JP2011119629A - Device and method of evaluating multijunction solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measurement, capable of finding partial troubles for each cell of a multijunction solar cell having a structure such that cells made of semiconductor materials having different forbidden band widths are laminated and connected in series. <P>SOLUTION: Only light of a wavelength allotted to cells to be evaluated is extracted small and irradiated to modulate its intensity. Other cells connected in series are sequentially radiated by light in the shared wavelength band of each cell. Characteristics of the cell to be evaluated are measured by analyzing changes corresponded to the above modulation in electrical output thereby. Characteristics of all the cells are measured by radiating light sources having wavelength bands corresponding to two or more cells in order. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus and method for evaluating a multijunction solar cell.

  The multi-junction solar cell divides the spectrum of sunlight into several wavelength bands, uses different materials for each wavelength band, and shares and photoelectrically converts them. In many cases, a pn junction made of a semiconductor material having a different forbidden bandwidth is used as a basic structure called a cell, and these cells are sequentially stacked and connected in series. The thickness of the p layer and n layer of each cell, the suitability of the surrounding impurity density, the number of defects such as holes, scratches or cracks in the material greatly affect the conversion efficiency.

  As an evaluation method of such a solar cell, from the beginning, a method has been adopted in which pseudo solar light from a solar simulator is irradiated to the solar cell to be evaluated and the electric output at that time is evaluated. However, with this method alone, improvement and improvement directions cannot be made if the performance is inferior to the design target. Especially in the case of multi-junction solar cells, the structure is more complicated than that of a single layer, so it is possible to know which part of which cell is inferior and what is likely to lead to it, and take measures Must be taken sequentially.

  A clue to know which cell has a problem is to know the spectral sensitivity of the solar cell. “Japanese Industrial Standard (JIS C 8944)” describes a “multijunction solar cell spectral sensitivity characteristic measurement method”. This is a solar cell to be evaluated by irradiating a multi-junction solar cell in which cells are connected in series with a chopper to irradiate light obtained by splitting continuous light from a light bulb with a spectroscope. Is obtained by lock-in detection of the electrical output at the frequency and phase of the optical chopper. If there is a problem such as poor sensitivity, it may be possible to estimate the problem for each cell from this spectrum. However, it is difficult to obtain a clue with this method when the cell does not go out of speculation and the cell has a partial defect. Furthermore, with this method, the apparatus becomes large and expensive, and its application range is limited.

  As a method for finding partial defects in each cell, a method has been recently developed in which a forward current is passed through a solar cell to emit light, and this EL emission is observed as an image to find defects such as fine holes and cracks. Equipment is also provided. This is because the phenomenon that light emission occurs when a forward current is applied to the pn junction is caused to the solar cell, and the intensity of the injected light emission indicates the quality of the cell junction and the material deposition. Out. Since the defective part can be visually observed as an image, it is attracting attention because it can be observed with a relatively large area with a view, and it is easy and appealing intuitively. However, since the EL emission wavelength is in the infrared region and image observation is not easy, the emission intensity varies greatly depending on the material, and not all cells can be evaluated for each cell. Even if the defect is excluded, the feedback for improvement is not enough.

  An evaluation method called LBIC method is also known in which a laser beam is irradiated to observe a current induced in a pn junction at an irradiation place. This is a natural phenomenon of a solar cell in which an electromotive force is generated when light hits the pn junction, using a narrowly squeezed laser beam as a light source, irradiating a limited area of the solar cell surface, and changing the irradiation position Compare the electromotive force and examine the superiority or inferiority depending on the location. However, in this method, in the case of a multi-junction solar cell, even if an electromotive force is generated in one of a plurality of cells connected in series, light is not applied unless light in a shared wavelength region is applied to the other cell. Since the cell does not conduct, an output cannot be obtained from the outside, and it has not been put to practical use in a multi-junction type.

  Patent Document 1 discloses an apparatus that irradiates the entire surface of a solar cell and conducts it, and then irradiates the measurement target portion of the solar cell with a spot-like light to evaluate the measurement target portion. According to this method, it is possible to evaluate only the measurement target portion, and it is considered useful for finding defects. However, with this apparatus, it is possible to obtain only the evaluation of the whole cell to which the measurement target portion is joined, and it is not possible to obtain the evaluation of individual cells, and it is not possible to identify a cell having a defect.

  Further, even if evaluation of individual cells is obtained and a cell having a defect is identified, it is difficult to guess the reason why the defect has occurred in the manufacturing process only by the characteristics of the entire cell. In order to infer such a reason, it is necessary to measure a portion of a cell obtained by subdividing the cell. This is because the information on the change in characteristics in the cell is an estimation material for the reason why the defect has occurred. For example, if the sensitivity decreases from the left to the right of the cell, it is estimated that there is a gradient in the gas flow and temperature of the film formation apparatus, and if there are linear or dotted defects in a part of the cell, the grain boundary Generation of dust and adhesion of dust during each process or between processes. Based on these results, improvement can be promoted by changing or correcting the estimated process and the apparatus and conditions (flow rate, temperature) between the processes.

  The estimation of the reason why the defect has occurred is useful for improving the production process in order to improve the yield of the cell (semiconductor device). However, there is no disclosure of a method for estimating the reason why a defect has occurred by measuring characteristics of a cell portion obtained by subdividing the cell.

JP 2009-11115 A

  To provide a measurement method and a measurement apparatus that can find a partial problem for each cell of a multi-junction solar cell having a structure in which cells made of semiconductor materials having different forbidden bandwidths are stacked and connected in series. Is an issue.

Only the light of the wavelength shared by the cell to be evaluated is irradiated with a small aperture, and the intensity is changed. Other cells connected in series are continuously irradiated with light in the shared wavelength band of each cell. Alternatively, the neighboring cells are continuously irradiated with light in the shared wavelength band of each cell and electrically connected. The characteristics of the cell to be evaluated are measured by detecting and analyzing the output change corresponding to the change in the electrical output at this time. The characteristics of all the cells are measured by sequentially irradiating a plurality of cells with light sources in the corresponding wavelength range in the same manner.
Further, the characteristics of the cell portion are measured by subdividing the cell, and when the cell has a defect, information contributing to the estimation of the reason why the defect has occurred is obtained based on the change in the characteristic in the cell.

An evaluation device for a multi-junction solar cell of the invention according to claim 1 comprises:
It has a convergent light irradiation unit that irradiates light only to the evaluation target region,
A divergent light irradiating unit that irradiates light to a region equivalent to or wider than the evaluation target region,
The convergent light irradiating unit irradiates light with a temporal change in emission intensity of a semiconductor light emitting element as a light source,
It comprises a measuring unit for measuring the electrical output of the solar cell that has a predetermined relationship with the change.
A means to solve the problem described in the previous paragraph is realized.
Here, the “evaluation target region” refers to a region where the evaluation target cell is included as one of the cells connected in series in the region.
“A region equal to or wider than the evaluation target region” is, in principle, a wider region including the evaluation target region itself or the evaluation target region. However, the light irradiated by the divergent light irradiation unit is for irradiating a cell connected in series with the evaluation target cell, and may not necessarily be a region in principle as long as this object is achieved.
“Changed in time” means that the light emission intensity of the convergent light irradiating unit is temporally modulated, or light emission / quenching is performed based on an instruction from a separate commanding unit. The “system control information processing unit” in Example 1 below corresponds to the issuing unit.
“Predetermined relationship” refers to a relationship between a change in light emission intensity of a light source and a portion of an electric signal representing the electric output of a solar cell. A relationship that increases or decreases in synchronization with emission intensity modulation, for example, when a light source is modulated at a certain frequency, a current obtained by lock-in detection at that frequency is in a “predetermined relationship”. Alternatively, the light emission / extinction of the convergent light irradiating unit is controlled based on an instruction from a separate commanding unit, and the measurement unit measures based on the command from the commanding unit. The value relationship is also in the “predetermined relationship”.
It is possible to reliably measure the characteristics of the cell to be evaluated by changing the emission intensity of the convergent light irradiator over time and measuring the solar cell electrical output that has a predetermined relationship with the change. It is.
By using a semiconductor light emitting element as the light source, the wavelength of the emitted light can be easily selected, and the light of the wavelength shared by the evaluation target cell and the light of the wavelength shared by other cells connected in series can be selected. Can be easily obtained. Compared to the case where light from a continuous spectrum light source such as a light bulb is dispersed with a spectroscope to extract a specific wavelength, or when a specific wavelength is extracted with an interference filter and irradiated, the light emitting element is used as a light source. The selection of the wavelength will select the wavelength, and the irradiation light power density can be increased by several orders of magnitude. The increase / decrease / interruption of the current is directly linked to the intensity of the irradiation light, which makes the apparatus simple and compact.

An evaluation apparatus for a multi-junction solar cell according to a second aspect of the present invention provides:
It has a bias generator that applies a DC voltage bias to the solar cell,
A system control information processing unit that controls the convergent light irradiation unit, the divergent light irradiation unit, the measurement unit, and the voltage bias generation unit;
The system control information processing unit, from the convergent light irradiation unit and the diverging light irradiation unit in a state where a voltage bias corresponding to an open voltage generated in a solar cell is applied only by light irradiation from the diverging light irradiation unit. It is characterized in that control is performed so that the measurement unit measures the current at this time.
Since two or more cells connected in series are irradiated with light and a voltage is generated in each cell, one or more of the cells are reverse-biased, and the cells may be damaged. Generation of reverse bias is prevented by applying a voltage bias corresponding to the open circuit voltage.

An evaluation apparatus for a multi-junction solar cell according to a third aspect of the present invention provides:
The convergent light irradiation unit includes two or more semiconductor light emitting elements having different wavelengths,
The system control information processing unit controls a semiconductor light emitting element that emits light having a wavelength absorbed by the evaluation target cell from the two or more semiconductor light emitting elements so as to emit light.
The semiconductor light emitting device can emit light having a specific wavelength, and can easily obtain irradiation light having a wavelength shared by the cell to be evaluated.

An evaluation apparatus for a multi-junction solar cell according to a fourth aspect of the present invention provides:
The system control information processing unit controls the wavelength distribution of light emitted from the divergent light irradiation unit so that the wavelength emitted from the convergent light irradiation unit is not included.
The evaluation target cell does not react to the light emitted by the divergent light irradiation unit, and the evaluation of the evaluation target cell by the light emitted from the convergent light irradiation unit is easy.
In addition, it is not necessary to use light of the same wavelength for both the divergent light irradiating part and the converging light irradiating part, and in principle, only one semiconductor element of the light source is required per wavelength, and the cost for manufacturing the device is reduced.

An evaluation device for a multi-junction solar cell of the invention according to claim 5 is:
The semiconductor light emitting element as a light source of the convergent light irradiation unit is a semiconductor laser.
Since the semiconductor laser has good coherence, the region irradiated with light from the convergent irradiation light irradiation unit can be narrowed down to a small part, and a finer part of the cell can be evaluated.

An evaluation device for a multi-junction solar cell of the invention according to claim 6 is:
The convergent light irradiating unit and the diverging light irradiating unit each irradiate light through one optical fiber.
An optical fiber can be used, which is convenient for routing, and light can be easily guided from the light source toward the evaluation target region. Moreover, it can be used only by changing a part of the existing parts for optical communication.

An evaluation device for a multi-junction solar cell of the invention according to claim 7 comprises:
The convergent light irradiator and the divergent light irradiator share a semiconductor light emitting element as a light source, and the light from the shared semiconductor light emitting element is switched by an optical switch so that the convergent light irradiator or the divergent type is emitted. It is used for any one of the light irradiation sections.
The number of semiconductor elements of the light source can be reduced, and the cost for creating the device is reduced.

An evaluation device for a multi-junction solar cell according to an invention according to claim 8 comprises:
A moving mechanism for moving at least one of the solar cell, the convergent light irradiating unit, and the divergent light irradiating unit to place the evaluation target region at a position irradiated with light from the convergent light irradiating unit. It is characterized by providing.
At least one of the solar cell, the convergent light irradiating unit, and the divergent light irradiating unit can be moved by the moving mechanism, and two or more evaluation target regions can be continuously evaluated.

The method for evaluating a multi-junction solar cell according to claim 9 is as follows:
The evaluation apparatus for the multi-junction solar cell described above is used.
The multijunction solar cell can be evaluated by utilizing the merit of the evaluation device for the multijunction solar cell.

The solar cell evaluation apparatus of the invention according to claim 10 comprises:
It has a convergent light irradiation unit that irradiates light only to the evaluation target region,
A divergent light irradiating unit that irradiates light to a region equivalent to or wider than the evaluation target region,
The convergent light irradiating unit irradiates light with a temporal change in emission intensity of a semiconductor light emitting element as a light source,
It comprises a measuring unit for measuring the electrical output of the solar cell that has a predetermined relationship with the change.
The technology according to the multijunction solar cell evaluation apparatus of the present invention can be applied to other solar cells.

  Characteristics can be measured for each cell, and a cell having a defect can be identified. In addition, the characteristics of the subdivided cells can be evaluated, and it can be understood whether the problem lies in the processing method, the material used, or the design parameters, and accurate and prompt feedback for improvement Is possible. This significantly accelerates the development of multi-junction solar cells. In addition, manufacturing yields will improve and manufacturing costs will decrease, contributing to lower prices and higher profits.

FIG. 1 is a diagram showing a basic configuration of a two-junction solar cell, its spectral sensitivity, and an equivalent circuit. FIG. 2 is a diagram illustrating an example of a configuration of a two-junction solar cell evaluation apparatus and a light irradiation unit optical system. Example 1 FIG. 3 is a diagram showing the evaluation principle. Example 1 FIG. 4 is a diagram showing a spectral sensitivity curve of a three-junction solar cell. (Example 2) FIG. 5 is a schematic cross-sectional view of a three-junction solar cell. (Example 2) FIG. 6 is a diagram illustrating a light irradiation unit when an optical fiber is used for the light irradiation unit. (Example 3) FIG. 7 is a diagram illustrating an example of the optical system of the convergent light irradiating unit and the divergent light irradiating unit. Example 4 FIG. 8 is a diagram illustrating an example of an evaluation apparatus for a multi-junction solar cell. (Example 5)

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention will be described with reference to the drawings, taking as an example application to two-junction solar cell evaluation and three-junction solar cell evaluation.

  Fig.1 (a) is sectional drawing which shows the basic composition of a 2 junction type solar cell. The surface of the glass substrate 10 is coated with a conductive transparent electrode material 11 such as ITO. The glass substrate coated with the conductive transparent electrode material 11 is a substrate for manufacturing a solar cell. First, for example, an amorphous silicon p-layer and an n-layer are formed to form the first cell 12, and this (as a solar cell) The second cell 13 is formed by forming, for example, a p-layer and an n-layer of polycrystalline silicon in the lower part. Finally, after forming a metal film such as silver to form the electrode 14, the solar cell 1 is formed by covering with a protective film. In use, light is irradiated from the glass substrate 10 side as shown in the figure. λ1 represents a representative wavelength of light having a wavelength of 300 nm to 600 nm shared by the first cell (12). Most of the light having the wavelength λ1 is absorbed by the first cell (12), and the second cell (13 ) Is hardly reached. Similarly, λ2 indicates the wavelength of light from 600 nm to 900 nm, and light of wavelength λ2 is hardly absorbed in the first cell (12), but most of it is absorbed in the second cell (13).

  FIG.1 (b) is a figure which shows the spectral characteristic of this solar cell. In the figure, the broken line indicated as the first cell indicates the sensitivity characteristic of the first cell, and the broken line indicated as the second cell indicates the sensitivity characteristic of the second cell. The solid line denoted as the whole indicates the sensitivity characteristics of the entire two-junction solar cell. When irradiating light of 350 nm to 500 nm, only an electromotive force is generated only in the first cell, and when irradiating light having a wavelength longer than 700 nm, it is transmitted without being absorbed in the first cell, and an electromotive force is generated in the second cell. When light having a wavelength of 500 nm to 700 nm, which is the middle of these, is irradiated, an electromotive force is generated in both the first cell and the second cell. In Example 1 below, a wavelength of 405 nm indicating the characteristics of only the first cell is selected as λ1, and a wavelength of 780 nm reflecting the characteristics of only the second cell is selected as λ2.

  FIG. 1C shows an electrical equivalent circuit of this solar cell. In the figure, D1 indicates the pn junction of the first cell, and D2 indicates the pn junction of the second cell. When this D1 is irradiated with light of wavelength λ1, an electromotive force is generated. The open-circuit voltage Vo1 depends on the light intensity when the light is weak, but if it exceeds a certain level, even if the light intensity is increased, it converges to a value determined by the band gap energy of the material constituting the pn junction and the Fermi level difference. Therefore, the open / closed voltage Vo1 reflects only a little of the quality of the cell. This is the same for the open circuit voltage Vo2 with respect to D2.

FIG. 2 is a diagram illustrating a schematic configuration of an evaluation apparatus for a two-junction solar cell and an example of an optical system. FIG. 1A is a conceptual diagram of the system configuration. The solar cell 1 to be evaluated is irradiated with light from the converging light irradiating unit and the diverging light irradiating unit controlled by the system control information processing unit 4 coaxially through a half mirror and further irradiated perpendicularly to the irradiation surface. Yes. The electrical output is picked up by a probe and supplied to the measurement unit. The output of the measurement unit is processed by the system control information processing unit 4, and numerical information is output in comparison with the position information from the XY fine movement base drive unit. Also, these are sent to the image output unit, and the in-plane distribution for each cell is imaged and output.
In the figure, the optical axes of the light emitted from the convergent light irradiating unit and the divergent light irradiating unit coincide with each other, but they may not coincide as shown in FIG.

  FIG. 2B illustrates the optical system and its operation when evaluating the first cell. In the figure, LS1 denotes a converging light irradiating unit, which includes a semiconductor laser L11 having an oscillation wavelength of λ1, a semiconductor laser L12 having an oscillation wavelength of λ2, and a first lens for converging these lights on the surface of the target solar cell 1. And a second lens, a surface mirror that efficiently reflects light of wavelength λ2, and a first half mirror that reflects light of wavelength λ1 but transmits light of wavelength λ2. The light of wavelength λ1 emitted from the semiconductor laser L11 is reflected by the first half mirror through the first lens and the light axis after the light of wavelength λ2 emitted from the semiconductor laser L12 is reflected by the surface mirror through the second lens. Further, the light beam passes through the first half mirror and is aligned with the optical axis after the high accuracy, and both converge in a narrow area on the surface of the solar cell 1 to be evaluated. The convergent diameter is preferably 15 microns or less. These irradiation lights preferably have an optical axis perpendicular to the target surface and a maximum light intensity of 0.5 mW or less.

  In the figure, LS2 denotes a divergent light irradiating unit, a semiconductor laser L21 having an oscillation wavelength λ1, a semiconductor laser L22 having an oscillation wavelength λ2, a surface mirror that efficiently reflects light having a wavelength λ2, and light having a wavelength λ1. And a second half mirror that transmits light of wavelength λ2. After the light of wavelength λ1 emitted from the semiconductor laser L21 is reflected by the second half mirror, and after the light of wavelength λ2 emitted from the semiconductor laser L22 is reflected by the surface mirror and further passes through the second half mirror Is substantially coincident with the optical axis. In the divergent light irradiating unit, it is not necessary to limit the irradiation region, and even if the accuracy of matching the optical axes is low as compared with the convergent light irradiating unit, it is allowed. Moreover, it has set so that the periphery several millimeters may be irradiated centering on the point which the said convergent light irradiation part LS1 on the solar cell 1 surface of evaluation object irradiates. The irradiation light intensity is preferably about several mW. Both the convergent light irradiating unit and the divergent light irradiating unit are similar to parts called BIDI or BOSA, which are frequently used in wavelength multiplexing of optical communication. In the case of such an optical system, means for converging light on the irradiated surface is already provided if an external product with a ball lens is used for the semiconductor laser. The optical axis of the convergent light irradiation unit LS1 is perpendicular to the irradiation target surface, and the optical axis of the divergent light irradiation unit is slightly inclined with respect to the irradiation target surface to avoid mechanical interference. As shown in the figure (a), both optical axes may be aligned using a half mirror so that both are perpendicular to the target irradiation surface. The number of expensive parts can be reduced by slightly tilting to avoid mechanical interference as shown in FIG.

When the first cell of the two-junction solar cell 1 is evaluated using the optical system shown in FIG. 5B, the semiconductor laser L11 of the convergent light irradiation unit LS1 is temporally modulated (for example, turned on in a 1 kHz rectangular waveform). The light is irradiated on the surface of the solar cell 1 and the semiconductor laser L22 of the divergent light irradiating unit LS2 is continuously operated at a constant output to irradiate the periphery with light of the wavelength λ2. FIG. 5C similarly shows a case where the second cell is evaluated. In this case, the semiconductor laser L12 of the converging light irradiating unit LS1 is operated with time modulation, and the light of wavelength λ2 is irradiated onto the surface of the target solar cell 1, and at the same time the semiconductor of the divergent light irradiating unit LS2 The laser L21 is continuously operated at a constant output to irradiate light having a wavelength λ1.
The measuring unit applies a probe to the solar cell 1 to take out an electric output, and measures the voltage across the terminal by connecting a load resistance of 50Ω, for example. At this time, an output of about 10 mV as the direct current and about 0.1 mV to 2 mV as the component corresponding to the temporal modulation is obtained. The component corresponding to the temporal modulation avoids noise by detection corresponding to the modulation (for example, lock-in detection at 1 kHz using a lock-in amplifier when an on / off operation is performed in a 1 kHz rectangular waveform).

  FIG. 3 is a diagram showing the evaluation principle. Hereinafter, the physical meaning of this measurement will be described with reference to FIG. FIG. 2A shows a band structure diagram of a two-junction solar cell. The pn junctions of the first cell and the second cell are connected in series. A material having a wide band gap (for example, amorphous silicon) is used for the first cell on the front side, and a material having a narrow band gap (for example, for example, amorphous silicon) is used for the second cell. Polycrystalline silicon) is used. Between the two cells, there are a p + layer and an n + layer which are degenerated by adding a large amount of impurities, and are connected in ohmic fashion. As shown in FIG. 5B, when the light of wavelength λ2 is irradiated, the first cell is transmitted and unreacted, but the second cell absorbs and generates many electrons and holes. If both ends of the solar cell are open, an open circuit voltage Vo2 of approximately 0.7V is generated. When the wavelength λ1 is irradiated as shown in FIG. 5C, most of the light is absorbed by the first cell, and an open circuit voltage Vo1 of about 1.4V is generated, and the open circuit voltage between the terminals is about 2.1V.

  FIG. 4D shows a band diagram when the light of wavelength λ2 is irradiated from the divergent light irradiating unit and the light of wavelength λ1 is irradiated from the converging light irradiating unit, and the terminals are short-circuited. Such irradiation is performed for the purpose of measuring the characteristics of the first cell. Here, photoelectric conversion corresponding to a current of about 0.01 mA occurs because the light of wavelength λ2 is about 3 mW and is about 0.2 mA, and the light of wavelength λ1 is about 0.5 mW. The current value is limited by the first cell with a small amount of power generation, and about 0.01 mA flows. Since the two terminals are connected by a low resistance copper wire, there is no potential difference. In the second cell, surplus carriers are accumulated and the Fermi level of the n region is raised, that is, in the p region of the first cell. The level should be slightly lifted to form a weak reverse vice. Since the reverse bias value is up to 0.7 V at most, it is smaller than the band gap of the first cell and does not cause a great problem. However, when measuring the characteristics of the second cell, the intensities of the light of wavelength λ1 and the light of wavelength λ2 are opposite, the first cell having a large band gap is strongly excited and the second cell is not excited or weak. At this time, although it is up to the open circuit voltage of the first cell, the second cell may be largely reverse-biased as shown in FIG. A solar cell is likely to be vulnerable to such a reverse bias. In particular, in a multi-junction solar cell having three or more junctions, the open-circuit voltage also increases, and short-circuiting may destroy other cells.

  The above situation is shown in FIG. Curves 100, 101, and 102 show the characteristics of the first cell without irradiation, with light with wavelength λ2, and with light with wavelength λ2 and light with wavelength λ1, respectively. These show the characteristics when the second cell is not irradiated, irradiated with light of wavelength λ2, and irradiated with light of wavelength λ2 and light of wavelength λ1, respectively. The non-irradiated characteristics of the solar cell 1 as a result of the series connection of these two cells are a curve 300, and the characteristics of the solar cell 1 under irradiation with light of wavelength λ2 are curve 301, and light of wavelength λ2 and light of wavelength λ1 The characteristic under irradiation is indicated by curve 302. Only these curves 300, 301 and 302 are known from the outside. A point where the curve 301 intersects the horizontal axis (zero current line) is A, and a point on the curve 302 immediately above this point is B. A voltage at a point A obtained by irradiating light of wavelength λ2 is measured, and biased with the voltage, current under simultaneous irradiation of light of wavelength λ2 and light of wavelength λ1 is measured. By doing so, it is possible to know the short-circuit current of the targeted cell without creating the above-described reverse bias state. A band diagram during this period is shown in FIG. In the figure, the symbol of the battery represents the bias voltage.

  In FIG. 5F, the curve 301 is drawn slightly above the non-irradiated curve 300, but in principle, the first cell has no sensitivity to light of wavelength λ2, and the curve 301 is the curve 300. Matches. However, even when the first cell is slightly sensitive and photoelectric conversion occurs and electrons and holes are generated, the voltage bias value for preventing the reverse bias can be obtained as described above.

  The above description can be expressed by an electrical equivalent circuit as shown in FIGS. When light having a wavelength λ2 having sensitivity is mainly applied to the second cell, that is, D2, the open circuit voltage of the solar cell 1 appears as an open circuit voltage Vo2 of approximately D2, as shown in FIG. If this voltage is biased and light of wavelength λ1 is irradiated as shown in FIG. 5I, Vo1 is obtained as a potential difference. The short-circuit current Is1 is obtained by connecting a sufficiently low electric resistance R between these terminals as shown in (j). The voltage that is the product of R (for example, 50Ω) and Is1 (for example, 0.04 mA) is as small as several millivolts (here, 2 mV or less). When light having a wavelength λ1 is modulated and irradiated with a rectangular wave of 1 kHz, by locking the voltage at this frequency, only necessary current can be obtained without noise. If this short-circuit current Is1 is divided by the light output of wavelength λ1 from the convergent light irradiator, the local conversion efficiency at that location of the first cell can be obtained.

  Similarly, when evaluating the second cell, the convergent light irradiating unit is irradiated with light of wavelength λ1 from the divergent light irradiating unit LS2 as bias light and electrically biased with the obtained open-circuit voltage. Light having a wavelength λ2 is intermittently emitted from LS1, and a voltage that is a product of the low resistance R and Is2 is obtained using a lock-in amplifier. In this way, a short-circuit current Is2 at a certain point on the surface of the multi-junction solar cell 1 is obtained. Similarly, if the short-circuit current Is2 is divided by the light output of the wavelength λ2 from the convergent light irradiator, the local conversion efficiency at that location of the second cell can be obtained.

  Next, the evaluation point is moved by 1 mm to similarly obtain the short-circuit currents Is1 and Is2. The distribution of Is1 and Is2 is obtained by repeating the same measurement by moving 1 mm at a time. That is, the short-circuit current distribution of the first cell and the short-circuit current distribution of the second cell are obtained. The short-circuit current distribution obtained in this way can be easily imaged, and the change can be understood intuitively at a glance. Here, the movement of the position is set to 1 mm step, but fine movement to about 10 microns can be freely selected within the performance range of the moving mechanism. Even when the light source is a semiconductor laser, the irradiation area can be sufficiently narrowed by using, for example, the optical system shown in FIGS. 7D and 7E. Can be measured.

Control by the system control information processing unit 4 for realizing the above operation will be described.
First, when the operator confirms the operation of the position, etc., and presses the start button, the system control information processing unit 4 reads and stores the position, and then the light emitting element having the wavelength λ2 of the divergent light irradiation unit emits light. Give instructions. A voltage equal to the open circuit voltage of the solar cell to be evaluated is generated in the bias generator. In this state, an on / off light emission instruction is issued to the light emitting element having the wavelength λ1 of the convergent light irradiation unit. Subsequently, the current flowing between the electrode of the solar cell to be evaluated and the constant voltage power source is measured by the measurement unit by lock-in or the like. This value is stored.
Next, a light emission instruction is issued to the light emitting element having the wavelength λ1 of the divergent light irradiation unit. The measurement unit is made to check the open voltage of the electrode of the solar cell to be evaluated, and a voltage equal to this voltage is generated in the bias generation unit. In this state, an on-off light emission instruction is issued to the light emitting element having the wavelength λ2 of the convergent light irradiation unit. The measurement unit measures the current flowing between the electrode of the solar cell to be evaluated and the constant voltage power source via a lock-in or the like, and stores this value. Next, the light irradiation position is changed. The operator may move the XY drive unit by pressing a button or the like, and the system control information processing unit 4 may read and store the position, or to a position programmed in advance in the “system control information processing unit”. A method may be used in which an instruction is sent from the system control information processing unit 4 to the XY driving unit so that the position is changed by moving the pulse motor, and when the position information matches a predetermined position. Further, the light irradiation unit may be moved by the XY drive unit without moving the solar cell to be evaluated. At this position, the above control is repeated from the system control information processing unit 4.
The current values at the respective positions obtained in this way are sequentially output to the output display unit and graphed, and a current graph for each cell on the light receiving surface of the solar cell to be evaluated is displayed.

  In general, the short-circuit current reflects the thickness of the depletion layer of each cell, the depth of the pn junction, the lifetime of minority carriers induced by light, the diffusion distance, and the grain boundary. If the current value has an inclination to one side of the light receiving surface, this indicates a thickness distribution during film formation or a concentration distribution of impurity addition. If a local dent is visible, a hole due to the adhesion of dust during film formation is suspected. In addition, if there is a linear low place, it is suspected that the grain boundary or material cracks. If these abnormalities are found in the distribution of Is1, the film formation process of the first cell is triggered, and if the abnormalities are found in the distribution of Is2, it leads to an improvement centering on the manufacturing process of the second cell.

  Such a relative change in the short-circuit current can be easily grasped by imaging. For this purpose, the accuracy of the optical output and short-circuit current need only be such that the outline of the relative change can be seen by looking at the image, and the handling and maintenance of the apparatus becomes easy. However, since the change in the laser output during measurement also affects the image, it is preferable to perform so-called APC (automatic light output control) driving in which the drive current is finely adjusted by the light output.

  In this embodiment, it is necessary that the short-circuit current of other cells is larger than the short-circuit current of the cell to be evaluated. In other words, it is important that the light output of the divergent light irradiating unit is large and that it is in a wavelength range with sufficient power generation capability. From this point of view, in the silicon-based two-junction solar cell shown in FIG. 1B, it is preferable to select λ1 near 500 nm and λ2 near 700 nm. In this case, 405 nm and 780 nm are selected, respectively. This is because it is selected from the wavelength range of semiconductor lasers that can be obtained at low cost. In this case, when the first cell is evaluated, the light with the wavelength λ2, that is, 780 nm emitted from the divergent light irradiation unit as the bias light does not necessarily have to be at the peak of the power generation capability of the second cell. Further, there are individual differences in the cells to be measured, and the spectrum sensitivity as shown in FIG. Also in this case, it is preferable that the light output of each wavelength band irradiated from the divergent light irradiating unit is not less than 5 times the light output irradiated from the converging light irradiating unit so that a reverse bias does not occur.

  Up to this point, the evaluation of the two-junction solar cell has been described. Next, the evaluation of the three-junction solar cell will be described. FIG. 4 is a diagram showing a spectral sensitivity curve of a three-junction solar cell. FIG. 5 is a schematic cross-sectional view of a three-junction solar cell. The three-junction solar cell 2 is made of a compound crystal in which a Ge cell 511 is formed on a Ge substrate, an InGaAs cell 512 is formed thereon, an InGaP cell 513 is further formed thereon, and an output is obtained by irradiation from the InGaP cell side. In FIG. 5A, reference numerals 514 and 515 denote electrodes. As light wavelengths suitable for these three cell evaluations, 405 nm (λ1), 780 nm (λ2), and 1310 nm (λ3) were selected. At these wavelengths, one cell has strong sensitivity, and the other cells have almost no sensitivity. Similar to the application example to the previous two-junction solar cell, it can be similarly applied to the three-junction solar cell. FIG. 5A shows an electrical equivalent circuit, and FIG.

  In order to evaluate this three-junction solar cell, each of the convergent light irradiator and the divergent light irradiator is provided with a semiconductor laser that oscillates at wavelengths λ1, λ2, and λ3. When evaluating the InGaP cell, light of wavelengths λ2 and λ3 is irradiated from the divergent light irradiating unit, and biased with Vo2 + Vo3 corresponding to the open circuit voltage at that time. The light of λ1 modulated on-off is irradiated from the first light irradiation unit, and the current Is1 flowing between the terminals at that time is evaluated. At this time, the second light is irradiated with light of wavelengths λ2 and λ3 so that the density of electrons and holes generated in the InGaAs cell (D2) and Ge cell (D3) is sufficiently higher than that generated in the InGaP cell (D1). It is preferable that the light output from each of the light irradiators is approximately several mW, and the light output from the first light irradiator that irradiates light of wavelength λ1 is approximately 0.5 mW.

  Similarly, when the InGaAs cell (D2) is evaluated, light of wavelength λ3 and wavelength λ1 is irradiated from the divergent light irradiation unit, and biased with Vo3 + Vo1 corresponding to the open circuit voltage at that time. The light of wavelength λ2 that is on-off modulated there is irradiated from the convergent light irradiation unit, and the current Is2 flowing between the terminals at that time is evaluated. When evaluating the Ge cell (D3), light of wavelengths λ1 and λ2 is irradiated from the divergent light irradiation unit, and biased by Vo1 + Vo2 corresponding to the open circuit voltage at that time. The light of wavelength λ3 that is on-off modulated there is irradiated from the convergent light irradiation unit, and the current Is3 flowing between the terminals at that time is evaluated.

  Furthermore, solar cells with many 4 junctions and 5 junctions can be similarly evaluated by increasing the number of light sources. In any case, it is preferable that the irradiation light power from the divergent light irradiation unit is preferably several times to ten times larger than the irradiation light power from the convergent light irradiation unit.

The present embodiment relates to a convergent light irradiator and a divergent light irradiator. Portions other than the convergent light irradiator and the divergent light irradiator are the same as those in the first or second embodiment.
FIG. 6 is a diagram showing a light irradiation unit when an optical fiber is used for the light irradiation unit. In FIG. 2A, light source 1, light source 2,... Light source n of the convergent light irradiating unit represents n semiconductor lasers emitting at n wavelengths, and light source 1 and light source in the divergent light irradiating unit. 2,... The light source n represents a semiconductor light emitting element including the same wavelength as that in the convergent light irradiation section. The thin broken line represents optical coupling. If a semiconductor laser with an optical fiber is used as the light source, the broken line represents the optical fiber. In the figure, the means for combining means that light waves from a plurality of light sources are combined into one light wave, and usually a surface mirror or half as shown in FIG. 2 (b) or (c). This is realized by a configuration using a mirror. However, when making this half mirror, the film thickness of the dielectric multilayer must be controlled with high precision, and a small amount is extremely expensive. Therefore, on the premise that a semiconductor light emitting element is used as a light source, a slight increase in insertion loss is prepared, and an optical fiber multiplexer is used to emit several semiconductor light sources having different wavelength bands into one optical fiber. The convergent light irradiating part or the divergent light irradiating part may be used. However, it is preferable to provide convergence means as shown in FIG.

  Furthermore, the wavelength band of the light irradiated by the convergent light irradiation unit need not be in the wavelength band irradiated by the diffusion light irradiation unit. Therefore, when only one set of light emitting elements is arranged over all the wavelength bands and switched by the optical switch and irradiated from the first light irradiation unit, the drive current value is kept low, and the second light irradiation unit When irradiating from, the drive current may be set higher. In this way, it is not necessary to prepare a large number of expensive light sources, and it can be easily reduced. The light irradiation part in this case is shown in FIG.6 (b). One fiber-attached semiconductor laser is prepared for each of the n wavelength regions, the operating conditions of these lasers are adjusted in accordance with instructions from the system control information processing unit, and the path is switched by an optical switch. In principle, only one light source is used as the convergent light irradiating unit, and therefore, in this embodiment, no multiplexing means is required. Since the light source is used for the converging light irradiation unit, the semiconductor laser is used even when the diffusion light irradiation unit is used.

  Further, since the light from the divergent light irradiation unit is small and does not need to be converged, it is also possible to employ an LED or SLD as the light source. Recently, higher output of LEDs has progressed, and not only are LEDs of milliwatt class readily available, but LEDs are much cheaper than semiconductor lasers, leading to a reduction in the overall cost of the apparatus. If the LED output is insufficient, a plurality of LEDs can be used. In this case, in FIG. 6A, an LED or SLD is used as the light source of the divergent light irradiation unit.

  The present embodiment relates to an optical system of a convergent light irradiating unit and a divergent light irradiating unit. Specifically, the present invention relates to a portion that irradiates light from the multiplexing means shown in FIG. Except for the optical system of the convergent light irradiating part and the divergent light irradiating part, it is the same as in Examples 1-3. FIG. 7 is a diagram illustrating an example of the optical system of the convergent light irradiating unit and the divergent light irradiating unit.

  FIG. 4A is an example of a simple object in which two optical fibers coming from a convergent light irradiating unit and a divergent light irradiating unit are simply bundled. Light 701 from the convergent light irradiation unit is irradiated through the fiber 71, and light 702 from the divergent light irradiation unit is irradiated through the fiber 72. The fiber 71 has a core 711 and a clad 712, and the fiber 72 has a core 721 and a clad 722. Since both fibers are single mode fibers, the core diameter is about 10 microns at the maximum. The light emitted from the end face of the optical fiber spreads at about 10 degrees on one side. When the measurement is performed close to about 1 mm on the surface of the solar cell, the light from the convergent light irradiating part spreads in a region having a diameter of about 350 microns indicated by a black circle 710. The light from the divergent light irradiating part retreats the stump of the fiber 72 by about 500 microns and spreads on the irradiation surface to irradiate a region having a diameter of about 500 microns. This is enough for simple prototype evaluation.

  FIG. 5B shows an example in which the divergent light irradiating portion light 702 is greatly spread on the irradiation surface through the thick multimode fiber 73 of the core 731. In this case, care such as retreating the fiber end as in the previous example is not necessary. Furthermore, if the light from the converging light irradiating unit is transmitted to the core 741 of one single-mode optical fiber 74 as shown in FIG. From the end, the light 720 from the divergent light irradiating part is emitted concentrically around the light 710 from the converging light irradiating part, and there is concern about the positional relationship between the two lights on the irradiation surface and the positional relationship between the fiber ends. There is no need. Further, in this case, if a double clad fiber is used as the optical fiber 74, the original clad 743 is provided on the outer side, so that stable transmission and irradiation can be expected even when the fiber is bent.

  FIG. 4D shows an example in which a lens 76 is attached to the tip of the double clad fiber 74. A sleeve 75 is used to align and maintain the optical axes of the fiber 74 and the lens 76. As a result, the focal position can be adjusted. By placing the lens 76 in this way, it becomes possible to converge again the light that diverges after being emitted from the optical fiber 74, and the light can be narrowed down to about 15 microns close to the diameter of the core 741. The divergent light propagating as the cladding mode also tends to converge with this lens 76, but its diameter is about 150 microns because of the large mode size.

  FIG. 4E shows an example in which a GRIN lens 77 is used instead of the previous lens 76. The GRIN lens is made to be easily inserted into a sleeve 78 (which may be a ferrule) that can be easily coupled to an optical fiber for optical communication so that the optical axis can be aligned and held easily. It is conceivable to use a graded index fiber having the same principle as that of the GRIN lens 77. In any case, since it is easy to make the tip of the light irradiating portion narrow, it is difficult to cause a problem that the irradiation position cannot be seen even if the distance between the emitting end face and the object is reduced. Further, it is lighter and cheaper than the lens 76. If it is lightweight, it is possible to move the light irradiation unit at a high speed, and as a result, it is possible to quickly create an image and speed up the evaluation. As a result, the process processing time is shortened and the cost is reduced.

  In this embodiment, inspection is performed by applying the present invention in a production line for producing solar cells. In the production line, production is performed while moving the solar cell by a conveyor or the like. Solar cells are usually arranged so that the light-receiving surface is on the lower surface in order to perform production work from the side opposite to the light-receiving surface covered with the glass substrate. The movement of the solar cell by a conveyor or the like is stopped, and the stationary solar cell is inspected by irradiating light from below. FIG. 8 is a diagram illustrating an example of an evaluation apparatus for a multi-junction solar cell. When the multijunction solar cell evaluation apparatus shown in FIG. 8A is compared with the solar cell evaluation apparatus of Example 1 shown in FIG. 2A, there are the following differences. (1) The convergent light irradiating unit 21 and the divergent light irradiating unit 22 are integrated as a convergent and divergent light irradiating unit 83, and the convergent and divergent light irradiating unit 83 includes an LED irradiation head 84. Yes. (2) The LED irradiation head 84 arranged at the lower part of the solar cell to be evaluated moves to the XY coordinates according to the control of the system control information processing unit 4 without having the XY fine movement table driving unit. Other parts are the same as those in the first embodiment.

  As shown in FIG. 8B, there is an LED irradiation head 84 on the lower side of the solar cell to be evaluated, and the LED irradiation head 84 is controlled by the system control information processing unit 4 to inspect the solar cell to be evaluated. Move directly below (evaluation target area). This movement can be performed by the system control information processing unit 4 controlling a wire or a guide member (not shown) connected to the LED irradiation head 84. The LED irradiation head 84 is close to the glass substrate 86 of the solar cell 85 to be evaluated as shown in FIG. In the solar cell to be evaluated of this example, the entire solar cell module is divided into a number of elongated sub-modules 85 (indicated by 85a, 85b, 85c in the figure), and each sub-module is electrically connected to an adjacent sub-module. Are connected in series. The width of the submodule 85 is about 10 mm, and the length is about 1500 mm. This is a solar cell (having a size of about 1000 mm × 1500 mm) having about 100 submodules.

  When the LED irradiation head 84 is viewed from the side of the solar cell to be evaluated, as shown in FIG. 8 (d), it has a converging light irradiation head 81 at the center and a diverging light irradiation head 82 at the periphery. The LED irradiation head 84 is close to the solar cell to be evaluated, and the light irradiated from the convergent light irradiation head 81 is irradiated to the evaluation target region directly above it. The size and shape of the convergent light irradiation head 81 are the same as the size and shape of the evaluation target region. As described above, since the LED irradiation head 84 is close to the solar cell to be evaluated, it is not necessary to converge the convergent light irradiation, and the LED can be used as the light source. The light irradiated from the divergent light irradiation head 82 is irradiated to the portion of the solar cell to be evaluated including the evaluation target region. Note that the convergent light irradiation head 81 and the divergent light irradiation head 82 of the LED irradiation head 25 may be arranged as shown in FIG. According to the arrangement of FIG. 8E, the convergent light irradiation head 81 and the divergent light irradiation head 82 have the same shape, and the production cost of the LED irradiation head can be suppressed by using a single component. According to the arrangement of FIG. 8 (f), the periphery of the convergent light irradiation head 81 is completely surrounded by the divergent light irradiation head 81, and the light from the divergent light irradiation unit is reliably irradiated to the entire evaluation target region. be able to.

  The convergent light irradiation head 81 and the divergent light irradiation head 82 are connected to the light source by a bundle fiber, and the LED irradiation head is close to the solar cell to be evaluated. It is possible to irradiate light of uniform intensity over the entire portion of the solar cell to be evaluated. Thereby, evaluation with respect to a comparatively wide area can be performed by one irradiation. For example, in FIG. 8B, the size of the convergent light irradiation head 81 can be set to 10 mm × 3 mm. The large area makes it difficult to identify problematic cells, but in production-stage inspections for the purpose of confirming that there are no problems, the area to be evaluated by one irradiation is widened and the entire inspection is performed. Emphasis is placed on shortening the required time. Since the width of the convergent light irradiation head 81 can be set to 10 mm (the width of the submodule), the LED irradiation head 84 is arranged directly below the submodule and sequentially moved along the submodule to inspect one submodule. Can be done efficiently. When the inspection of one submodule is completed, the next submodule can be inspected by moving the LED irradiation head 84 directly below the next submodule.

  FIG. 8G shows the converging-type and diverging-type light irradiation unit 83. Light source 1, light source 2,... Light source n is n LEDs that emit light at n wavelengths. Each light source and the multiplexing means 87 and 88 are connected by a bundle fiber to transmit light. In order to make the light intensity of each fiber of the bundle fiber uniform, a uniform region as shown in FIG. 8H may be provided between the light source and the bundle fiber. The multiplexing means 87 and the convergent light irradiation head 81, and the multiplexing means 86 and the divergent light irradiation head 82 are also connected by a bundle fiber to transmit light. The system control information processing unit 4 time-modulates only one of the light source 1, the light source 2,..., The light source n to emit light, and transmits light having a single wavelength to the multiplexing unit 87. This light is transmitted to the convergent light irradiation head 81. The system control information processing unit 4 combines the light of the (n-1) types of wavelengths, excluding the light of the light source 1, the light source 2,. Is transmitted to the wave means 88. These lights are combined by the combining means 88 and transmitted to the divergent light irradiation head 82. All cells are evaluated by repeating this operation by sequentially switching the light source of single wavelength light.

  Two or more LED irradiation heads 84 may be provided instead of one. For example, instead of placing one LED irradiation head 84 directly under one evaluation target area of one submodule 85a as shown in FIG. 8 (i), three submodules 85a as shown in FIG. 8 (j). , 85b and 85c, and three LED irradiation heads can be provided to perform inspection of three submodules simultaneously. Alternatively, two or more LED irradiation heads may be provided immediately below two or more locations of one submodule, and the inspection may be performed simultaneously. The time required for the entire inspection of the solar cell can be shortened. At this time, a method of measuring the short-circuit current of two or more cells to be inspected simultaneously becomes a problem, but the short-circuit current of two or more cells to be inspected simultaneously based on the structure of the solar cell If the interference does not occur, two or more probes may be provided. Even in the case of interference, the modulation frequency or phase of the temporally modulated light emitted from the convergent light irradiating unit differs for each LED irradiation head. By doing so, the short-circuit current of each cell can be measured.

  Instead of providing two or more LED irradiation heads 84, one LED irradiation head having the shape shown in FIG. 8C is used as shown in FIG. You can also By using the bundle fiber, the light intensity of the LED irradiation head can be made constant regardless of the place, and one LED irradiation head can be used for two or more inspections. In this case, each submodule is equivalent to being connected in series as an electric circuit, and a probe for measuring the voltage and current of each submodule is provided. In addition, it is possible to simultaneously evaluate the number of submodules within the range in which the voltage and current of each submodule connected in series can be measured. It should be noted that the same inspection can be performed using a plurality of irradiation heads as shown in FIG.

(Extended example)
Embodiments of the present invention are not limited to the above examples. While maintaining the essence of the present invention, implementation different from the above embodiments is possible. Such an example is shown below.
Various types of temporal modulation of the light source can be considered in addition to the on / off of the rectangular wave. For example, it may be a sine wave. In short, it is only necessary that the measurement unit can measure a change in voltage or current corresponding to the modulation of the light irradiation unit. Since the system control information processing unit controls the light irradiation unit and the measurement unit, the measurement unit may be controlled in accordance with the modulation of the light irradiation unit.
The system control information processing unit may not automatically control the whole as in the embodiment. Some operations may include manual work, and instead of one system control information processing unit, for example, a light irradiation unit, a measurement unit, and a bias generation unit may be controlled separately.
You may control the position where light is irradiated by another mechanism, without providing a moving mechanism. For example, the solar cell may be scanned by rotating the convergent light irradiating unit and the divergent light irradiating unit.
Although the time change of the light amount of the convergent light irradiation unit is “modulation”, it may be “light emission / quenching”.
The light sources of the convergent light irradiating unit and the divergent light irradiating unit are not single and have redundancy. For example, two light sources are used for each wavelength, and another light source is used when one light source fails. It may be.
The method of simultaneously evaluating two or more cells shown in the fifth embodiment can be applied to other embodiments.
In Example 5, the solar cell is stationary and inspected, but the solar cell may be moved as long as the XY position of the LED irradiation head with respect to the solar cell can be controlled.

  It is a measuring apparatus and measuring method that can find a partial problem for each cell of a multi-junction solar cell, and is expected to be used in research and development of multi-junction solar cells. It is also expected to be used in the inspection process on the mass production line.

DESCRIPTION OF SYMBOLS 1 Solar cell 12 1st cell 13 2nd cell 21 Convergence type light irradiation part 22 Divergent type light irradiation part 23 Bias generation part 24 Measurement part 4 System | system | group control information processing part

Claims (10)

It has a convergent light irradiation unit that irradiates light only to the evaluation target region,
A divergent light irradiating unit that irradiates light to a region equivalent to or wider than the evaluation target region,
The convergent light irradiating unit irradiates light with a temporal change in emission intensity of a semiconductor light emitting element as a light source,
An evaluation device for a multi-junction solar cell, comprising: a measurement unit that measures a predetermined relationship with the change among the electrical outputs of the solar cell. It has a bias generator that applies a DC voltage bias to the solar cell,
A system control information processing unit that controls the convergent light irradiation unit, the divergent light irradiation unit, the measurement unit, and the voltage bias generation unit;
The system control information processing unit, from the convergent light irradiation unit and the diverging light irradiation unit in a state where a voltage bias corresponding to an open voltage generated in a solar cell is applied only by light irradiation from the diverging light irradiation unit. The multi-junction solar cell evaluation apparatus according to claim 1, wherein the light is irradiated and the current at this time is controlled to be measured by the measurement unit. The convergent light irradiation unit includes two or more semiconductor light emitting elements having different wavelengths,
The system control information processing unit performs control to select a semiconductor light emitting element that emits light having a wavelength absorbed by an evaluation target cell from the two or more semiconductor light emitting elements and to emit light. Item 3. The evaluation device for a multijunction solar cell according to Item 1 or 2.   The system control information processing unit controls the wavelength distribution of light emitted from the divergent light irradiating unit so that the wavelength emitted by the convergent light irradiating unit is not included. The multijunction solar cell evaluation apparatus according to any one of the preceding claims.   The multijunction solar cell evaluation apparatus according to any one of claims 1 to 4, wherein the semiconductor light emitting element as a light source of the convergent light irradiation unit is a semiconductor laser.   The multi-junction solar cell according to any one of claims 1 to 5, wherein each of the convergent light irradiating unit and the divergent light irradiating unit irradiates light through one optical fiber. Evaluation device.   The convergent light irradiator and the divergent light irradiator share a semiconductor light emitting element as a light source, and the light from the shared semiconductor light emitting element is switched by an optical switch so that the convergent light irradiator or the divergent type is emitted. The multijunction solar cell evaluation apparatus according to claim 6, wherein the evaluation apparatus is used for any one of the light irradiation units.   A moving mechanism for moving at least one of the solar cell, the convergent light irradiating unit, and the divergent light irradiating unit to place the evaluation target region at a position irradiated with light from the convergent light irradiating unit. The multi-junction solar cell evaluation apparatus according to claim 1, comprising:   A multi-junction solar cell evaluation method using the multi-junction solar cell evaluation device according to claim 1. It has a convergent light irradiation unit that irradiates light only to the evaluation target region,
A divergent light irradiating unit that irradiates light to a region equivalent to or wider than the evaluation target region,
The convergent light irradiating unit irradiates light with a temporal change in emission intensity of a semiconductor light emitting element as a light source,
An evaluation apparatus for a solar cell, comprising: a measurement unit that measures an electrical output of the solar cell having a predetermined relationship with the change.

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