Tandem solar cells

Abstract

The present invention provides a tandem solar cell that can suppress power generation irregularities in the silicon element positioned beneath the perovskite element. [Solution] The tandem solar cell 1 is a tandem solar cell 1 in which a plurality of perovskite elements 41 are arranged on the surface side of a plurality of silicon elements 51, at least a portion of the plurality of silicon elements 51 are arranged on the back side of the gap between the perovskite elements 41, or light passing through the gap between the perovskite elements 41 from the surface side to the back side reaches at least a portion of the plurality of silicon elements 51, and a light-transmitting filter 7 that cuts out the wavelength range absorbed by the perovskite elements 41 is provided in the gap between the perovskite elements 41.

Description

Technical Field

[0001] The present invention relates to a tandem solar cell.

Background Art

[0002] Patent Document 1 discloses a tandem solar cell in which a perovskite solar cell is laminated and joined on a silicon solar cell. This tandem solar cell has a perovskite solar cell including an absorption layer having a relatively large bandgap and a silicon solar cell including an absorption layer having a relatively small bandgap joined through a joining layer. The perovskite solar cell disposed on the upper part absorbs light in the short wavelength region and generates electricity, and the silicon solar cell disposed on the lower part absorbs light in the long wavelength region and generates electricity, so that the threshold wavelength can be shifted to a longer wavelength side. As a result, the wavelength band absorbed by the entire solar cell can be widened (the region of the total absorption wavelength can be widely used), and thus light energy in a wide spectral region can be efficiently utilized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Silicon solar cells have standardized cell sizes, offering little flexibility in terms of size (area). Perovskite solar cells, on the other hand, can be manufactured to have large-area cells according to the manufacturer's intentions. Larger-area cells have better area efficiency in receiving light such as sunlight, so it is desirable to use large-area cells whenever possible. This results in a difference in cell size between silicon solar cells and perovskite solar cells. When silicon solar cells and perovskite solar cells with different cell sizes are used in tandem, the number and position of cells that can be placed in the upper and lower solar cells (specifically, the silicon elements that make up the bottom cell and the perovskite elements that make up the top cell) will change, and some or all of the silicon elements may be placed below the gap between the perovskite elements.

[0005] When silicon solar cells and perovskite solar cells are used in tandem, the silicon element constituting the bottom cell receives afterglow from the perovskite solar cell, which absorbs some of the light energy, and generates electricity using this afterglow. On the other hand, there is no absorption of light energy by the perovskite solar cell in the gaps between the perovskite elements, and the light energy reaches the silicon element directly. If strong light that has passed through the gaps and not transmitted through the perovskite elements reaches the silicon element located below the gaps between the perovskite elements, power generation will become uneven within the silicon element (resulting in uneven power generation), raising concerns about overheating. Due to the temperature characteristics of solar cells, if the temperature rises due to overheating, the power generation efficiency of the solar cell will decrease.

[0006] The present invention has been made in view of the above problems, and aims to provide a tandem solar cell that can suppress power generation unevenness of the silicon element arranged below the perovskite element. [Means for solving the problem]

[0007] To solve the above problems, the tandem solar cell according to the present invention is a tandem solar cell in which a plurality of perovskite elements are arranged on the surface side of a plurality of silicon elements, at least a portion of the plurality of silicon elements are arranged on the back side of the gap between the perovskite elements, or light passing through the gap between the perovskite elements from the surface side to the back side reaches at least a portion of the plurality of silicon elements, characterized in that a light-transmitting filter is provided in the gap between the perovskite elements to cut out the wavelength range absorbed by the perovskite elements. [Effects of the Invention]

[0008] According to the present invention, by providing a light-transmitting filter in the gap between the perovskite elements that cuts out the wavelength range absorbed by the perovskite elements, it is possible to suppress uneven power generation of the silicon element positioned below the perovskite elements. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic plan view showing an example of mounting a tandem solar cell according to one embodiment of the present invention. [Figure 2] This is a schematic, enlarged cross-sectional view of a conventional tandem solar cell that does not have a light-transmitting filter in the gap between perovskite elements. [Figure 3] This is a schematic enlarged cross-sectional view showing a tandem solar cell according to one embodiment of the present invention, which is equipped with a light-transmitting filter in the gap between perovskite elements. [Figure 4] This figure shows the light transmittance of a perovskite element. [Figure 5] This figure shows the light transmittance of various light-transmitting filters, along with the light transmittance of perovskite elements. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below with reference to Figures 1 to 5. Note that the embodiments described below are only one aspect of the present invention and do not limit the technical scope of the present invention.

[0011] Figure 1 is a schematic plan view showing an example of mounting a tandem-type solar cell 1 (hereinafter sometimes simply referred to as solar cell 1) according to this embodiment. Specifically, it is a schematic plan view showing the solar cell 1 according to this embodiment mounted on an existing roof substrate of a vehicle 10. By mounting the solar cell 1 according to this embodiment on the roof substrate, it constitutes the roof 11 of the vehicle 10. The solar cell 1 has a curved plate-like shape. Therefore, it can be mounted on the roof substrate according to the similarly curved shape of the roof substrate of the vehicle 10.

[0012] The solar cell 1 has a tandem structure and has a translucent glass surface layer 2 on the uppermost layer of the roof 11 (i.e., the layer closest to the viewer in the orientation of Figure 1). When sunlight or other light is shone on the solar cell 1, the shone light passes through the surface layer 2 and reaches the inside of the solar cell 1. This generates an electromotive force between the positive and negative electrodes of the solar cell 1, and the generated electricity can be supplied to the vehicle 10 or the like.

[0013] Furthermore, the solar cell 1 is thin and lightweight. Taking advantage of these characteristics, the solar cell 1 can be mounted on various things, such as building roofs, in addition to the roof substrate of the vehicle 10 exemplified in Figure 1.

[0014] Figure 2 is a schematic enlarged cross-sectional view of a conventional tandem solar cell 1A (hereinafter sometimes simply referred to as solar cell 1A). Figure 3 is a schematic enlarged cross-sectional view of a tandem solar cell 1 according to this embodiment. Note that solar cells 1 and 1A are for vehicle mounting and are curved to correspond to the shape of the roof substrate of the vehicle 10, but for the sake of explanation, they are shown as flat plates in the cross-sectional view.

[0015] Solar cells 1 and 1A comprise a surface layer 2, a back layer 3, perovskite solar cells (units) 4 and silicon solar cells (units) 5 arranged sequentially from the surface layer 2 side between the surface layer 2 and the back layer 3, and a sealing material (also called an intermediate layer, etc.) 6 that seals the perovskite solar cells 4 and silicon solar cells 5. The back layer 3 is also made of glass, just like the surface layer 2. In other words, in solar cells 1 and 1A, the perovskite solar cells 4 are stacked on the surface layer 2 side (upper side) of the silicon solar cells 5 between the surface layer 2 and the back layer 3, and these are sealed and joined together by the sealing material 6.

[0016] The perovskite solar cell 4 has a plurality of roughly rectangular perovskite cells 40 (3 left-right x 4 front-back = 12 in the example of Figure 1), and the plurality of perovskite cells 40 are slightly spaced apart from each other and arranged in a matrix in a plan view. Each perovskite cell 40 has a perovskite element 41, electrodes, etc., and is curved according to the curved shape of the solar cells 1, 1A. The perovskite element 41 is a power generation element made from titanite and is flexible.

[0017] The silicon solar cell 5 has a plurality of silicon cells 50 that are roughly rectangular in shape (5 left-right x 7 front-back = 35 in the example of Figure 1). The plurality of silicon cells 50 are arranged in a matrix, slightly spaced apart from each other in a plan view, so as to face the plurality of perovskite cells 40 from above and below. Each silicon cell 50 has a silicon element 51, electrodes, etc., and is curved according to the curved shape of the solar cells 1 and 1A. The silicon element 51 is also a type of power generation element, and the silicon element 51 may be a single crystal or a polycrystalline material.

[0018] As described above, after the irradiation light passes through the surface layer 2, it reaches the inside of the solar cells 1 and 1A. When this irradiation light first reaches the perovskite element 41, depending on the wavelength range of the irradiation light, the irradiation light is absorbed by the perovskite element 41 or passes through the perovskite element 41 and is absorbed by the silicon element 51. Specifically, light in a wavelength range shorter than a predetermined value such as visible light is absorbed by the perovskite element 41, and light in a wavelength range longer than a predetermined value such as infrared light passes through the perovskite element 41 and is absorbed by the silicon element 51. That is, by laminating power generation elements with different absorption wavelength lengths, light of a wide spectrum range can be absorbed for power generation, and the energy of the irradiation light can be converted into electrical energy with high conversion efficiency.

[0019] Each perovskite element 41 and each silicon element 51 are electrically connected by an interconnector (not shown), and current flows through the interconnector to the perovskite solar cell 4 and the silicon solar cell 5. Specifically, each perovskite element 41 and each silicon element 51 are electrically connected by an interconnector separately or independently, and the perovskite element 41 (perovskite solar cell 4) and the silicon element 51 (silicon solar cell 5) are not electrically connected. The solar cells 1 and 1A that separately generate and extract power from the perovskite solar cell 4, which is such a top cell, and the silicon solar cell 5, which is a bottom cell, are called four-terminal tandem solar cells.

[0020] The perovskite elements 41 that make up the top cell and the silicon elements 51 that make up the bottom cell have different cell sizes (area in a plan view). Specifically, the perovskite elements 41 have a larger cell size (area in a plan view) than the silicon elements 51. Therefore, fewer cells can be arranged using the perovskite elements 41 than using the silicon elements 51. In the example in Figure 1, 12 perovskite elements 41 are arranged at predetermined intervals from each other: 3 in the left-right direction (vehicle width direction) and 4 in the front-rear direction (vehicle length direction). Also, 35 silicon elements 51 are arranged at predetermined intervals from each other: 5 in the left-right direction (vehicle width direction) and 7 in the front-rear direction (vehicle length direction). When silicon solar cells 5 and perovskite solar cells 4 with different cell sizes are used in tandem, the number and position of cells that can be placed in the upper and lower solar cells (specifically, the silicon elements 51 that make up the bottom cell and the perovskite elements 41 that make up the top cell) change, and some or all of the silicon elements 51 may be placed on the back layer 3 side (lower side) of the gap between the perovskite elements 41. In the example in Figure 1, for the 12 silicon elements 51, the entire silicon element 51 is placed below the perovskite elements 41, but for the 23 silicon elements 51, some (or all) of each silicon element 51 is placed below the gap between the perovskite elements 41.

[0021] When a silicon solar cell 5 (silicon element 51 thereof) and a perovskite solar cell 4 (perovskite element 41 thereof) are used tandemly (stacked), in the silicon element 51 that constitutes the bottom cell, the remaining light after a part of the light energy is absorbed by the perovskite solar cell 4 reaches, and power generation is carried out with the remaining light. On the other hand, there is no absorption of light energy by the perovskite solar cell 4 in the gap between the perovskite elements 41, and the light energy will reach the silicon element 51 as it is. When strong light that has passed through the gap between the perovskite elements 41 (from the upper side to the lower side) and has not passed through the perovskite elements 41 reaches the silicon element 51 arranged below the gap between the perovskite elements 41, power generation in the silicon element 51 becomes non-uniform (power generation unevenness occurs), and there is a concern of heat generation. From the temperature characteristics of the solar cell, when the temperature rises due to heat generation, the power generation efficiency of the solar cell decreases (see particularly FIG. 2).

[0022] Therefore, the solar cell 1 according to the present embodiment has a light-transmitting filter 7 that absorbs (cuts) a part of the light energy in the gap between the perovskite elements 41, specifically, in the gap between the perovskite elements 41 where the silicon element 51 is arranged on the lower side (see particularly FIG. 3). Specifically, the light-transmitting filter 7 is composed of a filter (a filter corresponding to the dotted line in FIG. 5) that cuts the wavelength range absorbed by the perovskite element 41 (see the dotted line in FIG. 4). The light-transmitting filter 7 preferably has flexibility similar to the perovskite element 41. As a result, in the gap between the perovskite elements 41, light with the wavelength range absorbed by the perovskite element 41 cut by passing through the light-transmitting filter 7 provided in the gap reaches the silicon element 51 on the lower side.

[0023] As described above, the tandem solar cell 1 according to this embodiment is a tandem solar cell 1 in which a plurality of perovskite elements 41 are arranged on the surface side (surface layer 2 side) of a plurality of silicon elements 51, at least a portion of the plurality of silicon elements 51 are arranged on the back side (back layer 3 side) of the gap between the perovskite elements 41, or light passing through the gap between the perovskite elements 41 from the surface side (surface layer 2 side) to the back side (back layer 3 side) reaches at least a portion of the plurality of silicon elements 51, wherein a light-transmitting filter 7 that cuts out the wavelength range absorbed by the perovskite elements 41 is provided in the gap between the perovskite elements 41.

[0024] According to this embodiment, by providing a light-transmitting filter 7 in the gap between the perovskite elements 41 that cuts out the wavelength range absorbed by the perovskite elements 41, it is possible to suppress power generation unevenness (non-uniformity of power generation) of the silicon element 51 located below the perovskite elements 41. This makes it possible to suppress a decrease in the power generation efficiency of the tandem solar cell 1.

[0025] In the above embodiment, for some of the silicon elements 51 (12 elements), the entire silicon element 51 is positioned below the perovskite element 41, and for some of the silicon elements 51 (23 elements), part (or all) of each silicon element 51 is positioned below the gap between the perovskite elements 41. However, even if, for all of the silicon elements 51, part or all of each silicon element 51 is positioned below the gap between the perovskite elements 41, if the area of ​​the silicon element 51 that overlaps (is below) the gap between the perovskite elements 41 changes among the silicon elements 51, power generation unevenness will occur within the silicon element 51. Therefore, by providing a light-transmitting filter 7 in the gap between the perovskite elements 41 as in the above embodiment, power generation unevenness in the silicon element 51 can be suppressed.

[0026] Furthermore, the present invention is not limited to the embodiments described above, and can be appropriately modified and altered without departing from the objective of the present invention. [Explanation of Symbols]

[0027] 1: Tandem solar cell, 2: Front layer, 3: Back layer, 4: Perovskite solar cell, 40: Perovskite cell, 41: Perovskite element, 5: Silicon solar cell, 50: Silicon cell, 51: Silicon element, 6: Encapsulation material, 7: Light-transmitting filter, 10: Vehicle, 11: Roof

Claims

1. Multiple perovskite elements are arranged on the surface side of multiple silicon elements. A tandem solar cell in which at least a portion of the plurality of silicon elements are arranged on the back side of the gap between the perovskite elements, or in which light passing through the gap between the perovskite elements from the front side to the back side reaches at least a portion of the plurality of silicon elements, A tandem solar cell characterized in that a light-transmitting filter is provided in the gap between the perovskite elements, which cuts out the wavelength range absorbed by the perovskite elements.

2. The tandem solar cell according to claim 1, characterized in that the perovskite element has a larger area than the silicon element.

Images