auxiliary template, fills metal oxide sol in gaps between spheres, and removes the nanosphere auxiliary template while crystallizing metal oxide at high temperature, thereby obtaining a nano resonant cavity which is large in area, low in cost and easy to prepare; finally, coating the mixture of the perovskite precursor solution and PMMA on a substrate containing a nano resonant cavity, and heating to promote solvent evaporation and nanocrystalline growth so as to obtain a nanocrystalline composite film;
step 1: assembling a two-dimensional compact nanosphere array;
2.5wt%330nm Polystyrene (PS) nanosphere colloidal solution to ethanol in a volume ratio of 1:1, mixing and using, and performing ultrasonic treatment for 30-60 min;
directly spreading the PS nanospheres on the water surface based on a micro-propulsion injection (MPI) system at a feeding speed of 0.5 mL/h; the solution finally evolves into a two-dimensional hexagonal close-packed PS nanosphere monolayer at the air/water interface;
then, the PS nanosphere monolayer is transferred to a preset substrate by slowly pumping water or lifting the substrate; the nanospheres are tightly attached to the substrate by self-evaporation or low-temperature baking (below 60 ℃);
ethanol is added as a dispersant to the water-based PS colloidal solution to lower the surface tension, thereby more effectively dispersing the PS nanospheres on the water surface; the amount of ethanol additive depends on the size and concentration of the nanospheres;
by finely controlling 4 key parameters in a micro-propulsion injection (MPI) system, including the contact state between an ejector and the water surface (the nozzle is just contacted with the water surface), the ejection speed (0.5-6 mL/h), the number of the ejectors and the concentration (2.5-5 wt%) of the PS nanosphere colloidal solution, a large-area PS single layer with the size of more than 1 square meter can be easily realized;
the substrate can be a quartz sheet, a mica sheet, a silicon wafer or a flexible material; ultrasonically cleaning the substrate for 20-30 min by deionized water, acetone and ethanol in sequence, drying the substrate, and treating the substrate for 20-30 min by an ultraviolet ozone cleaning machine to obtain a preset substrate;
step 2: processing the nanosphere array by dry etching;
treating the two-dimensional dense nanosphere array in the step 1 by using an inductively coupled plasma etcher, and introducing combined gas of oxygen and argon (the power is 100W, the gas flow is 50sccm, and the time is 9 s) to obtain a nanosphere array subjected to dry etching treatment;
and step 3: tiO 2 2 Preparing sol;
mixing titanium isopropoxide (TTIP, 5 mL) with ethanol (45 mL) and acetylacetone (1 mL) as a precursor solution, and stirring uniformly using a magnetic stirrer (stirring speed set at 800rpm to 1200 rpm); then, hydrochloric acid (0.85 mL) and deionized water (4.5 mL) were added to the above solution, and the mixture was stirred for 5h to 8h to form TiO 2 Sol;
and 4, step 4: tiO 2 2 Processing a base nano resonant cavity;
taking the TiO prepared in the step 3 2 20-50 mu L of sol is spin-coated on the nano array etched in the step 2 by a spin coater at the rotating speed of 1000-2000rpm for 30-60 s; then, transferred to an oven (60-75 ℃,12-24 h) and calcined at 480 ℃ for 2-3h, with the aim of removing the nanospheres and crystallizing the TiO 2 Framework of TiO formation 2 A base nano resonant cavity;
to ensure formation of the nano-resonator structure, the TiO is 2 The thickness of the sol coating is required to be smaller than the diameter of the nanospheres subjected to dry etching treatment;
and 5: csPbCl 1.5 Br 1.5 Preparing a mixture of perovskite precursor solution and PMMA;
by dissolving 0.14mmol of CsCl, 0.14mmol of CsBr, and 0.15mmol of PbCl in 10mL of N, N-Dimethylformamide (DMF) solvent 2 、0.15mmol PbBr 2 A perovskite precursor solution of 0.028mmol/mL was obtained and mixed with 1g of polymethyl methacrylate (PMMA) powder; wherein, stirring at 800rpm-1200rpm for 30min-60min;
step 6: csPbCl preparation by scraper method 1.5 Br 1.5 A nanocrystalline composite film;
CsPbCl obtained in the step 5 is coated by a scraper film coating machine 1.5 Br 1.5 Coating the mixture of perovskite precursor solution and PMMA on the TiO-containing material in step 4 2 On a substrate based on a nano-resonator and at a temperature of 80-130 deg.CHeat is applied to the thermal platform to promote solvent evaporation and nanocrystal growth. Heating for 2-12min, and stripping to obtain CsPbCl with independent photoluminescence spectrum at 400-500nm wavelength 1.5 Br 1.5 A nanocrystalline composite film;
the preparation of the nano resonant cavity by taking the nanospheres as the auxiliary chemical template is a flexible, low-cost and large-scale preparation method; the special structure and periodic pattern endow the material with unique light-matter interaction; csPbCl 1.5 Br 1.5 Photoluminescence (PL) spectrum of nanocrystalline composite films due to TiO 2 The base nano resonant cavity is embedded and strongly reshaped, and the amplitude of PL enhancement can be tuned by changing the resonance of the nano resonant cavity in the composite film; when the resonance of the resonant cavity is tuned to the intrinsic emission peak of the nanocrystal, the emission signal of the coupling system is enhanced; at the same time, the spontaneous emission lifetime is shortened, indicating that this enhancement is radiative in nature; the PMMA polymer encapsulation also effectively improves the stability of the nanocrystal; can be widely applied to high-performance perovskite-based photoelectric devices such as biosensors, light-emitting diodes, lasers and the like.
Example 2
Step 1: assembling a two-dimensional dense nanosphere array;
390nm Polystyrene (PS) nanosphere colloidal solution 2.5wt% with ethanol in a volume ratio of 1:1, mixing and using, and performing ultrasonic treatment for 30-60 min; directly spreading the PS nanospheres on the water surface based on a micro-propulsion injection (MPI) system at a feeding speed of 0.5 mL/h; the solution finally evolves into a two-dimensional hexagonal close-packed PS nanosphere monolayer at the air/water interface; then, the PS nanosphere monolayer is transferred to a preset substrate by slowly pumping water or lifting the substrate; the nanospheres are tightly attached to the base material through self-evaporation or low-temperature baking (below 60 ℃);
step 2: processing the nanosphere array by dry etching;
treating the two-dimensional dense nanosphere array in the step 1 by using an inductively coupled plasma etcher, and introducing combined gas of oxygen and argon (the power is 100W, the gas flow is 50sccm, and the time is 10 s) to obtain a nanosphere array subjected to dry etching treatment;
and step 3: t is a unit ofiO 2 Preparing sol;
mixing titanium isopropoxide (TTIP, 5 mL) with ethanol (45 mL) and acetylacetone (1 mL) as a precursor solution, and stirring uniformly using a magnetic stirrer (stirring speed set at 800rpm to 1200 rpm); then, hydrochloric acid (0.85 mL) and deionized water (4.5 mL) were added to the above solution, and the mixture was stirred for 5h to 8h to form TiO 2 Sol;
and 4, step 4: tiO 2 2 Processing a base nano resonant cavity;
taking the TiO prepared in the step 3 2 20-50 mu L of sol is spin-coated on the nano array etched in the step 2 by a spin coater at the rotating speed of 1000-2000rpm for 30-60 s; then, transferred to an oven (60-75 ℃,12-24 h) and calcined at 480 ℃ for 2-3h, with the aim of removing the nanospheres and crystallizing the TiO 2 Framework of TiO formation 2 A base nano resonant cavity;
and 5: csPbBr 3 Preparing a mixture of perovskite precursor solution and PMMA;
by dissolving 0.28mmol CsBr and 0.3mmol PbBr in 10mL of N, N-Dimethylformamide (DMF) solvent 2 A perovskite precursor solution of 0.028mmol/mL was obtained and mixed with 1g of polymethyl methacrylate (PMMA) powder; wherein, stirring at 800rpm-1200rpm for 30min-60min;
step 6: csPbBr preparation by scraper method 3 A nanocrystalline composite film;
CsPbBr in step 5 is coated by a scraper film coating machine 3 Coating the mixture of perovskite precursor solution and PMMA on the TiO-containing material in step 4 2 The nano resonant cavity is arranged on a substrate and heated on a thermal platform at the temperature of 80-130 ℃ to promote the evaporation of the solvent and the growth of the nano crystal. Heating for 2-12min, and stripping from the substrate to form CsPbBr with independent photoluminescence spectrum at 500-600nm wavelength 3 A nanocrystalline composite film;
the preparation of the nano resonant cavity by taking the nanospheres as the auxiliary chemical template is a flexible, low-cost and large-scale preparation method; the special structure and periodic pattern give the material unique light-substance interaction; csPbBr 3 Photoluminescence (PL) spectrum of nanocrystalline composite films due to TiO 2 Radical nano meterThe resonant cavity is embedded and strongly reshaped, and the enhanced amplitude of PL can be tuned by changing the resonance of the nano resonant cavity in the composite film; when the resonance of the resonant cavity is tuned to the intrinsic emission peak of the nanocrystal, the emission signal of the coupling system is enhanced; at the same time, the spontaneous emission lifetime is shortened, indicating that this enhancement is radiative in nature; the PMMA polymer encapsulation also effectively improves the stability of the nanocrystalline; can be widely applied to high-performance perovskite-based photoelectric devices such as biosensors, light-emitting diodes, lasers and the like.
Example 3
Step 1: assembling a two-dimensional compact nanosphere array;
470nm Polystyrene (PS) nanosphere colloidal solution as 2.5wt% by volume ratio with ethanol 1:1, mixing and using, and carrying out ultrasonic treatment for 30-60 min; directly spreading the PS nanospheres on the water surface based on a micro-propulsion injection (MPI) system at a feeding speed of 0.5 mL/h; the solution finally evolves into a two-dimensional hexagonal close-packed PS nanosphere monolayer at the air/water interface; then, the PS nanosphere monolayer is transferred to a preset substrate by slowly pumping water or raising the substrate; the nanospheres are tightly attached to the substrate by self-evaporation or low-temperature baking (below 60 ℃);
step 2: processing the nanosphere array by dry etching;
treating the two-dimensional dense nanosphere array in the step 1 by using an inductively coupled plasma etching machine, and introducing combined gas of oxygen and argon (the power is 100W, the gas flow is 50sccm, and the time is 12 s) to obtain a nanosphere array subjected to dry etching treatment;
and step 3: tiO 2 2 Preparing sol;
mixing titanium isopropoxide (TTIP, 5 mL) with ethanol (45 mL) and acetylacetone (1 mL) as a precursor solution, and stirring uniformly using a magnetic stirrer (stirring speed set at 800rpm to 1200 rpm); hydrochloric acid (0.85 mL) and deionized water (4.5 mL) were then added to the solution and stirred for 5h-8h to form TiO 2 Sol;
and 4, step 4: tiO 2 2 Processing a base nano resonant cavity;
taking the TiO prepared in the step 3 2 20-50 μ L of sol is mixed with the mixture of the sol and the solvent through a spin coaterSpin-coating the nano-array etched in the step 2 at the rotation speed of 1000-2000rpm for 30-60 s; then, transferred to an oven (60-75 ℃,12-24 h) and calcined at 480 ℃ for 2-3h, with the aim of removing the nanospheres and crystallizing the TiO 2 Framework, forming TiO 2 A base nano resonant cavity;
and 5: csPbBrI 2 Preparing a mixture of perovskite precursor solution and PMMA;
by dissolving 0.09mmol CsBr, 0.19mmol CsI, 0.1mmol PbBr in 10mL of N, N-Dimethylformamide (DMF) solvent 2 、0.2mmol PbI 2 A perovskite precursor solution of 0.028mmol/mL was obtained and mixed with 1g of Polymethylmethacrylate (PMMA) powder; wherein, stirring at 800rpm-1200rpm for 30min-60min;
and 6: csPbBrI prepared by scraper method 2 A nanocrystalline composite film;
CsPbBr obtained in step 5 is coated by a scraper film coating machine 3 Coating the mixture of perovskite precursor solution and PMMA on the TiO-containing material in step 4 2 The nano-resonant cavity is arranged on a substrate and is heated on a thermal platform at the temperature of 80-130 ℃ to promote solvent evaporation and nanocrystal growth. Heating for 2-12min, and stripping to obtain CsPbBrI with independent photoluminescence spectrum at 600-700nm wavelength 2 A nanocrystalline composite film;
the preparation of the nano resonant cavity by taking the nanospheres as the auxiliary chemical template is a flexible, low-cost and large-scale preparation method; the special structure and periodic pattern give the material unique light-substance interaction; csPbBrI 2 Photoluminescence (PL) spectrum of nanocrystalline composite films due to TiO 2 The base nano resonant cavity is embedded and strongly reshaped, and the amplitude of PL enhancement can be tuned by changing the resonance of the nano resonant cavity in the composite film; when the resonance of the resonant cavity is tuned to the intrinsic emission peak of the nanocrystal, the emission signal of the coupling system is enhanced; while the spontaneous emission lifetime is shortened, indicating that this enhancement is radiative in nature; the PMMA polymer encapsulation also effectively improves the stability of the nanocrystalline; can be widely applied to high-performance perovskite-based photoelectric devices such as biosensors, light-emitting diodes, lasers and the like.
Photo-inducedThe luminescence spectrum is measured by a LabRAM HR Evolution confocal micro-fluorescence spectrum system; morphology and microstructure observations were made using a Hitachi Regulus8100 Scanning Electron Microscope (SEM). For reference, the photoluminescence spectra of perovskite nanocrystalline thin films not embedded in the nano-resonator were also measured. It is clear that the photoluminescence spectrum of the perovskite nanocrystalline thin film is strongly reshaped by the embedding of the resonator, and the emission signal of the coupled system is enhanced when the resonator resonance is tuned to the intrinsic emission peak of the perovskite nanocrystals, wherein CsPbCl 1.5 Br 1.5 、CsPbBr 3 And CsPbBrI 2 The perovskite nanocrystalline thin film is increased by 3.54 times, 3.89 times and 3.37 times respectively.
Overall, the problem of a single nanoresonator resonance being too weak can be solved by using an array of multiple Mie scatterers, adjacent resonances will effectively enhance the strength of the resonance mode. This enhancement will be further improved as the number of scatterers increases. It is worth mentioning that a nanoresonant cavity prepared by adjusting the etched nanosphere diameter, the metal oxide layer thickness and the lattice size (i.e. the original nanosphere diameter) will significantly increase the resonance intensity, thereby affecting the transmission spectrum;
with the rapid development of micro-nano manufacturing technology, the all-dielectric nano photonic device is widely prepared by combining the processes of Electron Beam Lithography (EBL), reactive Ion Etching (RIE), atomic layer deposition and the like; while these techniques are capable of producing high quality micro/nanostructures, these methods may face bottlenecks of high cost and process design complexity when large area production is involved; the method uses a more convenient chemical strategy for processing, and overcomes the obstacles of micro-nano structure preparation in time, cost and manufacturing area;
the nanoresonators provide an excellent platform for enhancing and tuning the spontaneous emission of a nanoscale light source located in their vicinity, which is crucial for many possible applications of the resonator (e.g., quantum light sources or displays); the photoluminescence spectrum of the perovskite nanocrystalline film is strongly reshaped due to the embedding of the nano resonant cavity, and when the resonant cavity is resonated and tuned to the intrinsic emission peak of the perovskite nanocrystalline, the emission signal of the coupling system is obviously enhanced;
the perovskite nanocrystalline thin film has good stability, and the high molecular polymer enables the PenCs to be mutually separated, thereby preventing further close contact and regeneration; furthermore, the polymer matrix with the compact molecular chains can passivate the perovskite surface and protect it from environmental influences;
the perovskite nanocrystalline thin film has excellent high luminescence and environmental stability, and is an ideal candidate material for a color conversion layer in lighting and display application due to the characteristics of low cost and large-area manufacturing; the manufactured LCD backlight module can reach 122% of the National Television Standards Committee (NTSC) standard and 180% of the traditional commercial screen; these results indicate that perovskite nanocrystalline thin films have great potential for photovoltaic applications.
The described embodiments are intended to embrace all such alterations, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of one or more embodiments of the present disclosure are intended to be included within the scope of the present disclosure.
Claims (10)
1. A packaging structure for enhancing the luminescent property of nanocrystals is characterized in that: the luminescent layer on the innermost layer is a nanocrystal, the resonant cavity on the middle layer is composed of a plurality of metal oxide cavities which are mutually independent, the packaging layer on the outermost layer is a transparent high polymer, when the emission wavelength of the nanocrystal is matched with the resonant cavity, resonance is formed, the luminescence of a coupling system is remarkably enhanced, and the high polymer plays a role in protecting and stabilizing the nanocrystal.
2. The encapsulation structure according to claim 1, wherein the resonant cavity has a shape of a hemisphere, a cone, an inverted pyramid, a polygon, or a barrel.
3. The encapsulation structure according to claim 1, wherein the nanocrystal is any one or a combination of CdS, cdSe, cdTe, znSe, inP, inA conventional nanocrystals and perovskite nanocrystals.
4. The encapsulation structure for enhancing luminescence property of nano-crystal according to claim 3, wherein the perovskite nano-crystal is of general formula ABX 3 Wherein the A site cation comprises MA + (CH 3 NH 3 + )、FA + ([(NH 2 ) 2 CH] + ) And Cs + (ii) a The B site is mainly Pb 2+ Or using different metal ions Sr 2+ 、Zn 2+ 、Ni 2+ 、Mn 2+ 、Cd 2+ 、Sn 2+ 、Co 2+ 、Eu 3+ 、Er 3+ 、Yb 3+ 、Bi 3+ Partial or complete substitution of Pb 2+ ；X＝Cl、Br、I。
5. The method for preparing the encapsulation structure for enhancing the luminescence property of the nanocrystal, according to claim 1, specifically comprising the following steps:
step 1, assembling a two-dimensional dense nanosphere array on a substrate and carrying out dry etching treatment;
step 2, depositing metal oxide sol among the etched nanosphere arrays, and forming a nano resonant cavity by removing nanospheres and crystallizing a metal oxide framework;
step 3, coating the mixture of the nano-crystal or the precursor liquid thereof and the high molecular polymer on a substrate containing a nano resonant cavity, and heating to promote the evaporation of the solvent and the growth of the nano-crystal;
and 4, stripping the substrate to obtain an independent nanocrystal composite film, namely the packaging structure for enhancing the luminescence performance of the nanocrystal.
6. The method for preparing the packaging structure for enhancing the luminescence property of the nanocrystals, according to claim 5, wherein the assembly of the two-dimensional dense nanosphere array is any one of gravity self-assembly method, langmuir-Blodgett deposition, spin coating, electrophoretic deposition, vertical deposition method or MPI system using micro-propulsion injection.
7. The method for preparing the packaging structure for enhancing the luminescence property of the nanocrystal, according to claim 5, wherein the photoluminescence spectrum of the nanocrystal composite film has wavelengths of 400-500nm, 500-600nm, 600-700nm, respectively, wherein,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 400-500nm, the nanospheres are selected as follows: polystyrene spheres with the diameter of 300-370nm and the concentration of 2.5-5 wt%;
when the photoluminescence spectrum of the nanocrystalline composite film is 500-600nm, the selected nanospheres are as follows: polystyrene spheres with a diameter of 370-450nm and a concentration of 2.5-5 wt%;
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 600-700nm, the nanospheres are selected as follows: polystyrene spheres with a diameter of 450-530nm and a concentration of 2.5-5 wt%.
8. The method for preparing the packaging structure for enhancing the luminescence property of the nanocrystal, as recited in claim 5, wherein the dry etching process comprises selecting an inductively coupled plasma etcher to complete the etching, selecting a power of 100-150W, and introducing oxygen and argon into the inductively coupled plasma etcher at a flow rate of 20-50sccm,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 400-500nm, the etching time is 5-9s,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 500-600nm, the etching time is 6-10s,
when the photoluminescence spectrum of the nanocrystalline composite film is at the wavelength of 600-700nm, the etching time is 8-12s.
9. The method for preparing the encapsulation structure for enhancing the luminescence property of the nanocrystal, according to claim 5, wherein the nanospheres are removed and dissolved by dry etching, high temperature calcination or solution of any one of toluene, xylene, chloroform, dichloroethane, acetone, tetrahydrofuran and ethyl acetate.
10. The method for preparing the packaging structure for enhancing the luminescence property of the nanocrystal, according to claim 5, wherein the metal oxide is TiO 2 ,ZnO,VO 2 ,HfO 2 After removing the nanospheres and crystallizing the metal oxide framework, the formed nano resonant cavity can generate resonant peaks with resonant wavelengths of 400-500nm, 500-600nm and 600-700nm to match with the nano crystal or precursor liquid thereof with the photoluminescence spectrum of the nano crystal composite film of 400-500nm, 500-600nm and 600-700 nm.
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