JP5618234B2 - Multi-junction solar cell - Google Patents

Description

The present invention relates to a multijunction solar cell, and more particularly to a solar cell having a function of mitigating output fluctuations in a multijunction solar cell.

Conventionally, various structures have been disclosed as solar cell structures. For example, Patent Document 1 describes a solar cell module in which solar cell elements formed on a plurality of conductive substrates are integrated. The solar cell element used in the solar cell module has a structure in which a metal electrode layer 108, a semiconductor layer 109, and a transparent electrode layer 110 are sequentially formed on a conductive substrate 106.

In Patent Document 2, as an example of a more efficient solar cell, a multi-junction solar cell having a structure in which a plurality of solar cell elements are formed in one element is described. The solar cell includes, as an element having a semiconductor junction, a first impurity semiconductor layer having one conductivity type, a second impurity semiconductor layer having a conductivity type opposite to the one conductivity type, the first impurity semiconductor layer, and the second impurity semiconductor layer. The photoelectric conversion device is configured to include a semiconductor layer including a crystal region penetrating between the impurity semiconductor layer and an amorphous structure.

Now, a place where a solar cell is installed is basically a place where a large amount of sunlight is expected. Industrially, it is often installed in a place where a large area with good sunshine conditions such as a desert can be secured, or on the roof of a house for personal demand.

Once installed, solar cells are often used for about 10 years or longer. A solar cell receives light irradiation and converts light energy into electricity by a photovoltaic effect which is a kind of photoelectric effect, and a semiconductor is used as the conversion material. From a long-term perspective, the conversion efficiency decreases as the semiconductor deteriorates, affecting the performance of the solar cell.

As a deterioration factor of a semiconductor, for example, intense light is irradiated over a long period of time. When intense light is irradiated, dangling bonds (unbonded hands) in the semiconductor used in the solar cell increase, and the lattice defect density in the semiconductor increases, resulting in a decrease in conductivity and output as a solar cell. Will go down. Further, since the solar cell is used outdoors, the temperature of the solar cell increases with sunshine, and the band gap (forbidden band width) of the semiconductor decreases when the temperature becomes high (about 70 to 80 degrees). As a result, the output voltage of the solar cell may decrease.

Thus, for example, Patent Document 2 discloses a photovoltaic device that is stable against changes with time. In Patent Document 3, a semiconductor layer of a solar cell is configured using a polysilane compound that is an organic semiconductor, and a refractive index adjusting agent is further distributed in advance along the film pressure direction of the organic semiconductor layer. Is described.

As the refractive index adjuster, inorganic compounds such as CaF2 and LiF, metals such as Be and Mg, organic compounds such as ebonite and amber, and synthetic resins are used, and these are used in the form of powder or ultrafine particles in the polysilane compound. By distributing them along the film pressure direction of the organic semiconductor layer alone or in combination, it becomes possible to absorb light of a relatively wide range of wavelength components and provide a photovoltaic device that is stable against changes over time. It describes what you can do.

Japanese Patent Laid-Open No. 3-239377 FIG. 2 JP 2010-10667 A JP-A-4-199687

In such a photovoltaic element, it can be expected that light degradation with respect to a change with time is reduced as compared with a conventional photovoltaic element. However, because it slows down the rate of photodegradation, when viewed from the viewpoint of maintaining the performance of photovoltaic power over a long period of time, semiconductor degradation gradually proceeds from the initial installation state, and accordingly It is inevitable that the photovoltaic power will gradually decrease. In addition, when the semiconductor is degraded, the photovoltaic power is not normally restored. Therefore, when viewed in a period of about 10 to 15 years corresponding to the usage period of the solar cell, the decrease in the amount of power generation is the cost. The performance will be greatly affected. In particular, if the amount of sunshine is higher than expected due to climate warming or climate change in the future, the photodegradation of the semiconductor has progressed more than expected and expected during use There is a risk that the amount of power generation cannot be obtained. That is, there is a possibility that the usable period that was initially planned may be shortened. Moreover, when the amount of sunshine becomes small, there is a possibility that the initially assumed power generation amount cannot be obtained.

Therefore, the present invention has been made in view of the above problems, and while maintaining the maximum output as a solar cell constant over a long period of time, the value of the maximum output is appropriately increased or decreased according to climate change after installation. It is an object of the present invention to provide a multi-junction solar cell capable of adjusting the power and performing stable output.

The solar cell according to the present invention is configured to solve the above-described problems,
On the light receiving surface of a multi-junction solar cell formed by stacking a plurality of solar cell elements in layers,
A transmittance control layer is formed,
A control IC electrically connected to an electrode layer provided in the solar cell element is formed adjacent to the solar cell element,
The control IC includes a power generation amount measuring unit in the semiconductor layer,
To chromatic comparison means with the default value of the measured power generation amount and the power generation amount stored in the memory unit, and a timer means for measuring an elapsed time which is a time to make a comparison in the comparison means, the computing means having a With
The control IC sets the predetermined output amount after a lapse of time as the initial set value, and controls the transmissivity so that the maximum output amount at the time of installation becomes the initial set value,
The control IC has at least frequency data obtained by adjusting the maximum output value,
Control content data of power generation amount,
In the memory unit,
Each time the maximum output value is adjusted, these data are checked by the calculation means,
If the same power generation amount control content data continues three times,
Multiplexing is characterized in that when the third data is confirmed, the power generation amount is adjusted by decreasing or increasing the initial value of the power generation amount by a predetermined amount in the continuous direction. A junction type solar cell may be configured.

According to such a configuration, after installing the multi-junction solar cell and starting to use, when the power generation amount is larger than the predetermined initial power generation amount, the light transmission amount is adjusted so that the power generation amount approaches the initial setting value. By controlling to reduce the light transmittance of the rate control layer, the solar cell is not irradiated with more light than necessary, the maximum output as the solar cell is kept constant over a long period of time, and the climate after installation It is possible to provide a solar cell that can adjust the value of the maximum output as appropriate according to fluctuations and the like and perform stable output.

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In addition , when climate change occurs in a direction where the amount of sunshine decreases, the output of the solar cell is lower than the initial setting value, so that the initially assumed output cannot be obtained, and is stabilized. A solar cell capable of outputting can be provided.

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Further , since the light transmittance can be controlled in accordance with the deterioration characteristics of the semiconductor used in the multijunction solar cell, fine control can be performed, and control suitable for the multijunction solar cell can be performed. As a result, it is possible to easily maintain the maximum output at the beginning and after the lapse of time.

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In addition , the initial maximum output can be set to an output amount that anticipates deterioration over time in a semiconductor used in the solar cell, and the maximum output after aging of the solar cell can be held at a predetermined value.

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In addition , it is easy to form a light transmittance control layer according to the shape and size of the semiconductor layer in the solar cell element, and liquid crystal is easy to change its molecular orientation continuously by applying voltage, so that Easy to control light rate.

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In addition , predict trends such as climate change over the long term by the number of consecutive increases in the amount of sunshine or in the direction of decrease in sunshine, and increase or decrease the initial value of power generation according to the prediction. Since it controls, the solar cell which can perform the stable output according to a long-term climate can be provided, without applying an excessive load to the semiconductor which comprises a solar cell.

As described above, according to the present invention, the maximum output as a solar cell can be achieved by performing control to correct the set value of the power generation amount so that the power generation amount appropriately reflects the long-term trend of climate change. A multi-junction solar cell capable of maintaining stable output over a long period of time and adjusting the increase / decrease in the maximum output value as appropriate according to climate change after installation, etc., can be provided.

The schematic block diagram of the solar cell element which shows 1st Embodiment is shown. The schematic block diagram of the translucency control layer which concerns on the same embodiment is shown. The block block diagram of the control IC which concerns on the embodiment is shown. The change of the electric power generation amount which concerns on the embodiment is shown. The method of controlling the light transmittance over time according to the embodiment will be shown. The characteristic view of the output current and output voltage which concern on a solar cell is shown. The schematic block diagram of the solar cell element which shows 2nd Embodiment is shown. The change of the electric power generation amount which concerns on the embodiment is shown. The schematic block diagram of the solar cell element which shows 3rd Embodiment is shown. The method of controlling the amount of power generation and translucency over time according to the fourth embodiment will be described. The figure which connected and provided multiple solar cells is shown.

Next, an embodiment of the present invention will be described in detail with reference to FIGS.
(First embodiment)
(Description of solar cell)
FIG. 1 is a schematic configuration diagram showing a first embodiment of a solar cell in the present invention. FIG. 1 shows a cross section of a solar cell element having a layered structure in the solar cell 1, and the solar cell element is formed in layers on a conductive substrate 101. On the conductive substrate 101, a metal electrode layer 102, a semiconductor layer 103 bonded to the metal electrode layer 102, a transparent electrode layer 104 bonded to the semiconductor layer 103, and a bond to the transparent electrode layer 104 The translucency control layer 105 to be formed is sequentially formed in layers.

The semiconductor layer 103 is formed by stacking a plurality of pn junction elements having different band gaps in the light traveling direction. In FIG. 1, the semiconductor layer is composed of three layers (1031, 1032, 1033) of semiconductors. When light is incident, the semiconductor layer 103 is sequentially absorbed by the semiconductor layers 1033, 1032, and 1031 from the short wavelength side, and generates a voltage corresponding to each band gap. The generated voltage is transmitted through transparent electrodes provided between the respective semiconductor layers.

As the pn junction element forming the layer, various combinations such as a combination of GaAlAs and GaAs and a combination of amorphous Si and amorphous SiGe are assumed.

A control IC 106 for controlling the light transmittance control layer 105 is disposed on the conductive substrate 101. The control IC 106 includes a current collecting electrode 107 provided on the transparent electrode layer, and the metal electrode. A power source is obtained by being electrically connected to the layer 102. The control IC has a time counting function and a function of changing an output voltage output to a light transmittance control layer, which will be described later, according to the time counting.

The control IC 106 measures the power generation amount in the semiconductor layer, and when the power generation amount is equal to or larger than a predetermined initial setting value, the control IC 106 decreases the power generation amount so as to approach the initial setting value. Control to reduce the light transmittance in the light transmittance control layer 105 is performed. Further, when the power generation amount is equal to or less than a predetermined initial setting value, the light transmittance in the light transmittance control layer 105 is increased in the direction of increasing the power generation amount so as to approach the initial setting value. Control is performed.

FIG. 3 shows a block diagram of the control IC 106. The control IC 106 includes a power input unit 1061 for obtaining power from the electrodes, a power generation amount measuring unit 10631 for measuring a power generation amount in the semiconductor layer based on a voltage input to the power input unit, and an initial value in advance. A memory unit 10633 that stores power generation amount data set as a set value, a timer unit 10634 that counts the passage of time, a comparison unit 10632 that performs comparison operations by the comparison means at predetermined intervals, and a comparison by the comparison unit 10632 A power output unit 1062 for controlling the light transmittance in the light transmittance control layer 105 according to the result is provided.

The power generation amount measurement unit 10631 converts the voltage value and current value input to the power input unit 1061 into digital data by A / D conversion and outputs the digital data to the comparison unit 10632.

The comparison unit 10632 reads the power generation amount data from the memory unit 10633 at a predetermined interval and compares the data with the voltage value and current value data measured by the power generation amount measurement unit 10631. As a result, the power generation amount is an initial set value. When the power generation amount data is larger than a certain amount of power generation data, an output signal from the comparison unit 10632 is received and control for reducing the light transmittance in the light transmittance control layer 105 is performed.

In addition, when the power generation amount is smaller than the power generation amount data that is the initial setting value, the light transmission rate in the light transmittance control layer 105 is controlled in response to the output signal from the comparison unit 10632.

The timer unit 10634 counts time over time, and the predetermined time that is a timing for comparison by the comparison unit 10632 is every several hours, every day, every week, every month. It is good to set it appropriately based on the passage of time.

In addition to the timing based on the passage of time, the temporal change in the measurement data of the voltage value and the current value measured by the power generation amount measuring unit 10631 is measured, and the change in the power generation amount originally assumed (Po) is measured. To PB) may occur as a timing when the comparison unit 10632 performs a comparison when a large change (for example, a change of 2 times or more) occurs. In addition to the elapse of a predetermined time, by using the timing of the comparison calculation when the amount of power generation has actually changed significantly, it is possible to prevent excessive sunshine on the semiconductor layer at an early stage and prevent photodegradation of the semiconductor layer. can do.

The light transmittance control layer 105 controls the light transmittance applied to the semiconductor layer 103, and the amount of sunlight irradiated onto the semiconductor layer 103 is thereby controlled. In this embodiment, the liquid crystal is used to change the molecular orientation by applying a voltage.

(Description of translucency control layer)
FIG. 2 shows a schematic configuration diagram of the light transmittance control layer 105. FIG. 2 shows a cross section of the translucency control layer 105, and the translucency control layer 105 is formed on the transparent electrode layer 104 in layers. The light transmittance control layer 105 includes a polarizing plate 1051 bonded to the transparent electrode layer 104, a transparent electrode layer 1052 bonded to the polarizing plate 1051, and two alignment layers 1053 bonded to the transparent electrode layer 1052. A liquid crystal layer 1055 sandwiched between 1054, a transparent electrode layer 1056 bonded to the liquid crystal layer 1055, and a polarizing plate 1057 bonded to the transparent electrode layer 1056 are formed in layers.

The transparent electrodes 1052 and 1056 in the light transmittance control layer 105 are electrically connected to the control IC 106. The liquid crystal 1055 can change the orientation of the liquid crystal 1055 by controlling the application state of power from the control IC 106.

(Explanation of control)
Next, how to control the light transmittance control layer 105 by the control IC 106 will be described with reference to FIGS. FIG. 4 shows the state of change in the maximum output of the solar cell 1 over time. The horizontal axis is the period, and the vertical axis is the maximum output P. The maximum output P used here is the output P of the portion where the product of Vp (output voltage) and Ip (output current) is maximum in the graph showing the output characteristics of the solar cell shown in FIG. Vo is an open circuit voltage and Io is a short circuit current.

The maximum output of the solar cell at the time of installation is Po, and as a time factor, for example, when the period is assumed to be 10 years, the maximum output after 10 years is PB, and the maximum output due to the deterioration of the semiconductor constituting the solar cell Let ΔP (delta P = Po−PB) be the amount of decrease. In order to keep the maximum output as a solar cell constant over time, control is performed so that the maximum output at the time of installation is kept at PB in advance.

Here, as shown in FIG. 5A, when the light transmittance at the beginning of installation is τo and the light transmittance after 10 years is the first light transmittance τB, the first light transmittance The rate τB maximizes the transmissivity in the transmissivity control layer 105, and τo is the translucency at which the highest output of the solar cell 1 becomes the output PB obtained by subtracting the ΔP from the Po. Rate.

The relationship between the output P of the solar cell and the transmissivity τ can be expressed as P ∝ A · τ (t), where time is t and A is a constant, and is proportional to the temporal change in transmissivity. Specifically, since the transmissivity is controlled so as to gradually increase from the initial value, it changes as τ = {(τB−τo) / (tB−to)} · t so as to increase with time. .
τB, τo, and constant A need to be considered together with the PB after 10 years because it is necessary to consider the overall transmittance of the liquid crystal, polarizing plate, transparent electrode, etc. as the transmittance control layer used in the solar cell. Determine as appropriate.

Based on such a control that monotonously increases the light transmittance, as shown in FIGS. 5B and 5C, the power generation amount increases from the initial setting value PB at time tc as shown in FIGS. In such a case, the comparison unit 10632 measures the increase ΔP1 in the power generation amount, and performs the second control for controlling the light transmittance to be decreased by Δτ1 so as to decrease the increase ΔP1 in the power generation amount. Do.

When the power generation amount changes in a direction to be smaller than the initial set value, control is performed to increase the transmissivity in a direction to increase the power generation amount so as to approach the initial set value.

The control of the light transmittance by the control IC 106 is performed by changing the voltage applied from the power supply output unit 1062 toward the light transmittance control layer 105. That is, the orientation of the liquid crystal is changed by changing the voltage applied to the transparent electrode layers 1052 and 1054 bonded to the liquid crystal layer 1055, and the initial maximum output in the solar cell is changed from the initial maximum output Po to the time of the semiconductor. Control is performed to supply a voltage to the transmissivity control layer so as to control the transmissivity so that the output PB is obtained by subtracting the output decrease due to the output decrease accompanying the general deterioration.

Further, as a method of controlling the transmittance control layer 105 in the control IC 106, the voltage is determined depending on the characteristics of the liquid crystal sandwiched between the alignment layers in the transmittance control layer 105, that is, the orientation of liquid crystal molecules. When the voltage to be applied is gradually reduced when viewed over time according to characteristics such as those that increase the transmittance when not applied and those that increase when the voltage is applied It is assumed that the applied voltage is gradually increased. In such a case, the output PB after 10 years is set from the output P of the solar cell, taking into account changes over time in the size of the power source for driving the control IC and the power source for controlling the transmittance control layer. Good.

The period is 10 years as an example, but assuming a period for guaranteeing the output of the solar cell as a product and a recommended replacement period for the solar cell, an appropriate period such as 15 years or 5 years is set. Thus, it is preferable to perform control so as to change the light transmittance in accordance with the output PB at that time.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. The difference from the first embodiment is that the light transmittance control layers 105A and 105B are provided between the semiconductor layers 1031 and 1032, 1032 and 1033, respectively. The transparent electrodes in the respective light transmittance control layers 105A and 105B are electrically connected to the control IC 106, and the orientation of the liquid crystal can be changed by controlling the application state of power from the control IC 106.

The control IC 106 used in the case of this embodiment includes a plurality of channels for changing the output voltage output to the light transmittance control layer according to the time count described above according to the number of the transmittance control layers to be controlled. Those are preferred. By controlling each channel independently with time count, the transmissivity can be changed according to the degradation characteristics of the semiconductor used as the semiconductor layer, so it can be finely controlled and suitable for multijunction solar cells. Control can be performed.

That is, as shown in FIG. 8, when the decrease in the maximum output after 10 years in each of the semiconductor layers 1031, 1032, and 1033 is ΔPa, ΔPb, ΔPc (ΔPb <ΔPa <ΔPc), This is because the transmittance can be changed in accordance with the decrease in output, and optimal control can be performed.

The control IC 106 determines that the initial maximum output of the solar cell is the initial maximum output Po (Poa, Pob, Poc) minus the output decrease (ΔPa, ΔPb, ΔPc) due to the output decrease due to the deterioration of the semiconductor over time. In order to obtain the output PB (PBa, PBb, PBc), control is performed to supply a voltage to the light transmittance control layer so as to control each light transmittance.

The transmittance τo (τoa, τob, τoc) when the output of the solar cell becomes the PB (PBa, PBb, PBc) is determined in advance when the solar cell is manufactured, and the transmittance of the transmittance control layer is The control voltage when the light transmittance τo is reached is an initial applied voltage, and the light transmittance control layer is controlled from the control IC. Note that the transmittance in the lower layer as viewed from the light receiving surface takes into account the overall transmittance of a liquid crystal, a polarizing plate, a transparent electrode, a semiconductor, and the like as the transmittance control layer used in the solar cell.

The control IC is provided with a storage unit for storing the initial applied voltage for each of these semiconductor layers, the applied data over time of the applied voltage, and the like, and these data are read from the storage unit over time and controlled. Good.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. The difference from the first and second embodiments is that the power supply of the control IC 106 is supplied from a part of semiconductor layers forming a multi-junction, and a power source generated by another semiconductor layer forming a multi-junction is not used. is there. FIG. 9 shows an example in which the power supply for the control IC is obtained from the lowermost semiconductor layer as viewed from the light receiving surface.

In this case, since the power supply for the control IC and the power supply for supplying to the outside as a solar cell are separated, for example, due to a control failure of the control IC or a failure of the semiconductor layer in the long term, In the case where power generation and control cannot be performed normally, it is possible to prevent a problem from spreading as compared with a case where power is supplied from all the semiconductor layers.

(Fourth embodiment)
Next, a fourth embodiment of the solar cell will be described with reference to FIG. In the fourth embodiment, in addition to the control described in the first embodiment, the number of consecutive changes in the direction in which the amount of sunshine increases or the direction in which the amount of sunshine decreases decreases in a long-term trend such as climate change. And control to increase or decrease the initial set value of the power generation amount according to the prediction.

In addition to the configuration of the first embodiment, the control IC 106 accumulates the number-of-times data for adjusting the maximum output value and the control content data of the power generation amount in the memory unit 10633, and adjusts the maximum output value. Each time, these data are confirmed by the calculation means.

First, when the power generation amount increases from the initial setting value PB at time tc (FIG. 10A), the comparison unit 10632 measures the power generation amount increase ΔP1, and the power generation amount increase amount. Control is performed to reduce the light transmittance by Δτ1 so as to decrease ΔP1 (FIG. 10B).

As shown in FIG. 10A, when the power generation amount increases from the initial set value PB three times, ΔP1, ΔP2, and ΔP3, the control IC 106 sets the transmittance in the transmittance control layer to Δτ1, Each time Δτ2 and Δτ3 are decreased, the control content data indicating that the transmissivity is increased and the transmissivity is decreased are accumulated in the memory unit 10633. Then, when the comparison unit reads and confirms from the memory unit that the same control content data for reducing the transmissivity is continued three times, the same control as the continuous control content is performed in advance.

That is, in the case of FIG. 10B, the light transmittance is previously reduced by Δτ4, and the initial set value of the power generation amount is reduced from PB by ΔP4. In the long term, the climate is predicted to increase in the amount of sunshine, and the power generation is reduced in advance, and the semiconductor layer of the solar cell is protected from excessive sunshine, and controlled so that stable output can be achieved. To do.

Further, when the power generation amount continuously decreases, the light transmission rate is increased and the initial set value of the power generation amount is increased from PB. In the long run, it is predicted that the climate will change in the direction that the amount of sunshine will decrease, so that the power generation amount will be increased in advance, so that the semiconductor layer of the solar cell can obtain appropriate sunshine, and stable output can be performed To control.

The magnitude of ΔP4 (Δτ4) described above is obtained by accumulating change data (change data of transmittance) of the power generation amount continuously changed in the past in the memory unit, and changing the power generation amount (transmittance). ) May be used as an average power generation amount (transmittance). As a result, as the amount of change in the amount of power generation, the amount of change corresponding to the actual climate change can be obtained, and the amount of power generation of an appropriate size can be controlled at the place where the solar cell is installed. .

(About the types of solar cells to be controlled)
In addition, as semiconductors used for solar cells, crystalline single crystal silicon, polycrystalline silicon, group IV semiconductors typified by amorphous silicon, GaAs, CdS, CuInSe2, III-V group, II-VI The transmissivity control layer in the present application is also provided in solar cells using compound semiconductors such as Group I, III-VI, etc., organic semiconductors such as phthalocyanine, and dye-sensitized solar cells typified by wet solar cells. Thus, it is possible to control the output by controlling the light transmittance over time and controlling the magnitude of sunlight applied to these semiconductors and the like. In addition, any battery that generates power by being irradiated with light such as sunlight or illumination can be controlled by adjusting the amount of irradiation such as sunlight or illumination.

Further, regarding the control IC 106 provided on the conductive substrate 101, the control IC and the electrode may be electrically connected by a fine wire, or may be connected by providing a pattern wiring on the conductive substrate. Good.

Further, when a plurality of solar cells 1 are used for modularization, the solar cells 1 may be connected in series or in parallel as shown in FIG. FIG. 11A shows an example in which a plurality of solar cells 1 are formed on the conductive substrate 101. Each solar cell is connected by an electrode 108 formed on the conductive substrate 101, and a control IC 106 is provided in each solar cell. When the modules are connected to each other, the electrodes 108 may be sequentially connected.

FIG. 11B shows an example in which a plurality of solar cells 1 are formed and these solar cells are controlled by one control IC. In this case, power supply to the control IC may be performed from one solar cell or from a plurality of solar cells. In order to increase the efficiency of wiring, the control IC 106 is provided in the middle of the substrate.

(Other examples)
In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

For example, in the first embodiment, an example in which liquid crystal is used for the light transmittance control layer 105 is shown. This liquid crystal has been described on the assumption that the orientation of molecules changes with the application of voltage. However, in order to reduce the control power in the control IC and save power, for example, the liquid crystal A ferroelectric liquid crystal having a memory effect that maintains the alignment state may be used. As a result, it is not necessary to always apply a voltage, and during the 10 years, a short-time voltage application is performed at predetermined predetermined time intervals, and the light transmittance is gradually changed. It is possible.

Further, as the output PB after 10 years given as an example, an output amount that is lower than the PB determined in the first embodiment by providing a predetermined margin for the semiconductor degradation expected after 10 years. A PC may be determined, and an initial light transmittance and a light transmittance after time may be determined and controlled for the PC. As a result, when the deterioration of the semiconductor progresses more than expected, when the transparency of the transparent electrode layer decreases over time, or when the transmissivity of the transmissivity control layer becomes lower than the expected change, etc. In addition, a solar cell that can ensure a certain output can be configured.

In the case of controlling a plurality of solar cells, a solar cell to be controlled and a solar cell not to be controlled may be provided, and the solar cell not to be controlled may be used as a power source for the control IC 106.

Furthermore, as shown in FIG. 11C, a circuit pattern of the control IC may be created in advance adjacent to a semiconductor layer used for the solar cell, and the control IC may be provided integrally with the solar cell. In this case, the wiring for connecting the power supply for the control IC can be eliminated, and the production efficiency can be improved as compared with the case where the solar cell and the control IC are individually produced.

DESCRIPTION OF SYMBOLS 1 Solar cell 101 Conductive substrate 102 Metal electrode layer 103 Semiconductor layer 104 Transparent electrode layer 105 Light transmittance control layer 1051 Polarizing plate 1052 Transparent electrode 1053 Transparent electrode 1054 Alignment layer 1055 Alignment layer 1056 Liquid crystal 1057 Polarizing plate 106 Control IC
1061 Power supply input unit 1062 Power supply output unit 1063 Comparison calculation unit 10631 Power generation amount measurement unit 10632 Comparison unit 10633 Memory unit 10634 Timer unit 107 Current collecting electrode

Claims (1)

On the light receiving surface of a multi-junction solar cell formed by stacking a plurality of solar cell elements in layers,
A transmittance control layer is formed,
A control IC electrically connected to an electrode layer provided in the solar cell element is formed adjacent to the solar cell element,
The control IC includes a power generation amount measuring unit in the semiconductor layer,
To chromatic comparison means with the default value of the measured power generation amount and the power generation amount stored in the memory unit, and a timer means for measuring an elapsed time which is a time to make a comparison in the comparison means, the computing means having a With
The control IC sets the predetermined output amount after a lapse of time as the initial set value, and controls the transmissivity so that the maximum output amount at the time of installation becomes the initial set value,
The control IC has at least frequency data obtained by adjusting the maximum output value,
Control content data of power generation amount,
In the memory unit,
Each time the maximum output value is adjusted, these data are checked by the calculation means,
If the same power generation amount control content data continues three times,
When the third data is confirmed, the power generation amount is adjusted by decreasing or increasing the initial value of the power generation amount by a predetermined amount in the continuous direction. Multi-junction solar cell.

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