A transparent conductive film for the flexible photovoltaic industry

Abstract

This invention discloses a transparent conductive film for the flexible photovoltaic industry, belonging to the field of flexible optoelectronic device technology, including conductive films. The invention employs a buffer anchoring layer with multiple matrix-arranged grooves at its top. Wedge-shaped grooves extend upwards along the bottom wall of the grooves to the plane of the buffer anchoring layer, forming an inverted conical anchor structure. When the conductive layer fills the grooves and wedge-shaped grooves and bridges the upper surface of the protrusions between adjacent grooves, the conductive layer forms an anchor foot within the wedge-shaped groove, constituting a mechanically interlocking interface with the grooves and wedge-shaped grooves. This structure transforms the peeling force acting between the conductive layer and the buffer anchoring layer during bending into compressive stress on the sidewalls of the grooves, significantly improving interface adhesion and avoiding the problem of delamination between the conductive layer and the substrate due to interfacial shear stress in traditional flexible transparent conductive films.

Description

Technical Field

[0001] This invention relates to the field of flexible optoelectronic device technology, specifically a transparent conductive film for use in the flexible photovoltaic industry. Background Technology

[0002] Flexible photovoltaic devices (including flexible perovskite solar cells, flexible organic photovoltaic cells, and flexible copper indium gallium selenide thin-film batteries) have become a research hotspot and industrialization direction in the photovoltaic field in recent years due to their advantages such as lightweight, bendability, rollability, portability, and integration into wearable devices. Unlike rigid photovoltaic devices, flexible photovoltaic devices require that each functional layer (especially the transparent electrode) can maintain stable photoelectric performance under repeated bending, folding, and rolling mechanical deformation conditions. As the front electrode of the flexible photovoltaic cell, the transparent conductive film undertakes the dual functions of transmitting incident light and collecting photogenerated carriers. Its performance directly determines the photoelectric conversion efficiency and service life of the device. Flexible photovoltaic devices require the transparent electrode to have high transmittance, low sheet resistance, and excellent mechanical flexibility.

[0003] Existing transparent conductive films used in the flexible photovoltaic industry are prone to microcracks when indium tin oxide (ITO) films are bent on flexible substrates, leading to a sharp increase in resistance. Although alternative materials such as metal meshes, silver nanowires, and graphene have improved flexibility, they still suffer from problems such as high surface roughness, weak interlayer adhesion, and mesh node breakage after bending. In particular, mechanical mismatch between the conductive layer and the organic substrate can easily lead to interface delamination under repeated roll-to-roll processing or dynamic bending conditions. Therefore, there is an urgent need to improve the technology of transparent conductive film structures used in the flexible photovoltaic industry to perfect this equipment. Summary of the Invention

[0004] The purpose of this invention is to provide a transparent conductive film for the flexible photovoltaic industry. By setting an anchor structure between the buffer anchor layer and the conductive layer, the peeling force acting between the conductive layer and the buffer anchor layer during bending can be converted into compressive stress on the sidewall of the groove, which significantly improves the interface adhesion and avoids the problem of delamination between the conductive layer and the substrate due to interface shear stress in traditional flexible transparent conductive films, thereby solving the problems mentioned in the background art that are currently on the market.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a transparent conductive film for the flexible photovoltaic industry, comprising a conductive film, wherein a flexible polymer substrate is disposed inside the conductive film, a buffer anchoring layer is disposed on the top of the flexible polymer substrate, a conductive layer is disposed on the side of the buffer anchoring layer away from the flexible polymer substrate, a transparent protective layer is disposed on the top of the conductive layer, and a plurality of matrix-arranged grooves are formed at the top of the buffer anchoring layer, wherein each groove has eight wedge-shaped grooves.

[0006] Preferably, the flexible polymer substrate is polyethylene terephthalate.

[0007] Preferably, the conductive layer fills the groove and spans the upper surface of the protrusion between adjacent grooves, and the conductive layer is a network structure combining embedded and overhead structures.

[0008] Preferably, the conductive layer is a silver nanowire or copper nanowire mesh.

[0009] Preferably, the transparent protective layer is a transparent polyimide film deposited by atomic layer deposition.

[0010] Preferably, the vertical cross-section of the groove is a straight cone, and the wedge-shaped groove extends upward along the bottom wall of the groove to the plane of the buffer anchoring layer.

[0011] Preferably, the groove and the wedge-shaped groove together form an inverted conical anchor bolt structure, and the length of the bottom opening of the groove and the wedge-shaped groove is greater than the length of the top opening of the groove.

[0012] Preferably, eight wedge-shaped grooves are arranged around the inside of the groove, the distance between the eight wedge-shaped grooves is equal, and the cross-section of the wedge-shaped grooves is V-shaped.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention incorporates a buffer anchoring layer with multiple matrix-arranged grooves at its top. Wedge-shaped grooves extend upwards along the bottom wall of the grooves to the plane of the buffer anchoring layer, forming an inverted conical anchor structure. When the conductive layer fills the grooves and wedge-shaped grooves and spans the upper surface of the protrusions between adjacent grooves, the conductive layer forms an anchor foot within the wedge-shaped groove, creating a mechanically interlocking interface together with the grooves and wedge-shaped grooves. This structure transforms the peeling force between the conductive layer and the buffer anchoring layer during bending into compressive stress on the sidewalls of the grooves, significantly improving interface adhesion and avoiding the problem of delamination between the conductive layer and the substrate due to interfacial shear stress in traditional flexible transparent conductive films.

[0014] This invention utilizes a radial structure composed of grooves and eight equidistant wedge-shaped grooves, combined with a network structure that integrates embedded and suspended conductive layers. When the film is bent and stretched, the suspended conductive layer, which spans the upper surface of the protrusions between adjacent grooves, acts as a flexible bridge, preferentially elongating and deforming to concentrate and dissipate strain energy. Meanwhile, the embedded conductive layer, filling the grooves, acts as a rigid island, maintaining its integrity. Simultaneously, the wedge-shaped grooves actively guide and deflect microcracks extending to the edge of the groove, terminating them at the bottom of the groove, thus preventing through-cracks from causing overall failure of the conductive network. This dual mechanism enables the conductive layer to achieve a gradual increase in resistance rather than abrupt failure under repeated bending, effectively extending the bending life of the transparent conductive film and solving the problems of metal mesh node breakage and silver nanowire network node slippage and separation in the prior art. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the internal structure of the present invention; Figure 2 This is a schematic diagram of the buffer anchoring layer and conductive layer structure of the present invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the buffer anchoring layer of the present invention; Figure 4 For the present invention Figure 3 A magnified schematic diagram of the structure at point A in the middle.

[0016] In the figure: 1. Conductive thin film; 2. Flexible polymer substrate; 3. Buffer anchoring layer; 4. Conductive layer; 5. Transparent protective layer; 6. Groove; 7. Wedge-shaped trench. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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. Example

[0018] Please see Figures 1 to 4 The present invention provides a technical solution: a transparent conductive film for the flexible photovoltaic industry, comprising a conductive film 1, a flexible polymer substrate 2 disposed inside the conductive film 1, a buffer anchoring layer 3 disposed on the top of the flexible polymer substrate 2, a conductive layer 4 disposed on the side of the buffer anchoring layer 3 away from the flexible polymer substrate 2, a transparent protective layer 5 disposed on the top of the conductive layer 4, and a plurality of matrix-arranged grooves 6 formed at the top of the buffer anchoring layer 3, each groove 6 having eight wedge-shaped grooves 7 formed therein.

[0019] By setting a buffer anchoring layer 3 and opening multiple matrix-arranged grooves 6 at the top of the buffer anchoring layer 3, and extending wedge-shaped grooves 7 upward along the bottom wall of the grooves 6 to the plane of the buffer anchoring layer 3, the grooves 6 and wedge-shaped grooves 7 together form an inverted conical anchor structure. When the conductive layer 4 fills the grooves 6 and wedge-shaped grooves 7 and spans the upper surface of the protrusion between adjacent grooves 6, the conductive layer 4 forms an anchor foot in the wedge-shaped groove 7, which together with the grooves 6 and wedge-shaped grooves 7 constitutes a mechanical interlocking interface. This structure transforms the peeling force acting between the conductive layer 4 and the buffer anchoring layer 3 during bending into compressive stress on the sidewall of the groove 6, which significantly improves the interface adhesion and avoids the problem of the conductive layer 4 peeling and delaminating from the substrate due to interface shear stress in the traditional flexible transparent conductive film 1.

[0020] Please see Figures 1 to 3 The flexible polymer substrate 2 is made of polyethylene terephthalate. Using polyethylene terephthalate as the flexible polymer substrate 2, this material has high light transmittance, good flexibility, low Young's modulus, and excellent chemical stability. It can form a good bonding interface with the buffer anchoring layer 3, while meeting the requirements of flexible photovoltaic devices for lightweight, flexible, and low-cost substrates. The conductive layer 4 fills the pits in the grooves 6 and spans the upper surface of the protrusions between adjacent grooves 6. The conductive layer 4 is a network structure that combines embedded and suspended structures. When the film is bent and stretched, the suspended part deforms first and consumes strain energy, while the embedded part remains intact because it is anchored by the grooves 6. This avoids the entire conductive layer 4 being damaged at the same time, so that the resistance of the film increases gradually under repeated bending rather than abruptly failing, which significantly extends the bending life.

[0021] Please see Figures 2 to 3 The conductive layer 4 is a network of silver or copper nanowires. Silver and copper nanowires have a high aspect ratio, excellent conductivity, and high light transmittance. Their network structure can form continuous conductive paths within the grooves 6 and wedge-shaped trenches 7. Simultaneously, the flexibility of the nanowires allows them to adapt to the complex geometry of the grooves 6 and wedge-shaped trenches 7, forming anchors in the embedded parts and bridging bridges in the suspended parts. The transparent protective layer 5 is a transparent polyimide film deposited by atomic layer deposition. Atomic layer deposition enables precise control of nanometer-level thickness and forms a dense, pinhole-free protective layer on the surface of the conductive layer 4. The transparent polyimide has high light transmittance, excellent water and oxygen barrier properties, and good flexibility, effectively inhibiting the oxidation and electrochemical migration of the silver or copper nanowires in the conductive layer 4, while preventing surface scratches during mechanical bending, significantly improving the environmental reliability and service life of the film. The vertical cross-section of the groove 6 is a right cone, and the wedge-shaped trenches 7 extend upwards along the bottom wall of the groove 6 to the plane of the buffer anchoring layer 3.

[0022] Please see Figures 2 to 4The groove 6 and the wedge-shaped groove 7 together form an inverted cone-shaped anchor bolt structure. The length of the bottom opening of the groove 6 and the wedge-shaped groove 7 is greater than the length of the top opening of the groove 6. Eight wedge-shaped grooves 7 are arranged around the inside of the groove 6. The distance between the eight wedge-shaped grooves 7 is equal. The cross-section of the wedge-shaped groove 7 is V-shaped.

[0023] After the conductive layer 4 is filled and cured, the conductive material forms an inverted conical anchor foot in the wedge-shaped groove 7. The anchor foot is held in place by the narrow opening of the wedge-shaped groove 7, creating a geometric locking effect, which further enhances the peel strength between the conductive layer 4 and the buffer anchoring layer 3.

[0024] Working principle: When using this transparent conductive film for the flexible photovoltaic industry, firstly, during the preparation process, a dispersion of silver or copper nanowires is coated onto the surface of the buffer anchoring layer 3. Driven by capillary force, the nanowire dispersion is drawn into the grooves 6 and wedge-shaped trenches 7. After drying and annealing, the conductive layer 4 forms a two-part structure: an embedded portion filling the pits of the grooves 6 and the wedge-shaped trenches 7, and an overhead portion bridging the upper surface of the protrusions between adjacent grooves 6. These two parts together constitute a two-dimensional continuous network structure combining embedded and overhead components. The groove 6 and the wedge-shaped groove 7 together form an inverted conical anchor structure. The length of the bottom opening of this structure is greater than the length of the top opening of the groove 6. The wedge-shaped groove 7 forms a partial undercut on the side wall of the groove 6. After the conductive layer 4 is filled and cured, the silver nanowire or copper nanowire forms an inverted conical anchor foot in the wedge-shaped groove 7. The anchor foot is stuck by the narrow opening of the wedge-shaped groove 7. At the same time, the conductive layer 4 filled in the groove 6 forms a wider anchor end at the bottom of the groove 6 due to the straight conical cross section of the groove 6. Therefore, the embedded part of the conductive layer 4 and the buffer anchoring layer 3 form a mechanical interlocking interface, rather than relying solely on van der Waals forces for bonding in the traditional way. When the transparent conductive film 1 is applied to a flexible photovoltaic device and subjected to bending and stretching, the embedded conductive layer 4 filled in the groove 6 is anchored by the groove 6 and the wedge-shaped groove 7. During the bending process, it mainly bears compressive stress and shear force, and its conductive network remains intact. The transparent protective layer 5 has a dense, pinhole-free structure, which can effectively block oxygen and moisture from penetrating into the conductive layer 4 and inhibit the oxidation and electrochemical migration of silver nanowires or copper nanowires. At the same time, the transparent protective layer 5 fills the micro-unevenness on the surface of the conductive layer 4, reduces the surface roughness, and provides a flat substrate for the deposition of subsequent functional layers (such as hole transport layer and perovskite layer) of the flexible photovoltaic device.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A transparent conductive film for use in the flexible photovoltaic industry, comprising a conductive film (1), characterized in that: The conductive film (1) has a flexible polymer substrate (2) inside, a buffer anchoring layer (3) on the top of the flexible polymer substrate (2), a conductive layer (4) on the side of the buffer anchoring layer (3) away from the flexible polymer substrate (2), a transparent protective layer (5) on the top of the conductive layer (4), and a plurality of matrix-arranged grooves (6) on the top of the buffer anchoring layer (3), with eight wedge-shaped grooves (7) in each groove (6).

2. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: The flexible polymer substrate (2) is polyethylene terephthalate.

3. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: The conductive layer (4) fills the pit of the groove (6) and spans the upper surface of the protrusion between adjacent grooves (6). The conductive layer (4) is a network structure that combines embedded and overhead structures.

4. The transparent conductive film for the flexible photovoltaic industry according to claim 3, characterized in that: The conductive layer (4) is a silver nanowire or copper nanowire mesh.

5. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: The transparent protective layer (5) is a transparent polyimide film deposited by atomic layer deposition.

6. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: The vertical cross section of the groove (6) is a straight cone, and the wedge-shaped groove (7) extends upward along the bottom wall of the groove (6) to the plane of the buffer anchoring layer (3).

7. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: The groove (6) and the wedge groove (7) together form an inverted cone-shaped anchor bolt structure. The length of the bottom opening of the groove (6) and the wedge groove (7) together is greater than the length of the top opening of the groove (6).

8. The transparent conductive film for the flexible photovoltaic industry according to claim 1, characterized in that: Eight wedge-shaped grooves (7) are arranged around the inside of the groove (6), and the distance between the eight wedge-shaped grooves (7) is equal. The cross-section of the wedge-shaped grooves (7) is V-shaped.

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