Preparation method of cesium-lead-iodine perovskite

Abstract

The invention relates to the field of nano materials, in particular to a preparation method of cesium-lead-iodine perovskite. A hot injection method is adopted for synthesis, the operation is simple, and the pure inorganic red light perovskite quantum dots are synthesized in cooperation with Zn ion doping and subsequent centrifugation in a non-glove box environment. The efficient synthesis of the pure inorganic red light perovskite ink is realized, and the subsequent ink printing problem caused by the impure perovskite in the synthesis is also avoided.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials, and particularly to a preparation method of cesium lead iodide perovskite. Background Art

[0002] In 2012, the International Telecommunication Union (ITU) issued the "ITU-R Recommendation BT2020" (Rec.2020) for Ultra-High Definition Televisions (UHDTV). The color gamut area of this standard covers 75.8% of the CIE chromaticity diagram, where the coordinates of red, green, and blue are (0.708, 0.292), (0.170, 0.797), and (0.131, 0.046) respectively. It is also the color gamut standard for 4K digital displays and has a high recognition rate. When the CIE coordinates of a red perovskite LED are closer to (0.708, 0.292), its color purity is higher. Moreover, only when the electroluminescence (EL) peak is within the wavelength range of 620 nm - 650 nm, the LEDs within this range are defined as pure red perovskite LEDs.

[0003] This literature (Nano Letters, 2015, 15(6), 3692 - 3696) first reported the synthesis of pure inorganic cesium lead halide perovskite by the hot injection method, using CsPbI with a conventional single-component halogen composition 3 Quantum dots have a relatively narrow bandgap, and the emission peak is usually located at 680 nm. Its PL emission peak is still after 680 nm, which cannot meet the requirements of high-definition displays for red color purity. By regulating the halogen components, the bandgap and emission position of the mixed-halide CsPbBrxI3-x can be precisely adjusted to achieve pure red emission. However, the migration of halogen ions will lead to phase separation, which seriously affects the color stability and working stability of pure red PeLEDs. Summary of the Invention

[0004] Aiming at the above-mentioned deficiencies of CsPbI 3 quantum dots synthesized by the traditional hot injection method, the present invention provides a preparation method of cesium lead iodide perovskite.

[0005] The technical solution of the present invention is realized as follows: A preparation method of cesium lead iodide perovskite is provided, including the following steps:

[0006] S1. Synthesize a cesium source precursor: Add octadecene, oleic acid, and cesium carbonate to a reactor in sequence, and stir in a vacuum environment at 100 °C - 150 °C until cesium carbonate is completely dissolved to form cesium oleate;

[0007] S2. Prepare a halogen lead salt: Mix ODE, Pbl 2 and Znl 2, oleic acid, and oleylamine are successively added to the reactor, and deoxygenation and dehydration stirring are carried out in a vacuum environment at 100 °C - 150 °C until the solution becomes clear and light yellow;

[0008] S3. Preparation of perovskite: Adjust the temperature of the prepared halogen lead salt to the reaction temperature of 140 °C - 160 °C, take 10 - 15% volume equivalent of the cesium source precursor, quickly inject it into the halogen lead salt, react for 3 - 7 s, and then quickly cool down to below 90 °C;

[0009] S4. Separation: Centrifuge at 16 °C - 20 °C and 7000 rpm - 9000 rpm for 4 min - 10 min, discard the precipitate and take the supernatant. After adding an anti-solvent to the supernatant, centrifuge again to obtain a cesium lead iodide perovskite precipitate. Cool down to prevent the grains from continuing to grow and resulting in uneven sizes. Thus, a crude perovskite solution is obtained, which needs further separation.

[0010] In one embodiment of the present invention, in the step S1, the molar ratio of the addition of octadecene, oleic acid, and cesium carbonate is (5 - 20):4:(0.5 - 3).

[0011] In one embodiment of the present invention, in the step S2, the molar ratio of the addition of ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine is (5 - 20):1:3:4:4.

[0012] In one embodiment of the present invention, in the step S4, the precipitate separated by the first centrifugation is large-sized CsPbI 3 and Zn 2+ , unreacted precursors. The precipitate has a darker color and is black, and there are yellow bad spots. Discard the precipitate and take the supernatant for secondary separation.

[0013] In one embodiment of the present invention, in the step S4, the volume ratio of the supernatant to methyl acetate during the second centrifugation is 1:(1 - 3); the centrifugation conditions after mixing with the anti-solvent are: centrifuge at 16 °C - 20 °C and 7000 rpm - 9000 rpm for 4 min - 10 min. It should be noted that a layer of precipitate sticking to the tube wall indicates good dispersibility. In addition, the lower the temperature, the more beneficial it is for the separation of CsPbI 3 , but the freezing point of ODE is at 14 - 16 degrees Celsius, so the centrifugation temperature is set at 16 - 20 degrees Celsius.

[0014] In one embodiment of the present invention, in the step S4, a third centrifugation is further included, and the specific process is as follows:

[0015] The supernatant after the second centrifugation is added with an anti-solvent equivalent to 80-110% of the volume and then centrifuged again. The centrifugation conditions are: centrifugation at 16°C - 20°C and 7000 rpm - 9000 rpm for 4 min - 10 min.

[0016] In one embodiment of the present invention, in step S4, the anti-solvent is at least one of methyl acetate, acetonitrile or 1-butanol.

[0017] The beneficial effects are as follows:

[0018] In the present invention, by adding ZnI in the traditional hot injection method 2 as a co-precursor and surface passivator, this process inhibits the further growth of CsPbI nanocrystals, thereby achieving size control, and thus controlling the position of the EL peak, and preparing pure red light CsPbI 3 quantum dots with the EL peak located at 620 - 650 nm. And through multiple centrifugations, nanocrystals with different particle sizes are separated, so that the CsPbI 3 perovskite ink meets the usage standards of LEDs. Description of the Drawings

[0019] Figure 1 Schematic diagram of the preparation process of red light CsPbI 3 perovskite.

[0020] Figure 2 PL characterization diagram of the ink prepared using red light CsPbI 3 perovskite. Detailed Description of the Embodiments

[0021] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] The present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0023] In the past decade, perovskite light-emitting diodes (LEDs) have witnessed rapid development, and their performance in various aspects is gradually catching up with that of organic light-emitting diodes (OLEDs), showing great potential to become the main force of the next-generation ultra-high-definition display technology. Among them, as one of the three primary colors of displays, the development of red perovskite LEDs is crucial. Pure red light emission in the range of 620 - 650 nm is essential for high-definition displays and is the key issue. However, it is not easy to regulate red light emission by controlling the size of strongly quantum-confined nanocrystals. Moreover, when the quantum dot size is reduced, the surface area-to-volume ratio of the quantum dots will increase rapidly, which will exacerbate the negative impact of surface defects on the optical properties of quantum dots, thereby increasing the challenge of manufacturing high-performance LEDs.

[0024] The pure inorganic red light CsPbI involved in the present invention 3 The main preparation process of the perovskite is as Figure 1 shown. When synthesizing pure inorganic red light perovskite by the hot injection method, ZnI is added to the halogen precursor 2 to create an iodine-rich environment and limit the growth of nanocrystals. At the same time, unreacted Zn is removed during the subsequent centrifugal separation process 2+ . This not only realizes the efficient synthesis of pure inorganic red light perovskite ink but also avoids the subsequent ink printing problems caused by the impurity of perovskite during synthesis.

[0025] Example 1

[0026] Preparation steps of cesium lead iodide perovskite:

[0027] The first step is to synthesize the cesium source precursor: Octadecene, oleic acid, and cesium carbonate are successively added to the reactor and stirred in a vacuum environment at 100 °C until cesium carbonate is completely dissolved to form cesium oleate; the molar ratio of octadecene, oleic acid, and cesium carbonate added is 20:4:3.

[0028] The second step is to prepare the halogen lead salt: ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine are successively added to the reactor and deoxygenated and dehydrated and stirred in a vacuum environment at 150 °C until the solution becomes clear and light yellow; the molar ratio of ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine added is 5:1:3:4:4.

[0029] The third step is the preparation of perovskite: The temperature of the prepared halogen lead salt is adjusted to the reaction temperature of 140 °C, and 16% of the cesium source precursor is taken and quickly injected into the halogen lead salt, and after reacting for 3 s, it is quickly cooled to 90 °C;

[0030] Step 4, First separation: Centrifuge at 16 °C and 7000 rpm for 10 min, discard the precipitate and take the supernatant; Second centrifugation: Mix the supernatant with 100% volume equivalent of acetonitrile and centrifuge at 16 °C and 7000 rpm for 10 min to obtain a cesium lead iodide perovskite precipitate. Dissolve the precipitate in non-polar solvents such as octane, DMSO, DMF, etc. for subsequent research and characterization. After testing, the PL excitation peak is 640 - 650 nm, and the PLQY can reach 77 - 85%.

[0031] Example 2

[0032] Preparation steps of cesium lead iodide perovskite:

[0033] Step 1, Synthesis of cesium source precursor: Add octadecene, oleic acid, and cesium carbonate to the reactor in sequence, and stir in a vacuum environment at 150 °C until cesium carbonate is completely dissolved to form cesium oleate; The molar ratio of octadecene, oleic acid, and cesium carbonate added is 5:4:0.5.

[0034] Step 2, Preparation of halogen lead salt: Add ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine to the reactor in sequence, and deoxygenate and dehydrate and stir in a vacuum environment at 100 °C until the solution becomes clear and light yellow; The molar ratio of ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine added is 20:1:3:4:4.

[0035] Step 3, Preparation of perovskite: Adjust the temperature of the prepared halogen lead salt to the reaction temperature of 160 °C, take 1.7 ml of the cesium source precursor, quickly inject it into the halogen lead salt, react for 7 s, and then quickly cool down to 90 °C;

[0036] Step 4, First separation: Centrifuge at 20 °C and 9000 rpm for 4 min, discard the precipitate and take the supernatant; Second centrifugation: Mix the supernatant with 300% volume equivalent of 1-butanol and centrifuge at 9000 rpm for 4 min to obtain a cesium lead iodide perovskite precipitate. Dissolve the precipitate in alkanes such as octane and hexane to obtain a stable perovskite colloid for subsequent characterization. After testing, under 365 nm excitation, the excitation peak is located at 640 - 650 nm. Under TEM observation, the crystal grains are uniformly arranged, of the same size, and the size does not exceed 15 nm. The PLQY can reach 70 - 80%.

[0037] Example 3

[0038] Preparation steps of cesium lead iodide perovskite:

[0039] First step, synthesize the cesium source precursor: Add octadecene, oleic acid, and cesium carbonate to the reactor in sequence, and stir in a vacuum environment at 120 °C until cesium carbonate is completely dissolved to form cesium oleate; the molar ratio of octadecene, oleic acid, and cesium carbonate added is 16:4:3.

[0040] Second step, prepare the lead halide salt: Add ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine to the reactor in sequence, and carry out deoxygenation and dehydration stirring in a vacuum environment at 120 °C until the solution becomes clear and light yellow; the molar ratio of ODE, Pbl 2 , Znl 2 , oleic acid, and oleylamine added is 10:1:3:4:4.

[0041] Third step, prepare perovskite: Adjust the temperature of the prepared lead halide salt to the reaction temperature of 150 °C, take 10% of the cesium source precursor, and quickly inject it into the lead halide salt and react for 5 s, then quickly cool down to below 70 °C.

[0042] Fourth step, the first separation: Centrifuge and separate at 18 °C and 8000 rpm for 5 min, discard the precipitate and take the supernatant; the second centrifugation: Mix the supernatant with methyl acetate at a volume ratio of 1:2, and the centrifugation conditions are 18 °C and 8000 rpm for 5 min to obtain large-sized cesium lead iodide perovskite precipitate; the third centrifugation: Add 90% volume equivalent of methyl acetate to the supernatant after the second centrifugation and then centrifuge and separate, and the centrifugation conditions are: 18 °C and 8000 rpm for 5 min to obtain small-sized cesium lead iodide perovskite precipitate. Dissolve the two cesium lead iodide perovskite precipitates obtained above in an acrylic monomer solution, and add 3-8% photoinitiator to prepare a photocurable ink. The PL characterization diagram is as Figure 2 shown.

[0043] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing cesium lead iodine perovskite, characterized in that: The steps include: S1. Synthesizing a cesium source precursor: adding octadecene, oleic acid and cesium carbonate to a reactor in sequence, and stirring under a vacuum environment at 100°C-150°C until cesium carbonate is completely dissolved to generate cesium oleate; S2. Prepare halogen lead salt: ODE, Pbl2, Znl2, oleic acid, and oleylamine are sequentially added to the reactor, and deoxygenated and dehydrated under vacuum at 100°C-150°C with stirring until the solution is clear and light yellow; S3. Preparation of perovskite: The prepared halogen lead salt temperature is adjusted to a reaction temperature of 140°C-160°C, 10-15% volume equivalent of the cesium source precursor is taken, and it is rapidly injected into the halogen lead salt and reacted for 3-7s and then rapidly cooled to below 90°C; S4. Separation: centrifuge at 16°C-20°C and 7000rpm-9000rpm for 4min-10min, discard the precipitate and take the supernatant, add anti-solvent to the supernatant and centrifuge again to obtain cesium lead iodine perovskite precipitate.

2. The method for preparing cesium lead iodine perovskite according to claim 1, characterized in that: In the step S1, the molar ratio of octadecene, oleic acid and cesium carbonate added is (5-20):4:(0.5-3).

3. The method for preparing cesium lead iodine perovskite according to claim 1, characterized in that: In the step S2, the added molar ratio of ODE, Pbl2, Znl2, oleic acid and oleylamine is (5-20):1:3:4:

4.

4. The method for preparing cesium lead iodine perovskite according to claim 1, characterized in that: In the step S4, during the second centrifugation, the mixed volume ratio of the supernatant and the methyl acetate is 1:(1-3); the centrifugation conditions after mixing with the anti-solvent are: 16°C-20°C, 7000rpm-9000rpm, and centrifugal separation for 4min-10min.

5. The method for preparing cesium lead iodine perovskite according to claim 4, characterized in that: The step S4 also includes a third centrifugation, and the specific process is as follows: The supernatant after the second centrifugation is added with 80-110% volume equivalent of anti-solvent and then centrifuged again. The centrifugation conditions are: 16° ​​C.-20° C., 7000 rpm-9000 rpm, centrifugation for 4 min-10 min.

6. The method for preparing cesium lead iodine perovskite according to claim 1, characterized in that: The anti-solvent is at least one of methyl acetate, acetonitrile or 1-butanol.

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