A flexible photovoltaic stress luminescent thin film sensor and its preparation method

Abstract

The present invention discloses a flexible photovoltaic stress luminescent thin film sensor and a preparation method thereof, comprising a flexible stress luminescent thin film layer at the bottom, a photovoltaic sensing thin film layer in the middle, and an opaque thin film protective layer at the top. The flexible stress luminescent thin film sensor prepared by combining stress luminescent materials with thin film photovoltaic components has the characteristics of safety and strength, good flexibility and elasticity, and good weak light effect. It also integrates surface source fluorescence signal perception and photoelectric conversion functions, and can realize real-time, online, and in-situ monitoring of structural stress and strain. Specifically, the photovoltaic sensing thin film layer vertically absorbs the surface source fluorescence signals of different intensities released by the stress luminescent layer, thereby maximizing the collection and photoelectric conversion of the stress luminescent surface source fluorescence signals. In addition, the structure has low preparation cost, simple operation, environmental friendliness, and excellent mechanical properties, and can be applied in the field of structural health monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of stress luminescent materials and sensors, and in particular to a flexible photovoltaic stress luminescent thin film sensor and a preparation method thereof. Background Art

[0002] With the continuous deepening of research on stress luminescent materials, the structural engineering community is actively exploring the application of stress / strain sensors designed and developed based on the stress luminescence phenomenon in the structural health monitoring of infrastructure. Stress luminescence is a type of force-induced luminescence phenomenon produced when a material is subjected to external mechanical stimulation, such as friction, pressure, impact, fracture, etc. According to the different forms of stress excitation, stress luminescence can be divided into four categories: friction stress luminescence, fracture stress luminescence, elastic stress luminescence, and plastic stress luminescence. Among them, sensors developed based on the elastic stress luminescence phenomenon have the characteristics of stable and recoverable luminescence, and the luminescence intensity has a good linear relationship with the excitation load. They can form a visual image of the structural stress load distribution in situ and in real time, and have broad application potential in the monitoring of structural deformation, fatigue damage, and fracture damage.

[0003] One existing technology involves directly combining a stress-luminescent material with an elastic matrix to form a stress-luminescent thin film sensor. The sensor then uses a CCD / CMOS industrial camera or fiber spectrometer to detect the fluorescence emitted by the stress-luminescent thin film sensor after mechanical stress excitation. However, this approach suffers from poor collection efficiency for scattered, weak fluorescence signals, a low level of integration, and susceptibility to interference from ambient light. Furthermore, the sensor cannot transmit the stress-luminescent signal in real time, making it unsuitable for remote online monitoring in complex field environments. Another approach involves coating or depositing the stress-luminescent material on the surface of a bare optical fiber to form a flexible stress-luminescent optical fiber sensor. The fluorescence signal generated by the stress-luminescent material upon excitation is collected and transmitted through the optical fiber core, achieving the integrated fluorescence signal sensing and transmission capabilities of the stress-luminescent optical fiber sensor. However, the structural design and fabrication of the stress-luminescent material and optical fiber composite sensor is challenging, and it is difficult to ensure that the fluorescence signal emitted by the stress-luminescent coating is transmitted maximally along the axial direction of the optical fiber core. To address these issues, an ideal flexible stress-luminescent thin film sensor requires both a rational structural design to accurately sense structural stress and strain changes and a stable and efficient stress-luminescent fluorescence signal transmission method to meet the needs of real-time online monitoring.

[0004] Photovoltaic sensors, particularly flexible thin-film sensors, offer advantages such as stretchability, high weak-light reception efficiency, and self-integrated photovoltaic modules. They combine sensing and transmission functions, making them a highly efficient means of collecting and transmitting stress-induced luminescence (SEL) signals. Therefore, developing a flexible, photovoltaic-based SEL thin-film sensor to address the aforementioned challenges in existing SEL sensing technology is highly valuable. Summary of the Invention

[0005] The present invention provides a flexible photovoltaic stress luminescent thin film sensor and a preparation method thereof, which can effectively integrate the stress luminescent effect and the photovoltaic effect. While sensing structural stress and strain information through stress luminescent materials, flexible photovoltaic components are used to collect and process stress luminescent signals, thereby solving the problems existing in the above-mentioned prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a flexible photovoltaic stress luminescent thin film sensor, comprising:

[0007] The flexible stress-luminescent film layer is located at the bottom and is used to sense the stress-luminescent fluorescent signal released by the structural stress change;

[0008] The photovoltaic sensing film layer is located in the middle part, vertically absorbs the surface source fluorescent signals of different intensities released by the stress luminescent layer, converts them into current signals, and transmits the current signals through the wires;

[0009] An opaque thin film protective layer located on top of the photovoltaic sensing layer.

[0010] Preferably, the stress luminescent layer, the photovoltaic sensing layer and the opaque protective layer are all bonded, cured and encapsulated by a high-strength adhesive with high light transmittance.

[0011] A method for preparing a flexible photovoltaic stress-luminescent thin film sensor comprises the following steps:

[0012] S1. Mixing the elastic stress luminescent material, the polydimethylsiloxane solution, and the curing agent solution, stirring thoroughly with a magnetic stirrer, and performing vacuum degassing until the elastic stress luminescent material is evenly distributed in the polydimethylsiloxane solution;

[0013] S2. Prepare a thin film from the mixed solution, and solidify the solution at a temperature of 60-70° C. for 2-3 hours to obtain a solidified flexible stress-induced luminescent film;

[0014] S3, using a high-transmittance and high-strength adhesive to adhere a cadmium telluride flexible thin film photovoltaic module to the flexible stress luminescent film to form a photovoltaic sensing film layer;

[0015] S4. Bonding an opaque film on the photovoltaic sensing film layer.

[0016] Preferably, in step S1, the elastic stress luminescent material includes sulfide, sulfur oxide, aluminate, titanate or silicate doped with transition metal ions or rare earth ions.

[0017] Preferably, in step S1 , the mass ratio of polydimethylsiloxane to the elastic stress luminescent material is 1:10 to 1:1, and the mass ratio of polydimethylsiloxane to the curing agent is 10:1 to 5:1.

[0018] Preferably, in step S2, a film is prepared from the mixed solution by using a casting method, a doctor blade method or a molding method.

[0019] Preferably, in step S3, a photoelectric signal conversion, amplification and analysis module is encapsulated in the cadmium telluride flexible thin-film photovoltaic module.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the flexible stress luminescent thin film sensor prepared by the composite of stress luminescent materials and thin-film photovoltaic components has the characteristics of safety and strength, good flexibility and elasticity, and good weak light effect, and integrates surface source fluorescence signal perception and photoelectric conversion functions, which can realize real-time, online, and in-situ monitoring of structural stress and strain. Among them, the photovoltaic sensing thin film layer in the present invention vertically absorbs the surface source fluorescence signals of different intensities released by the stress luminescent layer, and realizes the collection and photoelectric conversion of stress luminescent surface source fluorescence signals to the greatest extent. In addition, the structure has low preparation cost, simple operation, environmental friendliness, and excellent mechanical properties, and can be applied to the field of structural health monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0022] In the attached figure:

[0023] Figure 1 This is a schematic structural diagram of the flexible photovoltaic stress luminescent thin film sensor of the present invention;

[0024] Figure 2 Schematic diagram of the structure of the sensor of the present invention attached to a dog-bone-shaped mild steel specimen;

[0025] Figure 3 It is a linear relationship diagram between the current signal and the stress of the test piece of the present invention;

[0026] Numbers in the figure: 1. Flexible stress luminescent film layer; 2. Photovoltaic sensing film layer; 3. Wire; 4. Opaque film protective layer; 5. Test piece; 6. Signal processing unit. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] Example: Figure 1 As shown, a flexible photovoltaic stress luminescent film sensor comprises a flexible stress luminescent film layer 1 at the bottom, a photovoltaic sensing film layer 2 in the middle, and an opaque film protective layer 4 at the top; wherein:

[0029] The flexible stress luminescent film layer 1 is used to sense the stress luminescent fluorescent signal released by the structural stress change;

[0030] The photovoltaic sensing film layer 2 vertically absorbs the surface source fluorescence signals of different intensities released by the stress luminescent layer and converts them into current signals. The current signals are then transmitted to the signal processing unit 6 through the wire 3. The signal processing unit 6 processes and analyzes the received signals.

[0031] The light-proof film protective layer 4 is used to eliminate the interference of ambient stray light on the fluorescent signal collected by the photovoltaic sensing film layer 2 and to provide mechanical protection for the sensor.

[0032] The stress luminescent layer, the photovoltaic sensing layer and the opaque protective layer are all bonded, cured and packaged by a high-strength adhesive with high light transmittance.

[0033] A method for preparing a flexible photovoltaic stress-luminescent thin film sensor comprises the following steps:

[0034] S1. Mixing the elastic stress luminescent material, the polydimethylsiloxane solution, and the curing agent solution, stirring thoroughly with a magnetic stirrer, and performing vacuum degassing until the elastic stress luminescent material is evenly distributed in the polydimethylsiloxane solution;

[0035] Among them, the elastic stress luminescent material as the stress luminescent material mainly includes sulfide or sulfur oxide or aluminate or titanate or silicate doped with transition metal ions or rare earth ions, and polydimethylsiloxane as the elastic matrix of the stress luminescent material;

[0036] The mass ratio of polydimethylsiloxane to the elastic stress luminescent material is 1:10 to 1:1, and the mass ratio of polydimethylsiloxane to the curing agent is 10:1 to 5:1.

[0037] S2. Prepare a thin film from the mixed solution, and solidify the solution at a temperature of 60-70° C. for 2-3 hours to obtain a solidified flexible stress-induced luminescent film;

[0038] Wherein, the mixed solution is prepared into a thin film by using a casting method, a doctor blade method or a molding method;

[0039] S3. A cadmium telluride flexible thin-film photovoltaic module is attached to the flexible stress-luminescent film using a high-transmittance, high-strength adhesive to form a photovoltaic sensing film layer 2; wherein the cadmium telluride flexible thin-film photovoltaic module is encapsulated with a photoelectric signal conversion, amplification, and analysis module, which helps the photovoltaic sensor automatically absorb and convert the surface-source fluorescence signal released by the stress-luminescent substrate layer;

[0040] S4. Adhere an opaque film on the photovoltaic sensing film layer 2 to form an ambient light-isolating mechanical protection layer for the sensor.

[0041] In a specific embodiment, the elastic stress luminescent material selected is ZnS:Cu 2+ The elastic matrix is ​​a polydimethylsiloxane solvent, wherein the mass ratio of the polydimethylsiloxane elastic matrix to the elastic stress luminescent phosphor is 1:5, and the mass ratio of the polydimethylsiloxane solvent to the curing agent is 9:1;

[0042] Weigh the required amount of stress luminescent material, polydimethylsiloxane solvent and curing agent respectively, mix them thoroughly with a magnetic stirrer, and place them in a vacuum environment for degassing;

[0043] The mixed solution was placed in a small casting machine and heated at 60°C for 3 hours using a casting method to prepare a flexible stress-luminescent elastic film.

[0044] A cadmium telluride (CdTe) flexible thin film photovoltaic module is bonded to the prepared flexible stress luminescent film substrate using a high-transmittance and high-strength AB glue to form an intermediate layer of the sensor of the present invention;

[0045] A non-transparent PVC plastic film is pasted on the photovoltaic sensor film layer 2 to form the sensor's ambient light isolation mechanical protection layer. Figure 2 As shown in the figure, the prepared flexible photovoltaic stress luminescent film sensor was pasted onto the surface of the dog-bone-shaped mild steel specimen 5 test area and a standard axial tensile test was carried out. Figure 3 As shown in FIG, the detected current signal has a good linear relationship with the stress of the specimen 5.

[0046] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a flexible photovoltaic stress-luminescent thin film sensor, characterized by: The flexible photovoltaic stress luminescent film sensor includes a flexible stress luminescent film layer located at the bottom, which is used to sense the stress luminescent fluorescent signal released by the structural stress change; The photovoltaic sensing film layer is located in the middle part, vertically absorbs the surface source fluorescent signals of different intensities released by the stress luminescent layer, converts them into current signals, and transmits the current signals through the wires; An opaque thin film protective layer located on top of the photovoltaic sensing layer; The stress luminescent layer, the photovoltaic sensing layer and the opaque protective layer are all bonded, cured and encapsulated by a high-strength adhesive with high light transmittance; The preparation method comprises the following steps: S1. Mixing the elastic stress luminescent material, the polydimethylsiloxane solution, and the curing agent solution, stirring thoroughly with a magnetic stirrer, and performing vacuum degassing until the elastic stress luminescent material is evenly distributed in the polydimethylsiloxane solution; S2. Prepare a thin film from the mixed solution, and solidify the solution at a temperature of 60-70° C. for 2-3 hours to obtain a solidified flexible stress-induced luminescent film; S3, using a high-transmittance and high-strength adhesive to adhere a cadmium telluride flexible thin film photovoltaic module to the flexible stress luminescent film to form a photovoltaic sensing film layer; S4. Bonding an opaque film on the photovoltaic sensing film layer.

2. The method for preparing a flexible photovoltaic stress-luminescent thin film sensor according to claim 1, characterized in that: In step S1 , the elastic stress luminescent material includes sulfide, oxysulfide, aluminate, titanate, or silicate doped with transition metal ions or rare earth ions.

3. The method for preparing a flexible photovoltaic stress-luminescent thin film sensor according to claim 1, characterized in that: In step S1 , the mass ratio of polydimethylsiloxane to the elastic stress luminescent material is 1:10 to 1:1, and the mass ratio of polydimethylsiloxane to the curing agent is 10:1 to 5:

1.

4. The method for preparing a flexible photovoltaic stress-luminescent thin film sensor according to claim 1, characterized in that: In step S2, a stress luminescent film is prepared from the mixed solution by using a casting method, a doctor blade method or a molding method.

5. The method for preparing a flexible photovoltaic stress luminescent thin film sensor according to claim 1, characterized in that: In step S3, a photoelectric signal conversion, amplification and analysis module is encapsulated in the cadmium telluride flexible thin-film photovoltaic module.

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