A multi-junction solar cell structure and method of fabrication

Abstract

This invention relates to a multi-junction solar cell structure and manufacturing method. Each junction of the multi-junction solar cell includes: a transparent front electrode laid on the surface of a transparent substrate, in an L-shape, placed along the outer edge of the transparent substrate; a photovoltaic layer laid on the surface of the transparent front electrode; a metal back electrode laid on the surface of the photovoltaic layer; and an insulating layer disposed between adjacent positions of the multi-junction solar cells. Except for the solar cell connected to the negative electrode of an external power supply device, all other solar cells in the multi-junction solar cell include: a protrusion on the side of the transparent front electrode away from the transparent substrate, the protrusion being located at the electron outflow position in the transparent front electrode. By providing a protrusion structure on the transparent front electrode, and ohmically connecting the side of the metal back electrode to the side of the protrusion, the visibility of the metal back electrode and the reflection of the metal are eliminated, thereby improving the appearance of the multi-junction solar cell structure.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a multi-junction solar cell structure and manufacturing method. Background Technology

[0002] In recent years, organic photovoltaic (OPV) solar cells and perovskite solar cells (PSC), as emerging third-generation solar cells, have sparked a surge of research and development in the scientific research field. More and more wearable devices are incorporating solar cells to ensure their long-term use. To maintain the aesthetic appeal of solar cells within these devices, patterned designs are necessary.

[0003] In related technologies, to achieve patterned design of multi-junction solar cells, the positive and negative electrode overlap areas of adjacent solar cells are usually designed inside the photovoltaic pattern, or on the outer edge of the photovoltaic pattern. However, since the transparent front electrode is colorless and transparent, there is no photovoltaic layer in the positive and negative electrode overlap area; only the transparent front electrode and the metal back electrode are stacked together. This results in the metal back electrode of the solar cell being visible from the transparent substrate side. The metal back electrode is mostly made of metals with low resistivity, such as silver, aluminum, molybdenum, chromium, and gold, and has extremely high reflectivity. Users can easily perceive the metal reflection phenomenon from the transparent substrate surface. Although a film layer (such as ink) of similar color can be used to cover the corresponding position on the transparent front electrode side to cover the metal in the overlap area, there will be color difference problems, as well as other process problems caused by the film thickness (such as potentially affecting the sheet resistance of the TCO and the film formation effect of the photovoltaic layer).

[0004] Multi-junction solar cells in related technologies have two main drawbacks. First, the appearance of stacked metal back electrodes is visible through the transparent substrate, which makes wearable devices look unattractive. Second, the high reflectivity of the metal back electrodes can cause eye discomfort for users.

[0005] The above problems urgently need to be addressed. Summary of the Invention

[0006] This invention discloses a multi-junction solar cell structure and fabrication method, aiming to solve the technical problems existing in the prior art.

[0007] The present invention adopts the following technical solution: On one hand, the present invention provides a multi-junction solar cell structure, comprising: each junction of the multi-junction solar cell includes: a transparent front electrode, laid on the surface of a transparent substrate, in an L-shaped structure, placed along the outer edge of the transparent substrate, the transparent front electrode being used to conduct electrons; a photovoltaic layer, laid on the surface of the transparent front electrode, being used to absorb light energy and generate electron-hole pairs; and a metal back electrode, laid on the surface of the photovoltaic layer; except for the solar cell connected to the negative electrode of an external power supply device, all other solar cells in the multi-junction solar cell include: a protrusion; a protrusion is provided on the side of the transparent front electrode away from the transparent substrate, the protrusion being located at the electron outflow position in the transparent front electrode; the photovoltaic layer is laid on the surface of the transparent front electrode and does not cover the protrusion; there is a gap between the metal back electrode and the protrusion in the solar cell, the vertical side of the metal back electrode forms an electrical connection with the side of the protrusion in the adjacent solar cell, the contact surface between the metal back electrode and the protrusion in the adjacent solar cell is set as a wavy sawtooth shape, the metal back electrode being used to conduct holes.

[0008] Optionally, in a multi-junction solar cell, the transparent front electrodes are arranged in a ring structure around each other, wherein there is a gap between adjacent transparent front electrodes; an insulating layer is disposed between adjacent transparent front electrodes in the multi-junction solar cell, and the insulating layer is placed within the gap between adjacent transparent front electrodes.

[0009] Optionally, the photovoltaic layer of the first solar cell extends to the gap between the first solar cell and the second solar cell, and contacts and connects with the transparent front electrode in the second solar cell. The first solar cell is the solar cell where the current photovoltaic layer is located, and the second solar cell is the solar cell adjacent to the first solar cell in the direction of electron inflow. The metal back electrode of the first solar cell extends to the gap between the first solar cell and the second solar cell, and contacts and connects with the transparent front electrode in the second solar cell.

[0010] Optionally, the multi-junction solar cell further includes: a transparent front electrode lead-out terminal, disposed on the third solar cell and connected to the transparent front electrode on the third solar cell, located on one side of the electron outflow direction of the transparent front electrode, wherein the third solar cell is any one of the multi-junction solar cells; the transparent front electrode of the solar cell connected to the transparent front electrode lead-out terminal does not have a protrusion.

[0011] Optionally, the multi-junction solar cell further includes: a metal back electrode lead-out terminal disposed on the fourth solar cell and connected to the metal back electrode on the fourth solar cell, located on the side of the metal back electrode close to the third solar cell, wherein the fourth solar cell is the solar cell adjacent to the side of the transparent front electrode lead-out terminal of the third solar cell.

[0012] Optionally, the multi-junction solar cell further includes: a back electrode lead-out terminal bridging block, disposed below the metal back electrode lead-out terminal and located at the same horizontal plane as the transparent front electrode, for supporting the metal back electrode lead-out terminal.

[0013] Optionally, the photovoltaic layer includes: a groove disposed around the outer edge of the photovoltaic layer, the groove being filled with the insulating layer.

[0014] Optionally, the sum of the height of the photovoltaic layer and the height of the metal back electrode is equal to the height of the protrusion.

[0015] Optionally, the visible light transmittance of the transparent substrate is set between 40% and 90%.

[0016] Optionally, the photovoltaic layer includes: a photovoltaic active layer for absorbing sunlight of a preset wavelength to form electron-hole pairs; an electron transport layer disposed on the surface of the photovoltaic active layer for transporting electrons generated in the photovoltaic active layer; and a hole transport layer disposed on the side of the photovoltaic active layer away from the electron transport layer for transporting holes generated in the photovoltaic active layer.

[0017] According to another aspect of the present invention, a method for fabricating a multi-junction solar cell is also provided, comprising: disposing a transparent front electrode on the surface of a transparent substrate; using photolithography and etching processes to create a recessed groove on the transparent front electrode to form a protrusion on the transparent front electrode; disposing an insulating layer between the transparent front electrode and an adjacent transparent front electrode, and simultaneously laying an insulating layer along the outer edge of the transparent front electrode; coating an electron transport layer, a photovoltaic active layer, and a hole transport layer layer by layer on the surface of the transparent front electrode to form a photovoltaic layer, wherein the outer edge of the photovoltaic layer is aligned with the insulating layer laid along the outer edge of the transparent front electrode; laying a metal back electrode on the surface of the photovoltaic layer based on a metal mask and thermal evaporation, the metal back electrode extending towards the adjacent solar cell while covering the photovoltaic layer, and forming an electrical connection on the side with the transparent front electrode of the adjacent solar cell that is thicker than the photovoltaic layer; and encapsulating the transparent front electrode, the insulating layer, the photovoltaic layer, and the metal back electrode.

[0018] Optionally, a transparent front electrode is disposed on the surface of a transparent substrate. Using photolithography and etching processes, a recessed groove is formed on the transparent front electrode to create a protrusion on the transparent front electrode. This includes: fabricating a transparent front electrode layer on the transparent substrate; applying a photoresist coating to the entire surface of the transparent front electrode for the first time, followed by exposure, development, hardening, and etching to form a transparent front electrode with a smooth surface; applying a photoresist coating to the surface of the smooth transparent front electrode for the second time, followed by exposure, development, and hardening to expose the area outside the junction of the transparent front electrode and the adjacent solar cell; and creating a recessed groove by etching to form the protrusion on the electron outflow direction side of the transparent front electrode.

[0019] Optionally, the transparent front electrode, the insulating layer, the photovoltaic layer, and the metal back electrode can be encapsulated by: vacuum bonding the solar cell with the completed metal back electrode to a back cover coated with frame adhesive and desiccant, curing the frame adhesive to form an encapsulation, while exposing the electrode lead terminals; or by using a thin-film encapsulation method to cover and encapsulate the area of ​​the solar cell other than the electrode lead terminals.

[0020] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: In this embodiment of the invention, by setting a protruding structure on the transparent front electrode, the photovoltaic layer and the metal back electrode are placed on one side of the protruding structure, and the side of the metal back electrode is ohmically connected to the side of the protrusion, thereby eliminating the visibility of the metal back electrode and the reflection of the metal, and thus improving the appearance of the multi-junction solar cell structure. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a top view of the transparent front electrode of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 2 As in Embodiment 1 of the present invention, along Figure 1 A schematic diagram of the cross-section cut at point AA'; Figure 3 This is a diagram showing the positional relationship between the photovoltaic layer, the metal back electrode, and the protrusion in Embodiment 1 of the present invention; Figure 4 This is Embodiment 1 of the present invention. Figure 3 Enlarged view at point B in the middle; Figure 5 This is a top view of the first optional transparent front electrode of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 6 This is a top view of a second optional transparent front electrode of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 7 This is a diagram showing the positional relationship between the protrusion of the first optional transparent front electrode and the photovoltaic layer and the metal back electrode in Embodiment 1 of the present invention. Figure 8 This is a top view of the metal back electrode of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 9 This is a diagram showing the positional relationship between the protrusion of the second optional transparent front electrode and the photovoltaic layer and the metal back electrode in Embodiment 1 of the present invention. Figure 10 This is a side view of the photovoltaic layer of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 11 This is a top view of the insulating layer of a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 12 Embodiment 1 of the present invention: A diagram of the internal structure of the photovoltaic layer in a multi-junction solar cell structure; Figure 13 This is a diagram of the internal structure of the photovoltaic layer of a perovskite solar cell in a multi-junction solar cell structure according to Embodiment 1 of the present invention; Figure 14 This is a flowchart of a method for fabricating a multi-junction solar cell according to Embodiment 2 of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Transparent substrate; 2. Transparent front electrode; 3. Protrusion; 4. Photovoltaic layer; 5. Metal back electrode; 6. Insulating layer; 7. Transparent front electrode lead-out terminal; 8. Metal back electrode lead-out terminal; 9. Back electrode lead-out terminal overlap block; 10. Groove; 11. Photovoltaic active layer; 12. Electron transport layer; 13. Hole transport layer; 14. Auxiliary metal electrode structure; 15. Electron injection layer; 16. Hole blocking layer; 17. SAM self-assembly layer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[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 a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0025] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] First, to facilitate understanding of the embodiments of the present invention, some terms or nouns involved in the present invention will be explained below: Multi-junction solar cells typically have two structures: one is a photovoltaic device composed of multiple vertically stacked semiconductor photovoltaic sub-junctions with different band gaps; the other is a photovoltaic device in which multiple sub-cells with essentially the same structure are connected in series on the same horizontal plane through the positive and negative electrodes of adjacent sub-cells. The device structure described in this invention is the latter.

[0027] To address the problems existing in related technologies, this application provides a multi-junction solar cell structure and manufacturing method.

[0028] Example 1 This embodiment provides a multi-junction solar cell structure, such as Figure 1 As shown, the structure includes: Each junction solar cell in a multi-junction solar cell includes: a transparent front electrode 2, deposited on the surface of a transparent substrate 1 in an L-shaped structure, placed along the outer edge of the transparent substrate 1, and used for conducting electrons; a photovoltaic layer 4, deposited on the surface of the transparent front electrode 2, used for absorbing light energy and generating electron-hole pairs; and a metal back electrode 5, deposited on the surface of the photovoltaic layer 4. Except for the solar cell connected to the negative electrode of an external power supply device, all other solar cells in the multi-junction solar cell include: protrusions 3; such as... Figure 2As shown, a protrusion 3 is provided on the side of the transparent front electrode 2 away from the transparent substrate 1, and the protrusion 3 is located at the electron outflow position in the transparent front electrode 2; as Figure 3 As shown, the photovoltaic layer 4 is laid on the surface of the transparent front electrode 2 and does not cover the protrusion 3; there is a gap between the metal back electrode 5 and the protrusion in the solar cell, the vertical side of the metal back electrode 5 forms an electrical connection with the side of the protrusion in the adjacent solar cell, the contact surface between the metal back electrode 5 and the protrusion in the adjacent solar cell is set as a wavy sawtooth shape, and the metal back electrode 5 is used to conduct holes.

[0029] Optional, such as Figure 3 As shown, a protrusion 3 is provided on the surface of the transparent front electrode 2, and the metal back electrode 5 is placed on one side of the protrusion 3. The side of the metal back electrode 5 contacts the side wall of the protrusion 3 on the surface of the transparent front electrode 2 to form an ohmic contact. At this time, the metal back electrode 5 is only laid in the position where the protrusion 3 is not provided, and a photovoltaic layer 4 is also laid below the metal back electrode 5. That is, the metal back electrode 5 and the photovoltaic layer 4 are both laid in the recessed groove next to the protrusion 3. Therefore, when viewed from a direction perpendicular to the transparent substrate 1, the metal back electrode 5 cannot be directly seen due to the obstruction of the photovoltaic layer 4, and there is no phenomenon of metal reflection. This effectively improves the aesthetics of the multi-junction solar cell structure and avoids the reflection phenomenon of the metal back electrode 5, thereby improving user satisfaction.

[0030] Optionally, a transparent front electrode 2, a photovoltaic layer 4, and a metal back electrode 5 are sequentially stacked on one side of the transparent substrate 1. Since the transparent front electrode 2 has a protrusion 3, the metal back electrode 5 can contact the sidewall of the protrusion 3 of the transparent front electrode 2 without overlapping the transparent front electrode 2. It only needs to contact the sidewall of the protrusion 3 through the side of the metal back electrode 5. At this time, even if the photovoltaic layer 4 completely covers the metal back electrode 5, it will not hinder the contact between the metal back electrode 5 and the transparent front electrode 2, thus ensuring the connection function of the positive and negative electrodes of adjacent cells in the multi-junction series solar cell, while improving the aesthetics and avoiding the reflection phenomenon.

[0031] The metal back electrode 5 in the first solar cell has wavy serrations on the side facing the second solar cell, and the transparent front electrode 2 in the second solar cell has wavy serrations on the side facing the first solar cell. The wavy serrations of the metal back electrode 5 mesh with the wavy serrations of the transparent front electrode 2.

[0032] Optional, such as Figure 4As shown, in order to effectively increase the electrical contact area between the metal back electrode 5 and the transparent front electrode 2 in the film thickness direction, the side of the transparent front electrode 2 that forms an ohmic contact with the metal back electrode 5 is processed into a wavy or sawtooth shape. This can effectively increase the contact area between the positive and negative electrodes of the two solar cells, thereby effectively reducing the impedance of the contact surface and improving the electrical conductivity between the positive and negative electrodes.

[0033] In some preferred embodiments, the transparent front electrodes in the multi-junction solar cell are arranged in a ring structure around each other, wherein there is a gap between adjacent transparent front electrodes; an insulating layer is disposed between adjacent transparent front electrodes in the multi-junction solar cell, and the insulating layer is placed in the gap between adjacent transparent front electrodes.

[0034] Optionally, multiple transparent front electrodes 2 are arranged in a ring on a transparent substrate 1. The central part of the transparent substrate 1 forms a visible area, and the edge positions form a multi-junction solar cell composed of the transparent front electrodes 2, the photovoltaic layer 4, and the metal back electrode 5. In each junction solar cell, the transparent front electrode 2 corresponds to the negative electrode, and the metal back electrode 5 corresponds to the positive electrode. There are gaps between the transparent front electrodes 2 and other adjacent transparent front electrodes 2, meaning that the negative electrodes of each junction solar cell in the multi-junction solar cell cannot be directly connected.

[0035] In the transparent front electrode 2 of the first solar cell, only one side of the two positions connected to the adjacent solar cell has a protrusion. The side with the protrusion 3 is located on the side of the adjacent fourth solar cell. The first solar cell is the solar cell where the current transparent front electrode 2 is located, and the fourth solar cell is the solar cell adjacent to the first solar cell in the direction of electron outflow.

[0036] Optionally, a multi-junction solar cell is a series connection of multiple solar cell junctions with their positive and negative electrodes connected together. The negative electrode of the left solar cell is connected to the positive electrode of the right solar cell, thus realizing the series connection of multiple cells. The positive electrode of the transparent front electrode 2 of the first solar cell at the current position is connected to the negative electrode of the metal back electrode 5 of the adjacent right fourth solar cell. In this case, it is only necessary to set the height of the sidewall of the protrusion 3 near the position of the first solar cell and the fourth solar cell, that is, the metal back electrode 5 on the right can directly contact the sidewall of the transparent front electrode 2 on the left.

[0037] Optionally, a metal back electrode 5 needs to be placed on the left side of the first solar cell and connected to the transparent front electrode 2 of the adjacent solar cell on the left. Therefore, only the right side of the transparent front electrode 2 of each solar cell is not etched, that is, a protruding structure is formed on the right side.

[0038] Optional, such as Figure 1 , Figure 5 as well as Figure 6 As shown, the protrusion 3 of the transparent front electrode 2 is formed by etching the entire transparent front electrode downwards to create a recessed groove. The recessed groove is almost entirely distributed throughout the transparent front electrode 2, but some areas are left unetched, forming a protruding structure. The protruding structure can be varied, such as... Figure 1 The raised structure is a cuboid structure, positioned in the charge outflow direction of each junction solar cell, such as... Figure 5 The protruding structure is a concave structure, with the opening of the concave structure facing the adjacent fourth solar cell location, and is also positioned in the charge outflow direction of each junction solar cell; for example... Figure 6 The raised structure shown is a rectangular strip structure, which extends to a position parallel to the adjacent solar cell. At this time, the contact area between the metal back electrode 5 and the raised rectangular strip structure is larger. The rectangular strip structure is also arranged in the electron outflow direction of each junction solar cell.

[0039] Optionally, the thickness of the transparent front electrode 2 layer in the overlap area of ​​the positive and negative electrodes of two adjacent solar cells should be greater than the thickness of the transparent front electrode 2 layer in the effective photovoltaic absorption area, so as to form a stepped structure of the transparent front electrode 2. Specifically, depending on the type of solar cell, different height differences are set for the film steps of the transparent front electrode 2 in the overlap area: when the device type is an organic photovoltaic (OPV) solar cell, the height difference of the protrusion 3 of the transparent front electrode 2 is set between 500 nm and 3000 nm, and the preferred thickness is between 800 nm and 2000 nm; when the device type is a perovskite solar cell (PSC), the height difference of the transparent front electrode 2 is set between 800 nm and 3000 nm, and the preferred thickness is between 1000 nm and 2500 nm.

[0040] In some preferred embodiments, the photovoltaic layer 4 of the first solar cell extends to the gap between the first solar cell and the second solar cell, and contacts and connects with the transparent front electrode 2 in the second solar cell. The first solar cell is the solar cell where the current photovoltaic layer is located, and the second solar cell is the solar cell adjacent to the first solar cell in the direction of electron inflow. The metal back electrode 5 of the first solar cell extends to the gap between the first solar cell and the second solar cell, and contacts and connects with the transparent front electrode 2 in the second solar cell. A gap is provided between the metal back electrode 5 of the first solar cell and the part of the protrusion 3 of the transparent front electrode 2 in the first solar cell, and the metal back electrode 5 of the first solar cell and the transparent front electrode 2 in the first solar cell do not contact each other.

[0041] Optionally, the transparent front electrode 2 of the first solar cell and the metal back electrode 5 of the second solar cell on its left side are in contact with each other at multiple cross sections in the film thickness direction, forming a series connection structure of the positive and negative electrodes of the two adjacent cells. This allows the metal back electrode 5 to form a sufficient electrical overlap with the sidewall of the protrusion 3 in the film thickness direction while covering the photovoltaic layer 4, thereby effectively connecting the positive and negative electrodes of the two adjacent cells of the multi-junction solar cell.

[0042] Optionally, to ensure that the photovoltaic layer 4 completely covers the metal back electrode 5, the area of ​​the photovoltaic layer 4 facing the metal back electrode 5 needs to be exactly the same as that of the metal back electrode 5, and the position also needs to be the same. Since the metal back electrode 5 needs to overlap with the gap of the adjacent solar cells to connect with the transparent front electrode 2 on the left, the photovoltaic layer 4 also needs to overlap with the gap of the two solar cells to ensure that the metal back electrode 5 cannot be seen, thus preventing the phenomenon of metal reflection. This effectively improves the aesthetics of the multi-junction solar cell structure and avoids the reflection phenomenon of the metal back electrode 5, thereby improving user satisfaction.

[0043] Optional, such as Figure 3 as well as Figure 7 As shown, the metal back electrode 5 in the first solar cell is extended to the left until it contacts the transparent front electrode 2 in the second solar cell. Figure 3 The metal back electrode 5 extends only to the gap, and has a side contact with the transparent front electrode 2. Figure 7 The metal back electrode 5 extends into the opening of the concave structure of the transparent front electrode 2, targeting Figure 6 The metal back electrode 5 of the long strip structure moves closer to the adjacent transparent front electrode 2 and contacts the protrusion in the long strip structure.

[0044] In some preferred embodiments, the multi-junction solar cell further includes: a transparent front electrode lead-out terminal 7, disposed on the third solar cell and connected to the transparent front electrode 2 on the third solar cell, located on one side of the electron outflow direction in the transparent front electrode 2, wherein the third solar cell is any one of the multi-junction solar cells; the transparent front electrode 2 of the solar cell connected to the transparent front electrode lead-out terminal 7 does not have a protrusion.

[0045] In some preferred embodiments, the multi-junction solar cell further includes: a metal back electrode lead-out terminal 8 disposed on the fifth solar cell and connected to the metal back electrode 5 on the fifth solar cell, located on the side of the metal back electrode 5 close to the third solar cell, wherein the fifth solar cell is the solar cell adjacent to the side of the transparent front electrode lead-out terminal 7 in the third solar cell.

[0046] Optional, such as Figure 1 , Figure 5 and Figure 6 As shown, the multi-junction solar cells are connected in series. A transparent front electrode lead-out terminal 7 needs to be set in one of the solar cell junctions to bring out the negative electrode of the multi-junction solar cell so as to connect to the desired wearable device and power the wearable device. Meanwhile, as... Figure 8 As shown, the metal back electrode 5 also has a metal back electrode lead-out terminal 8, which leads out the positive electrode of the multi-junction solar cell and connects it to the required wearable device, thus realizing the effect of connecting the positive and negative electrodes of the multi-junction solar cell to the wearable device for power supply.

[0047] Optionally, the metal back electrode lead 8 and the transparent front electrode lead 7 need to be on adjacent solar cells, that is, the metal back electrode lead 8 and the transparent front electrode lead 7 are adjacent to each other.

[0048] In some preferred embodiments, the multi-junction solar cell further includes a back electrode lead-out terminal bridging block 9, which is disposed below the metal back electrode lead-out terminal 8 and at the same level as the transparent front electrode 2, for supporting the metal back electrode lead-out terminal 8.

[0049] Optional, such as Figure 9 As shown, to improve the stability of the electrical characteristics output of the transparent electrode, an auxiliary metal electrode structure 14 is fabricated on the lower surface of the positive and negative output electrodes of the solar cell, which is in direct contact with the transparent front electrode 2. This auxiliary metal is only disposed in the output terminal area, so it does not affect the absorption of light by the solar cell. The material of the auxiliary metal electrode structure 14 is not limited to low resistivity materials such as gold, silver, copper, aluminum, platinum, titanium, molybdenum, and chromium.

[0050] In some preferred embodiments, the photovoltaic layer 4 includes a groove 10 disposed around the outer edge of the photovoltaic layer 4, and the groove 10 is filled with an insulating layer 6.

[0051] Optional, such as Figure 10 As shown, after the transparent front electrode 2 is fabricated, an insulating layer 6 is fabricated on the surface of the transparent front electrode 2 to set the effective photovoltaic area and reduce the risk of leakage at the edge of the transparent front electrode 2 pattern.

[0052] Optional, such as Figure 11 As shown, by creating a groove 10 at the edge of the photovoltaic layer 4 and filling it with an insulating layer 6, the insulating layer 6 is arranged around the edge of the photovoltaic layer 4 in each junction solar cell and is also arranged between the intervals of the multi-junction solar cells, thereby achieving electrical isolation of the multi-junction solar cell units, suppression of edge leakage current, and protection of interlayer structure.

[0053] Optionally, the photovoltaic layer 4 of the multi-junction cell is a single-layer or multi-layer heterojunction stacked structure with many interlayer interfaces, a large carrier concentration gradient, and far more lattice defects and interface states at the edge than in the central photosensitive region. This makes it very easy to form an edge leakage current path, that is, the current leaks directly from the positive electrode to the negative electrode at the edge of the photovoltaic layer 4 without passing through the external circuit. A groove 10 is set at the outer edge of the photovoltaic layer 4, and the groove 10 is filled with an insulating layer 6 to ensure that the current at the edge of the photovoltaic layer 4 does not leak directly to the outside, electrically blocking the remaining edge leakage current path and suppressing the leakage current phenomenon.

[0054] In some preferred embodiments, the sum of the height of the photovoltaic layer 4 and the height of the metal back electrode 5 is equal to the height of the protrusion 3.

[0055] Optionally, the height of the photovoltaic layer 4 and the metal back electrode 5 can be set to be equal to the height of the protrusion 3. At this time, the upper end of the metal back electrode 5 is at the same height as the protrusion of the transparent front electrode 2, forming a planar structure, which is convenient for placement and installation.

[0056] In some preferred embodiments, the visible light transmittance of the transparent substrate 1 is set between 40% and 90%.

[0057] Optional, such as Figure 9 As shown, the display panel of the wearable device is positioned below the solar cell, stacked on top of it, and bonded to one side of the solar cell's encapsulation cover using transparent optical adhesive (OCR) or transparent optical film (OCA). The solar cell structure includes an opaque or semi-transparent photovoltaic power generation area (photovoltaic layer 4) and a light-transmitting area, forming a ring-shaped structure in the middle of which multiple solar cells are arranged. The light-transmitting area overlaps with the display area (VA) of the display panel. The visible light transmittance of the solar cell's light-transmitting area is between 40% and 90%, and a grid-type photovoltaic function can also be simultaneously installed within the light-transmitting area. The grid type is not limited to linear, ring-shaped, or honeycomb structures.

[0058] In some preferred embodiments, such as Figure 12 As shown, the photovoltaic layer 4 includes: a photovoltaic active layer 11, used to absorb sunlight of a preset wavelength to form electron-hole pairs; an electron transport layer 12, disposed on the surface of the photovoltaic active layer 11, used to transport electrons generated in the photovoltaic active layer 11; and a hole transport layer 13, disposed on the side of the photovoltaic active layer 11 away from the electron transport layer 12, used to transport holes generated in the photovoltaic active layer 11.

[0059] Optionally, the photovoltaic layer 4 includes a photovoltaic active layer 11, an electron transport layer 12, and a hole transport layer 13, such as... Figure 13As shown, when the device is a perovskite solar cell, an electron injection layer 15 is also included between the photovoltaic active layer 11 and the electron transport layer 12. A hole blocking layer 16 is also provided between the electron transport layer 12 and the cathode. A self-assembled monolayer (SAM) layer 17 and an interface modification layer are also included between the hole transport layer 13 and the photovoltaic active layer 11. Similarly, a monolayer, a passivation layer and an interface modification layer are also included between the electron transport layer 12 and the photovoltaic active layer 11. This effectively improves the carrier mobility and the surface smoothness and stability of the perovskite active layer, thereby improving the stability of the perovskite solar cell and the repeatability of the product performance.

[0060] Example 2 Based on the above embodiments and optional embodiments, the present invention also proposes a method implementation method. Figure 14 This is a flowchart of a method for fabricating a multi-junction solar cell according to Embodiment 2 of the present invention, as shown below. Figure 14 As shown, the method includes: Step S1: The transparent front electrode 2 is placed on the surface of the transparent substrate 1. Using photolithography and etching processes, a recessed groove is made on the transparent front electrode 2 to form a protrusion 3 on the transparent front electrode 2. In some preferred embodiments, a transparent front electrode 2 is disposed on the surface of a transparent substrate 1. A recessed groove is formed on the transparent front electrode 2 using photolithography and etching processes to form a protrusion 3 on the transparent front electrode 2. This includes: fabricating a transparent front electrode 2 on the transparent substrate 1; applying a photoresist coating to the entire surface of the transparent front electrode 2 for the first time, followed by exposure, development, hardening, and etching to form a transparent front electrode 2 with a smooth surface; applying a photoresist coating to the surface of the smooth transparent front electrode 2 for the second time, followed by exposure, development, and hardening to expose the area outside the contact position between the transparent front electrode 2 and the adjacent solar cell; and forming a recessed groove by etching to form a protrusion 3 on the electron outflow direction side of the transparent front electrode 2.

[0061] Optionally, a transparent front electrode 2 is disposed on the surface of a transparent substrate 1, and a stepped transparent front electrode 2 pattern with a significant height difference is created by using two photolithography and two etching processes. The specific process for forming the stepped transparent front electrode 2 is as follows: A layer of transparent conductive material TCO with a thickness greater than 1 μm is fabricated on the surface of the transparent substrate 1 by coating, physical vapor deposition (PVD), or chemical vapor deposition (CVD). The transparent conductive material can be selected from AZO, ITO, FTO, graphene, etc., and the preferred TCO thickness is between 1 μm and 10 μm. Photoresist is coated on the TCO surface, and then exposed, developed, hardened, and etched to first form a transparent front electrode 2 with no height difference and a smooth surface. Photoresist is then coated on the surface of the transparent front electrode 2, and then exposed, developed, hardened, and etched to form a transparent front electrode 2 with a height difference in the recessed groove. The pattern of the transparent front electrode 2 includes an effective photovoltaic absorption area pattern, positive and negative electrode interconnection lines, and two electrodes (positive and negative).

[0062] Step S2: An insulating layer 6 is provided between the transparent front electrode 2 and the adjacent transparent front electrode 2, and the insulating layer 6 is laid along the outer edge of the transparent front electrode 2. Step S3: Electron transport layer 12, photovoltaic active layer 11 and hole transport layer 13 are coated layer by layer on the surface of transparent front electrode 2 to form photovoltaic layer 4, wherein the outer edge of photovoltaic layer 4 is aligned with insulating layer 6 laid along the outer edge of transparent front electrode 2. Optionally, an electron transport layer 12ETL, a photovoltaic active layer 11ACTL, and a hole transport layer 13HTL are sequentially coated on the surface of the transparent substrate 1, and patterning is achieved through photolithography, etching, and vapor deposition. The metal back electrode 5 is then formed by thermal vapor deposition using a metal mask.

[0063] Step S4: Based on the metal mask and thermal evaporation method, a metal back electrode 5 is laid on the surface of the photovoltaic layer 4. While covering the photovoltaic layer 4, the metal back electrode 5 extends towards the adjacent solar cell and forms an electrical connection with the transparent front electrode 2 of the adjacent solar cell, which is thicker than the photovoltaic layer 4, on the side. Step S5: Encapsulate the transparent front electrode 2, the insulating layer 6, the photovoltaic layer 4, and the metal back electrode 5.

[0064] In some preferred embodiments, the transparent front electrode 2, insulating layer 6, photovoltaic layer 4 and metal back electrode 5 are encapsulated, including: vacuum bonding the solar cell with the metal back electrode 5 to a back cover coated with frame adhesive and desiccant, curing the frame adhesive to form an encapsulation, while exposing the electrode lead terminals; or by using thin-film encapsulation (TFE) to cover the area of ​​the solar cell except for the electrode lead terminals.

[0065] Optionally, the solar cell can be encapsulated using either a solid structure or a thin-film structure. For solid encapsulation, the solar cell substrate with the completed metal back electrode 5 is vacuum-bonded to a back cover coated with frame adhesive and desiccant. UV curing of the frame adhesive, supplemented by thermal curing, completes the encapsulation of the multi-junction solar cell. For thin-film encapsulation, an insulating film is deposited or an insulating resin is coated on the surface of the metal back electrode 5 to completely seal and cover the area outside the positive and negative output electrode contact points of the solar cell. The thin-film encapsulation process is not limited to chemical vapor deposition (CVD), liquid phase precision coating (IJP), or high-density vapor deposition (ALD).

[0066] Through the above steps S1 to S5, by optimizing the process and product structure design, the visibility of the metal back electrode 5 and the reflection of the metal are effectively eliminated, thereby improving the appearance of the device.

[0067] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-junction solar cell structure, characterized in that, Each junction solar cell in a multi-junction solar cell includes: A transparent front electrode (2) is laid on the surface of a transparent substrate (1) in an L-shaped structure and placed along the outer edge of the transparent substrate (1). The transparent front electrode (2) is used to conduct electrons. A photovoltaic layer (4) is laid on the surface of the transparent front electrode (2) to absorb light energy and generate electron-hole pairs; A metal back electrode (5) is laid on the surface of the photovoltaic layer (4); Except for the solar cell connected to the negative electrode of the external power supply equipment, all other solar cells in the multi-junction solar cell include: protrusions (3). The transparent front electrode (2) has a protrusion (3) on the side away from the transparent substrate (1), and the protrusion (3) is located at the electron outflow position in the transparent front electrode (2). The photovoltaic layer (4) is laid on the surface of the transparent front electrode (2) and does not cover the protrusion (3); There is a gap between the metal back electrode (5) and the protrusion in the solar cell. The vertical side of the metal back electrode (5) is electrically connected to the side of the protrusion in the adjacent solar cell. The contact surface between the metal back electrode (5) and the protrusion in the adjacent solar cell is set as a wavy sawtooth shape. The metal back electrode (5) is used to conduct holes.

2. The multi-junction solar cell structure according to claim 1, characterized in that, In a multijunction solar cell, the transparent front electrodes are connected to form a ring structure, wherein there is a gap between adjacent transparent front electrodes; An insulating layer is disposed between adjacent transparent front electrodes in a multijunction solar cell, and the insulating layer is placed within the gap between adjacent transparent front electrodes.

3. The multi-junction solar cell structure according to claim 2, characterized in that, The photovoltaic layer of the first solar cell extends to the gap between the first solar cell and the second solar cell, and is in contact with the transparent front electrode in the second solar cell. The first solar cell is the solar cell where the current photovoltaic layer is located, and the second solar cell is the solar cell adjacent to the first solar cell in the direction of electron inflow. The metal back electrode of the first solar cell extends to the gap between the first solar cell and the second solar cell, and contacts and connects with the transparent front electrode in the second solar cell.

4. The multi-junction solar cell structure according to claim 1, characterized in that, The multijunction solar cell also includes: A transparent front electrode lead-out terminal (7) is disposed on the third solar cell and connected to the transparent front electrode (2) on the third solar cell. It is located on one side of the direction of electron outflow in the transparent front electrode (2). The third solar cell is any one of the multi-junction solar cells. The transparent front electrode (2) of the solar cell connected to the transparent front electrode lead-out terminal (7) does not have a protrusion.

5. A multi-junction solar cell structure according to claim 4, characterized in that, The multijunction solar cell also includes: A metal back electrode lead-out terminal (8) is disposed on the fourth solar cell and connected to the metal back electrode (5) on the fourth solar cell. It is located on the side of the metal back electrode (5) close to the third solar cell, wherein the fourth solar cell is the solar cell adjacent to the side of the transparent front electrode lead-out terminal (7) of the third solar cell.

6. A multi-junction solar cell structure according to claim 5, characterized in that, The multijunction solar cell also includes: The back electrode lead-out terminal bridging block (9) is disposed below the metal back electrode lead-out terminal (8) and at the same level as the transparent front electrode (2), and is used to support the metal back electrode lead-out terminal (8).

7. A multi-junction solar cell structure according to claim 2, characterized in that, The photovoltaic layer (4) includes: A groove (10) is provided around the outer edge of the photovoltaic layer (4), and the groove (10) is filled with the insulating layer (6).

8. A multi-junction solar cell structure according to claim 1, characterized in that, The sum of the height of the photovoltaic layer (4) and the height of the metal back electrode (5) is equal to the height of the protrusion (3).

9. A multi-junction solar cell structure according to claim 1, characterized in that, The visible light transmittance of the transparent substrate (1) is set between 40% and 90%.

10. A multi-junction solar cell structure according to claim 1, characterized in that, The photovoltaic layer (4) includes: A photovoltaic active layer (11) is used to absorb sunlight of a preset wavelength to form electron-hole pairs; An electron transport layer (12) is disposed on the surface of the photovoltaic active layer (11) for transporting electrons generated in the photovoltaic active layer (11); A hole transport layer (13) is disposed on the side of the photovoltaic active layer (11) away from the electron transport layer (12) for transporting holes generated in the photovoltaic active layer (11).

11. A method for fabricating a multi-junction solar cell, applied to the multi-junction solar cell structure described in any one of claims 1 to 10, characterized in that, include: A transparent front electrode (2) is placed on the surface of a transparent substrate (1). A recessed groove is made on the transparent front electrode (2) using photolithography and etching processes to form a protrusion (3) on the transparent front electrode (2). An insulating layer (6) is provided between the transparent front electrode (2) and the adjacent transparent front electrode (2), and an insulating layer (6) is laid along the outer edge of the transparent front electrode (2). An electron transport layer (12), a photovoltaic active layer (11), and a hole transport layer (13) are coated layer by layer on the surface of the transparent front electrode (2) to form a photovoltaic layer (4), wherein the outer edge of the photovoltaic layer (4) is aligned with the insulating layer (6) laid along the outer edge of the transparent front electrode (2); Based on the metal mask and thermal evaporation method, a metal back electrode (5) is laid on the surface of the photovoltaic layer (4). While covering the photovoltaic layer (4), the metal back electrode (5) extends towards the adjacent solar cell and forms an electrical connection with the transparent front electrode (2) of the adjacent solar cell that is thicker than the photovoltaic layer (4) on the side. The transparent front electrode (2), the insulating layer (6), the photovoltaic layer (4) and the metal back electrode (5) are encapsulated.

12. The method for fabricating a multi-junction solar cell according to claim 11, characterized in that, A transparent front electrode (2) is disposed on the surface of a transparent substrate (1). A recessed groove is formed on the transparent front electrode (2) using photolithography and etching processes, forming a protrusion (3) on the transparent front electrode (2), including: A transparent front electrode (2) is fabricated on the transparent substrate (1); The entire surface of the transparent front electrode (2) is coated with photoresist for the first time, and then exposed, developed, hardened and etched to form a transparent front electrode (2) with a smooth surface. On the surface of the smooth transparent front electrode (2), a second photoresist is applied, and then exposed, developed, and hardened to expose the area outside the contact position between the transparent front electrode (2) and the adjacent solar cell. A sinking groove is formed by etching to create the protrusion (3) on the electron outflow direction side of the transparent front electrode (2).

13. The method for fabricating a multi-junction solar cell according to claim 11, characterized in that, The method for encapsulating the transparent front electrode (2), the insulating layer (6), the photovoltaic layer (4), and the metal back electrode (5) includes: The solar cell with the completed metal back electrode (5) is vacuum bonded to the back cover coated with frame adhesive and desiccant, the frame adhesive is cured to form an encapsulation, and the electrode lead terminals are exposed at the same time. Alternatively, a thin-film encapsulation method can be used to cover and encapsulate the area of ​​the solar cell except for the electrode lead terminals.

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