Series solar cell

Abstract

The present disclosure relates to a series solar cell, and more particularly, to a series solar cell in which a plurality of solar cells are electrically connected. A tandem solar cell according to an exemplary embodiment of the present disclosure includes: a first solar cell having a first upper electrode and a first lower electrode disposed spaced apart from each other; a second solar cell disposed below the first solar cell and having a second upper electrode and a second lower electrode disposed spaced apart from each other; a first output terminal connected to the first upper electrode; a second output terminal connected to the second lower electrode; and a third output terminal connected to both the first lower electrode and the second upper electrode.

Description

Technical Field

[0001] The present disclosure relates to a series-connected solar cell, and more particularly, to a series-connected solar cell in which a plurality of solar cells are electrically connected. Background Art

[0002] A solar cell is a device that converts solar energy (ie, sunlight) into electrical energy by utilizing the characteristics of semiconductors and outputs the electrical energy.

[0003] A solar cell has a PN junction structure in which a P (positive) type semiconductor and an N (negative) type semiconductor are bonded together, and when sunlight is incident on a solar cell having this structure, holes and electrons are generated in the semiconductor by the energy of the incident light. In this case, through the electric field generated at the PN junction, holes move toward the P-type semiconductor and electrons move toward the N-type semiconductor, thus generating an electric potential, thereby generating electrical energy, that is, electricity.

[0004] In recent years, in order to improve the efficiency of solar cells, development has been actively carried out to form a series solar cell by stacking a plurality of solar cells and electrically connecting them. However, the limitation of the series solar cell is that the amount of light incident on each solar cell is different from each other, and current matching between solar cells is very difficult, so the photoelectric conversion efficiency is low.

[0005] (Prior Art Documents)

[0006] Korean patent document with patent number 10-2246070 Summary of the invention

[0007] Technical issues

[0008] The present disclosure provides a series-connected solar cell capable of utilizing idle current generated by a plurality of solar cells.

[0009] Technical Solution

[0010] According to an exemplary embodiment, a tandem solar cell includes: a first solar cell unit having a first upper electrode and a first lower electrode spaced apart from each other; a second solar cell unit disposed below the first solar cell unit and having a second upper electrode and a second lower electrode spaced apart from each other; a first output terminal connected to the first upper electrode; a second output terminal connected to the second lower electrode; and a third output terminal connected to both the first lower electrode and the second upper electrode.

[0011] The first load may be connected between the first output terminal and the second output terminal, the second load may be connected between the first output terminal and the third output terminal, and the third load may be connected between the second output terminal and the third output terminal.

[0012] The series solar cell may further include a first current controller, a second current controller and a controller, wherein the first current controller is arranged between the first output terminal and the third output terminal, the second current controller is arranged between the second output terminal and the third output terminal, and the controller is configured to control the operation of the first current controller and the second current controller.

[0013] The series solar cells may further include a first light amount sensing unit and a second light amount sensing unit, the first light amount sensing unit being configured to detect the amount of sunlight incident on the first solar cell unit, the second light amount sensing unit being configured to detect the amount of sunlight incident on the second solar cell unit, and the controller may be configured to selectively operate the first current controller and the second current controller according to the amount of sunlight detected by the first light amount sensing unit and the second light amount sensing unit.

[0014] The controller can be configured to: operate the first current controller when the amount of light detected by the first light sensing unit is greater than a preset first reference light amount or the amount of light detected by the second light sensing unit is less than a preset second reference light amount; and operate the second current controller when the amount of light detected by the first light sensing unit is less than the first reference light amount or the amount of light detected by the second light sensing unit is greater than the preset second reference light amount.

[0015] The series solar cell may further include a current sensing unit disposed between the first output terminal and the second output terminal, and the controller may be configured to control operation of at least one of the first current controller and the second current controller according to a current amount detected by the current sensing unit.

[0016] At least one of the first current controller and the second current controller may include a switching element.

[0017] The controller may be configured to switch the switching element in the off state to the on state when the amount of current detected by the current sensing unit does not change within a set time.

[0018] The controller may be configured to switch the switching element in the on-state to the off-state when the amount of current detected by the current sensing unit decreases after the switching element is switched to the on-state.

[0019] At least one of the first current controller and the second current controller may include a variable resistance element.

[0020] The controller may be configured to reduce a resistance value of the variable resistance element set to a maximum resistance value when the amount of current detected by the current sensing unit does not change within a set time.

[0021] The controller may be configured to maintain a reduced resistance value of the variable resistance element when the amount of current detected by the current sensing unit decreases while the resistance value of the variable resistance element decreases.

[0022] The first solar cell unit may include a first transparent substrate for transmitting sunlight incident from above, and the second solar cell unit includes a second transparent substrate for transmitting sunlight incident from below.

[0023] The tandem solar cell may further include an adhesive layer disposed between the first lower electrode and the second upper electrode.

[0024] At least one of the first load, the second load, and the third load may include a secondary battery.

[0025] Beneficial Effects

[0026] By utilizing the series-connected solar cells according to an exemplary embodiment, in addition to the first output terminal and the second output terminal for supplying power to the main load, by including a third output terminal for supplying power to the auxiliary load, an idle current generated by the difference in the amount of current generated from each solar cell can be additionally supplied to the auxiliary load. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a view schematically showing a series-connected solar cell according to an exemplary embodiment of the present disclosure.

[0028] Figure 2 is a view illustrating a state in which a current controller is installed according to an exemplary embodiment of the present disclosure.

[0029] Figure 3 is a view showing the flow of current when sunlight of a reference light amount is incident on each of the first solar cell and the second solar cell.

[0030] Figure 4 is a view showing the flow of current when sunlight having a light amount exceeding a reference light amount is incident on the first solar cell unit.

[0031] Figure 5 is a view showing the flow of current when sunlight having a light amount exceeding a reference light amount is incident on the second solar cell unit. DETAILED DESCRIPTION

[0032] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the exemplary embodiments disclosed below, but will be implemented in various different forms. The exemplary embodiments of the present disclosure are provided only to make the present disclosure complete and to fully inform the scope of the present disclosure to those of ordinary skill in the art.

[0033] It will also be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

[0034] In addition, relative terms such as "above" or "below" may be used herein to describe the relative relationship of some elements to other elements as shown in the figures. It will be understood that these relative terms are intended to cover different orientations of the device in addition to the orientation depicted in the figures. Here, the drawings may be exaggerated to describe the present disclosure in detail, and in the drawings, like reference numerals refer to like elements.

[0035] Figure 1 is a view schematically illustrating a series-connected solar cell according to an exemplary embodiment of the present disclosure.

[0036] Reference Figure 1 According to an exemplary embodiment, a series solar cell includes a first solar cell unit 100, a second solar cell unit 200, a first output terminal T1, a second output terminal T2, and a third output terminal T3, the first solar cell unit 100 having a first upper electrode 120 and a first lower electrode 140 spaced apart from each other, the second solar cell unit 200 is disposed below the first solar cell unit 100 and having a second upper electrode 240 and a second lower electrode 220 spaced apart from each other, the first output terminal T1 is connected to the first upper electrode 120, the second output terminal T2 is connected to the second lower electrode 220, and the third output terminal T3 is connected to both the first lower electrode 140 and the second upper electrode 240.

[0037] Here, the first load 310 may be connected between the first output terminal T1 and the second output terminal T2 , the second load 320 may be connected between the first output terminal T1 and the third output terminal T3 , and the third load 330 may be connected between the second output terminal T2 and the third output terminal T3 .

[0038] The first solar cell unit 100 absorbs sunlight incident from above and converts the sunlight into electrical energy. The first solar cell unit 100 may include a crystalline solar cell, an amorphous solar cell, a thin film solar cell, a dye-sensitized solar cell, an organic solar cell, a quantum dot solar cell, and a perovskite solar cell. Hereinafter, an exemplary structure in which the first solar cell unit 100 includes a first substrate 110, a first upper electrode 120 disposed below the first substrate 110, a first light absorbing layer 130 disposed below the first upper electrode 120, and a first lower electrode 140 disposed below the first light absorbing layer 130 will be described, but the structure is not limited thereto and can of course be applied to various types of known solar cells.

[0039] The first substrate 110 may include a transparent substrate for transmitting sunlight incident from above. When the first substrate 110 includes a transparent substrate, the first substrate 110 may be made of glass.

[0040] The first upper electrode 120 is disposed under the first substrate 110. The first upper electrode 120 may be made of a transparent conductive material to transmit sunlight passing through the first substrate 110 to the first light absorbing layer 130 disposed under the first upper electrode 120. Such a transparent conductive material may include a material having high light transmittance and excellent conductivity, such as ZnO:Al, ZnO:B, or ZnO:Ga(GZO).

[0041] The first output terminal T1 may be provided to be connected to the first upper electrode 120. Such a first output terminal T1 may be electrically connected to the first upper electrode 120 through a conductive line or line, and thus connected to one terminal of the first load 310 receiving the power generated from the series-connected solar cells. In this case, the first load 310 may include a secondary battery capable of storing the power generated from the series-connected solar cells and supplying the power to the outside, but is not limited thereto, and the first load 310 may include various electrical devices capable of receiving the power generated from the series-connected solar cells.

[0042] The first light absorbing layer 130 is disposed under the first upper electrode 120. The first light absorbing layer 130 may be made of a silicon-based material such as amorphous silicon or crystalline silicon, but is not limited thereto, and may be made of various materials that generate holes and electrons from incident sunlight.

[0043] For example, the first light absorbing layer 130 may be formed as a NIP structure including an N (negative) type semiconductor layer, a P (positive) type semiconductor layer, and an I (intrinsic) type semiconductor layer disposed between the N type semiconductor layer and the P type semiconductor layer. When the light absorbing layer 115 is formed as a NIP structure in this manner, the I type semiconductor layer may be depleted by the P type semiconductor layer and the N type semiconductor layer, thereby generating an electric field therein, and therefore, holes and electrons generated by incident sunlight may drift by the electric field, so that the holes and electrons are collected in the P type semiconductor layer and the N type semiconductor layer, respectively.

[0044] The first lower electrode 140 is disposed under the first light absorbing layer 130. The first lower electrode 140 may be made of a transparent conductive material to transmit sunlight passing through the first light absorbing layer 130 or sunlight passing through the second solar cell unit 200 to be described below. As described above, such a transparent conductive material may include a material having high light transmittance and excellent conductivity, such as ZnO:Al, ZnO:B, or ZnO:Ga (GZO).

[0045] The second solar cell unit 200 absorbs sunlight and converts the sunlight into electrical energy. The second solar cell unit 200 may also include a crystalline solar cell, an amorphous solar cell, a thin film solar cell, a dye-sensitized solar cell, an organic solar cell, a quantum dot solar cell, and a perovskite solar cell, etc. Hereinafter, an exemplary structure in which the second solar cell unit 200 includes a second substrate 210, a second lower electrode 220 disposed above the second substrate 210, a second light absorbing layer 230 disposed above the second lower electrode 220, and a second upper electrode 240 disposed above the second light absorbing layer 230 will be described, but the structure is not limited thereto and can of course be applied to various types of known solar cells.

[0046] Here, the second solar cell unit 200 can absorb sunlight passing through the above-mentioned first solar cell unit 100 and convert the sunlight into electric energy, and can absorb sunlight incident from below and convert the sunlight into electric energy. That is, the tandem solar cell according to the exemplary embodiment may be a single-sided light receiving type tandem solar cell in which the second solar cell unit 200 absorbs sunlight passing through the first solar cell unit 100 and converts the sunlight into electric energy; or may be a double-sided light receiving type tandem solar cell in which the first solar cell unit 100 absorbs sunlight incident from above and converts the sunlight into electric energy, and the second solar cell unit 200 absorbs sunlight incident from below and converts the sunlight into electric energy.

[0047] The second substrate 210 may include an opaque substrate or a transparent substrate. That is, the second substrate 210 may include an opaque substrate for a single-sided light receiving type, and may include a transparent substrate for a double-sided light receiving type. However, of course, for the single-sided light receiving type, the second substrate 210 may include a transparent substrate. When the second substrate 210 includes a transparent substrate, the second substrate 210 may be made of glass to transmit sunlight incident from below.

[0048] The second lower electrode 220 is disposed over the second substrate 210. In addition, the second light absorbing layer 230 may be disposed over the second lower electrode 220 to absorb sunlight passing through the first solar cell unit 100 or absorb sunlight incident from below and passing through the second substrate 210. In addition, the second upper electrode 240 may be disposed over the second light absorbing layer 230, and the structure of the electrode and the light absorbing layer with respect to the first solar cell unit 100 may be similarly applied to the structure of the electrode and the light absorbing layer with respect to the second lower electrode 220, the second light absorbing layer 230, and the second upper electrode 240, and thus repeated description thereof will be omitted.

[0049] The second output terminal T2 may be provided to be connected to the second lower electrode 220. Such a second output terminal T2 may be electrically connected to the second lower electrode 220 through a conductive line or wire, and thus connected to another terminal of the first load 310 receiving power generated from the series-connected solar cells.

[0050] The tandem solar cell according to the exemplary embodiment may further include an adhesive layer 800 for bonding the first solar cell unit 100 and the second solar cell unit 200. Such an adhesive layer 800 may be provided between the second upper electrode 240 located on the upper side of the second solar cell unit 200 and the first lower electrode 140 located on the lower side of the first solar cell unit 100, so that the first solar cell unit 100 is stacked and bonded to the second solar cell unit 200. The adhesive layer 800 may include a light-transmitting material, and the light-transmitting material may include polyolefin elastomer (POE), thermosetting resin, photocurable resin, and the like.

[0051] At the same time, the second upper electrode 240 located on the upper side of the second solar cell unit 200 and the first lower electrode 140 located on the lower side of the first solar cell unit 100 can be electrically connected to each other. In this way, when the second upper electrode 240 and the first lower electrode 140 are electrically connected, the power generation efficiency of the solar cell can be improved, but since the first solar cell unit 100 and the second solar cell unit 200 are connected in series, current matching is required to match the current output from the first solar cell unit 100 and the current output from the second solar cell unit 200.

[0052] In order to perform current matching, the tandem solar cell according to the exemplary embodiment may pattern at least one of the first light absorbing layer 130 and the second light absorbing layer 230 into a plurality of unit cells, and the second upper electrode 240 and the first lower electrode 140 may connect the unit cells obtained by patterning the first light absorbing layer 130 and the unit cells obtained by patterning the second light absorbing layer 230 in a combination of a series structure and a parallel structure. For example, when sunlight of a first reference light amount is expected to be incident on the first solar cell 100 and sunlight of a second reference light amount is expected to be incident on the second solar cell 200, at least one of the first light absorbing layer 130 and the second light absorbing layer 230 may be patterned into a plurality of unit cells, and the second upper electrode 240 and the first lower electrode 140 may connect the respective patterned unit cells in a combination of a series structure and a parallel structure so that the current output from the first solar cell 100 when the sunlight of the first reference light amount is incident and the current output from the second solar cell 200 when the sunlight of the second reference light amount is incident have the same value.

[0053] In this way, since at least one of the first light absorbing layer 130 and the second light absorbing layer 230 can be patterned into a plurality of unit cells, and the second upper electrode 240 and the first lower electrode 140 connect the respective patterned unit cells in a combination of a series structure and a parallel structure, when sunlight of a reference light amount is incident, the first solar cell unit 100 and the second solar cell unit 200 can be matched in terms of current. However, when sunlight exceeding the reference light amount or less than the reference light amount is incident on at least one of the first solar cell unit 100 and the second solar cell unit 200, the current output from the first solar cell unit 100 and the current output from the second solar cell unit 200 are limited to currents having relatively small values, thereby reducing the photoelectric conversion efficiency of the series solar cells. When the tandem solar cell is a double-sided light receiving type tandem solar cell (in which the first solar cell unit 100 absorbs sunlight incident from above and converts the sunlight into electrical energy, and the second solar cell unit 200 absorbs sunlight incident from below and converts the sunlight into electrical energy), the photoelectric conversion efficiency will be more seriously reduced because it is almost impossible to keep the sunlight incident from above and below at a reference light amount.

[0054] Therefore, in the series solar cell according to the exemplary embodiment, the third output terminal T3 is formed to be commonly connected to the first lower electrode 140 and the second upper electrode 240, so that the idle current generated by the difference between the current output from the first solar cell unit 100 and the current output from the second solar cell unit 200 is utilized. To this end, the third output terminal T3 can be electrically connected to each of the first lower electrode 140 and the second upper electrode 240 through a conductive line or line. When the third output terminal T3 is formed, the first output terminal T1 can be connected to one terminal of the second load 320 set separately from the first load 310, and the third output terminal T3 can be connected to the other terminal of the second load 320. In addition, the third output terminal T3 can be connected to one terminal of the third load 330 set separately from the first load 310, and the second output terminal T2 can be connected to the other terminal of the third load. In this case, the second load 320 and the third load 330 may include a secondary battery capable of storing power generated from the idle current and supplying the power to the outside, but are not limited thereto, and may include various electrical devices capable of receiving power generated from the idle current.

[0055] Furthermore, in order to maximize the idle current generated by the difference between the current output from the first solar cell unit 100 and the current output from the second solar cell unit 200, the series solar cell according to the exemplary embodiment may further include a first current controller 170 disposed between the first output terminal T1 and the third output terminal T3, a second current controller 270 disposed between the second output terminal T2 and the third output terminal T3, and a controller 400 for controlling the operation of the first current controller 170 and the second current controller 270. The first current controller 170 and the second current controller 270 may include a switching element or a variable resistance element.

[0056] Figure 2 is a view showing a state in which a current controller is installed according to an exemplary embodiment of the present disclosure. Here, Figure 2 (a) is a view exemplarily showing a case where the current controller includes a switching element, and Figure 2 (b) in FIG. 1 is a view exemplarily showing a case where the current controller includes a variable resistance element.

[0057] Reference Figure 2(a) in the figure, the current controller may include a switching element. That is, at least one of the first current controller 170 and the second current controller 270 may include a switching element, for example, the first current controller 170 may include a first switching element 170a, and the second current controller 270 may include a second switching element 270a. Here, the second load 320 and the first switching element 170a may be installed to be connected in series on a path electrically connecting the first output terminal T1 and the third output terminal T3, that is, connected in series in a conductive line or line. In this case, the first switching element 170a may be set to an off state, in which the path connecting the first output terminal T1 and the third output terminal T3 is disconnected, that is, open circuit. Then, according to the instruction of the controller 400, the first switching element 170a operates in a conducting state, in which the path connecting the first output terminal T1 and the third output terminal T3 is connected, that is, short-circuited; and the first switching element 170a operates in an off state, in which the path connecting the first output terminal T1 and the third output terminal T3 is disconnected, that is, open circuit. In addition, the third load 330 and the second switch element 270a can be installed to be connected in series on the path electrically connecting the third output terminal T3 and the second output terminal T2, that is, connected in series in a conductive line or line. In this case, the second switch element 270a can be set to an off state, in which the path connecting the third output terminal T3 and the second output terminal T2 is disconnected, that is, open circuit. Then, according to the instruction of the controller 400, the second switch element 270a operates in a conducting state, in which the path connecting the third output terminal T3 and the second output terminal T2 is connected, that is, short-circuited; and the second switch element 270a operates in an off state, in which the path connecting the third output terminal T3 and the second output terminal T2 is disconnected, that is, open circuit.

[0058] Reference Figure 2(b) in the current controller may include a variable resistance element. That is, at least one of the first current controller 170 and the second current controller 270 may include a variable resistance element, for example, the first current controller 170 may include a first variable resistance element 170b, and the second current controller 270 may include a second variable resistance element 270b. Here, the second load 320 and the first variable resistance element 170b may be installed to be connected in series on a path electrically connecting the first output terminal T1 and the third output terminal T3, that is, connected in series in a conductive line or line. In this case, the first variable resistance element 170b may be set to have a maximum resistance value, and may be operated so that the resistance value is reduced according to the instruction of the controller 400. In addition, the third load 330 and the second variable resistance element 270b may be installed to be connected in series on a path electrically connecting the third output terminal T3 and the second output terminal T2, that is, connected in series in a conductive line or line. In this case, the second variable resistance element 270b may also be set to have a maximum resistance value, and may be operated so that the resistance value is reduced according to the instruction of the controller 400.

[0059] Furthermore, the tandem solar cell according to the exemplary embodiment may further include a first light amount sensing unit 500 for detecting the amount of sunlight incident on the first solar cell unit 100 and a second light amount sensing unit 600 for detecting the amount of sunlight incident on the second solar cell unit 200 .

[0060] As described above, the tandem solar cell may be a double-sided light receiving type tandem solar cell in which the first solar cell unit 100 absorbs sunlight incident from above and converts the sunlight into electrical energy, and the second solar cell unit 200 absorbs sunlight incident from below and converts the sunlight into electrical energy. In this case, the first light amount sensing unit 500 may detect the amount of sunlight incident from above, and the second light amount sensing unit 600 may detect the amount of sunlight incident from below. However, the tandem solar cell is not limited thereto, and when the tandem solar cell is a single-sided light receiving type tandem solar cell, the second light amount sensing unit 600 may detect the amount of light absorbed by the second solar cell unit 200. The first light amount sensing unit 500 and the second light amount sensing unit 600 may include sensors for detecting the amount of light, and various known configurations for detecting the amount of light may be applied to the sensors.

[0061] Meanwhile, the series solar cell according to the exemplary embodiment may further include a current sensing unit 700 disposed between the first output terminal T1 and the second output terminal T2 .

[0062] In addition, the current sensing unit 700 can be installed to be connected in series with the first load 310 on the path electrically connecting the first output terminal T1 and the second output terminal T2, that is, connected in series in a conductive line or line. Therefore, the current sensing unit 700 can measure the amount of current flowing along the path electrically connecting the first output terminal T1 and the second output terminal T2. The current sensing unit 700 may include a sensor for detecting current, and various known configurations for sensing current may be applied to the sensor.

[0063] As described above, the controller 400 controls the operation of the first current controller 170 and the second current controller 270. In this case, the controller 400 may selectively operate the first current controller 170 and the second current controller 270 according to the light amount of sunlight detected by the first light amount sensing unit 500 and the second light amount sensing unit 600. In addition, the controller 400 may control at least one of the first current controller 170 and the second current controller 270 to operate according to the current amount detected by the current sensing unit 700.

[0064] In the following, reference is made to Figures 3 to 5 , details of the controller 400 that controls operations of the first current controller 170 and the second current controller 270 will be described.

[0065] Figure 3 is a view showing the flow of current when sunlight of a reference light amount is incident on each of the first solar cell and the second solar cell.

[0066] In the series solar cell according to the exemplary embodiment, a situation is set that sunlight of a first reference light amount A is incident on the first solar cell unit 100, sunlight of a second reference light amount B is incident on the second solar cell unit 200, and the first solar cell unit 100 and the second solar cell unit 200 are matched in terms of current.

[0067] When the light amount detected by the first light amount sensing unit 500 has the same value as the preset first reference light amount A, and the light amount detected by the second light amount sensing unit 600 has the same value as the preset second reference light amount B, the current (I a ) and the current (I a ) have the same amount of current, so no idle current is generated.

[0068] Therefore, the controller 400 does not operate the first switching element 170a and the second switching element 270a. As described above, the first switching element 170a is initially set to the off state in which the path connecting the first output terminal T1 and the third output terminal T3 is disconnected, and the second switching element 270a is also initially set to the off state in which the path connecting the third output terminal T3 and the second output terminal T2 is disconnected. Therefore, all the current (I a ) output from the first solar cell unit 100 and the second solar cell unit 200 is supplied to the first load 310 and not supplied to the second load 320 and the third load 330.

[0069] Although not shown, the first current controller 170 and the second current controller 270 may respectively include a first variable resistance element 170b and a second variable resistance element 270b. Even in this case, the controller 400 does not operate the first variable resistance element 170b and the second variable resistance element 270b. As described above, the first variable resistance element 170b is initially set to have the maximum resistance value, and the second variable resistance element 270b is also initially set to have the maximum resistance value. Therefore, most of the current (I a ) output from the first solar cell unit 100 and the second solar cell unit 200 is supplied to the first load 310, and almost no current is supplied to the second load 320 and the third load 330.

[0070] Figure 4 is a view showing the flow of current when sunlight with a light amount exceeding the reference light amount is incident on the first solar cell unit.

[0071] When the light amount detected by the first light amount sensing unit 500 is greater than the preset first reference light amount A (A'>A), and the light amount detected by the second light amount sensing unit 600 has the same value as the preset second reference light amount B, the amount of current (I a +I b ) output from the first solar cell unit 100 is greater than the amount of current (I a ) output from the second solar cell unit 200, so idle current is generated. The same situation also occurs when the light amount detected by the first light amount sensing unit 500 is equal to the preset first reference light amount A, and the light amount detected by the second light amount sensing unit 600 is less than the preset second reference light amount B (B'<B), or when the increase rate of the light amount detected by the first light amount sensing unit 500 is greater than the increase rate of the light amount detected by the second light amount sensing unit 600, or even when the decrease rate of the light amount detected by the first light amount sensing unit 500 is less than the decrease rate of the light amount detected by the second light amount sensing unit 600.

[0072] In this case, the controller 400 operates only the first switching element 170a and does not operate the second switching element 270a. As described above, since the second switching element 270a is initially set to the off state where the path connecting the third output terminal T3 and the second output terminal T2 is disconnected, current is not supplied to the third load 330.

[0073] In this case, when the first switching element 170a is operated, the controller 400 controls the operation of the first switching element 170a according to the amount of current detected by the current sensing unit 700. That is, the first switching element 170a is initially set to an off state in which the path connecting the first output terminal T1 and the third output terminal T3 is disconnected. Here, when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 switches the first switching element 170a in the off state to the on state. Then, when the amount of current detected by the current sensing unit 700 decreases after the first switching element 170a is switched to the on state, the controller 400 switches the first switching element 170a in the on state to the off state.

[0074] That is, even when the amount of light detected by the first light amount sensing unit 500 is greater than the preset first reference light amount A (A'>A), and the amount of light detected by the second light amount sensing unit 600 has the same value as the preset second reference light amount B, because the first solar cell unit 100 and the second solar cell unit 200 are connected in series, the amount of current detected by the current sensing unit 700 does not change. However, when the amount of current detected by the current sensing unit 700 does not change within the set time despite the difference in the amount of light detected, the controller 400 supplies the idle current (I ) to the second load 320 by switching the first switching element 170a from the off state to the on state. b In this case, since the second load 320 and the first switch element 170a have low resistance values, the idle current (I b) is supplied to the second load 320, which may cause a decrease in the amount of current supplied to the first load 310. In this case, when the amount of current detected by the current sensing unit 700 decreases after the first switching element 170a is switched to the on state, the controller 400 switches the first switching element 170a to the off state. In this way, a constant current is supplied to the first load 310 again, and when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 switches the first switching element 170a from the off state to the on state. Therefore, the first switching element 170a continuously switches between the off state and the on state, so when the first switching element 170a is in the on state, the current can be intermittently supplied to the second load 320.

[0075] Although not shown, the first current controller 170 and the second current controller 270 may include a first variable resistance element 170b and a second variable resistance element 270b, respectively. Even in this case, the controller 400 operates only the first variable resistance element 170b and does not operate the second variable resistance element 270b. As described above, since the second variable resistance element 270b is initially set to have a maximum resistance value, almost no current is supplied to the third load 330.

[0076] In this case, when the first variable resistance element 170b is operated, the controller 400 controls the operation of the first variable resistance element 170b according to the amount of current detected by the current sensing unit 700. That is, the first variable resistance element 170b is initially set to have a maximum resistance value. Here, when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 gradually reduces the resistance value of the first variable resistance element 170b set to the maximum resistance value. Then, when the amount of current detected by the current sensing unit 700 decreases while the resistance value of the first variable resistance element 170b decreases, the controller 400 keeps the resistance value of the first variable resistance element 170b in a reduced state.

[0077] That is, even when the amount of light detected by the first light amount sensing unit 500 is greater than the preset first reference light amount A (A'>A), and the amount of light detected by the second light amount sensing unit 600 has the same value as the preset second reference light amount B, the amount of current detected by the current sensing unit 700 does not change because the first solar cell unit 100 and the second solar cell unit 200 are connected in series. However, when the amount of current detected by the current sensing unit 700 does not change within the set time despite the difference in the amount of light detected, the controller 400 reduces the idle current (I b) is supplied to the second load 320. At this time, since the first variable resistance element 170b is initially set to the maximum resistance value, a current having a smaller current amount compared to the idle current (I b ) is supplied to the second load 320, and the current amount supplied to the first load 310 may not change. In this case, when the current amount detected by the current sensing unit 700 decreases after the resistance value of the first variable resistance element 170b continuously decreases, the controller 400 maintains the resistance value of the first variable resistance element 170b. In this way, the idle current (I a +I b ) corresponding to the difference between the current (I a ) output from the first solar cell unit 100 and the current (I b ) output from the second solar cell unit 200 can be supplied to the second load 320 as it is.

[0078] Figure 5 is a view showing the flow of current when sunlight having a light amount exceeding a reference light amount is incident on the second solar cell unit.

[0079] When the light amount detected by the first light amount sensing unit 500 has the same value as a preset first reference light amount A, and the light amount detected by the second light amount sensing unit 600 is greater than a preset second reference light amount B (B'>B), the current amount of the current (I a +I b ) output from the second solar cell unit 200 is greater than the current amount of the current (I a ) output from the first solar cell unit 100, and thus an idle current is generated. The same situation also occurs when the light amount detected by the first light amount sensing unit 500 is less than a preset first reference light amount A (A'<A), and the light amount detected by the second light amount sensing unit 600 is equal to the preset second reference light amount B, or when the increase rate of the light amount detected by the first light amount sensing unit 500 is less than the increase rate of the light amount detected by the second light amount sensing unit 600, or even when the decrease rate of the light amount detected by the first light amount sensing unit 500 is greater than the decrease rate of the light amount detected by the second light amount sensing unit 600.

[0080] In this case, the controller 400 only operates the second switching element 270a and does not operate the first switching element 170a. As described above, since the first switching element 170a is initially set to the off state in which the path connecting the first output terminal T1 and the third output terminal T3 is disconnected, current is not supplied to the second load 320.

[0081] In this case, when the second switch element 270a is operated, the controller 400 controls the operation of the second switch element 270a according to the amount of current detected by the current sensing unit 700. That is, the second switch element 270a is initially set to an off state in which the path connecting the third output terminal T3 and the second output terminal T2 is disconnected. Here, when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 switches the second switch element 270a in the off state to the on state. Then, when the amount of current detected by the current sensing unit 700 decreases after the second switch element 270a is switched to the on state, the controller 400 switches the second switch element 270a in the on state to the off state.

[0082] That is, even when the light amount detected by the first light amount sensing unit 500 has the same value as the preset first reference light amount A, and the light amount detected by the second light amount sensing unit 600 is greater than the preset second reference light amount B (B'>B), because the first solar cell unit 100 and the second solar cell unit 200 are connected in series, the current amount detected by the current sensing unit 700 does not change. However, when the current amount detected by the current sensing unit 700 does not change within the set time despite the difference in the detected light amount, the controller 400 supplies the idle current (I ) to the third load 330 by switching the second switching element 270a from the off state to the on state. b In this case, since the third load 330 and the second switch element 270a have low resistance values, the idle current (I b ) is supplied to the third load 330, which may cause a decrease in the amount of current supplied to the first load 310. In this case, when the amount of current detected by the current sensing unit 700 decreases after the second switch element 270a is switched to the on state, the controller 400 switches the second switch element 270a to the off state. In this way, a constant current is supplied to the first load 310 again, and when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 switches the second switch element 270a from the off state to the on state. Therefore, the second switch element 270a continuously switches between the off state and the on state, so when the second switch element 270a is in the on state, the current can be intermittently supplied to the third load 330.

[0083] Although not shown, the first current controller 170 and the second current controller 270 may include a first variable resistance element 170b and a second variable resistance element 270b, respectively. Even in this case, the controller 400 operates only the second variable resistance element 270b and does not operate the first variable resistance element 170b. As described above, since the first variable resistance element 170b is initially set to have a maximum resistance value, almost no current is supplied to the second load 320.

[0084] In this case, when the second variable resistance element 270b is operated, the controller 400 controls the operation of the second variable resistance element 270b according to the amount of current detected by the current sensing unit 700. That is, the second variable resistance element 270b is initially set to have a maximum resistance value. Here, when the amount of current detected by the current sensing unit 700 does not change within a set time, the controller 400 gradually reduces the resistance value of the second variable resistance element 270b set to the maximum resistance value. Then, when the amount of current detected by the current sensing unit 700 decreases while the resistance value of the second variable resistance element 270b decreases, the controller 400 keeps the resistance value of the second variable resistance element 270b in a reduced state.

[0085] That is, even when the light amount detected by the first light amount sensing unit 500 has the same value as the preset first reference light amount A, and the light amount detected by the second light amount sensing unit 600 is greater than the preset second reference light amount B (B'>B), because the first solar cell unit 100 and the second solar cell unit 200 are connected in series, the current amount detected by the current sensing unit 700 does not change. However, when the current amount detected by the current sensing unit 700 does not change within the set time despite the difference in the detected light amount, the controller 400 reduces the idle current (I b ) is supplied to the third load 330. At this time, since the second variable resistance element 270b is initially set to the maximum resistance value, the idle current (I b ) is supplied to the third load 330, and the current amount supplied to the first load 310 may not change. In this case, when the current amount detected by the current sensing unit 700 decreases after the resistance value of the second variable resistance element 270b is continuously decreased, the controller 400 maintains the resistance value of the second variable resistance element 270b. In this way, the current (I a +I b ) and the current (I a ) corresponds to the idle current (I b) can be supplied to the third load 330 as is.

[0086] As described above, using the series solar cells according to the exemplary embodiment, in addition to the first output terminal and the second output terminal for supplying power to the main load, by including the third output terminal for supplying power to the auxiliary load, the idle current generated by the difference between the current amounts generated from each solar cell can be additionally supplied to the auxiliary load.

[0087] Above, although specific terms are used to describe and illustrate the preferred embodiments of the present disclosure, these terms are only used to clearly describe the present disclosure, and it is obvious that various modifications and changes can be made to the exemplary embodiments of the present disclosure without departing from the spirit and scope of the present disclosure as defined by the following claims and their equivalents. Such modified embodiments should not be understood solely from the spirit and scope of the present disclosure, and should be interpreted as falling within the scope of the claims of the present disclosure.

Claims

1. A series solar cell comprising: A first solar cell unit having a first upper electrode and a first lower electrode spaced apart from each other; a second solar cell unit disposed below the first solar cell unit and having a second upper electrode and a second lower electrode disposed spaced apart from each other; a first output terminal connected to the first upper electrode; a second output terminal connected to the second lower electrode; as well as A third output terminal is connected to both the first lower electrode and the second upper electrode.

2. The tandem solar cell according to claim 1, wherein: A first load is connected between the first output terminal and the second output terminal. A second load is connected between the first output terminal and the third output terminal, and The third load is connected between the second output terminal and the third output terminal.

3. The tandem solar cell according to claim 1, further comprising: A first current controller is arranged between the first output terminal and the third output terminal; A second current controller is arranged between the second output terminal and the third output terminal; as well as A controller is configured to control the operation of the first current controller and the second current controller.

4. The tandem solar cell according to claim 3, further comprising: a first light amount sensing unit configured to detect a light amount of sunlight incident on the first solar cell unit; a second light amount sensing unit configured to detect a light amount of sunlight incident on the second solar cell unit, The controller is configured to selectively operate the first current controller and the second current controller according to the amount of sunlight detected by the first light amount sensing unit and the second light amount sensing unit.

5. The tandem solar cell according to claim 4, wherein: The controller is configured to: When the light amount detected by the first light amount sensing unit is greater than a preset first reference light amount or the light amount detected by the second light amount sensing unit is less than a preset second reference light amount, operating the first current controller; and When the amount of light detected by the first light amount sensing unit is smaller than the first reference light amount or the amount of light detected by the second light amount sensing unit is larger than the second reference light amount, the second current controller is operated.

6. The series-connected solar cell according to claim 3, further comprising a current sensing unit disposed between the first output terminal and the second output terminal, in, The controller is configured to control an operation of at least one of the first current controller and the second current controller according to an amount of current detected by the current sensing unit.

7. The tandem solar cell according to claim 6, wherein: At least one of the first current controller and the second current controller includes a switching element.

8. The tandem solar cell according to claim 7, wherein: The controller is configured to switch the switching element in an off state to an on state when the amount of current detected by the current sensing unit does not change within a set time.

9. The tandem solar cell according to claim 8, wherein: The controller is configured to switch the switching element in the on-state to the off-state when the amount of current detected by the current sensing unit decreases after the switching element is switched to the on-state.

10. The tandem solar cell according to claim 6, wherein: At least one of the first current controller and the second current controller includes a variable resistance element.

11. The tandem solar cell according to claim 10, wherein: The controller is configured to reduce a resistance value of the variable resistance element set to a maximum resistance value when the amount of current detected by the current sensing unit does not change within a set time.

12. The tandem solar cell according to claim 10, wherein: The controller is configured to maintain a reduced resistance value of the variable resistance element when the amount of current detected by the current sensing unit decreases while the resistance value of the variable resistance element decreases.

13. The tandem solar cell according to claim 1, wherein: The first solar cell unit includes a first transparent substrate for transmitting sunlight incident from above, and The second solar cell unit includes a second transparent substrate for transmitting sunlight incident from below. 14 . The tandem solar cell of claim 1 , further comprising an adhesive layer disposed between the first lower electrode and the second upper electrode.

15. The tandem solar cell according to claim 2, wherein: At least one of the first load, the second load, and the third load includes a secondary battery.

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