Laser annealing method and device for perovskite thin film

Abstract

The invention discloses a laser annealing method and device for a perovskite thin film, and belongs to the technical field of solar cells, and the method comprises the steps: 1, scanning a perovskite wet film coated on a substrate through first laser, carrying out the laser-assisted crystallization, enabling the perovskite wet film to be converted into a perovskite crystal structure from a low crystal structure, and obtaining a perovskite intermediate phase thin film; step 2, irradiating the perovskite intermediate phase thin film by using second laser to perform laser-assisted crystal growth, promoting growth of perovskite crystal grains, and removing the residual solvent in the perovskite intermediate phase thin film to obtain a perovskite thin film; through first-time laser-assisted crystallization and second-time laser-assisted crystal growth, the crystal quality in the formed perovskite thin film can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a laser annealing method and apparatus for perovskite thin films. Background Technology

[0002] With increasing global emphasis on renewable energy and growing environmental awareness, the solar cell industry is poised for even greater development. Perovskite thin films, acting as light-absorbing layers in solar cells, efficiently absorb sunlight and convert it into electricity. Their high light absorption coefficient and efficient charge separation capabilities significantly enhance the photoelectric conversion efficiency of solar cells.

[0003] The production of perovskite thin films generally involves dissolving perovskite material in a solvent to form a perovskite precursor solution, coating the perovskite precursor solution onto a substrate to form a perovskite wet film, and then annealing the perovskite wet film to form a perovskite thin film.

[0004] In existing technologies, the annealing of perovskite wet films typically involves using a tunnel furnace or layered furnace, where heat generated by an infrared filament is transferred to the perovskite wet film substrate via a fan. However, this method results in slow substrate heating, and the heat conducted by the hot air causes the surface of the perovskite wet film to dry and crystallize before the interior, potentially leading to ineffective removal of residual solvents and impacting crystallization quality and the interface between the perovskite layer and the transport layer. Existing technologies also employ laser annealing of perovskite wet films to obtain thin perovskite films, but this usually involves a single infrared laser annealing process. This method suffers from rapid shrinkage of the perovskite wet film volume, insufficient time for solute diffusion, and consequently, a rough surface and continuous cracking at grain boundaries in the resulting perovskite film. Summary of the Invention

[0005] In view of one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a laser annealing method and apparatus for perovskite thin films, which performs laser-assisted crystallization and laser-assisted crystal growth in two separate laser processes to ensure the uniformity of the film formation.

[0006] To achieve the above objectives, one aspect of the present invention provides a laser annealing method for perovskite thin films, comprising: Step 1: using a first laser to scan a wet perovskite film coated on a substrate to perform laser-assisted crystallization, thereby obtaining a perovskite mesophase thin film;

[0007] Step 2: Laser-assisted crystal growth is performed by irradiating the perovskite mesophase film with a second laser to obtain the perovskite film;

[0008] Wherein, the first laser is an infrared laser, and the wavelength of the second laser is between 420 and 700 nm, or the second laser is an infrared laser.

[0009] As a further improvement of the present invention, the wavelength of the first laser is 1000-1200 nm, and / or the power density of the first laser is 5-10 W / cm². 2 And / or the scanning speed of the first laser is 1000 to 5000 mm / s.

[0010] As a further improvement of the present invention, the focal point of the first laser is set in the middle, lower or bottom of the perovskite wet film.

[0011] As a further improvement of the present invention, the wavelength of the second laser is any value between 420 and 700 nm, or one or more narrowband bands in the 420-700 nm band, and / or the power density of the second laser is 0.1-10 W / cm². 2 And / or the single irradiation time of the second laser is 2 to 10 seconds.

[0012] As a further improvement of the present invention, the power density of the second laser is 6-10 W / cm². 2 The pulse width is 10–50 ns, and the single pulse energy is 0.1–0.5 mJ.

[0013] As a further improvement of the present invention, the wavelength of the second laser is 1000-1200 nm, and / or the power density of the second laser is 0.1-1 W / cm². 2 The single irradiation time of the second laser is 10 to 30 seconds.

[0014] As a further improvement of the present invention, in step one, the first laser scans once or multiple times to complete the assisted crystallization of the perovskite wet film; and / or,

[0015] In step two, the second laser irradiates the perovskite mesophase film once or multiple times to assist in crystal growth.

[0016] As a further improvement of the present invention, step one further includes temperature control of the substrate, wherein the temperature is controlled to be -10 to 50°C; and / or,

[0017] Step two also includes temperature control of the substrate, with the temperature controlled at 50-60°C.

[0018] As a further improvement of the present invention, steps one and two are carried out in an inert atmosphere or a reducing atmosphere.

[0019] In another aspect, the present invention provides a laser annealing apparatus for perovskite thin films, for implementing the laser annealing method for the above-mentioned perovskite thin films, comprising a support stage, a laser processing mechanism, and a motion mechanism;

[0020] The support platform is used to support the substrate, the laser processing mechanism includes a first laser processing module capable of emitting a first laser and a second laser processing module capable of emitting a second laser, and the motion mechanism is used to change the relative position of the support platform and the laser processing mechanism.

[0021] As a further improvement of the present invention, the first laser processing module includes a galvanometer and a field lens; the second laser processing module includes a Z-axis moving module and modules such as a second laser processing head and an optical shaping lens disposed on the Z-axis moving module.

[0022] As a further improvement of the present invention, the first laser processing module and the second laser processing module are set at two different workstations, and the support platform is moved to the two workstations respectively under the drive of the horizontal motion module; or, the first laser processing module and the second laser processing module are set at the same workstation.

[0023] As a further improvement of the present invention, a temperature control module is provided inside the support platform to control the temperature of the substrate; and / or,

[0024] It also includes a cavity that is connected to a ventilation device to introduce an inert gas or a reducing gas into the cavity through the ventilation device.

[0025] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0026] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0027] The laser annealing method for perovskite thin films of this invention significantly reduces annealing time and improves production efficiency compared to traditional thermal annealing. In contrast to single-stage laser annealing, which leads to rapid shrinkage of the perovskite wet film volume and insufficient time for solute diffusion, resulting in a rough surface and continuous cracking at grain boundaries, the laser annealing method of this invention, through two laser annealing processes (assisted crystallization + assisted crystal growth), forms a gradient annealing process. This effectively reduces the evaporation rate of organic solvents, slows down the film crystallization rate, and effectively improves the crystal quality of the formed perovskite thin film. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a SEM image of perovskite crystals after thermal annealing in the existing technology;

[0030] Figure 2 This is a schematic diagram of the structure of a laser annealing device for perovskite thin films in one embodiment of the present invention;

[0031] Figure 3 This is a simplified process diagram of step one in the laser annealing method for perovskite thin films according to an embodiment of the present invention;

[0032] Figure 4 This is a simplified process diagram of step two in the laser annealing method for perovskite thin films according to an embodiment of the present invention;

[0033] Figure 5 This is a process flow diagram of a laser annealing method for perovskite thin films according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the structure of a laser annealing device for perovskite thin films in another embodiment of the present invention;

[0035] Figure 7 This is a simplified process diagram of a laser annealing method for perovskite thin films according to another embodiment of the present invention;

[0036] Figure 8 This is a process flow diagram of a laser annealing method for perovskite thin films according to another embodiment of the present invention;

[0037] Figure 9a This is a high-magnification optical image of a perovskite wet film coated on a substrate in one embodiment of the present invention;

[0038] Figure 9b yes Figure 9a A high-magnification optical image of a perovskite wet film after laser-assisted crystallization in step one of an embodiment of the present invention.

[0039] Figure 10 This is a SEM image of a perovskite film treated with the laser annealing method of a perovskite film according to an embodiment of the present invention.

[0040] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1, support stage; 2, first laser processing module; 21, first laser processing head; 22, first laser; 3, second laser processing module; 31, second laser processing head; 32, second laser; 4, substrate; 5, cavity; 6, perovskite wet film; 7, perovskite mesophase film; 8, perovskite film. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] In the description of this invention, it should be understood that, unless otherwise expressly specified and limited, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] Furthermore, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0046] Example:

[0047] Please see Figure 2 ~Figure 9, the laser annealing method for perovskite thin films in a preferred embodiment of the present invention includes:

[0048] Step 1: Use the first laser 22 to scan the perovskite wet film 6 coated on the substrate 4 to perform laser-assisted crystallization. The perovskite wet film 6 is transformed from a low crystallinity to a perovskite crystal structure, and a perovskite mesophase film 7 is obtained.

[0049] Step 2: Use the second laser 32 to irradiate the perovskite mesophase film 7 to perform laser-assisted crystal growth, promote the growth of perovskite grains, and remove the remaining solvent in the perovskite mesophase film 7 to obtain the perovskite film 8.

[0050] Specifically, the perovskite wet film 6 is generally prepared by uniformly coating a perovskite precursor solution onto a substrate 4 using spin coating or blade coating. Preferably, the substrate 4 is pre-wetted before coating to prevent uneven coating of the perovskite precursor solution. This perovskite precursor solution can be FAPbI3, MABrI3, or MAPbI3, etc. Those skilled in the art will understand that a conductive layer is disposed near the perovskite wet film 6 on the substrate 4. The substrate 4 described in this invention includes a conductive layer. Furthermore, those skilled in the art will understand that it can also include the structure prior to the coating of the perovskite wet film in the existing perovskite solar cell fabrication process.

[0051] Furthermore, in step one, the first laser 22 is used to assist crystallization by laser scanning. The heat generated by the laser removes most of the solvent in the perovskite wet film 6, making the solution supersaturated, crystal nuclei precipitate, and perovskite mesophase film 7 is obtained. At this time, the light yellow or light green precursor solution on the substrate 4 is transformed into a dark yellow or dark brown film, and the deposited wet film changes from low crystallinity to light-absorbing perovskite crystal structure.

[0052] Preferably, in step one, the first laser 22 is a continuous infrared laser with a wavelength between 1000 and 1200 nm, which can be 1000 nm, 1050 nm, 1064 nm, 1100 nm, 1150 nm or 1200 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the focal point of the first laser 22 is set in the middle, lower or bottom of the perovskite wet film 6 to heat both the surface and bottom of the perovskite precursor solution. This avoids the phenomenon of surface crystallization first and heat transfer not reaching the bottom, effectively removing residual solvent in the solution. At the same time, it also allows the substrate to absorb the laser heat and guide the solvent to evaporate at high speed to achieve supersaturated precipitation and crystallization, thereby improving the crystal quality of the subsequently prepared perovskite thin film 8.

[0054] Preferably, the spot size of the first laser 22 is not less than 0.5 cm. 2 Laser-assisted crystallization can be completed in a single scan or multiple scans; the power density of the first laser 22 is 5–10 W / cm². 2 The scanning speed ranges from 1000 to 5000 mm / s, depending on the specific requirements. For example, in actual settings, a low scanning rate can be selected to complete the scan in one operation, or a high scanning rate can be selected to complete the scan in multiple operations. For instance, if the scanning speed of the first laser 22 is set to 2000 mm / s, a single scan will be completed; or if the scanning speed of the first laser 22 is set to 4000 mm / s, two scans will be performed.

[0055] As will be understood by those skilled in the art, the first laser processing can be performed using a first laser processing module comprising a galvanometer and a field lens. Since the processing area of ​​a single laser processing device is limited, the processing of the perovskite wet film on the entire substrate can be completed by changing the relative position of the first laser processing module and the substrate. For example, the processing of the perovskite wet film on the entire substrate can be accomplished by moving the first laser processing module or by moving the substrate. For processing large-area products, the processing efficiency can also be improved by increasing the number of first laser heads.

[0056] Using the method of this invention, the instantaneous high-temperature treatment by the first laser in a short time can induce the removal of organic solvents in the perovskite wet film, establish supersaturation conditions, accelerate perovskite nucleation, and increase the nucleation density, thereby achieving assisted crystallization of the perovskite wet film. Rapid cooling after the first laser treatment can effectively prevent thermal diffusion and unnecessary diffusion effects. The rapid sweep of the first laser can improve the coarsening of perovskite grains, and the rapid and multiple processing by the first laser can reduce the evaporation rate of organic solvents and slow down the crystallization process of the perovskite mesophase film 7. By controlling the power density and scanning rate of the first laser, the grain size of the subsequently prepared perovskite film 8 can be precisely and effectively controlled, reducing the formation of pores.

[0057] Preferably, when using the first laser 22 to assist in the crystallization of the perovskite wet film 6, the temperature of the substrate 4 can be controlled to provide a uniform base temperature environment for the perovskite wet film 6. In the preferred embodiment, the substrate 4 is placed on the support stage 1 during processing. The temperature of the bottom of the substrate 4 can be controlled by the support stage 1, with the temperature controlled between -10°C and 50°C. The base temperature is uniformly transferred to the perovskite wet film 6 through the substrate 4, forming temperature control of the perovskite wet film 6. Then, the temperature difference between the instantaneous high temperature formed by the first laser 22 and the base temperature is used to induce crystallization, which can better control the crystallization rate, allowing the crystal nuclei to grow in an orderly manner in the early stage, and generating regular grain morphology after reaching the crystallization temperature in the later stage.

[0058] Furthermore, in one embodiment of the present invention, in step two, the wavelength of the second laser 32 can be any value between 420 and 700 nm, for example, it can be 425 nm or 650 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Alternatively, one or more narrowband bands in the 420 nm to 700 nm band can be selected as the light source of the second laser 32.

[0059] Preferably, the spot size of the second laser 32 is not less than 5 cm. 2 The power density is 0.1–10 W / cm³. 2 The specific value is determined based on the nucleation size, ordered growth state, and grain size of the perovskite thin film, among other crystal growth effects. More preferably, the power density of the second laser 32 is 6–8 W / cm². 2 The pulse width is between 10 and 50 ns, and the single pulse energy is between 0.1 and 0.5 mJ. In actual operation, the second laser 32 can be used to assist in the growth of perovskite mesophase thin film 7 by one or multiple irradiations, with an irradiation time of 2 to 10 seconds.

[0060] Because the perovskite layer has a large coefficient of thermal expansion, while the conductive layer of substrate 4 has a small coefficient of thermal expansion, continuing laser-assisted crystal growth using the first laser 22 would lead to the perovskite layer peeling off from the substrate. Furthermore, using an ultraviolet laser for annealing the perovskite film would result in the perovskite film ablation, causing the perovskite material to transform into an amorphous state. Therefore, after obtaining the perovskite mesophase film 7 using the first laser 22 for assisted crystallization, this invention employs a second laser 32, which has characteristics such as high photon energy, high single-pulse energy, short pulse time, large spot area, uniform energy distribution, and low thermal effect, to perform laser-assisted crystal growth on the perovskite mesophase film 7. This avoids the high-temperature decomposition and failure of the perovskite film and the problem of peeling off from the substrate, and effectively reduces the surface defect concentration of the perovskite film 8.

[0061] In another embodiment of the present invention, in step two, the second laser 32 is a continuous infrared laser with a spot size of 50mm×50mm to 180mm×180mm. In actual operation, a large spot size can be obtained by means of optical shaping modules, etc., with a power density of 0.1 to 1W / cm². 2 The irradiation time is 10-30 seconds. It is understood that in step two of this embodiment, although infrared laser-assisted crystal growth is also used, compared to the first laser 22, the second laser 32 in step two uses a low-power-density infrared laser. Combined with a longer irradiation time, this allows heat to penetrate from the film surface into the film interior, thereby controlling the longitudinally ordered growth of the perovskite crystals. This also avoids the high-temperature decomposition and failure of the perovskite film and the problem of peeling off from the substrate, and effectively reduces the surface defect concentration of the perovskite film 8.

[0062] Compared to the rapid shrinkage of the perovskite wet film caused by a single annealing process, which leaves insufficient time for solute diffusion and leads to problems such as rough surface and continuous cracking at grain boundaries, the laser annealing method for perovskite films in this invention, through two laser annealing processes (assisted crystallization + assisted crystal growth), forms a gradient annealing process. This effectively reduces the evaporation rate of organic solvents, slows down the crystallization rate of the film, and effectively improves the crystal quality in the formed perovskite film.

[0063] As those skilled in the art will know, the irradiation time in step two refers to the irradiation time acting on a unit area. It should be noted that, for ease of understanding, the unit area here can be the size of the laser spot.

[0064] As will be understood by those skilled in the art, when processing a perovskite mesophase thin film on an entire substrate, the processing of the entire perovskite film layer can be completed by the relative movement of the second laser and the perovskite substrate. For example, by moving the processing module including the second laser, or by moving the substrate, the second laser can complete the processing of the entire perovskite substrate.

[0065] Preferably, in step two, the temperature of the substrate 4 can be further controlled to provide a uniform temperature control environment for the perovskite mesophase film 7. The controlled temperature is 50-60°C. At this time, the laser power density of the second laser 32 can be appropriately reduced, and / or the irradiation time of the second laser can be reduced.

[0066] Preferably, steps one and two are performed in a protective gas atmosphere that is isolated from air, to prevent the perovskite wet film 6 and the perovskite mesophase film 7 from reacting with water vapor in the air. The protective gas can be an inert gas such as nitrogen or argon, or other protective gases such as reducing gases.

[0067] Furthermore, in a preferred embodiment of the present invention, the laser annealing apparatus for the perovskite thin film 8 includes a support stage 1, a laser processing mechanism, and a motion mechanism. The support stage 1 supports the substrate 4 coated with the perovskite wet film 6, and the motion mechanism changes the relative position between the support stage 1 and the laser processing mechanism. For example, the motion mechanism causes the laser processing mechanism and the support stage 1 to move relative to each other in the X-axis, Y-axis, and Z-axis directions. The laser processing mechanism completes the processing of the entire area of ​​the perovskite wet film 6, thereby achieving assisted crystallization and assisted crystal growth of the perovskite wet film 6.

[0068] Preferably, the support platform 1 is equipped with a temperature control module to control the temperature of the substrate 4 placed on the support platform 1. In actual installation, the temperature control module can be a resistance heating device, infrared heating device, etc., installed in the support platform 1 to heat the support platform 1, or a water cooling module or other cooling equipment can be provided to cool the support platform 1.

[0069] Furthermore, the laser processing mechanism includes a first laser processing module 2 and a second laser processing module 3; wherein, the first laser processing head 21 of the first laser processing module 2 can emit a first laser 22 to perform laser scanning-assisted crystallization on the perovskite wet film 6 on the substrate 4, forming a perovskite mesophase thin film 7. In this application, the first laser processing head 21 is a laser processing device including a galvanometer and a field lens, realizing rapid scanning.

[0070] Accordingly, the second laser processing head 31 of the second laser processing module 3 can emit a second laser 32 to irradiate the perovskite mesophase thin film 7 with laser-assisted crystal growth, forming a perovskite thin film 8. In this application, the second laser processing head 31 can be mounted on a linear motor to control its movement.

[0071] Preferably, in one embodiment of the present invention, the first laser processing module 2 and the second laser processing module 3 are respectively disposed at two workstations, such as... Figure 2As shown, the carrier platform 1 is first moved to the workstation where the first laser processing module 2 is located, and then transferred to the workstation where the second laser processing module 3 is located after the first laser processing module 2 has finished processing.

[0072] Preferably, in another embodiment of the present invention, the first laser processing module 2 and the second laser processing module 3 are arranged at the same workstation, such as... Figure 6 As shown, while the first laser processing module 2 is scanning, the second laser processing module 3 also follows closely behind to be irradiated.

[0073] Furthermore, the motion mechanism includes a horizontal motion module and a lifting module. The horizontal motion module can move along the X and Y axes, and the lifting module can move along the Z axis. In actual installation, the support platform 1 can be connected and mounted on the horizontal motion module, allowing the support platform 1 to move relative to the laser processing mechanism along the X and Y axes. The laser processing mechanism can be mounted on the lifting module, allowing the laser processing mechanism to move relative to the support platform 1 along the Z axis. In this invention, the lifting module controls the first laser processing module 2 to move up and down to adjust the focus of the first laser 22, so that the focus of the first laser 22 is located in the middle, lower or bottom of the perovskite wet film 6 on the substrate 4. At the same time, in this invention, if the substrate is small in size (e.g., less than or equal to 180mm × 180mm), the second laser 32 does not need to move the X and Y axes during processing, and large spot irradiation is sufficient. For processing larger substrates, the support stage 1 or the laser processing mechanism can be set on the horizontal motion module and the lifting module at the same time, as long as the movement of the laser processing mechanism relative to the support stage 1 in the X, Y and Z axis directions can be realized to complete the laser focal length adjustment and complete the processing configuration of the entire area of ​​the substrate 4.

[0074] Preferably, the system further includes a cavity 5, and both the support platform 1 and the laser processing mechanism are sealed inside the cavity 5. The cavity 5 is connected to a ventilation device to introduce protective gas into the cavity 5, thus isolating the processing environment from the outside air. In another embodiment, the laser processing mechanism is located outside the cavity 5, and a transparent glass is provided on the upper part of the cavity 5. The first laser 22 and the second laser 32 process the material on the support platform 1 through the transparent glass.

[0075] Furthermore, the operation method for preparing the perovskite thin film 8 using the laser annealing device of the present invention is as follows:

[0076] (1) First clean or wet the substrate 4, then coat the perovskite precursor solution on the substrate 4 by spin coating or scraping to form a perovskite wet film 6; in actual operation, it is necessary to ensure uniform coating so that the formed perovskite wet film 6 is relatively uniform.

[0077] (2) Place the substrate 4 carrying the perovskite wet film 6 on the support stage 1.

[0078] (3) The horizontal motion module controls the carrier platform 1 to move in the horizontal direction, so that the substrate 4 moves to the processing position of the first laser processing module 2; the lifting module controls the first laser processing module 2 to perform lifting motion to adjust the focus of the output first laser 22, so that the focus of the first laser 22 is located in the middle, lower or bottom of the perovskite wet film 6 on the substrate 4.

[0079] (4) The first laser processing module 2 outputs a first laser 22, and the horizontal motion module controls the movement of the support platform 1, so that the first laser 22 performs one or more laser scans on the entire perovskite wet film 6 to obtain a perovskite mesophase thin film 7, such as Figure 3 As shown in the image.

[0080] During operation, the light yellow or light green perovskite wet film 6 on the substrate 4 is transformed into a dark yellow or dark brown film after being scanned by the first laser 22, indicating that the deposited perovskite wet film 6 has changed from low crystallinity to light-absorbing perovskite crystal structure, thus obtaining a perovskite mesophase film 7.

[0081] This invention compares high-magnification optical images of the perovskite wet film 6 and the perovskite mesophase film 7 before and after processing by the first laser processing module 2. See [link to relevant documentation]. Figure 9a Before processing, the perovskite wet film 6 exhibits a dendritic, needle-like branched structure. Figure 9a (As shown in the red box), the crystal nuclei have varying morphologies, have not yet begun to grow, have low crystallinity, and exhibit stacking. See also Figure 9b After processing by the first laser 22, the crystal nuclei of the perovskite mesophase film 7 formed become larger, the stacking phenomenon of crystal nuclei is weakened, and the overall structure is arranged in a polycrystalline structure. This indicates that the use of near-infrared laser can effectively promote the drying and crystallization of perovskite wet film 6.

[0082] (5) The horizontal motion module controls the carrier platform 1 to move to the processing position of the second laser processing module 3. The second laser processing module 3 outputs the second laser 32. The horizontal motion module controls the carrier platform 1 to move, so that the second laser 32 irradiates the entire perovskite mesophase film 7 once or multiple times, to obtain the perovskite film 8, such as... Figure 4 As shown in the image.

[0083] like Figure 5 As shown, the perovskite mesophase film 7 obtained after scanning and assisted crystallization by the first laser 22 is in a semi-wet and semi-dry state, with some solvent remaining. After being irradiated and assisted by the second laser 32 to grow crystals, the remaining solvent in the film is removed, and the growth of perovskite grains is promoted, resulting in a perovskite film 8 formed from the perovskite dry film.

[0084] The SEM image of the perovskite film 8 obtained through the above steps is shown below. Figure 10 As shown in the image. Figure 1These are SEM images of perovskite crystals after thermal annealing in existing technologies. The comparison shows that the perovskite film 8 obtained using the annealing method of this invention has larger perovskite grains, clearer and more complete grain boundaries, fewer pores, and smaller gaps between grains.

[0085] Preferably, when the first laser processing module 2 and the second laser processing module 3 in the laser annealing apparatus are set in the same station, by controlling the movement of the support stage 1, the same area of ​​the perovskite wet film 6 passes through the first laser processing module 2 and the second laser processing module 3 in sequence. It is not necessary to wait for the first laser 22 to perform auxiliary crystallization on the entire area. After the first laser 22 scans, the second laser 32 immediately follows with a scan, completing steps (4) and (5) in one station. Figure 7 and Figure 8 As shown, the process of obtaining a perovskite mesophase film 7 by crystallization assisted by the first laser 22 and the process of obtaining a perovskite film 8 formed by crystal growth assisted by the second laser 32 are more continuous, which improves the overall annealing efficiency, increases the continuity of operation, simplifies equipment design, and reduces necessary labor costs. At the same time, it can reduce the time interval between the action of the first laser 22 and the second laser 32, thereby effectively reducing the probability of disordered growth of the perovskite mesophase film 7 during the intermediate interval, so that the grains in the film can grow in an orderly manner.

[0086] The laser annealing method for perovskite thin films in this invention greatly reduces annealing time and improves production efficiency compared with traditional thermal annealing.

[0087] Compared to the rapid shrinkage of the perovskite wet film caused by a single laser annealing process, which leaves insufficient time for solute diffusion and leads to problems such as rough surface and continuous cracking at grain boundaries, the laser annealing method for perovskite films in this invention, through two laser annealing processes (assisted crystallization + assisted crystal growth), forms a gradient annealing process. This effectively reduces the evaporation rate of organic solvents, slows down the crystallization rate of the film, and effectively improves the crystal quality in the formed perovskite film.

[0088] The laser annealing method for perovskite thin films in this invention utilizes laser processing. The first laser can heat the material to a high temperature in an extremely short time (typically on the nanosecond level or higher), and the wet perovskite film cools rapidly after the laser treatment ends, effectively preventing thermal diffusion and unnecessary diffusion effects. Simultaneously, rapid heating and cooling removes the solvent from the film, achieving a supersaturated state.

[0089] The laser annealing method and apparatus for perovskite thin films in this invention, compared with traditional layered furnace and other thermal annealing methods, can complete the thin film crystallization process of large-area perovskite modules at high speed, realize the film formation of large-area modules, and accelerate the industrialization process.

[0090] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser annealing method for perovskite thin films, characterized in that, include: Step 1: Use a first laser to scan the perovskite wet film coated on the substrate and perform laser-assisted crystallization to obtain a perovskite mesophase film; Step 2: Laser-assisted crystal growth is performed by irradiating the perovskite mesophase film with a second laser to obtain the perovskite film; Wherein, the first laser is an infrared laser, and the wavelength of the second laser is between 420 and 700 nm, or the second laser is an infrared laser.

2. The laser annealing method for perovskite thin films according to claim 1, characterized in that, The wavelength of the first laser is 1000–1200 nm, and / or the power density of the first laser is 5–10 W / cm². 2 And / or the scanning speed of the first laser is 1000 to 5000 mm / s.

3. The laser annealing method for perovskite thin films according to claim 1, characterized in that, The focal point of the first laser is located in the middle, lower or bottom of the perovskite wet film.

4. The laser annealing method for perovskite thin films according to claim 1, characterized in that, The wavelength of the second laser is any value between 420 and 700 nm, or one or more narrowband bands within the 420-700 nm band, and / or the power density of the second laser is 0.1-10 W / cm². 2 And / or the irradiation time of the second laser is 2 to 10 seconds.

5. The laser annealing method for perovskite thin films according to claim 4, characterized in that, The power density of the second laser is 6–10 W / cm². 2 The pulse width is 10–50 ns, and the single pulse energy is 0.1–0.5 mJ.

6. The laser annealing method for perovskite thin films according to claim 1, characterized in that, The second laser is an infrared laser with a wavelength of 1000–1200 nm, and / or the power density of the second laser is 0.1–1 W / cm². 2 The irradiation time of the second laser is 10 to 30 seconds.

7. The laser annealing method for perovskite thin films according to any one of claims 1 to 6, characterized in that, In step one, the first laser scans once or multiple times to assist in the crystallization of the perovskite wet film; and / or, In step two, the second laser irradiates the perovskite mesophase film once or multiple times to assist in crystal growth.

8. The laser annealing method for perovskite thin films according to any one of claims 1 to 6, characterized in that, Step one also includes temperature control of the substrate, controlling the temperature to be -10 to 50°C; and / or, Step two also includes temperature control of the substrate, with the temperature controlled at 50-60°C.

9. The laser annealing method for perovskite thin films according to any one of claims 1 to 6, characterized in that, Steps one and two are carried out in an inert or reducing atmosphere.

10. A laser annealing apparatus for perovskite thin films, characterized in that, A laser annealing method for realizing the perovskite thin films of claims 1 to 9 includes a stage, a laser processing mechanism, and a motion mechanism; The support platform is used to support the substrate, the laser processing mechanism includes a first laser processing module capable of emitting a first laser and a second laser processing module capable of emitting a second laser, and the motion mechanism is used to change the relative position of the support platform and the laser processing mechanism.

11. The laser annealing apparatus for perovskite thin films according to claim 10, characterized in that, The first laser processing module includes a galvanometer and a field mirror; the second laser processing module includes a Z-axis moving module and a second laser processing head disposed on the Z-axis moving module.

12. The laser annealing apparatus for perovskite thin films according to claim 10, characterized in that, The first laser processing module and the second laser processing module are set at two different workstations, and the support platform moves to the two workstations respectively under the drive of the motion mechanism; or, The first laser processing module and the second laser processing module are located at the same workstation.

13. The laser annealing apparatus for perovskite thin films according to any one of claims 10 to 12, characterized in that, The support platform is equipped with a temperature control module to control the temperature of the substrate; and / or, It also includes a cavity that is connected to a ventilation device to introduce an inert gas or a reducing gas into the cavity through the ventilation device.

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