Perovskite precursor multicolor aggregation-induced emission modulation method, system and application

Abstract

The invention provides a modulation method and system for perovskite precursor multicolor aggregation-induced emission and application. Dissolving a perovskite precursor component in a polar solvent to prepare a clear or slightly-turbid precursor solution; by adjusting the temperature of the precursor solution to 0-140 DEG C, the precursor solution is excited to generate visible fluorescence under the irradiation of ultraviolet light. When the temperature is 0 DEG C, yellow-green fluorescence can be excited at 30 DEG C, and red-orange fluorescence can be excited at 60 DEG C; after the solvent is volatilized for a long time at the temperature of 140 DEG C, visible fluorescence excited by the residual solution is white light; the temperature is 140 DEG C, and after the volatilized solvent is collected, the excited visible fluorescence is blue light. According to the invention, continuous light-emitting color change from red and yellow to white light and blue can be realized in a single precursor solution system only by means of adjusting the temperature of the solution, and the method has the advantages of rapidness, reversibility, fine controllability and the like. The multicolor light-emitting adjustable system provided by the invention has potential application value in the fields of photoelectric devices and sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic materials, and in particular relates to a method, system and application for modulating multicolor aggregation-induced luminescence of a perovskite precursor. Background Art

[0002] All-inorganic cesium lead halide perovskite (chemical formula CsPbX3, X = Cl, Br, I) nanocrystals are emerging high-performance luminescent materials with a narrow emission spectrum (half-maximum width of only 15-25nm), high defect tolerance, and luminous efficiency exceeding 90%. Light-emitting diode (LED) devices using CsPbX3 perovskite quantum dots as the light-emitting layer have achieved external quantum efficiencies exceeding 20%. However, the emission wavelength of such perovskite nanocrystals is mainly determined by their composition and size. Once prepared, each nanocrystal usually emits only a fixed single color. To obtain multiple luminous colors, nanocrystals of different compositions or sizes need to be synthesized separately and used in combination, which increases the complexity of the process.

[0003] Recent studies have found that a special luminescence phenomenon, namely "aggregation-induced emission" (AIE), also exists in perovskite precursor solutions. For example, a study conducted a systematic photophysical study on CsPbX3 precursor solutions and found that when the precursor concentration increases, the liquid precursor will gradually transform into a colloidal state and show obvious luminescence. This luminescence from the precursor has been shown to be caused by the coordination of solvent molecules with the PbBr2 precursor to form a polybromide lead complex. Specifically, PbBr2 can form two complexes in polar solvents: monocoordinate (PbBr2·solvent) and bidentate (PbBr2·2solvent), which produce photoluminescence peaks at approximately 610nm and 565nm, respectively. In other words, before perovskite nanocrystals are formed, the precursor coordination polymer in the solution itself can emit visible light fluorescence. This phenomenon has expanded people's understanding of the luminescence mechanism of perovskite precursor systems.

[0004] Subsequent studies further showed that the intensity and color of the above-mentioned aggregation-induced emission can be adjusted by changing the chemical conditions of the precursor. For example, different ratios of CsBr:PbBr2 precursors or solvents of different polarities will affect the luminescent properties of the colloidal precursor. Literature reports that by replacing solvents (such as dimethyl sulfoxide DMSO, N-methylpyrrolidone NMP, etc.) or adjusting the precursor ratio, the color and intensity of the luminescence of the precursor solution can be changed to a certain extent. However, these control methods are essentially still in the category of changing the chemical composition or concentration. The operation is relatively cumbersome and it is difficult to achieve continuous and precise adjustment of the luminescence color. In addition, existing research on the AIE of perovskite precursors mainly focuses on factors such as concentration and solvent. The influence of temperature factors has not been reported. There is still a research gap in regulating the multi-color luminescence of precursors by temperature.

[0005] Traditional methods for preparing perovskite luminescent materials include high-temperature hot injection and solution saturation crystallization. For example, Protesescu et al. reported a method for synthesizing perovskite quantum dots using high-temperature hot injection in 2015. Subsequently, there have been reports of perovskite quantum dots prepared using solvent saturation rapid crystallization. However, these liquid-phase synthesis methods require high temperatures and large amounts of organic solvents, resulting in high costs and a heavy environmental burden. To simplify the process, some researchers have developed mechanochemical methods for synthesizing perovskite materials at room temperature. For example, Chinese patent CN114057220A proposes a room-temperature, solvent-free ball milling method for preparing all-inorganic perovskite CsPbX3 nanocrystals. By adding a trace amount of water to the precursor to aid milling, this method eliminates the need for high-temperature heating, inert gas protection, and the use of organic solvents, directly yielding perovskite powders with high luminescence properties. The products produced by this method are highly stable and suitable for large-scale production, reducing production costs. However, the above-mentioned existing technologies focus on the preparation of perovskite nanocrystals themselves and cannot achieve dynamic and adjustable control of luminescent color. In particular, the luminescent peaks of perovskite materials obtained by the above-mentioned methods are usually fixed (for example, CsPbBr3 nanocrystals usually emit green light), and it is impossible to achieve multi-color luminescence in a single system. Summary of the Invention

[0006] The present invention aims to provide a method, system, and application for modulating the multicolor aggregation-induced luminescence of a perovskite precursor to address the prior art issue of perovskite luminescence having a single color and being unable to be dynamically controlled. The method, described herein, can modulate multiple luminescence colors, such as red, yellow, blue, and white, by adjusting the temperature of the perovskite precursor, thereby expanding the functionality and application range of perovskite luminescent materials.

[0007] The multicolor aggregation-induced luminescence modulation method of the perovskite precursor described in the present invention is characterized by comprising the following steps: first, dissolving the perovskite precursor components in a polar solvent to prepare a clear or slightly turbid precursor solution; then, adjusting the temperature of the precursor solution to 0-140°C and exciting the precursor solution under ultraviolet light to produce visible fluorescence.

[0008] Preferably, the perovskite precursor component is an inorganic salt combination of CsX and PbX2 with a molar ratio of 1:1, wherein X is a halide ion.

[0009] Preferably, the concentration of the perovskite precursor in the precursor solution is 0.1 to 0.5 mol / L.

[0010] Preferably, the polar solvent is an aprotic solvent having coordination ability.

[0011] Preferably, the polar solvent is N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP).

[0012] Preferably, the wavelength of the ultraviolet light is 365 nm.

[0013] Preferably, the wavelength of fluorescence generated by the precursor under ultraviolet light excitation is changed by adjusting the temperature of the precursor solution.

[0014] Preferably, when the temperature is 0°C and 30°C, the excited visible fluorescence is yellow-green; when the temperature is 60°C, the excited visible fluorescence is red-orange; when the temperature is 140°C and the solvent evaporates for a long time, the excited visible fluorescence of the remaining solution is white light; when the temperature is 140°C and the volatilized solvent is collected, the excited visible fluorescence is blue light.

[0015] The multicolor aggregation-induced luminescence modulation system for the multicolor aggregation-induced luminescence modulation method of the perovskite precursor is characterized in that it includes a transparent container for accommodating the perovskite precursor, a temperature control device for controlling the temperature of the perovskite precursor solution, and an ultraviolet light source; the temperature control device includes a heater and a cooling device.

[0016] The application of the multicolor aggregation-induced emission modulation system is characterized in that it is used for fluorescent temperature sensor devices and light-emitting devices.

[0017] The precursor salt was dissolved in a solvent at a concentration of 0.1–0.5 mol / L to form a clear or slightly turbid precursor solution. The precursor solution was then heated to 0°C, 30°C, 60°C, and 140°C and illuminated with 365 nm ultraviolet light. The precursor solution emitted visible fluorescence of varying colors, as observed by the naked eye. Lowering the temperature shifted the fluorescence toward shorter wavelengths, while increasing the temperature led to a red shift. Specifically, at low temperatures, such as around 0°C, the precursor solution exhibited a bright yellow-green fluorescence emission with a peak around 560 nm, indicating short-wavelength emission. At around 60°C, the emission gradually transitioned to a predominantly red-orange color with a peak around 600 nm. After prolonged heating at 140°C, which resulted in the evaporation of a large amount of solvent, the remaining solution emitted white light with peaks at approximately 460 and 560 nm, respectively. The solvent evaporated at 140°C, and the fluorescence was observed to shift to blue. This high-temperature blue light emission may originate from the formation of ultrasmall perovskite clusters or nanocrystals.

[0018] This invention enables continuous luminescence color change from red and yellow to white and blue in a single precursor solution system simply by adjusting the solution temperature. Compared to chemical control methods, temperature control offers the advantages of rapidity, reversibility, and precise control. It enables real-time adjustment and precise setting of luminescence color, and the modulation method is simple to operate.

[0019] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0020] 1. Achievement of a multi-color tunable single luminescent system: By applying different temperatures to the same precursor solution, the present invention achieves multiple visible light emission states, including red, yellow, blue, and white. This is an innovative feature that cannot be achieved with traditional perovskite materials (each material typically emits only monochromatic narrow-band fluorescence). In particular, the present invention can achieve near-white light emission, which requires mixing multiple luminescent components in existing perovskite nanocrystals. However, the present invention can achieve this using only a single system through temperature control.

[0021] 2. Simple and precise control: Compared to chemical methods such as adjusting luminescence through changes in precursor concentration, ratio, or doping, the present invention uses physical temperature regulation, which is more convenient and faster. The temperature can be precisely and continuously controlled, making the adjustment of luminescence color highly repeatable and precise, enabling continuous adjustment of multiple luminescence colors without the need for the step-by-step synthesis of different materials as in existing methods.

[0022] 3. Low cost and environmentally friendly process: The raw materials and equipment required for this invention are readily available. Only conventional inorganic salt precursors (such as CsBr and PbBr2) and organic solvents (such as DMF) are required, along with basic heating and cooling equipment. No expensive instruments or specialized reagents are required, reducing experimental and production costs. Compared to some traditional methods that require high-temperature inert atmospheres or complex synthesis steps, this method achieves luminescence modulation through temperature regulation at ambient pressure, making the process relatively environmentally friendly.

[0023] 4. Wide Range of Potential Applications: The multicolor tunable luminescence system provided by this invention has potential applications in optoelectronic devices and sensing. For example, the temperature-responsive luminescent precursor can be used as a fluorescent temperature sensor, directly indicating ambient temperature changes based on the emission color. It can also be combined with excitation sources such as LEDs to achieve the design of light-emitting devices with adjustable color temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1(a) and (b) show the UV-visible absorption and fluorescence emission spectra of CsPbBr3 precursor solutions at 273K, 303K, and 333K, respectively. These figures demonstrate the changes in the absorption edge, luminescence peak position, and intensity of the CsPbBr3 precursor solution as the temperature increases, spectrally demonstrating the effect of temperature on the luminescence properties of the CsPbBr3 precursor. At low temperatures, the absorption edge is relatively blue-shifted, and the emission peak intensity is higher and shifts toward shorter wavelengths. At higher temperatures, the absorption edge is red-shifted, and the emission intensity and peak position change.

[0025] Figure 2 Figures (a) and (b) show the UV-visible absorption and fluorescence spectra, respectively, of the CsPbBr3 precursor solution after volatilization at 413K, as described in Example 4. The figure demonstrates that under these specific conditions, the emission spectrum of the precursor solution covers a broad visible light band, with relatively balanced intensities across the wavelength components, resulting in an emission effect that approximates white light. The absorption spectrum characterizes the presence of precursor species in the solution, while the fluorescence spectrum demonstrates that the solution exhibits both long-wavelength and short-wavelength luminescence centers, achieving white light emission.

[0026] Figure 3 (a) and (b) show the UV-visible absorption and fluorescence spectra of the condensate after condensation of the volatiles collected during the high-temperature evaporation process described in Example 5, respectively. As can be seen in the figure, the condensate after high-temperature evaporation and condensation primarily exhibits a luminescence peak in the short-wavelength region, with blue emission around 460 nm, indicating the formation of luminescent species with smaller size or lower coordination number in the solution. The corresponding absorption spectrum may show a further blue shift, indicating that the energy level structure of the precursor solution changes at high temperature, resulting in blue fluorescence.

[0027] Figure 4 Comparative photographs of the actual luminescence colors of the precursor solutions of Examples 1-5 under 365nm UV illumination are shown, in order: (a) bright yellow-green fluorescence at 273K, (b) yellow-green fluorescence at 303K, (c) reddish-orange fluorescence at 333K, (d) white fluorescence of the precursor solution after evaporation at 413K, and (e) blue fluorescence of the condensate. These visually demonstrate that temperature control significantly changes the luminescence color of the precursor solutions of the present invention, achieving a multi-color modulation effect. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and examples, but the present invention is not limited to these specific examples.

[0029] Example 1: CsPbBr3 precursor solution is excited to emit yellow-green light at 303K

[0030] Weigh 0.4 mmol of anhydrous CsBr and 0.4 mmol of PbBr2 solids, place them in an inert atmosphere, add 2 mL of N,N-dimethylformamide (DMF) solvent, and gently heat and ultrasonically assist to completely dissolve them to obtain a transparent precursor solution with a concentration of 0.2 mol / L.

[0031] The solution was transferred to a sealed quartz cuvette and allowed to stand at room temperature (303K). The cuvette was illuminated with a handheld 365nm UV lamp, and visually observed to reveal yellow-green fluorescence under UV excitation. The emission spectrum, measured using a spectrometer, revealed a peak around 560nm. The nearly uniform fluorescence color indicates that the dominance of the doubly coordinated PbBr2·2 solvent complex is dominant.

[0032] Example 2: The precursor solution is excited to emit red-orange fluorescence at 333K

[0033] A CsBr-PbBr2 / DMF precursor solution with a concentration of 0.2 mol / L was prepared in the same manner as in Example 1.

[0034] The solution was transferred to a sealed quartz cuvette and allowed to stand at 333K. The cuvette was illuminated with a handheld 365nm UV lamp, and visually observed to exhibit reddish-orange fluorescence under UV excitation. Spectrometer measurement of the emission spectrum revealed that the solution's emission peak was primarily located around 600nm, significantly red-shifted compared to the yellow-green fluorescence in Example 1, indicating that the monocoordinated PbBr2·solvate complex dominated the emission.

[0035] Example 3: Bright yellow-green color of the precursor solution excited at 273K

[0036] A CsBr-PbBr2 / DMF precursor solution with a concentration of 0.2 mol / L was prepared in the same manner as in Example 1.

[0037] The solution was transferred to a sealed quartz cuvette, placed in an ice-water bath and cooled to 0°C (273K) and equilibrated for 15 minutes. The cuvette was then irradiated with a handheld 365nm ultraviolet lamp, and the solution was observed to emit obvious yellow-green fluorescence. The emission spectrum was measured using a spectrometer, and the main emission peak was located near 560nm, showing a luminescence characteristic dominated by the bidentate complex of the perovskite precursor. At this time, the visible light absorption spectrum of the solution was blue-shifted relative to 303K and 333K, indicating that the size of the precursor aggregates or the coordination number increased at low temperatures. In the process of restoring the temperature of the 273K precursor solution to 303K and 333K, under the irradiation of the ultraviolet lamp, the precursor solution gradually returned to yellow-green and reddish-orange luminescence, indicating that the luminescence enhancement and blue-shift process caused by the temperature reduction are reversible. The sample was repeatedly switched between 333K and an ice-water bath, and it was found that yellow-green fluorescence was stimulated each time after cooling, and orange-red luminescence was restored when the temperature returned to 333K, proving that the luminescence color change of the precursor solution has reversible thermal regulation properties.

[0038] Example 4: The precursor solution is excited to emit white light at 413K, which is close to the boiling point

[0039] The precursor solution of Example 1 was slowly heated to about 140°C (413K) under ultraviolet light. During the heating process, the light transmittance of the precursor solution increased slightly, indicating that some aggregates dissolved, and the fluorescence color gradually changed from the original yellow-green to a white color with a decreased brightness. When the temperature stabilized at 140°C and the solvent evaporated in large quantities, the naked eye observed a luminescence that was close to white. At this time, the emission spectrum of the solution was obtained. There were two main emission peaks in the 400-700nm band: one was located at about 570nm, green-yellowish light, and the other was located at about 460nm, blue light, and the intensities of the two were close, thus superimposing to produce a comprehensive emission close to white light. This proves that under this temperature condition, the precursor solution of the present invention can simultaneously excite both long-wave and short-wave luminescence centers and obtain white light output. The temperature was maintained for 30 minutes, and the luminescence intensity of the solution decayed slightly but the color remained basically unchanged. After the sample was slowly cooled back to room temperature, its emission state remained unchanged.

[0040] Example 5: High-temperature induced blue luminescent precursor system

[0041] During the high-temperature evaporation process of Example 4, the volatilized solvent was collected, and the condensed solution obtained after condensation was observed to emit obvious blue fluorescence under the irradiation of a purple light lamp. Its emission spectrum peak is about 460nm, which is consistent with the deep blue luminescence characteristics of ultra-small CsPbBr3 nanocrystals reported in the literature. This result shows that the original precursor coordination structure can be broken by high-temperature treatment, inducing the formation of a higher energy level luminescence center and realizing blue light emission. Therefore, this embodiment illustrates that the use of high-temperature means can expand the precursor luminescence to short-wave end blue light.

[0042] From the above examples, it can be seen that the multicolor AIE modulation method of the perovskite precursor provided by the present invention can realize the controllable switching of the luminescent color of a single solution system without introducing additional luminescent components. Within the scope of protection of the present invention, technicians can also make other modifications based on the above principles, such as changing the halogen composition of the precursor, such as partially using Cl - or I - To adjust the luminescence wavelength, or use pulse heating / cooling to achieve rapid luminescence color switching, etc., these equivalent changes all fall within the scope of protection required by the present invention.

[0043] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for modulating multicolor aggregation-induced luminescence of a perovskite precursor, characterized in that: The method comprises the following steps: first, dissolving the perovskite precursor components in a polar solvent to prepare a clear or slightly turbid precursor solution; then, adjusting the temperature of the precursor solution to 0-140° C. and exciting the precursor solution under ultraviolet light to generate visible fluorescence.

2. The multicolor aggregation-induced luminescence modulation method of the perovskite precursor according to claim 1, characterized in that The perovskite precursor component is an inorganic salt combination of CsX and PbX2 with a molar ratio of 1:1, wherein X is a halogen ion.

3. The multicolor aggregation-induced luminescence modulation method of the perovskite precursor according to claim 1, characterized in that The concentration of the perovskite precursor in the precursor solution is 0.1-0.5 mol / L.

4. The multicolor aggregation-induced emission modulation method of a perovskite precursor according to claim 1, characterized in that The polar solvent is an aprotic solvent with coordination ability.

5. The multicolor aggregation-induced emission modulation method of the perovskite precursor according to claim 1, characterized in that The polar solvent is N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP).

6. The multicolor aggregation-induced luminescence modulation method of a perovskite precursor according to claim 1, characterized in that The wavelength of the ultraviolet light is 365 nm.

7. The multicolor aggregation-induced emission modulation method of a perovskite precursor according to claim 1, characterized in that By adjusting the temperature of the precursor solution, the fluorescence wavelength generated by the precursor under ultraviolet light excitation is changed. When the temperature rises from 0°C to 60°C, the excited visible fluorescence light wave shifts from short wave to long wave, and the excited fluorescence wavelength can be restored with temperature cycling.

8. The multicolor aggregation-induced emission modulation method of a perovskite precursor according to claim 1, characterized in that When the temperature is 0°C, the excited visible fluorescence is yellow-green; when the temperature is 30°C, the excited visible fluorescence is yellow-green; when the temperature is 60°C, the excited visible fluorescence is red-orange; at 140°C and after a large amount of solvent evaporates, the excited visible fluorescence of the remaining solution is white light, and the visible fluorescence excited by collecting the solvent evaporated at 140°C is blue light.

9. A multicolor aggregation-induced emission modulation system for a multicolor aggregation-induced emission modulation method of a perovskite precursor according to any one of claims 1 to 8, characterized in that It includes a transparent container for accommodating a perovskite precursor, a temperature control device for controlling the temperature of the perovskite precursor solution, and an ultraviolet light source; the temperature control device includes a heater and a cooling device.

10. Application of the multicolor aggregation-induced emission modulation system according to claim 9, characterized in that Used for fluorescent temperature sensor devices and light-emitting devices.

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