A copper-doped bismuth-based perovskite light-emitting material and a preparation method thereof

Abstract

This invention relates to the field of luminescent materials, specifically disclosing a copper-doped bismuth-based perovskite luminescent material. The structural formula is Cs3Bi2Br9:Cu. 2+ The raw materials include a precursor solution, a CuBr2 ethanol solution, and an oleic acid-ethanol solution. The precursor solution consists of CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine, with the ratio of CsBr:BiBr3:dimethyl sulfoxide:n-octylamine being 0.3–0.5 mmol:0.2–3.3 mmol:5.8–6.3 ml:60–70 μl; the molar ratio of CsBr / BiBr3 is 1.3–1.6. The CuBr2 ethanol solution consists of anhydrous ethanol and CuBr2, with the ratio of anhydrous ethanol:CuBr2 being 2.3–2.6 ml:0.05–0.06 mmol. The oleic acid-ethanol solution consists of the following volume parts: 4.3–5 parts anhydrous ethanol and 0.35–0.6 parts oleic acid; the sum of the volumes of the CuBr2 ethanol solution and the oleic acid-ethanol solution is in the ratio of the volume of the precursor solution to 10:1. The copper-doped bismuth-based perovskite luminescent material in this scheme can improve the photoelectric properties and long-term stability of the material.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials, specifically to a copper-doped bismuth-based perovskite luminescent material and its preparation method. Background Technology

[0002] Perovskite materials are a class of ceramic oxides with special crystal structures, represented by the general chemical formula ABX3. Perovskites, with their unique crystal structure and excellent photoelectric properties, have shown great potential in the field of optoelectronic devices. However, the instability of traditional halide perovskites, especially under high temperature, light, polar solvents, humid environments, and in the presence of oxygen, severely limits their widespread application. Furthermore, lead halide perovskites (LHPs) have made significant progress in the photovoltaic field due to their strong optical absorption, low exciton binding energy, long diffusion length, high carrier mobility, and ease of preparation. However, the lead they contain is highly toxic and does not meet environmental regulations, hindering their promotion in consumer electronics and other fields. Therefore, lead-free perovskite materials are needed. However, tin-based and germanium-based perovskites both suffer from poor chemical stability and are easily oxidized, affecting the photoelectric properties and long-term stability of the materials.

[0003] Currently, although a perovskite / polymer composite luminescent material and its preparation method have been disclosed, such as the one in application number CN201510245596.6, which consists of two parts: perovskite and polymer, with perovskite particles embedded in the molecular gaps of the polymer, the mass ratio of perovskite particles to polymer is: perovskite particles: polymer = 1:(1~50); wherein the structural formula of the perovskite is R1NH3AB3 or (R2NH3)2AB4, where A and B form a coordination octahedral structure, and R1NH3 or R2NH3 fills the gaps between the coordination octahedra formed by A and B, R1 is methyl, R2 is a long-chain organic molecular group, A is any one of the metals Ge, Sn, Pb, Cu, Mn, Sb or Bi, and B is any one of Cl, Br or I; the polymer is any one of polyvinylidene fluoride (PVDF), polyvinyl acetate (PVAc), cellulose acetate (CA), and polysulfone (PSF). However, the aforementioned materials are composites of polymers and lead-based perovskites. Lead perovskites are highly toxic, making them less than satisfactory in terms of environmental protection. Secondly, there are interfacial issues between lead perovskites and polymers, which hinder electron transfer and thus affect photoelectric conversion efficiency. Furthermore, polymers are prone to aging, resulting in poor long-term stability of the materials. Summary of the Invention

[0004] The present invention aims to provide a copper-doped bismuth-based perovskite luminescent material and its preparation method, so as to improve the photoelectric properties and long-term stability of the material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a copper-doped bismuth-based perovskite luminescent material with the structural formula Cs3Bi2Br9:Cu2+.

[0006] Furthermore, the raw materials include a precursor solution, a CuBr2 ethanol solution, and an oleic acid-ethanol solution. The precursor solution contains CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine, with the following ratios: CsBr: BiBr3: dimethyl sulfoxide: n-octylamine: 0.3–0.5 mmol: 0.2–3.3 mmol: 5.8–6.3 ml: 60–70 μl; and the molar ratio of CsBr / BiBr3 is 1.3–1.6.

[0007] The raw materials for the CuBr2 ethanol solution include anhydrous ethanol and CuBr2, with anhydrous ethanol: CuBr2 ratio of 2.3–2.6 ml: 0.05–0.06 mmol.

[0008] The oleic acid-ethanol solution comprises the following parts by volume of raw materials: 4.3-5 parts anhydrous ethanol and 0.35-0.6 parts oleic acid;

[0009] The ratio of the sum of the volumes of CuBr2 ethanol solution and oleic acid-ethanol solution to the volume of the precursor solution is 10:1.

[0010] The beneficial effects of this plan are:

[0011] The copper doping ratio in this scheme refers to Cu 2+ The molar doping ratio is specifically Cu / (Cu+Bi) mol%. After Cu2+ doping, Cu2+ enters the Cs3Bi2Br9 perovskite lattice, causing lattice contraction, thereby reducing the interstitial value of Cs3Bi2X9 perovskite, optimizing the band structure, and improving the material's stability. Simultaneously, it introduces new luminescent centers or improves the electronic transition process, reducing non-radiative transitions and significantly enhancing the material's luminescent quantum yield.

[0012] Compared with other metal doping methods, copper doping is less expensive. Copper is a common metallic element with low cost and abundant reserves. It also enhances photoelectric properties, as copper ions can occupy specific positions in the perovskite structure to form a stable structure. At the same time, it changes the band structure of the perovskite, enhancing its light absorption and charge transport efficiency, thereby improving photoelectric conversion efficiency. Furthermore, it improves stability, as copper ions can form chemical bonds with other elements in the perovskite, further enhancing the stability of the perovskite.

[0013] A method for preparing a copper-doped bismuth-based perovskite luminescent material includes the following steps:

[0014] Step 1: CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine are mixed and completely dissolved in the particulate matter in the solution to obtain a precursor solution;

[0015] Step 2: Mix CuBr2 with anhydrous ethanol and stir until the particulate matter in the solution is completely dissolved to obtain CuBr2 ethanol solution;

[0016] Step 3: Mix anhydrous ethanol with oleic acid to obtain an oleic acid-ethanol solution;

[0017] Step 4: Mix CuBr2 ethanol solution with oleic acid-ethanol solution at 50-90℃, and then inject the mixture into the precursor solution to obtain quantum dot solution;

[0018] Step 5: Separate the supernatant of the quantum dot solution to obtain a colloidal solution.

[0019] In this scheme, the luminescent material exists as a particulate suspension in a colloidal solution, meaning the luminescent particles and the liquid together form a liquid luminescent material. This scheme first prepares a high-concentration CuBr2 ethanol solution, and then the concentration of CuBr2 can be easily adjusted by adding an oleic acid-ethanol solution, thereby improving the purity of the prepared material.

[0020] Furthermore, the stirring temperature in step 1 is room temperature.

[0021] The beneficial effects of this method are: the stirring temperature in this method can better promote the dissolution of CsBr and BiBr3, thereby preparing the precursor solution in a shorter time.

[0022] Furthermore, at least one of steps 1 and 2 involves stirring or ultrasonic dissolution during mixing.

[0023] The beneficial effects of this method are: stirring and ultrasonic dissolution can promote the dissolution of particulate matter more quickly, further improving the preparation efficiency.

[0024] Furthermore, step 4 involves mixing at 70–85°C.

[0025] The beneficial effect of this scheme is that the Cs3Bi2Br9:Cu2+ perovskite quantum dot colloidal fluorescence performance prepared in this scheme is the best.

[0026] Furthermore, the stirring time in step 4 is 5 to 10 minutes.

[0027] The beneficial effects of this scheme are: this scheme can ensure that Cu2+ has enough time to enter the Cs3Bi2Br9 lattice, and the fluorescence performance of the luminescent material is the best.

[0028] Furthermore, step 5 involves separation by centrifugation at a speed of 5000–8000 rpm for 5–10 min.

[0029] The beneficial effects of this scheme are as follows: the luminescent material obtained by this scheme is suspended in colloidal solution in the form of small particles. Since the particle size of the small particles is different, the centrifugal separation of this scheme can separate the relatively larger particles, thereby making the particle size of the remaining liquid material more uniform, and making the luminescent effect of the material more uniform when used in solution.

[0030] Furthermore, in step 5, the liquid material is separated again by centrifugation, with a centrifugation speed of ≥10000 rpm and a centrifugation time of ≥10 min, and the precipitate is separated to obtain the solid material.

[0031] The beneficial effects of this solution are: this solution can further separate the luminescent particles, at which point the luminescent material exists in a solid state, which can be applied to places where liquid is inconvenient to use. Attached Figure Description

[0032] Figure 1 These are microstructure diagrams of the luminescent materials obtained in Examples 2-7 of this invention;

[0033] Figure 2 The fluorescence emission spectrum of the colloidal solution;

[0034] Figure 3 XRD pattern of the material;

[0035] Figure 4 The fluorescence quantum yield diagram of the material;

[0036] Figure 5 This is a graph showing the relationship between the remaining relative fluorescence intensity of the material and the added water content.

[0037] Figure 6 This is a graph showing the relationship between the residual relative fluorescence intensity of the colloidal solution after the addition of 50% water content and time. Detailed Implementation

[0038] The following detailed description illustrates the specific implementation method:

[0039] Example

[0040] A copper-doped bismuth-based perovskite luminescent material, such as Figure 1 As shown, the structural formula is Cs3Bi2Br9:Cu2+. The raw materials include a precursor solution, a CuBr2 ethanol solution, and an oleic acid-ethanol solution.

[0041] The precursor solution consists of CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine, with the following ratios: CsBr:BiBr3:dimethyl sulfoxide:n-octylamine: 0.3–0.5 mmol: 0.2–3.3 mmol: 5.8–6.3 ml: 60–70 μl; and the molar ratio of CsBr / BiBr3 is 1.3–1.6.

[0042] The raw materials for the CuBr2 ethanol solution include anhydrous ethanol and CuBr2, with anhydrous ethanol: CuBr2 ratio of 2.3–2.6 ml: 0.05–0.06 mmol.

[0043] The oleic acid-ethanol solution comprises the following parts by volume of raw materials: 4.3-5 parts anhydrous ethanol and 0.35-0.6 parts oleic acid;

[0044] The ratio of the sum of the volumes of CuBr2 ethanol solution and oleic acid-ethanol solution to the volume of the precursor solution is 10:1.

[0045] This invention also discloses a method for preparing a copper-doped bismuth-based perovskite luminescent material. The specific proportions of the raw materials used in this preparation method are shown below:

[0046] The precursor solution consisted of 0.4 mmol CsBr, 0.268 mmol BiBr3, 6 ml dimethyl sulfoxide, and 66 μl n-octylamine.

[0047] The raw materials for the CuBr2 ethanol solution include 5 ml of anhydrous ethanol and 0.112 mmol of CuBr2;

[0048] The raw materials for the oleic acid-ethanol solution include 4.889 ml of anhydrous ethanol and 0.5 ml of oleic acid;

[0049] The ratio of the sum of the volumes of CuBr2 ethanol solution and oleic acid-ethanol solution to the volume of the precursor solution is 10:1.

[0050] A method for preparing a copper-doped bismuth-based perovskite luminescent material includes the following steps:

[0051] Step 1: Mix CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine, and stir at room temperature until the particulate matter in the solution is completely dissolved to obtain a precursor solution;

[0052] Step 2: Mix CuBr2 with anhydrous ethanol and stir until the particulate matter in the solution is completely dissolved to obtain CuBr2 ethanol solution;

[0053] Step 3: Mix anhydrous ethanol and oleic acid at a volume ratio of 4.889:0.5 to obtain an oleic acid-ethanol solution;

[0054] Step 4: Mix CuBr2 ethanol solution with oleic acid-ethanol solution and stir for 10 min. At 85 °C, while stirring, inject the precursor solution to obtain quantum dot solution.

[0055] Step 5: Centrifuge the quantum dot solution at 5000-8000 rpm for 5-10 minutes to separate the supernatant and obtain the liquid material. In practice, the precipitate in the quantum dot solution can be filtered out first to obtain a colloidal solution, and then the colloidal solution can be centrifuged at 5000-8000 rpm as described above. In this case, the relatively large luminescent particles in the colloidal solution can be separated.

[0056] When solid luminescent particles are needed to be used directly, the liquid material is then separated again by centrifugation at a speed of ≥10000 rpm for ≥10 min, and the precipitate is separated out. This precipitate is the solid material.

[0057] In practice, ultrasonic dissolution can also be used for stirring in steps 1 and 2 to improve the dissolution speed.

[0058] This invention discloses Examples 1 to 7, where the theoretical Cu2+ doping ratios differ. Example 1 has a doping ratio of 0, i.e., Undoped, as shown in Table 1 below:

[0059]

[0060] The luminescent particles obtained in step 5 were washed and dissolved in equal volumes of anhydrous ethanol to obtain sample solutions that met the requirements of ICP testing. Then, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to quantitatively analyze the elemental concentrations in the sample solutions using a standard curve. The contents of Cu and Bi in Examples 1-7 and the actual Cu2+ doping ratios were obtained as follows:

[0061] As shown in Table 2:

[0062]

[0063]

[0064] Since the sample had been treated by centrifugation, washing and re-dissolving before analysis, and the above analysis confirmed that the luminescent material prepared by this method contained Cu2+ ions, it is believed that Cu2+ ions had undergone partial ion exchange with Cs3Bi2Br9 perovskite quantum dots, and Cs3Bi2Br9:Cu2+ luminescent material was prepared.

[0065] The liquid materials prepared in Examples 1-7 were subjected to the following tests:

[0066] I. Fluorescence Emission Spectroscopy (PL) Test: The colloidal solution prepared in step 5 was tested using an FLS1000 stable transient fluorescence spectrometer. The parameters were set as follows: excitation wavelength 380 nm, slit width Ex: 1.03 nm; Em: 1.00 nm, and fast test speed. Please refer to the test results. Figure 2 .

[0067] The results show that the Cu2+-doped materials all exhibited stronger PL values ​​than the undoped Cu2+ materials in Example 1. The PL wavelengths of the Cu2+-doped materials showed a blue shift followed by a red shift in sequence, and Example 3 had the highest fluorescence emission intensity.

[0068] II. X-ray Powder Diffraction (XRD) Testing: The luminescent particles obtained in step 5 of Examples 1-7 were vacuum dried at 50°C for 24 hours to obtain dried powder. A Panalytical X'PERT Pro instrument was used for testing, and the crystal structure of the perovskite was characterized under parameters of 40 kV, 35 mA copper target Ka radiation, and 2θ = 5–60°. The spectral lines were processed using Jade 9 software, and the corresponding standard cards were selected. The tested XRD patterns are shown below. Figure 3 As shown.

[0069] The results show that doping with Cu2+ does not change the crystal structure of Cs3Bi2Br9 perovskite, but due to the radius of the Cu2+ ion... Smaller than the radius of Bi3+ ions When Cu2+ is incorporated into the Cs3Bi2Br9 perovskite lattice, it causes lattice contraction, thereby altering the material's band structure, particularly affecting the energy difference between the valence and conduction bands, i.e., the band gap. Changes in the band gap directly impact the material's optical and electrical properties: a smaller band gap allows the material to more easily absorb visible or infrared light, thus improving its photoelectric conversion efficiency or photocatalytic performance.

[0070] III. Fluorescence Quantum Yield (PLQY) Test: 2 mL of liquid material was placed in a quartz cuvette and tested at room temperature using an FLS980 fluorescence spectrometer (Edinburgh Instruments, UK). A specific 375 nm excitation source was selected, and the lifetime was obtained using software processing. Then, the emission quantum yield was obtained using an integrating sphere in the fluorometer. Finally, the quantum yield was calculated using the Edinburgh L980 software package. The results are shown below. Figure 4 As shown.

[0071] The results show that the PLQY of Example 3 was increased by 102% compared with Example 1, which indicates that doping effectively improved the fluorescence performance of Cs3Bi2Br9:Cu2+.

[0072] IV. Water Stability Test: Take 2 ml of the colloidal solution prepared in step 5, and add 0.0 ml, 0.2 ml, 0.4 ml, 0.6 ml, 0.8 ml, 1.0 ml, 1.5 ml, and 2.0 ml of ultrapure water respectively to conduct a water gradient stability experiment. To investigate the stability of bismuth-based perovskite nanocrystals after Cu2+ doping, the perovskite prepared with the optimal doping ratio and the undoped perovskite were dispersed in 50% water, and the relative fluorescence intensity of the two at different times was tested to obtain fluorescence change curves. The test results are as follows. Figure 5 and Figure 6 As shown.

[0073] The results show that Cu was doped 2+ The fluorescence intensity of Cs3Bi2Br9 quantum dots initially increased and then decreased after the addition of water. The fluorescence intensity reached its maximum when 0.8 ml of water was added, reaching 120% of the fluorescence intensity of Example 1. When the perovskites of Examples 3 and 1 were dispersed in 50% water, the fluorescence intensity also initially increased and then decreased over time. After standing for 18 hours, the quantum dots doped with Example 3 still maintained a relative fluorescence enhancement of 106%, and consistently maintained a stronger relative fluorescence intensity than those of Example 1.

[0074] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a copper-doped bismuth-based perovskite luminescent material, characterized in that: The structural formula of the luminescent material is Cs3Bi2Br9:Cu 2+ The preparation method includes the following steps: Step 1: CsBr, BiBr3, dimethyl sulfoxide, and n-octylamine are mixed and completely dissolved in the particulate matter in the solution to obtain a precursor solution; Step 2: Mix CuBr2 with anhydrous ethanol and stir until the particulate matter in the solution is completely dissolved to obtain CuBr2 ethanol solution; Step 3: Mix anhydrous ethanol with oleic acid to obtain an oleic acid-ethanol solution, wherein the oleic acid-ethanol solution comprises the following raw materials in volume parts: 4.3-5 parts of anhydrous ethanol and 0.35-0.6 parts of oleic acid; Step 4: Mix CuBr2 ethanol solution with oleic acid-ethanol solution, and then inject the precursor solution at 50~90℃ to obtain quantum dot solution; Step 5: Separate the supernatant of the quantum dot solution to obtain a colloidal solution.

2. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 1, characterized in that: The concentrations of CsBr:BiBr3:dimethyl sulfoxide:n-octylamine were 0.3~0.5 mmol:0.2~3.3 mmol:5.8~6.3 ml:60~70 μl; the molar ratio of CsBr / BiBr3 was 1.3~1.

6. The anhydrous ethanol: CuBr2 content is 2.3~2.6 ml: 0.05~0.06 mmol; The ratio of the sum of the volumes of the CuBr2 ethanol solution and the oleic acid-ethanol solution to the volume of the precursor solution is 10:

1.

3. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 1, characterized in that: At least one of steps 1 and 2 involves stirring or ultrasonic dissolution during mixing.

4. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 3, characterized in that: The stirring temperature in step 1 is room temperature.

5. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 1, characterized in that: Step 4: Inject the precursor solution at 85°C.

6. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 1, characterized in that: Step 4: Mix CuBr2 ethanol solution with oleic acid-ethanol solution and stir for 10 min.

7. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 1, characterized in that: Step 5 involves centrifugation at a speed of 5000-8000 rpm for 5-10 minutes to separate the clear liquid and obtain the liquid material.

8. The method for preparing a copper-doped bismuth-based perovskite luminescent material according to claim 7, characterized in that: The liquid material from step 5 is separated again by centrifugation at a speed of ≥10000 rpm for ≥10 min, and the precipitate is separated to obtain the solid material.

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