A photovoltaic module junction box, photovoltaic module and light-induced degradation suppression method

Abstract

This application discloses a photovoltaic module junction box, a photovoltaic module, and a method for suppressing light-induced degradation. The junction box includes a switchable bypass impedance module, capable of switching between at least two states: a first state with the bypass impedance connected, providing an outlet path for photogenerated carriers; and a second state with the bypass impedance disconnected, allowing the module to operate normally. This application effectively suppresses light-induced degradation of perovskite photovoltaic modules during storage, transportation, and standby through a simple low-resistance bypass design. It also integrates rapid on-site testing capabilities, featuring a simple structure, low cost, and convenient operation. Experimental verification shows that the power degradation rate of modules using this solution is reduced from the conventional 15%~25% to less than 3%.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic power generation technology, and specifically relates to a photovoltaic module junction box, a photovoltaic module, and a method for suppressing light-induced degradation. Background Technology

[0002] Perovskite solar cells are considered the core of next-generation photovoltaic technology due to their high efficiency and low cost. However, their industrialization faces a critical reliability issue: light-induced degradation. Specifically, when perovskite modules are exposed to sunlight outdoors and in an open-circuit state (i.e., without a load or inverter connected), their performance undergoes significant and irreversible degradation. The mechanism is as follows: under illumination, the perovskite layer generates a large number of photogenerated charge carriers (electron-hole pairs). In the open-circuit state, these charge carriers cannot be discharged and accumulate in large quantities inside the cell, exacerbating ion migration (especially iodide ion migration), disrupting the crystal structure, and inducing severe non-radiative recombination at defect sites, ultimately leading to a significant decrease in module output power. This phenomenon is particularly prominent during module storage, transportation, and standby at construction sites.

[0003] Conventional photovoltaic junction boxes are primarily designed for crystalline silicon cells, providing no carrier exit path in the open-circuit state, resulting in photogenerated carriers being "trapped" inside the perovskite cell. For a long time, the photovoltaic industry has generally believed that modules do not generate electricity and are risk-free in the open-circuit state; therefore, junction box designs have never considered carrier management in this state. This technological bias has led to the long-term neglect and lack of resolution of the light-induced degradation problem in perovskite modules. From module manufacturing to grid connection, there can be weeks or even months of repeated exposure to sunlight, causing irreversible power loss.

[0004] In addition, conventional junction boxes lack flexibility for on-site testing: testing short-circuit current requires carrying a special short-circuit clamp, which is inconvenient to operate and poses safety hazards; testing maximum power point current requires connecting to an inverter or an expensive IV curve tester, which is time-consuming and labor-intensive. Summary of the Invention

[0005] The purpose of this application is to provide a photovoltaic module junction box, a photovoltaic module, and a method for suppressing light-induced degradation. This addresses the problems mentioned in the background art, such as the inability of existing junction boxes to suppress light-induced degradation of perovskite modules and the inconvenience of on-site testing.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a photovoltaic module junction box, comprising: A switchable bypass impedance module, the bypass impedance module being able to switch between at least two states, the states including a first state and a second state; The first state is the bypass impedance access state, which is used to provide an outlet path for the photogenerated carriers of the photovoltaic module. The second state is the bypass impedance cut-off state, which is used to enable the photovoltaic module to work normally.

[0007] In one possible implementation, the switchable bypass impedance module includes a multi-position switch and at least one resistor, the multi-position switch having at least three selectable position positions.

[0008] In one possible implementation, the first position of the multi-position switch directly connects the positive and negative terminals of the junction box to form a short circuit; the second position electrically connects the resistor between the positive and negative terminals to form a resistor bypass; and the third position disconnects the positive and negative terminals from the resistor to form an open circuit.

[0009] In one possible implementation, the resistance value is configured to match the maximum power point equivalent resistance of the photovoltaic module.

[0010] In one possible implementation, the multi-position switching switch is a mechanical toggle switch or a mechanical rotary switch.

[0011] In one possible implementation, the housing is provided with a gear position indicator to indicate the current gear position of the multi-gear switch.

[0012] In one possible implementation, the positive and negative terminals are waterproof terminals.

[0013] In one possible implementation, the resistor module includes at least two resistors with different resistance values, and the multi-position switch has four or more positions, wherein at least two positions are respectively connected to the at least two resistors with different resistance values.

[0014] Secondly, this application provides a photovoltaic module, including a photovoltaic module body and a photovoltaic module junction box as described in any of the first aspects, wherein the positive terminal and the negative terminal of the junction box are electrically connected to the positive output terminal and the negative output terminal of the photovoltaic module body, respectively.

[0015] In one possible implementation, the photovoltaic module body is a perovskite solar cell module.

[0016] In one possible implementation, the junction box body is fixedly connected to the back panel of the photovoltaic module body by adhesive or snap-fit.

[0017] Thirdly, this application provides a method for suppressing light-induced degradation of photovoltaic modules, comprising the following steps: After the photovoltaic modules leave the factory and before they are connected to the grid, their output terminals are placed in a low-resistance conduction state through a switchable bypass impedance module to provide an outlet path for photogenerated carriers. When operating in grid-connected mode, the bypass impedance module is switched to the open-circuit state to enable the component to function normally.

[0018] In one possible implementation, the low-resistance on state includes a short-circuit state or a resistance state that matches the equivalent resistance of the component's maximum power point.

[0019] One possible implementation also includes a testing step: Switch the bypass impedance module to the short-circuit state and measure the short-circuit current of the component; And / or, Switch the bypass impedance module to resistance matching mode and measure the maximum power point current of the component.

[0020] Compared with the prior art, this application has the following beneficial effects: A photovoltaic module junction box features a switchable bypass impedance module, allowing for flexible switching between bypass impedance enabled and disabled states. During the storage, transportation, and standby phases after the photovoltaic modules leave the factory and before grid connection, the bypass impedance module is switched to the enabled state, providing a low-resistance path for photogenerated carriers and fundamentally preventing carrier accumulation within the perovskite cell, thus significantly suppressing light-induced degradation. During grid-connected operation, the bypass impedance module is switched to the disabled state, and the module resumes normal operation. This junction box, through simple circuit improvements and without increasing additional costs, solves the long-standing open-circuit degradation problem that has plagued the industrialization of perovskite modules, demonstrating significant substantive features and remarkable progress.

[0021] In one possible implementation, the bypass impedance module is further defined as a three-position selector switch, corresponding to short circuit, maximum power point resistance matching, and open circuit states. The short circuit position can maximize carrier extraction with the lowest impedance, providing the strongest suppression effect; the resistance position matches the equivalent resistance of the module's maximum power point, clamping the module's output voltage near the maximum power point while extracting carriers, resulting in low heat generation, good safety, and allowing direct measurement of the maximum power point current; the open circuit position is used for grid-connected operation. This three-position combination design covers three scenarios: strong protection, mild protection, and normal operation, achieving multi-functional integration of a single component.

[0022] In one possible implementation, the resistor value is configured to match the maximum power point equivalent resistance of the photovoltaic module, which has a synergistic effect: on the one hand, this resistance value provides the module with the optimal load that can just drain most of the photogenerated carriers without generating excessive heat loss; on the other hand, at this setting, the module's output voltage is automatically clamped near the maximum power point voltage, allowing installers to directly and safely measure the maximum power point current without connecting to the inverter. This on-site rapid diagnostic function is completely absent in conventional junction boxes.

[0023] In one possible implementation, multiple resistors with different resistance values ​​are further provided, offering four or more ranges. Different resistance values ​​can adapt to protection needs under different light intensities (such as using higher resistance values ​​to reduce heat generation under low light conditions), or provide more diverse bias conditions for scientific research and testing, thus expanding the applicability and testing flexibility of the junction box.

[0024] A photovoltaic module features a compact structure and is easy to install. The junction box is fixed to the module back panel by adhesive or snap-fit, ensuring a reliable, waterproof, and dustproof connection. During storage and transportation, the module effectively resists performance degradation caused by sunlight exposure. Electrical performance testing can be quickly completed on-site without additional tools, significantly improving the module's reliability and installation efficiency.

[0025] A method for suppressing light-induced degradation in photovoltaic modules is proposed. This method involves placing the output terminal of the module in a low-resistance conducting state before grid connection to provide an outlet path for photogenerated carriers, and then switching it to an open-circuit state during grid connection, forming a complete and operable control process. This method is simple to operate, requiring only a toggle switch, and does not require changes to existing module installation and wiring practices, making it highly valuable for industrial applications. Experimental verification shows that using this method, the power degradation rate of perovskite modules after simulated transport and sunlight exposure is reduced from the conventional 15%–25% to less than 3%, achieving unexpected technical results.

[0026] One possible implementation defines the testing steps, organically integrating the junction box's switch function with on-site testing operations. Installers no longer need to carry additional short-circuit clamps or expensive IV testers; they can simply toggle a switch and use commonly available instruments to perform rapid component health checks. This design not only reduces testing costs and safety risks but also shortens on-site testing time by approximately 70%, demonstrating significant economic benefits and practical value. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the multi-level bypass adjustment photovoltaic module junction box provided in the embodiments of this application.

[0028] The attached diagram is labeled as follows: 1. Box body; 2. Positive terminal; 3. Negative terminal; 4. Multi-position switch; 5. Photovoltaic module body. Detailed Implementation

[0029] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0030] In the description of this application, it should be understood that 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 application and 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, and therefore should not be construed as a limitation of this application.

[0031] Furthermore, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly defined. The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0032] In this application, unless otherwise expressly 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, an electrical connection, or a communication 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. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0033] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1 like Figure 1 As shown, this embodiment provides a photovoltaic module junction box, including a box body 1, a positive terminal 2, a negative terminal 3, a multi-position switch 4, and a resistor module. The resistor module includes a resistor (not shown in the figure).

[0036] The housing 1 is injection molded from weather-resistant plastic (such as polyphenylene oxide (PPO) or polyphenylene sulfide (PPS)) and has an internal cavity and a sealing cover (not shown in the figure) to house and protect the internal components. Waterproof connectors for cable insertion are provided at both ends or on the sides of the housing 1.

[0037] Positive terminal 2 and negative terminal 3 are metallic conductive terminals (e.g., copper plated with tin or silver), embedded in the side wall or bottom of housing 1. Their inner ends are electrically connected to the corresponding contacts of the multi-position switch 4, and their outer ends are used to connect the output cables or connectors of the photovoltaic module. To adapt to outdoor humid and rainy environments, positive terminal 2 and negative terminal 3 are preferably waterproof terminals, and their joints with housing 1 are provided with sealing rings or potting compound.

[0038] A multi-position selector switch 4 is installed inside the housing 1, with its operating handle (or toggle) extending from the top or side of the housing 1 for manual operation. In this embodiment, the multi-position selector switch 4 is a single-pole three-throw mechanical toggle switch, having one common moving contact and three stationary contacts. The common moving contact is electrically connected to the positive terminal 2 (or can be electrically connected to the negative terminal 3, depending on the design). The three stationary contacts correspond to the first position (short circuit position), the second position (resistance position), and the third position (open circuit position), respectively. The specific connection relationships are as follows: The first stationary contact is directly connected to the negative terminal 3 via a wire, forming a short circuit path.

[0039] The second stationary contact is connected to the negative terminal 3 via a resistor.

[0040] The third stationary contact is suspended and not connected to any circuit.

[0041] When the toggle switch is moved to the first position, the common moving contact connects to the first stationary contact, and the positive terminal 2 and the negative terminal 3 are directly connected, with resistance approximately zero. When the toggle switch is moved to the second position, the common moving contact connects to the second stationary contact, and a resistor is connected between the positive terminal 2 and the negative terminal 3. When the toggle switch is moved to the third position, the common moving contact connects to the third stationary contact (floating), and there is no bypass path between the positive terminal 2 and the negative terminal 3; the component is in normal operating condition (open circuit output).

[0042] The resistor module includes a resistor whose value is configured according to the electrical performance parameters of the connected photovoltaic module. Specifically, for a perovskite photovoltaic module, its maximum power point voltage Ump and maximum power point current Imp are known parameters, then the equivalent resistance at the maximum power point Rmp = Ump / Imp. For example, if a perovskite module has nominal parameters of Ump = 32V and Imp = 8A, then Rmp = 4Ω. In this case, a wire-wound resistor or metal oxide film resistor with a nominal value of 4Ω and a power capacity that meets the safety margin (e.g., above 20W) is selected. The resistor is fixed in the housing 1 by metal clips or screws and thermal grease is applied to facilitate heat dissipation.

[0043] The outer surface of the box 1 is marked with gear position indicators (not shown in the figure), such as "short circuit", "MPP resistance" or "open circuit" next to the switch knob, or marked with "I", "II" or "III" and accompanied by corresponding indicator arrows, so that the operator can easily identify the current gear position.

[0044] Working process and usage method: Before the photovoltaic modules leave the factory, production personnel switch the multi-position selector switch 4 to either the first position (short circuit position) or the second position (resistance position). Typically, if the modules are anticipated to be exposed to strong sunlight during storage and transportation, or if maximum degradation suppression is desired, the short circuit position is selected; if a certain degree of gentle conduction is desired to reduce heat generation, the resistance position is selected. Subsequently, the modules are packed and transported. During this period, even if the modules are accidentally exposed to sunlight, photogenerated carriers can be quickly conducted through the low-resistance bypass path (short circuit or resistance) inside the junction box, preventing accumulation inside the cells and thus significantly suppressing light-induced degradation.

[0045] When the components arrive on site and are ready for installation, installers can first use the junction box's range function for a quick test: Set the switch to the first position (short circuit position), and use a clamp meter to wrap around the positive or negative output cable of the component to directly read the short circuit current Isc. Comparing this reading with the component's nominal value can provide a preliminary assessment of whether the component is damaged. Then, set the switch to the second position (resistance position), switch the multimeter to the current range and connect it in series in the output circuit (or use a DC clamp meter) to measure the maximum power point current Imp. This process does not require connection to an inverter or an expensive IV tester; it can be completed with only commonly used instruments, greatly improving the convenience and safety of on-site testing.

[0046] After completing the installation of all components, the connection of the busbars and the inverter, before grid connection, the operator should switch the junction box switch of each component to the third position (open circuit position) to disconnect all bypass impedances and enable the component to output normal open circuit voltage, ready for connection to the inverter. Then, close the DC switch, and the system can be connected to the grid and generate electricity normally.

[0047] Example 2 The difference between this embodiment and Embodiment 1 is that the resistor module includes two resistors with different resistance values ​​(e.g., resistors R1 and R2), and the multi-position switching switch 4 is a single-pole four-throw switch with four positions. Wherein: First gear: Short circuit (0Ω).

[0048] Second setting: Connect resistor R1, the value of which corresponds to the equivalent resistance of the component at the maximum power point under low light conditions (e.g., Rmp at a nominal irradiance of 200W / m²).

[0049] Third position: Connect resistor R2. The resistance value of R2 corresponds to the maximum power point equivalent resistance of the component under standard lighting conditions (i.e., Rmp under STC).

[0050] Fourth gear: Open path (all bypasses are removed).

[0051] This solution allows users to select the most suitable bypass resistor based on the actual light intensity or light conditions in different seasons, thereby enabling more precise control of the bypass current and reducing unnecessary heat loss. Simultaneously, the four-position configuration provides researchers with more bias voltage testing conditions, facilitating component performance tracking outdoors.

[0052] The other structures in this embodiment (box 1, terminals, markings, etc.) are the same as in embodiment 1, and will not be described again.

[0053] Example 3 This embodiment provides a photovoltaic module, including a photovoltaic module body 5 and a junction box as described in any of the above embodiments. The photovoltaic module body 5 is preferably a perovskite solar cell module, which is composed of a glass substrate, a transparent conductive electrode, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, a back electrode, and an encapsulation layer. A positive busbar and a negative busbar are led out from the back of the photovoltaic module body 5.

[0054] The junction box body 1 is bonded and fixed to the back panel of the photovoltaic module body 5 using high-strength silicone sealant or double-sided foam tape, or it is secured to the module frame using clips. The positive terminal 2 and negative terminal 3 are welded or crimped to the positive and negative busbars of the photovoltaic module body 5, respectively. The junction box's lead cables (not shown in the figure) are connected to subsequent combiner boxes or inverters.

[0055] In practical applications, during the storage, transportation, and standby phases of perovskite photovoltaic modules, the junction boxes are kept in the short-circuit or resistance position; before final grid connection, all module junction boxes are switched to the open-circuit position. Experimental verification shows that, using the proposed solution, the power degradation rate of perovskite modules after simulated transportation and light exposure (cumulative 100 kWh / m²) is reduced from 15%–25% for conventional junction boxes to less than 3%, while on-site testing time is shortened by approximately 70%.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A photovoltaic module junction box, characterized in that, include: A switchable bypass impedance module, the bypass impedance module being able to switch between at least two states, the states including a first state and a second state; The first state is the bypass impedance access state, which is used to provide an outlet path for the photogenerated carriers of the photovoltaic module. The second state is the bypass impedance cut-off state, which is used to enable the photovoltaic module to work normally.

2. The photovoltaic module junction box according to claim 1, characterized in that, The switchable bypass impedance module includes a multi-position switch (4) and at least one resistor, the multi-position switch (4) having at least three selectable position positions.

3. The photovoltaic module junction box of claim 2, wherein, The first position of the multi-position switch (4) directly connects the positive terminal (2) and the negative terminal (3) of the junction box to form a short circuit. The second position connects the resistor between the positive terminal (2) and the negative terminal (3) to form a resistor bypass. The third position disconnects the positive terminal (2) and the negative terminal (3) from the resistor to form an open circuit.

4. The photovoltaic assembly junction box of claim 3, wherein, The resistance value is configured to match the maximum power point equivalent resistance of the photovoltaic module.

5. The photovoltaic module junction box of claim 2, wherein, The multi-position switching switch (4) is a mechanical toggle switch or a mechanical rotary switch.

6. The photovoltaic module junction box of claim 2, wherein, The resistors are multiple and have different resistance values. The multi-position switch (4) has four or more positions, of which at least two positions are respectively connected to resistors with different resistance values.

7. A photovoltaic module, characterized by The photovoltaic module body (5) includes a photovoltaic module junction box as described in any one of claims 1-6, wherein the positive terminal (2) and the negative terminal (3) of the junction box are electrically connected to the positive output terminal and the negative output terminal of the photovoltaic module body (5), respectively.

8. A method of inhibiting photodegradation of a photovoltaic module, comprising, Includes the following steps: After the photovoltaic modules leave the factory and before they are connected to the grid, their output terminals are placed in a low-resistance conduction state through a switchable bypass impedance module to provide an outlet path for photogenerated carriers. When operating in grid-connected mode, the bypass impedance module is switched to the open-circuit state to enable the component to function normally.

9. The method of claim 8, wherein, The low-resistance conduction state includes a short-circuit state or a state where a resistor is connected that matches the equivalent resistance of the component's maximum power point.

10. The method of claim 8, wherein, It also includes a test step: switching the bypass impedance module to a short-circuit state and measuring the short-circuit current of the component; And / or, Switch the bypass impedance module to resistance matching mode and measure the maximum power point current of the component.

Images