Preparation method of chemical vapor deposition full-inorganic lead halide perovskite thin film

Abstract

The invention discloses a preparation method of a chemical vapor deposition full-inorganic lead halide perovskite thin film. The method comprises the following steps: fixing a substrate in a low-temperature area of a high-temperature tube furnace; preparing a mixed precursor composed of cesium halide, lead halide and tin halide powder; placing the prepared mixed precursor in a heating constant-temperature area in the middle of a tubular furnace; introducing inert gas to form one-way airflow in the tubular furnace; and heating the mixed precursor in the tubular furnace, and reacting for a period of time to obtain the full-inorganic lead halide perovskite thin film. The thickness of the all-inorganic lead halide perovskite thin film can be effectively regulated and controlled by controlling the relative molar ratio of tin halide to lead halide, and the structural defect density in the thin film is effectively reduced, so that the stability of the all-inorganic lead halide perovskite thin film is effectively improved.

Description

Technical Field

[0001] This invention relates to a method for preparing all-inorganic lead halide perovskite thin films by chemical vapor deposition, belonging to the field of optoelectronic materials technology. Background Technology

[0002] All-inorganic lead halide perovskite (CsPbX3 (X=Cl,Br,I)) materials possess unique physicochemical properties and excellent optoelectronic characteristics, leading to extensive research on their applications in optoelectronic devices such as light-emitting diodes, ultra-high-definition displays, photovoltaic cells, lasers, and detectors. In fact, the quality of CsPbX3 thin films, such as grain size, crystallinity, growth orientation, and film thickness, is crucial for improving the performance of optoelectronic devices.

[0003] In recent years, researchers have typically employed solution-based or vapor-phase methods to prepare uniform and high-quality CsPbX3 thin films, and significant progress has been made in this area. However, solution-based methods require toxic solvents, demand high substrate flatness, and are difficult to control over large areas, hindering large-area industrial production of CsPbX3 thin films and limiting their practical applications. In contrast, vapor-phase methods offer advantages for the industrial production of large-area CsPbX3 thin films and are suitable for multilayer film preparation, making them a promising mainstream technology for CsPbX3 thin film preparation. Currently, chemical vapor deposition (CVD) for CsPbX3 thin film preparation allows for control over film crystallinity, crystal orientation, and thickness through optimization of deposition variables (such as precursor dosage, heating temperature, deposition time, deposition pressure, and substrate location). However, the optimization of these deposition variables has limitations and cannot simultaneously achieve the desired results of improved film crystallinity and precise thickness control. For example, reducing the amount of precursor can reduce the thickness of CsPbX3 films but is detrimental to their compactness and density improvement; reducing the deposition time can reduce the thickness of CsPbX3 films but is detrimental to their crystallinity improvement and structural defect density reduction. Therefore, effectively controlling the thickness of chemical vapor deposition CsPbX3 films while reducing their structural defect density is particularly important. Summary of the Invention

[0004] In view of the above-mentioned technical problems in the prior art, the purpose of this invention is to effectively control the thickness of chemical vapor deposition CsPbX3 thin films by incorporating tin halide into cesium halide / lead halide mixed precursors, while reducing structural defects inside the film, thereby effectively improving the stability of CsPbX3 thin films.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for preparing an all-inorganic lead halide perovskite thin film by chemical vapor deposition includes the following steps:

[0007] (1) Fix the substrate in the low-temperature zone of the high-temperature tube furnace;

[0008] (2) Preparation of a mixed precursor composed of cesium halide, lead halide and tin halide powders;

[0009] (3) Place the prepared mixed precursor in the heating and constant temperature zone in the middle of the tube furnace;

[0010] (4) Inert gas is introduced to create a unidirectional airflow inside the tubular furnace;

[0011] (5) The precursor is mixed in a heated tubular furnace and reacted for a period of time to obtain an all-inorganic lead halide perovskite thin film.

[0012] The advantages of this invention compared to existing technologies are summarized as follows:

[0013] (1) Currently, the vapor phase synthesis method mainly obtains CsPbX3 films with controllable thickness by controlling the heating time of the mixed precursors of cesium halide and lead halide. A common method is to reduce the heating time to thin the CsPbX3 film, but due to the short heating time, the quality of the synthesized CsPbX3 film is not high. The technical solution of this invention introduces tin halide powder into the mixed precursors of cesium halide and lead halide using a vapor phase method. On the one hand, by adding tin halide powder with a lower melting point, the "gas-solid" reaction energy barrier and reaction activation energy of the chemical vapor deposition process can be further reduced, promoting the transformation of lead halide into the perovskite phase; on the other hand, the thickness of the CsPbX3 film can be effectively controlled by controlling the relative molar ratio of tin halide to lead halide.

[0014] (2) This invention uses three mixed powder precursors of cesium halide, lead halide and tin halide to prepare CsPbX3 thin films. By increasing the relative molar ratio of tin halide to lead halide, the thickness of CsPbX3 thin films can be reduced without the need to reduce heating time. It can also effectively reduce the density of structural defects inside the film, and more effectively improve the stability of CsPbX3 thin films and enhance the photoelectric properties of CsPbX3 thin films. It is very suitable for the preparation of semiconductor light-emitting devices.

[0015] (3) The entire preparation process of this invention does not require expensive equipment and technology. The preparation process can adjust the process parameters to achieve precise control of the thickness of CsPbX3 film. The prepared film has a uniform structure and composition, good controllability and repeatability, low cost, and can realize large-area production of CsPbX3 film, improve production efficiency and is easy to put into practical use. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the apparatus for implementing the preparation method of the present invention;

[0017] Figure 2The images show cross-sectional scanning electron microscope (SEM) images (a), fluorescence spectra (b), and fluorescence lifetimes (c) of CsPbBr3 thin films prepared with PbBr2 / SnBr2 molar ratios M of 1 / 0 and 1 / 0.1, respectively.

[0018] Figure 3 The images show cross-sectional scanning electron microscope (SEM) images (a), fluorescence spectra (b), and fluorescence lifetimes (c) of CsPbBr3 thin films prepared with PbBr2 / SnBr2 molar ratios M of 1 / 0 and 1 / 0.2, respectively. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0020] The method for preparing all-inorganic lead halide perovskite thin films according to the present invention includes the following steps:

[0021] (1) In a high-temperature tube furnace system, the substrate that has undergone pre-cleaning and pre-treatment is fixed in the downstream low-temperature zone of the tube furnace. The substrate can be sapphire, single crystal silicon wafer, quartz wafer or optical glass, etc.

[0022] (2) Prepare a mixed precursor composed of cesium halide, lead halide and tin halide powders, control the molar ratio of cesium halide, lead halide and tin halide in the mixed precursor, wherein the molar ratio of cesium halide and lead halide is 1:1, and adjust the molar ratio of lead halide and tin halide to be in the range of 1:0.1 to 1.5.

[0023] (3) Place the prepared mixed precursor in the heating and constant temperature zone in the middle of the tube furnace;

[0024] (4) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas pressure in the tubular furnace is adjusted at the same time to keep the gas pressure in the tubular furnace between 0.1 and 200 Pa.

[0025] (5) The temperature of the mixed precursor in the tube furnace is heated to 550-630℃ at a heating rate of 10-20℃ / min, and the reaction time is controlled at 30-60min to finally obtain an all-inorganic lead halide perovskite thin film. This film can be used in optoelectronic devices.

[0026] The preparation apparatus used in this embodiment is as follows: Figure 1 As shown, a sapphire substrate is used. Before preparation, the substrate is pretreated by cleaning: first, the sapphire substrate is rinsed with deionized water, then boiled for 5 minutes with an alkaline cleaning solution composed of NH4OH, H2O2 and H2O in a ratio of 1:2:6, and then rinsed with deionized water. After rinsing, the sapphire substrate is dried.

[0027] Example 1

[0028] (1) In a high-temperature tube furnace system, a sapphire substrate that has been pre-cleaned and dried is fixed in the downstream low-temperature zone of the tube furnace.

[0029] (2) A mixed powder precursor of 0.04 mmol cesium bromide CsBr, 0.04 mmol lead bromide PbBr2 and 0.004 mmol tin bromide SnBr2 was placed in the heating isothermal zone in the middle of a tube furnace, wherein the purity of CsBr, PbBr2 and SnBr2 was 99.99%.

[0030] (3) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas extraction port of the tubular furnace is modulated to keep the gas pressure of the tubular furnace at 30Pa.

[0031] (4) The temperature of the mixed powder precursor in the tube furnace is heated to 630℃, the heating rate is 20℃ / min, and the reaction time is controlled to be 30min to obtain a thin film of all-inorganic CsPbBr3.

[0032] Figure 2 Images (a), (b), and (c) show cross-sectional scanning electron microscope (SEM) images, fluorescence spectra, and fluorescence lifetimes of CsPbBr3 films prepared with PbBr2 / SnBr2 molar ratios M of 1 / 0 and 1 / 0.1, respectively. Compared to CsPbBr3 films prepared using a PbBr2 / SnBr2 mixed powder with a M ratio of 1 / 0 as a precursor under the same conditions, the thickness of the CsPbBr3 film prepared with a M ratio of 1 / 0.1 decreased from 1.8 μm to 1.1 μm. The CsPbBr3 films prepared using the method of this embodiment exhibited an approximately 80% increase in fluorescence intensity, and their fluorescence lifetime increased from 4.35 ns to 14.55 ns. The increase in fluorescence lifetime indicates a reduction in non-radiative recombination centers formed by internal structural defects, leading to the enhanced fluorescence intensity.

[0033] The above results show that, compared with the existing method of reducing deposition time to reduce thickness, which leads to poor synthesis quality, the present invention uses SnBr2 mixed with CsBr / PbBr2 mixed precursor to simultaneously achieve the goals of reducing the thickness of CsPbBr3 film and reducing the density of internal structural defects in the film, and greatly improves the photoelectric properties of CsPbBr3 film.

[0034] Example 2

[0035] (1) In a high-temperature tube furnace system, a sapphire substrate that has been pre-cleaned and dried is fixed in the downstream low-temperature zone of the tube furnace.

[0036] (2) A mixed powder precursor of 0.04 mmol CsBr, 0.04 mmol PbBr2 and 0.008 mmol SnBr2 was placed in the heating isothermal zone in the middle of a tube furnace, wherein the purity of CsBr, PbBr2 and SnBr2 was 99.99%.

[0037] (3) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas extraction port of the tubular furnace is modulated to keep the gas pressure of the tubular furnace at 30Pa.

[0038] (4) The temperature of the mixed powder precursor in the tube furnace is heated to 600℃, the heating rate is 20℃ / min, and the reaction time is controlled to be 30min to obtain CsPbBr3 film.

[0039] Figure 3 Images (a), (b), and (c) show cross-sectional scanning electron microscope (SEM) images, fluorescence spectra, and fluorescence lifetimes of CsPbBr3 films prepared with PbBr2 / SnBr2 molar ratios M of 1 / 0 and 1 / 0.2, respectively. Compared to CsPbBr3 films prepared using a PbBr2 / SnBr2 mixed powder with a M ratio of 1 / 0 as a precursor under the same conditions, the thickness of the CsPbBr3 film prepared with a M ratio of 1 / 0.2 decreased from 1.8 μm to 0.55 μm. The CsPbBr3 films prepared using the method of this embodiment exhibited an order-of-magnitude increase in fluorescence intensity and a fluorescence lifetime increase to 21.12 ns. The increase in fluorescence lifetime indicates that the non-radiative recombination centers formed by internal structural defects further decrease with the increase of the PbBr2 / SnBr2 molar ratio M, leading to a significant increase in fluorescence intensity.

[0040] The above results demonstrate that by controlling the relative molar ratio of PbBr2 / SnBr2, the thickness of CsPbBr3 films can be effectively regulated and the density of internal structural defects can be reduced, making them suitable for different types of optoelectronic device applications.

[0041] Example 3

[0042] (1) In a high-temperature tube furnace system, a sapphire substrate that has been pre-cleaned and dried is fixed in the downstream low-temperature zone of the tube furnace.

[0043] (2) A mixed powder precursor of 0.04 mmol CsBr, 0.04 mmol PbBr2 and 0.06 mmol SnBr2 was placed in the heating isothermal zone in the middle of a tube furnace, wherein the purity of CsBr, PbBr2 and SnBr2 was 99.99%.

[0044] (3) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas pressure in the tubular furnace is adjusted at the same time to keep the gas pressure in the tubular furnace at 0.1 Pa.

[0045] (4) The temperature of the mixed powder precursor in the tube furnace is heated to 580℃, the heating rate is 10℃ / min, and the reaction time is controlled to be 60min to obtain CsPbBr3 film.

[0046] Compared to CsPbBr3 films prepared under the same conditions using a PbBr2 / SnBr2 mixed powder with a precursor ratio of M=1 / 0, the thickness of the CsPbBr3 film prepared with a precursor ratio of M=1 / 1.5 was reduced from 2 μm to 0.25 μm. These results demonstrate that the thickness of the CsPbBr3 film can be effectively controlled by adjusting the relative molar ratio of PbBr2 / SnBr2.

[0047] Example 4

[0048] (1) In a high-temperature tube furnace system, a sapphire substrate that has been pre-cleaned and dried is fixed in the downstream low-temperature zone of the tube furnace.

[0049] (2) A mixed powder precursor of 0.04 mmol cesium chloride (CsCl), 0.04 mmol lead chloride (PbCl2) and 0.06 mmol tin chloride (SnCl2) was placed in the heating isothermal zone in the middle of a tube furnace, wherein the purity of CsCl, PbCl2 and SnCl2 was 99.99%.

[0050] (3) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas extraction port of the tubular furnace is adjusted to keep the gas pressure of the tubular furnace at 50Pa.

[0051] (4) The temperature of the mixed powder precursor in the tube furnace is heated to 550℃, the heating rate is 10℃ / min, and the reaction time is controlled to be 60min to obtain CsPbCl3 film.

[0052] By controlling the relative molar ratio of PbCl2 / SnCl2, it is possible to simultaneously reduce the thickness of CsPbCl3 films and decrease the density of internal structural defects, thereby significantly improving the photoelectric properties of CsPbCl3 films.

[0053] Example 5

[0054] (1) In a high-temperature tube furnace system, a sapphire substrate that has been pre-cleaned and dried is fixed in the downstream low-temperature zone of the tube furnace.

[0055] (2) A mixed powder precursor of 0.04 mmol cesium iodide CsI, 0.04 mmol lead iodide PbI2 and 0.06 mmol tin iodide SnI2 was placed in the heating isothermal zone in the middle of a tube furnace, wherein the purity of CsI, PbI2 and SnI2 was 99.99%.

[0056] (3) Inert gas is introduced to form a unidirectional airflow inside the tubular furnace, and the gas extraction port of the tubular furnace is modulated to keep the gas pressure of the tubular furnace at 200Pa.

[0057] (4) The temperature of the mixed powder precursor in the tube furnace is heated to 600℃, the heating rate is 15℃ / min, and the reaction time is controlled to be 45min to obtain CsPbI3 film.

[0058] By controlling the relative molar ratio of PbI2 / SnI2, the goals of reducing the thickness of CsPbI3 films and reducing the density of internal structural defects can be achieved simultaneously, and the photoelectric properties of CsPbI3 films can be greatly improved.

[0059] There are many methods and approaches to implement the technical solution of this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technology.

Claims

1. A method for preparing an all-inorganic lead halide perovskite thin film by chemical vapor deposition, characterized in that, The preparation method includes the following steps: (1) Fix the substrate in the low-temperature zone of the high-temperature tube furnace; (2) Preparation of a mixed precursor composed of cesium halide, lead halide and tin halide powders; (3) Place the prepared mixed precursor in the heating and constant temperature zone in the middle of the tube furnace; (4) Inert gas is introduced to create a unidirectional airflow inside the tubular furnace; (5) The precursor is mixed in a heated tubular furnace and reacted for a period of time to obtain an all-inorganic lead halide perovskite thin film.

2. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (1), the substrate is sapphire, single-crystal silicon wafer, quartz wafer or optical glass.

3. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (1), the substrate is first cleaned and dried.

4. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (2), the molar ratio of cesium halide to lead halide in the mixed precursor is 1:1, and the molar ratio of lead halide to tin halide is 1:0.1 to 1.

5.

5. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (4), the exhaust port of the tubular furnace is adjusted to keep the gas pressure of the tubular furnace between 0.1 and 200 Pa.

6. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (5), the temperature of the mixed precursor in the heating tube furnace reaches 550-630℃.

7. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (5), the heating rate of the mixed precursor in the heating tube furnace is 10-20℃ / min.

8. The method for preparing a chemical vapor deposition all-inorganic lead halide perovskite thin film according to claim 1, characterized in that, In step (5), the heating reaction time is 30 to 60 minutes.

9. An application of a chemical vapor deposition all-inorganic lead halide perovskite thin film, characterized in that, The all-inorganic lead halide perovskite thin films prepared using the methods of claims 1-8 are applied in optoelectronic devices.

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