A flexible piezoelectric energy harvester and method of making the same

Abstract

The application discloses a flexible piezoelectric energy collector and a preparation method thereof, and comprises the following steps: forming a patterned sacrificial layer on a first surface of a substrate; forming a bottom electrode on a surface of the sacrificial layer away from the substrate; forming a piezoelectric layer on a surface of the bottom electrode away from the sacrificial layer by using a parity layer differential annealing process; forming a top electrode on a surface of the piezoelectric layer away from the bottom electrode; etching the sacrificial layer to transfer the piezoelectric structure to a flexible substrate to obtain the flexible piezoelectric energy collector. By implementing the application, the sacrificial layer is patterned, the device etching and peeling time is reduced, and the transfer success rate is improved; when the piezoelectric layer is formed, each thin film is subjected to heat treatment once, and the heat treatment processes of the odd layers and the even layers are different, so that the piezoelectric layer thin film has high compactness, thereby improving the output performance of the finally formed collector. In addition, the finally prepared flexible piezoelectric energy collector can be used for collecting vibration energy in a power scene, and meets the current vibration energy collection demand.

Description

Technical Field

[0001] This invention relates to the field of electric energy harvesting technology, specifically to a flexible piezoelectric energy harvester and its preparation method. Background Technology

[0002] With the continuous advancement of smart grids, the number of parameters that need to be monitored is increasing, making the power supply problem of online monitoring devices more and more prominent. Currently, common power supply methods for online monitoring devices include battery power, solar power, laser power, and vibration power. However, there are abundant sources of vibration energy in the power environment, such as transmission lines, and vibration energy harvesters have the characteristics of simple structure and high energy density. Therefore, vibration energy harvesting has a very promising application prospect in powering online monitoring devices for transmission lines.

[0003] However, the following problems remain to be solved in the fabrication process of vibration energy harvesters for power applications: (1) Flexible energy harvesters with deformability have great advantages in power applications in order to adapt to various irregular power equipment, but the current transfer process for transferring devices from rigid substrates to flexible substrates has defects such as low success rate and complex steps; (2) The output performance of vibration energy harvesters is generally weak, and vibration energy harvesters with piezoelectric ceramics as the core functional material are prone to piezoelectric layer fatigue and desquamation during long-term operation; (3) The power environment is complex and harsh, and there is currently a lack of packaging process methods that can effectively protect the core structure of energy harvesters for power applications. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a flexible piezoelectric energy harvester and its preparation method to solve the technical problems of low device preparation success rate, poor harvester output performance and insufficient reliability in actual power field applications in the prior art, which cannot meet the current requirements for vibration energy harvesting.

[0005] The technical solutions provided by the embodiments of the present invention are as follows:

[0006] The first aspect of this invention provides a method for fabricating a flexible piezoelectric energy harvester, comprising: forming a patterned sacrificial layer on a first surface of a substrate; forming a bottom electrode on the surface of the sacrificial layer away from the substrate; forming a piezoelectric layer on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process; forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode; and etching the sacrificial layer to transfer the piezoelectric structure including the bottom electrode, the piezoelectric layer, and the top electrode onto a flexible substrate, thereby obtaining a flexible piezoelectric energy harvester.

[0007] Optionally, a piezoelectric layer is formed on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process, comprising: forming a PZT film of a predetermined number of layers on the surface of the bottom electrode away from the sacrificial layer, wherein the predetermined number of layers is even; wherein the formation process of the odd-numbered PZT film involves spooling a layer of PZT precursor solution, drying it in an oven at 180℃-200℃ for 5-6 minutes, and preheating it in a muffle furnace at 340℃-360℃ for 5-6 minutes; the formation process of the even-numbered PZT film involves spooling a layer of PZT precursor solution, drying it in an oven at 180℃-200℃ for 5-6 minutes, preheating it in a muffle furnace at 340℃-360℃ for 5-6 minutes, and annealing it in a muffle furnace at 580℃-620℃ for 8-10 minutes.

[0008] Optionally, forming a bottom electrode on the surface of the sacrificial layer away from the substrate includes: forming a titanium thin film layer on the surface of the sacrificial layer away from the substrate; forming a platinum thin film layer on the surface of the titanium thin film away from the sacrificial layer; and performing wet etching on the titanium thin film layer and the platinum thin film layer to obtain a patterned bottom electrode.

[0009] Optionally, forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode includes: forming a chromium thin film layer on the surface of the piezoelectric layer away from the bottom electrode; forming a gold thin film layer on the surface of the chromium thin film layer away from the bottom electrode; and performing wet etching on the chromium thin film layer and the gold thin film layer to obtain a patterned top electrode.

[0010] Optionally, after forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the method further includes: forming an encapsulation layer on a first surface of the substrate, the encapsulation layer covering the bottom electrode, the piezoelectric layer, and the top electrode, and exposing the electrode leads of the bottom electrode and the top electrode; and forming a protective layer on the surface of the encapsulation layer away from the substrate.

[0011] Optionally, etching the sacrificial layer to transfer the piezoelectric structure, including the bottom electrode, piezoelectric layer, and top electrode, onto a flexible substrate to obtain a flexible piezoelectric energy harvester includes: cutting the substrate carrying the complete piezoelectric structure of the bottom electrode, piezoelectric layer, and top electrode into several small pieces; etching the sacrificial layer to peel the small pieces of piezoelectric structure off the substrate; forming a polyimide gel on the flexible substrate; contacting the small pieces of piezoelectric structure with a PDMS film, removing the piezoelectric structure from the substrate and transferring it onto the polyimide gel, and performing a curing process to obtain the flexible piezoelectric energy harvester.

[0012] Optionally, after forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the process further includes etching the formed piezoelectric layer to obtain a patterned piezoelectric layer.

[0013] Optionally, after forming the bottom electrode on the surface of the sacrificial layer away from the substrate, the process further includes drying the substrate in a muffle furnace at a temperature of 350°C-450°C.

[0014] A second aspect of the present invention provides a flexible piezoelectric energy harvester, which is prepared using the preparation method of the flexible piezoelectric energy harvester described in the first aspect and any one of the first aspects of the present invention.

[0015] Optionally, the bottom electrode, piezoelectric layer, and top electrode are arranged in a stepped manner.

[0016] The technical solution of this invention has the following advantages:

[0017] The method for fabricating a flexible piezoelectric energy harvester provided in this invention employs patterning of the sacrificial layer to reduce device etching and peeling time and improve transfer success rate. During the formation of the piezoelectric layer, each film layer undergoes a heat treatment, with different heat treatment processes used for odd-numbered and even-numbered layers. This results in highly dense piezoelectric layer films, thereby improving the output performance of the final harvester. Furthermore, the resulting flexible piezoelectric energy harvester can be used for collecting vibration energy in power applications, meeting current vibration energy harvesting requirements.

[0018] The flexible piezoelectric energy harvester fabrication method provided in this invention is geared towards power applications. It enhances the adhesion between the bottom electrode and the flexible substrate by sputtering a titanium thin film and spin-coating polyimide gel to prevent fatigue-induced delamination of the core structural layer during long-term operation. A flexible polyimide encapsulation layer is fabricated on the critical structure using spin-coating and stepped curing processes. This effectively protects the critical structure from the complex environment of power applications while ensuring the device's flexible deformation performance. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the fabrication method of the flexible piezoelectric energy harvester in this embodiment of the invention;

[0021] Figure 2 The diagram shows the structural block diagrams corresponding to the various steps of the preparation method of the flexible piezoelectric energy harvester in the embodiments of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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 also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] This invention provides a method for fabricating a flexible piezoelectric energy harvester, such as... Figure 1 As shown, the preparation method includes the following steps:

[0027] Step S101: A patterned sacrificial layer is formed on the first surface of the substrate. Specifically, a rigid substrate, such as a silicon wafer, is selected. After selecting the substrate, a sacrificial layer film is formed on the substrate surface. During subsequent transfer, the structure on the sacrificial layer can be released by etching. In addition, the formed sacrificial layer can also prevent the subsequent bottom electrode from conducting with the silicon substrate. The sacrificial layer film is formed on the first surface of the substrate using SiO2 material and a dry-wet oxidation method. The thickness of the sacrificial layer film is approximately 1 μm. After forming the sacrificial layer film, it can be patterned using photolithography, which can increase the contact area between the etchant and the sacrificial layer in the subsequent wet etching release process, and shorten the time for the device to be peeled off from the silicon wafer.

[0028] In one embodiment, the patterned sacrificial layer is mainly achieved by the following steps: spin-coating BP212 photoresist onto the SiO2 sacrificial layer film at a spin speed of 2300 r / min, and patterning the photoresist by pre-baking, mask exposure, and development, and completely etching away the SiO2 film not protected by the photoresist in HF acid buffer solution to complete the pre-patterning of the SiO2 sacrificial layer film and obtain the patterned sacrificial layer.

[0029] Step S102: A bottom electrode is formed on the surface of the sacrificial layer away from the substrate. Specifically, titanium and platinum are used when forming the bottom electrode. That is, a titanium layer is formed before forming the platinum thin film. Forming the titanium thin film first can enhance the adhesion of the platinum metal. In addition, platinum metal has good physicochemical stability and can guide the cell growth of the subsequent piezoelectric layer.

[0030] Step S103: A piezoelectric layer is formed on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process. The piezoelectric layer is formed from a PZT precursor solution through a heat treatment process. Specifically, a heat treatment can be performed after each PZT film layer is formed, and the heat treatment processes for odd and even layers are different. The resulting piezoelectric layer film has high density, thereby improving the output performance of the final collector.

[0031] Step S104: A top electrode is formed on the surface of the piezoelectric layer away from the bottom electrode; specifically, the top electrode is composed of chromium metal and gold metal, that is, a chromium film is formed before forming the gold film, which can enhance the adhesion of the gold film. In addition, gold has good physicochemical stability and is suitable as an electrode material for flexible devices.

[0032] Step S105: Etching the sacrificial layer transfers the piezoelectric structure, including the bottom electrode, piezoelectric layer, and top electrode, onto the flexible substrate to obtain a flexible piezoelectric energy harvester. Specifically, a wet etching process removes the sacrificial layer, releasing the piezoelectric structure from the substrate. The released piezoelectric structure is then transferred onto the flexible substrate using a transfer process to obtain the flexible piezoelectric energy harvester.

[0033] The method for fabricating a flexible piezoelectric energy harvester provided in this invention employs patterning of the sacrificial layer to reduce device etching and peeling time and improve transfer success rate. During the formation of the piezoelectric layer, each film layer undergoes a heat treatment, with different heat treatment processes used for odd-numbered and even-numbered layers. This results in highly dense piezoelectric layer films, thereby improving the output performance of the final harvester. Furthermore, the resulting flexible piezoelectric energy harvester can be used for collecting vibration energy in power applications, meeting current vibration energy harvesting requirements.

[0034] In one embodiment, a piezoelectric layer is formed on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process, comprising: forming a PZT film of a predetermined number of layers on the surface of the bottom electrode away from the sacrificial layer, wherein the predetermined number of layers is even; wherein the formation process of the odd-numbered PZT film involves spooling a layer of PZT precursor solution, drying it in an oven at 180℃-200℃ for 5-6 minutes, and preheating it in a muffle furnace at 340℃-360℃ for 5-6 minutes; the formation process of the even-numbered PZT film involves spooling a layer of PZT precursor solution, drying it in an oven at 180℃-200℃ for 5-6 minutes, preheating it in a muffle furnace at 340℃-360℃ for 5-6 minutes, and annealing it in a muffle furnace at 580℃-620℃ for 8-10 minutes.

[0035] In practical applications, the preset number of PZT thin films can be 6-10 layers; for example, an 8-layer PZT thin film can be prepared to form a piezoelectric layer. A spin coating process is used to form the PZT thin film, with one layer formed at 3000 r / min. Furthermore, before forming the piezoelectric layer, the substrate for forming the bottom electrode is dried in a muffle furnace at a temperature of 350℃-450℃.

[0036] In one embodiment, forming a bottom electrode on the surface of the sacrificial layer away from the substrate includes the following steps:

[0037] Step S201: A titanium thin film layer is formed on the surface of the sacrificial layer away from the substrate. Specifically, the titanium thin film is formed using a sputtering process, and the thickness of the formed titanium thin film layer is approximately 50 nm.

[0038] Step S202: A platinum film layer is formed on the surface of the titanium film away from the sacrificial layer; specifically, the platinum film is formed by sputtering process, and the thickness of the formed platinum film layer is about 150 nm.

[0039] Step S203: Perform wet etching on the titanium thin film layer and the platinum thin film layer to obtain a patterned bottom electrode. The patterning process is implemented as follows: spin-coat BN308 photoresist on the platinum thin film at a spin speed of 2300 r / min, and complete the patterning of the photoresist through standard photolithography and development processes. Perform wet etching in aqua regia (temperature 90℃) for about 3 minutes to etch away the platinum layer, and then perform wet etching in HF acid buffer (HF:H2O = 1:10) for about 15 seconds to remove the titanium layer, completing the fabrication and patterning of the bottom electrode.

[0040] In one embodiment, forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode includes the following steps:

[0041] Step S301: A chromium thin film layer is formed on the surface of the piezoelectric layer away from the bottom electrode; specifically, the chromium thin film is formed by sputtering process, and the thickness of the formed chromium thin film layer is about 20nm-30nm.

[0042] Step S302: A gold thin film layer is formed on the surface of the chromium thin film layer away from the bottom electrode; specifically, the gold thin film is formed by sputtering process, and the thickness of the formed gold thin film layer is about 70nm-100nm.

[0043] Step S303: Perform wet etching on the chromium thin film layer and the gold thin film layer to obtain a patterned top electrode. The patterning process is implemented as follows: spin-coat BP212 photoresist on the gold thin film at a spin speed of 2600 r / min, and pattern the photoresist by pre-baking, mask exposure, and development. Then, perform wet etching in I2-KI solution for 15 s to etch away the chromium layer. Finally, perform wet etching in K3[Fe(CN)6] for 70 s to remove the gold layer, thus completing the patterning and fabrication of the top electrode.

[0044] In one embodiment, after forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the method further includes: forming an encapsulation layer on a first surface of the substrate, the encapsulation layer covering the bottom electrode, the piezoelectric layer, and the top electrode, and exposing the electrode leads of the bottom electrode and the top electrode; and forming a protective layer on the surface of the encapsulation layer away from the substrate.

[0045] Specifically, after forming the top electrode, an encapsulation layer and a protective layer are formed. The encapsulation layer is formed by spin-coating a PW-1500S type polyimide precursor and then curing it. The specific process is as follows: a layer of PW-1500S type polyimide precursor is spin-coated on the substrate at a spin speed of 2200 r / min, then pre-baked at 120℃ for 5 min, and then cured in a nitrogen oven using a stepped heating process. The stepped heating process parameters are: 50℃ / 30 min, 150℃ / 40 min, 275℃ / 150 min, completing the preparation of the polyimide encapsulation layer. The protective layer is composed of photoresist. After forming the encapsulation layer, a layer of BP212 photoresist is spin-coated at a spin speed of 1600 r / min, and then pre-baked, exposed with a mask, and developed to pattern the photoresist, completing the preparation of the positive resist protective layer. In this embodiment, the encapsulation layer effectively protects the critical structure from the complex environment of the power scenario while ensuring the device's flexible deformation performance. The protective layer can form a protective layer for the device structure during subsequent transfer printing.

[0046] In one embodiment, etching the sacrificial layer transfers a piezoelectric structure comprising a bottom electrode, a piezoelectric layer, and a top electrode onto a flexible substrate to obtain a flexible piezoelectric energy harvester, comprising the following steps:

[0047] Step S401: Cut the substrate containing the complete piezoelectric structure of the bottom electrode, piezoelectric layer and top electrode into several small pieces; specifically, a diamond cutter can be used to divide the silicon wafer into several small pieces according to the size of the complete piezoelectric structure, and the integrity of the structure must be ensured during the division process.

[0048] Step S402: Etch the sacrificial layer to peel the small piezoelectric structure off the substrate; specifically, each small piece can be placed in HF acid buffer to etch away the SiO2 layer. The etching ends when the device structure is completely peeled off the silicon wafer, thus completing the device structure release process.

[0049] Step S403: Form a layer of polyimide gel on a flexible substrate. The flexible substrate can be a commercially available flexible polyimide film with a thickness of 70 μm. A layer of polyimide gel is then spin-coated onto this film at a spin speed of 3500 r / min.

[0050] Step S404: A PDMS film is brought into contact with a small piezoelectric structure. The piezoelectric structure is removed from the substrate and transferred to a polyimide gel for curing to obtain a flexible piezoelectric energy harvester. Specifically, a 1 mm thick PDMS film is made into complete conformal contact with the device. The device is removed from the silicon wafer at a uniform speed and transferred to the flexible polyimide film. Curing is then performed in a nitrogen oven. After curing, the BP212 adhesive protective layer is removed in an acetone solution.

[0051] In one embodiment, after forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the process further includes etching the formed piezoelectric layer to obtain a patterned piezoelectric layer. The patterning process specifically involves: spin-coating BP212 photoresist onto the piezoelectric layer at a spin speed of 2300 r / min; patterning the photoresist through pre-baking, mask exposure, and development; and using PZT etchant to etch away the PZT layer not protected by the photoresist in multiple stages. During the etching process, careful control of the etching time is crucial to prevent lateral etching that could lead to conductivity between the bottom and top electrodes.

[0052] This invention provides a fabrication process for a flexible piezoelectric energy harvester, geared towards power applications. First, a pre-patterning process is used to pre-pattern the sacrificial layer, reducing device etching and peeling time and improving transfer success rate. An odd-even layer differential annealing process is employed to improve the density of the PZT film, thereby enhancing output performance. Furthermore, sputtering a metallic Ti film and spin-coating polyimide gel strengthen the adhesion between the bottom electrode and the flexible substrate, preventing fatigue-induced detachment of the core structural layer during long-term operation. A flexible polyimide encapsulation layer is fabricated on the critical structure using spin-coating and stepped curing processes. This effectively protects the critical structure from the complex environment of power applications while ensuring the device's flexible deformation performance.

[0053] The fabrication process of the flexible piezoelectric energy harvester provided in this embodiment of the invention is specifically implemented using the following steps:

[0054] Step 1: Provide a 4-inch single-crystal silicon wafer substrate 1. Prepare a 1μm thick SiO2 sacrificial layer film on the silicon wafer substrate using a dry-wet oxidation method, such as... Figure 2 The structure shown in section ① is illustrated. BP212 photoresist is spin-coated onto the SiO2 sacrificial layer film at a spin speed of 2300 r / min. The photoresist is then patterned through pre-baking, mask exposure, and development. The unprotected SiO2 film is completely etched away in HF acid buffer, completing the pre-patterning of the SiO2 sacrificial layer film and obtaining patterned sacrificial layer 2, as shown in section ①. Figure 2 The structure shown in number ② is an example. The sacrificial layer serves two main functions: first, it is etched away during the subsequent wet etching process to release the structure on it; second, it acts as an insulating layer to prevent the silicon and the bottom electrode from conducting. The purpose of patterning the sacrificial layer is to increase the contact area between the etchant and the sacrificial layer during the subsequent wet etching process, thereby shortening the time it takes for the device to peel off from the silicon wafer.

[0055] Step two: First, a 50nm thick titanium film is prepared on the SiO2 sacrificial layer using a sputtering process, followed by sputtering a 150nm thick platinum metal layer. The sputtered titanium layer enhances the adhesion of platinum to the silicon wafer. Platinum metal possesses good physicochemical stability and can guide the cell growth of the piezoelectric film. Next, BN308 photoresist is spin-coated onto the platinum film at a spin speed of 2300 rpm, and the photoresist is patterned using standard photolithography and development processes. Wet etching is then performed in aqua regia (90℃) for approximately 3 minutes to remove the platinum layer, followed by wet etching in HF acid buffer (HF:H2O = 1:10) for approximately 15 seconds to remove the titanium layer, completing the fabrication and patterning of the bottom electrode 3. Figure 2 The structure of number ③ in the middle is shown;

[0056] Step 3: First, the silicon wafer carrying the bottom electrode is dried in a muffle furnace at 400℃. Then, a layer of PZT precursor solution is spin-coated onto the silicon wafer at a spin speed of 3000 r / min. The PZT precursor solution is heat-treated using an odd-even layer differential annealing process. The heat treatment steps for odd-numbered layers are: drying in an oven at 200℃ for 5 minutes, followed by preheating in a muffle furnace at 350℃ for 5 minutes. The heat treatment steps for even-numbered layers are: drying in an oven at 200℃ for 5 minutes, preheating in a muffle furnace at 350℃ for 5 minutes, followed by annealing in a muffle furnace at 600℃ for 10 minutes. Following the above process steps, 8 layers of PZT film are replicated, with a film thickness of approximately 800 nm, completing the preparation of piezoelectric layer 4. Figure 2 The structure of number ④ in the middle is shown.

[0057] Step four involves preparing a 20-30 nm thick chromium film on the prepared piezoelectric layer using a sputtering process, followed by a 70-100 nm thick gold film. The sputtered chromium layer enhances the adhesion of gold to the piezoelectric film. Gold possesses excellent physicochemical stability, making it highly suitable as an electrode material for flexible devices. Next, BP212 photoresist is spin-coated onto the gold film at a spin speed of 2600 r / min. The photoresist is patterned through pre-baking, mask exposure, and development. A 15-second wet etching process using I2-KI solution removes the chromium layer, followed by a 70-second wet etching process using K3[Fe(CN)6] to remove the gold layer. This completes the patterning and fabrication of the top electrode 5. Figure 2 The structure of number ⑤ in the middle is shown.

[0058] Step 5: Spin-coat BP212 photoresist onto the piezoelectric layer at a spin speed of 2300 r / min. Pattern the photoresist through pre-baking, mask exposure, and development. Use PZT etchant to etch away the PZT layer not protected by the photoresist in multiple stages. Carefully control the etching time during the etching process to prevent lateral etching that could lead to conductivity between the bottom and top electrodes. Figure 2 The structure of number ⑥ in the middle is shown.

[0059] Step 6: Spin-coat a layer of PW-1500S type polyimide precursor onto the silicon wafer at a spin speed of 2200 r / min. Then, pre-bake at 120℃ for 5 min, followed by curing in a nitrogen oven using a stepped heating process. The stepped heating process parameters are: 50℃ / 30 min, 150℃ / 40 min, 275℃ / 150 min. This completes the preparation of polyimide encapsulation layer 6. Figure 2 The structure of number ⑦ in the middle is shown.

[0060] Step 7: Spin-coat a layer of BP212 photoresist onto the silicon wafer at a spin speed of 1600 r / min. Then, pattern the photoresist through pre-baking, mask exposure, and development to complete the preparation of the positive resist protective layer 7. Figure 2 The structure of number ⑧ is shown.

[0061] Step 8: Using a diamond etchant, divide the silicon wafer into several smaller pieces according to the device structure size, ensuring the integrity of the structure during the division process. Then, etch away the SiO2 layer in HF acid buffer solution. The etching process ends when the device structure is completely peeled off the silicon wafer. Figure 2 The structure is shown in section ⑨. A layer of polyimide gel is spin-coated onto a 70 μm thick commercial flexible polyimide film 8 at a spin-coating speed of 3500 r / min. A 1 mm thick PDMS film is made into complete conformal contact with the device. The device is then uniformly removed from the silicon wafer and transferred onto the flexible polyimide film, and cured in a nitrogen oven. After curing, the BP212 adhesive layer is removed in an acetone solution, as shown. Figure 2 The structure shown in the middle number ⑩ is illustrated.

[0062] This invention also provides a flexible piezoelectric energy harvester, which is prepared using the preparation method of the flexible piezoelectric energy harvester described in the above embodiments.

[0063] The flexible piezoelectric energy harvester provided in this invention is prepared using the aforementioned method. Specifically, the sacrificial layer is patterned to reduce etching and peeling time and improve transfer success rate. During the formation of the piezoelectric layer, each film layer undergoes a heat treatment, with different heat treatment processes used for odd-numbered and even-numbered layers. This results in a highly dense piezoelectric layer film, thereby improving the harvester's output performance. Furthermore, the flexible piezoelectric energy harvester can be used to collect vibration energy in power applications, meeting current vibration energy harvesting requirements.

[0064] In one embodiment, the bottom electrode, piezoelectric layer, and top electrode are arranged in a stepped manner. Specifically, the flexible piezoelectric energy harvester prepared by the above method, after patterning the bottom electrode, piezoelectric layer, and top electrode, can be arranged in a stepped manner, which facilitates the subsequent lead-out of electrode wires.

[0065] While exemplary embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions, and modifications to these embodiments without departing from the spirit of the invention and the scope of protection defined by the appended claims. Such modifications and variations all fall within the scope defined by the appended claims. For other examples, those skilled in the art should readily understand that the order of process steps can be changed while remaining within the scope of the invention.

[0066] Furthermore, the scope of this invention is not limited to the processes, mechanisms, manufacturing methods, material compositions, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of this invention, those skilled in the art will readily understand that any existing or future processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described in this invention can be applied according to this invention. Therefore, the appended claims are intended to include these processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps within their scope of protection.

Claims

1. A method for preparing a flexible piezoelectric energy harvester, characterized in that, include: A patterned sacrificial layer is formed on the first surface of the substrate; A bottom electrode is formed on the surface of the sacrificial layer away from the substrate; A piezoelectric layer is formed on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process. A top electrode is formed on the surface of the piezoelectric layer away from the bottom electrode; Etching the sacrificial layer transfers the piezoelectric structure, including the bottom electrode, piezoelectric layer, and top electrode, onto a flexible substrate to obtain a flexible piezoelectric energy harvester. A piezoelectric layer is formed on the surface of the bottom electrode away from the sacrificial layer using an odd-even layer differential annealing process, including: A PZT film of a predetermined number of layers is formed on the surface of the bottom electrode away from the sacrificial layer. The predetermined number of layers is even. The formation process of the odd-numbered PZT film layers is as follows: spin-coating a layer of PZT precursor solution, drying in an oven at 180℃-200℃ for 5-6 minutes, and preheating in a muffle furnace at 340℃-360℃ for 5-6 minutes. The formation process of the even-numbered PZT film layers is as follows: spin-coating a layer of PZT precursor solution, drying in an oven at 180℃-200℃ for 5-6 minutes, preheating in a muffle furnace at 340℃-360℃ for 5-6 minutes, and annealing in a muffle furnace at 580℃-620℃ for 8-10 minutes.

2. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, A bottom electrode is formed on the surface of the sacrificial layer away from the substrate, comprising: A titanium thin film layer is formed on the surface of the sacrificial layer away from the substrate; A platinum film layer is formed on the surface of the titanium film away from the sacrificial layer; The titanium thin film layer and the platinum thin film layer are subjected to wet etching to obtain a patterned bottom electrode.

3. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, A top electrode is formed on the surface of the piezoelectric layer away from the bottom electrode, comprising: A chromium thin film layer is formed on the surface of the piezoelectric layer away from the bottom electrode; A gold thin film layer is formed on the surface of the chromium thin film layer away from the bottom electrode; The chromium thin film layer and the gold thin film layer are subjected to wet etching to obtain a patterned top electrode.

4. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, After forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the method further includes: An encapsulation layer is formed on a first surface of the substrate, the encapsulation layer covering the bottom electrode, the piezoelectric layer and the top electrode, and exposing the electrode leads of the bottom electrode and the top electrode; A protective layer is formed on the surface of the encapsulation layer away from the substrate.

5. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, Etching the sacrificial layer transfers the piezoelectric structure, including the bottom electrode, piezoelectric layer, and top electrode, onto a flexible substrate, resulting in a flexible piezoelectric energy harvester, comprising: The substrate containing the complete piezoelectric structure of the bottom electrode, piezoelectric layer and top electrode is cut into several small pieces; The sacrificial layer is etched to peel off small pieces of piezoelectric structure from the substrate; A layer of polyimide gel is formed on a flexible substrate; A flexible piezoelectric energy harvester is obtained by contacting a PDMS thin film with a small piece of piezoelectric structure, removing the piezoelectric structure from the substrate, transferring it onto a polyimide gel, and then curing it.

6. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, After forming a top electrode on the surface of the piezoelectric layer away from the bottom electrode, the method further includes: The formed piezoelectric layer is etched to obtain a patterned piezoelectric layer.

7. The method for preparing the flexible piezoelectric energy harvester according to claim 1, characterized in that, After forming the bottom electrode on the surface of the sacrificial layer away from the substrate, the method further includes: The substrate forming the bottom electrode is dried in a muffle furnace at a temperature of 350℃-450℃.

8. A flexible piezoelectric energy harvester, characterized in that, The flexible piezoelectric energy harvester is prepared using the preparation method of the flexible piezoelectric energy harvester according to any one of claims 1-7.

9. The flexible piezoelectric energy harvester according to claim 8, characterized in that, The bottom electrode, piezoelectric layer, and top electrode are arranged in a stepped manner.

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