Photoelectric conversion efficiency measuring method, solar cell manufacturing method, and photoelectric conversion efficiency measuring device

Abstract

To provide a photoelectric conversion efficiency measuring method capable of accurately and quickly measuring photoelectric conversion efficiency at low photon flux density.SOLUTION: A photoelectric conversion efficiency measuring method includes the steps of: sequentially irradiating a solar cell with PL measurement light having a plurality of measured photon flux densities higher than a corresponding photon flux density corresponding to a desired target photon flux density; respectively capturing photoluminescence images of the solar cell after being irradiated with the plurality of PL measurement lights; calculating the emission intensity at each of the plurality of measured photon flux densities of the solar cell from the photoluminescence images at the plurality of measured photon flux densities; estimating the emission intensity when the PL measurement light of the corresponding photon flux density is radiated, from the emission intensity at the plurality of measured photon flux densities; and calculating the photoelectric conversion efficiency at the target photon flux density by substituting the emission intensity at the estimated corresponding photon flux density into a predetermined relational expression.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion efficiency measuring method, a solar cell manufacturing method, and a photoelectric conversion efficiency measuring device. [Background technology]

[0002] A method using photoluminescence is known as a method for measuring the photoelectric conversion efficiency of a solar cell. Photoluminescence is a phenomenon in which, when light is irradiated onto a solar cell in an open state, carriers are excited inside the solar cell, and light is emitted when these carriers recombine and return to the ground state. The photoelectric conversion efficiency of the solar cell can be calculated by measuring the emission intensity of this photoluminescence. Specifically, the emission intensity of the solar cell, and therefore the photoelectric conversion efficiency, can be calculated from the brightness of a photoluminescence image obtained by photographing the solar cell after being irradiated with light (see, for example, Patent Document 1).

[0003] By using this method, for example, when forming photoelectric conversion structures of multiple solar cells on one semiconductor wafer, the photoelectric conversion efficiency of each solar cell can be calculated by taking a photoluminescence image of the entire semiconductor wafer. Also, by using the photoluminescence image, the photoelectric conversion efficiency of the photoelectric conversion structure can be measured before forming the electrode structure of the solar cell, so that defective products can be excluded before forming the electrode structure, which is expected to improve production efficiency and reduce production costs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-149890 A Summary of the Invention [Problem to be solved by the invention]

[0005] Among solar cells, for example, solar cells for portable devices such as wristwatches are desired to be able to perform photoelectric conversion with high efficiency even with light of low photon flux density compared to direct sunlight outdoors such as indoor light. To measure the photoelectric conversion efficiency in light of low photon flux density using a photoluminescence image, light of low photon flux density may be irradiated and a photoluminescence image may be taken. However, if the photon flux density of the irradiated light is low, errors due to the influence of ambient light become large, and it becomes necessary to extend the exposure time when taking the photoluminescence image. If a darkroom is provided to eliminate the influence of ambient light, the equipment cost increases. In addition, if the exposure time when taking the photoluminescence image is extended, the processing capacity decreases, and there is a risk that the capacity of the entire solar cell manufacturing equipment may be limited during the photoluminescence image taking process.

[0006] Therefore, an object of the present invention is to provide a photoelectric conversion efficiency measuring method, a solar cell manufacturing method, and a photoelectric conversion efficiency measuring device that can accurately and quickly measure photoelectric conversion efficiency at low photon flux density. [Means for solving the problem]

[0007] A photoelectric conversion efficiency measurement method according to one embodiment of the present invention includes the steps of: sequentially irradiating a solar cell with PL measurement light of a plurality of measured photon flux densities having a higher photon flux density than the PL measurement light of a corresponding photon flux density corresponding to a desired target photon flux density for calculating the photoelectric conversion efficiency; capturing photoluminescence images of the solar cell after irradiation with the PL measurement light of the plurality of measured photon flux densities; calculating luminescence intensities of the solar cell at the plurality of measured photon flux densities from the photoluminescence images at the plurality of measured photon flux densities; estimating the luminescence intensities when irradiating the solar cell with PL measurement light of the corresponding photon flux density from the luminescence intensities at the plurality of measured photon flux densities; and calculating the photoelectric conversion efficiency at the target photon flux density by substituting the estimated luminescence intensities at the corresponding photon flux densities into a predetermined relational equation.

[0008] In the photoelectric conversion efficiency measuring method, the luminous intensity at the corresponding photon flux density may be estimated as a logarithm of the luminous intensity expressed as a quadratic function of the logarithm of the photon flux density.

[0009] In the photoelectric conversion efficiency measuring method, the relational expression may be a sum of a peak function and a linear function or a logarithmic function.

[0010] In the photoelectric conversion efficiency measuring method, the peak function may be a Gaussian function or a Lorentzian function.

[0011] In the photoelectric conversion efficiency measurement method, the coefficients of the relational expression may be determined by a least squares method to approximate the relational expression for a combination of the luminous intensity when the solar cell is irradiated with PL measurement light of the corresponding photon flux density, which is obtained in advance for a plurality of the solar cells, and the photoelectric conversion efficiency calculated based on the IV characteristics measured by irradiating the solar cell with IV measurement light of the target photon flux density.

[0012] In the photoelectric conversion efficiency measuring method, the corresponding photon flux density may be a photon flux density of the IV measurement light such that an open circuit voltage when IV characteristics are measured while irradiating the solar cell with IV measurement light coincides with a maximum power point voltage for the IV measurement light of the target photon flux density.

[0013] In determining the coefficients of the relational equation in the photoelectric conversion efficiency measurement method, from among the actual measured values ​​of the luminous intensity and the actual measured values ​​of the photoelectric conversion efficiency, values ​​having relatively small and large ratios of the actual measured values ​​of the photoelectric conversion efficiency to the actual measured values ​​of the luminous intensity may be excluded for each category of the actual measured values ​​of the luminous intensity.

[0014] A solar cell manufacturing method according to one embodiment of the present invention includes the steps of forming a solar cell structure on a semiconductor substrate, measuring the photoelectric conversion efficiency of the solar cell structure using the photoelectric conversion efficiency measurement method, and sorting the semiconductor substrate based on the measured photoelectric conversion efficiency.

[0015] A photoelectric conversion efficiency measuring device according to one aspect of the present invention includes a light source that sequentially irradiates a solar cell with PL measuring light of a plurality of measuring photon flux densities having a higher photon flux density than a PL measuring light of a corresponding photon flux density corresponding to a desired target photon flux density for calculating a photoelectric conversion efficiency, an imaging device that captures photoluminescence images of the solar cell after the PL measuring light of the plurality of measuring photon flux densities is irradiated from the light source, and a photoelectric conversion efficiency measuring device that calculates the photoelectric conversion efficiency of the solar cell at the target photon flux density from the photoluminescence images at the plurality of PL measuring photon flux densities. and an image processing device configured to calculate a photoelectric conversion efficiency of the target photon flux density by substituting the emission intensity at the corresponding photon flux density estimated by the emission intensity calculation unit into a predetermined relational equation. The image processing device includes an emission intensity calculation unit that calculates emission intensities at the multiple measured photon flux densities of the solar cell from the photoluminescence images at the multiple measured photon flux densities, an emission intensity estimation unit that estimates an emission intensity at the corresponding photon flux density from the emission intensities at the multiple measured photon flux densities calculated by the emission intensity calculation unit, and an efficiency calculation unit that calculates a photoelectric conversion efficiency of the target photon flux density by substituting the emission intensity at the corresponding photon flux density estimated by the emission intensity estimation unit into a predetermined relational equation. Effect of the Invention

[0016] According to the present invention, the photoelectric conversion efficiency at a low photon flux density can be measured accurately and quickly. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a configuration of a photoelectric conversion efficiency measuring device according to one embodiment of the present invention. [Diagram 2] 1 is a flowchart showing the steps of a photoelectric conversion efficiency measuring method according to one embodiment of the present invention. [Diagram 3] 1 is a flowchart showing the steps of a photoelectric conversion efficiency measuring method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of a photoelectric conversion efficiency measuring device 1 according to an embodiment of the present invention.

[0019] The photoelectric conversion efficiency measuring device 1 is a device that measures the photoelectric conversion efficiency at a desired target photon flux density of the solar cell C. The target photon flux density at which the photoelectric conversion efficiency measuring device 1 measures the photoelectric conversion efficiency is a low photon flux density assuming indoor light such as an LED, and is a region in which the photoelectric conversion efficiency of the solar cell C may be lower than the photoelectric conversion efficiency due to direct sunlight outdoors. Specifically, the photon flux density can be controlled by attenuating or cutting the light generated by a solar simulator or the like using an optical filter such as an ND filter or a bandpass filter.

[0020] The photoelectric conversion efficiency measuring device 1 includes a light source 10 that sequentially irradiates a solar cell C with PL measurement light of a plurality of measurement photon flux densities having a higher photon flux density than a corresponding photon flux density corresponding to a desired target photon flux density, an imaging device 20 that captures photoluminescence images of the solar cell C after the PL measurement light of the plurality of measurement photon flux densities is irradiated by the light source 10, and an image processing device 30 that calculates the photoelectric conversion efficiency of the solar cell C at a target photon flux density from the photoluminescence images at the plurality of measurement photon flux densities. Note that "irradiating in sequence" the PL measurement light of the plurality of measurement photon flux densities is intended to sequentially irradiate the PL measurement light of each measurement photon flux density with an interval so as not to overlap with the irradiation of the PL measurement light of another measurement photon flux density, and is not intended to determine the order of irradiation of the plurality of PL measurement light by the photon flux density of the measurement light.

[0021] The light source 10 irradiates the solar cell C with PL measurement light in an open circuit state, thereby exciting carriers inside the solar cell C. When the solar cell C is irradiated with the PL measurement light, the excited carriers recombine and return to the ground state, emitting energy as light. This type of light emission phenomenon is called photoluminescence.

[0022] The light source 10 is configured to have adjustable output so that the PL measurement light can be irradiated at any photon flux density onto the solar cell C. The light source 10 is preferably a surface light source that can irradiate the entire solar cell C with the PL measurement light at a constant photon flux density.

[0023] The number of measured photon flux densities of the PL measurement light is required to be 3 or more when calculating the luminescence intensity of the solar cell C when irradiated with PL measurement light of a corresponding photon flux density corresponding to the target photon flux density using a quadratic function, as described below, and it is preferable to set the number to the minimum of 3 in order to shorten the measurement cycle time.

[0024] For example, the lower limit of the photon flux density of the PL measurement light incident on the solar cell C is 5.0 × 10 14 cm -2 s -1 is preferred, 7.0×10 14 cm -2 s -1 On the other hand, the upper limit of the photon flux density of the PL measurement light is 1.6×10 16 cm -2 s -1 is preferred, 5.6×10 15 cm -2 s -1 is more preferable. By setting the minimum photon flux density of the PL measuring light to be equal to or higher than the lower limit, the influence of light caused by the environment on the photoluminescence image can be reduced. Also, by setting the maximum photon flux density of the PL measuring light to be equal to or lower than the upper limit, a light source 10 with small variation in photon flux density can be prepared relatively easily.

[0025] The imaging device 20 captures an image (photoluminescence image) of the solar cell C that emits light after being irradiated with the PL measurement light. A camera having a two-dimensional imaging element can be used as the imaging device 20. The imaging device 20 may have an optical filter. By attaching a bandpass filter corresponding to the band gap of the solar cell to be measured to the imaging device 20, it is possible to detect only the photoluminescence between bands in the solar cell, thereby improving the PL measurement accuracy. In addition, by attaching an ND filter to the imaging device 20, when the photoluminescence of the solar cell C after being irradiated with the PL measurement light is too large (saturated) and it is not possible to obtain the emission intensity difference of the photoluminescence in different solar cells C, it is possible to obtain the emission intensity difference, thereby improving the measurement accuracy.

[0026] The image processing device 30 calculates the photoelectric conversion efficiency of the solar cell C at a target photon flux density by analyzing multiple photoluminescence images captured by the imaging device 20 by irradiating the same solar cell C with PL measurement light of different photon flux densities.

[0027] The image processing device 30 includes an emission intensity calculation unit 31 that calculates the emission intensities at multiple measured photon flux densities of the solar cell C from photoluminescence images of PL measurement light at multiple measured photon flux densities, an emission intensity estimation unit 32 that estimates the emission intensity when PL measurement light of a corresponding photon flux density corresponding to a target photon flux density of the solar cell C is irradiated from the emission intensities at the multiple measured photon flux densities calculated by the emission intensity calculation unit 31, and an efficiency calculation unit 33 that calculates the photoelectric conversion efficiency at the target photon flux density of the solar cell C from the emission intensity at the corresponding photon flux density estimated by the emission intensity estimation unit 32.

[0028] The image processing device 30 can be realized by causing a computer device having, for example, a CPU, a memory, etc. to execute an appropriate program. In the image processing device 30, the emission intensity calculation unit 31, the emission intensity estimation unit 32, and the efficiency calculation unit 33 are merely classifications of the functions of the image processing device 30, and do not necessarily have to be clearly distinguishable in terms of physical structure and program structure. Furthermore, the image processing device 30 may have components that realize further functions.

[0029] The luminance calculation unit 31 calculates the luminance of the pixels of the solar cell C in each photoluminescence image by tallying up the luminance of the pixels of the solar cell C in each photoluminescence image. The value calculated by the luminance calculation unit 31 may be any value that can specify the luminance, and may be, for example, radiance (W / sr m 2 ) or the like. The region for which the radiance is collected may be the entire photoluminescence image, or a partial region set in accordance with the structure of the solar cell C.

[0030] The emission intensity estimation unit 32 estimates the emission intensity at the corresponding photon flux density of the solar cell C based on the emission intensity in the PL measurement light of different photon flux densities calculated for the same solar cell C by the emission intensity calculation unit 31. The estimation of the emission intensity at the corresponding photon flux density can be calculated assuming that the logarithm of the photon flux density and the logarithm of the emission intensity in each PL measurement light have a predetermined correlation. In order to improve the accuracy of the emission intensity at the estimated corresponding photon flux density while reducing the number of photoluminescence images required for the estimation (the number of combinations of the PL measurement light of different photon flux densities and the emission intensity), it is preferable that the emission intensity estimation unit 32 estimates the emission intensity at the corresponding photon flux density as the logarithm of the emission intensity is expressed as a quadratic function of the logarithm of the photon flux density. In this case, the number of photoluminescence images required for the estimation of the emission intensity at the corresponding photon flux density is three.

[0031] The corresponding photon flux density is the photon flux density of the PL measurement light that provides a high correlation between the photoelectric conversion efficiency of the solar cell C at the target photon flux density and the photoluminescence emission intensity. The photoelectric conversion efficiency is the efficiency under the condition that the product of the current measured when a bias voltage is applied while irradiating the solar cell C with IV measurement light of the target photon flux density and the output power is maximized (maximum power point power = maximum power point current x maximum power point voltage). In order to obtain a high correlation between the photoelectric conversion efficiency and the photoluminescence emission intensity, it is preferable to make the amount of excess minority carriers generated in the photoelectric conversion layer of the solar cell C as close as possible during light irradiation in each of the IV and photoluminescence measurements (because the carrier lifetime of the solar cell C varies depending on the amount of excess minority carriers). Specifically, the corresponding photon flux density can be determined by performing an IV measurement while irradiating an IV measurement light on the solar cell C, and determining the photon flux density such that the open circuit voltage at that time roughly coincides with the maximum operating point voltage in the IV measurement light for the target photon flux density (because the photoluminescence measurement is performed in an open state). If an error is acceptable, the corresponding photon flux density may be determined to be an appropriate photon flux density in the vicinity of these values. Also, although an example in which the photoluminescence measurement is performed in an open state has been described here, the photoluminescence measurement may also be performed while applying a bias.

[0032] The efficiency calculation unit 33 calculates the photoelectric conversion efficiency of the solar cell C at the target photon flux density by substituting the luminous intensity at the corresponding photon flux density estimated by the luminous intensity estimation unit 32 into a predetermined relational expression.

[0033] The relational expression for calculating the photoelectric conversion efficiency is preferably the sum of a peak function and a linear function or a logarithmic function. The peak function is preferably a Gaussian function or a Lorentz function. By using such a relational expression, an accurate photoelectric conversion efficiency can be derived and the relational expression can be set relatively easily. The photoelectric conversion efficiency can be calculated with high accuracy only for a low photon flux density assuming indoor light such as an LED, which has a lower photon flux density than direct sunlight outdoors (because at the low photon flux density, the current generated when the solar cell C is irradiated with light is small and the effect of this can be ignored for a normal series resistance value).

[0034] For example, if the luminous intensity at the corresponding photon flux density is X, the photoelectric conversion efficiency E at the target photon flux density can be expressed as E=k1*k2 / {(X-k3)^2+k2^2}+k4*LN(X)+k5, where k1 to k5 are predetermined coefficients.

[0035] The coefficients of the relational expression for calculating the photoelectric conversion efficiency, such as k1 to k5 in the relational expression, can be determined by the least squares method to approximate the relational expression for a combination of the luminous intensity when the solar cell C is irradiated with PL measurement light of the corresponding photon flux density, which is obtained in advance for a plurality of solar cells C, and the photoelectric conversion efficiency calculated based on the IV characteristics measured by irradiating with IV measurement light (steady light) of the target photon flux density. Measurement of the luminous intensity by irradiation with PL measurement light of the corresponding photon flux density and measurement of the IV characteristics by irradiating with IV measurement light of the target photon flux density are both time-consuming and cannot be performed easily, but by measuring the luminous intensity at the corresponding photon flux density and the photoelectric conversion efficiency at the target photon flux density for a certain number of solar cell C samples in advance and specifying the relationship between the luminous intensity at the corresponding photon flux density and the photoelectric conversion efficiency at the target photon flux density in advance, it becomes possible to quickly and accurately calculate the photoelectric conversion efficiency at the target photon flux density of the solar cell C from the photoluminescence image in the PL measurement light of the photon flux density, which can be easily photographed.

[0036] In determining the coefficients of the relational equation, from among the actual measured values ​​of luminous intensity and the actual measured values ​​of photoelectric conversion efficiency, for each category of the actual measured values ​​of luminous intensity, values ​​having relatively small and large ratios of the actual measured values ​​of photoelectric conversion efficiency to the actual measured values ​​of luminous intensity, for example, values ​​within the upper and lower 10%, may be excluded. In this way, by excluding extreme actual measured values, the influence of measurement errors in the data for setting the relational equation can be reduced, and a relatively accurate relational equation can be set.

[0037] The photoelectric conversion efficiency measuring device 1 implements an embodiment of a photoelectric conversion efficiency measuring method according to the present invention shown in Fig. 2. The photoelectric conversion efficiency measuring method in Fig. 2 includes an irradiation step (step S11), an imaging step (step S12), and an emission intensity calculation step (step S13) that are repeated a predetermined number of times (three times using one loop parameter n in the illustrated example) for one solar cell C, and an emission intensity estimation step (step S14) and an efficiency calculation step (step S15) that are performed only once for one solar cell C.

[0038] In the irradiation step of step S11, the light source 10 irradiates the solar cell C with PL measurement light having a photon flux density specified according to the value of the loop parameter n.

[0039] In the photographing step of step S12, the imaging device 20 photographs a photoluminescence image of the solar cell C after it has been irradiated with the PL measurement light in the irradiating step.

[0040] In the emission intensity calculation step of step S13, the emission intensity at the photon flux density of the solar cell C is calculated from the photoluminescence image captured in the imaging step.

[0041] In the luminescence intensity estimation process in step S14, the luminescence intensity at the corresponding photon flux density is estimated based on multiple luminescence intensities calculated from multiple photoluminescence images taken of the same solar cell C using PL measurement light of different photon flux densities.

[0042] In the efficiency calculation step S15, the photoelectric conversion efficiency at the target photon flux density is calculated by substituting the emission intensity at the corresponding photon flux density estimated in the emission intensity estimation step into the relational expression.

[0043] Further, a procedure of one embodiment of a solar cell manufacturing method according to the present invention is shown in Fig. 3. The solar cell manufacturing method of Fig. 3 includes a solar cell structure forming step (step S21), a photoelectric conversion efficiency measuring step (step S22), and a sorting step (step S23).

[0044] In the solar cell structure forming step S21, one or more solar cell structures are formed on a semiconductor substrate by a known method. Specifically, by stacking semiconductor layers having different conductivity types on the semiconductor substrate in a predetermined pattern, it becomes possible to collect carriers formed when light is incident on the semiconductor substrate and output the resulting charge to the outside.

[0045] In the photoelectric conversion efficiency measuring process of step S22, the photoelectric conversion efficiency of the solar cell structure of the semiconductor substrate is measured by the photoelectric conversion efficiency measuring method of FIG.

[0046] In the sorting step of step S23, the semiconductor substrates each including one or more solar cells are sorted based on the photoelectric conversion efficiency measured in the photoelectric conversion efficiency measuring step. Specifically, in the sorting step, the semiconductor substrates may be arranged in order of photoelectric conversion efficiency or grouped based on the photoelectric conversion efficiency. This can improve the efficiency of subsequent handling of the semiconductor substrates on which the solar cell structure is formed.

[0047] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes and modifications are possible. [Explanation of symbols]

[0048] 10 light source 20 Imaging device 30 Image processing device 31 Luminescence Intensity Calculation Unit 32 Luminescence Intensity Estimation Unit 33 Efficiency calculation section C solar cell

Claims

1. Sequentially irradiating the solar cell with PL measurement light having a plurality of measurement photon flux densities higher than a corresponding photon flux density corresponding to a desired target photon flux density; taking photoluminescence images of the solar cell after being irradiated with the PL measurement light having the plurality of measurement photon flux densities; calculating luminescence intensities of the solar cell at the plurality of measured photon flux densities from the photoluminescence images at the plurality of measured photon flux densities; estimating an emission intensity when irradiated with PL measurement light of the corresponding photon flux density from the emission intensities at the plurality of measured photon flux densities; calculating a photoelectric conversion efficiency at the target photon flux density by substituting the estimated luminous intensity at the corresponding photon flux density into a predetermined relational expression; Equipped with The corresponding photon flux density is a photon flux density of PL measurement light that has a high correlation between the photoelectric conversion efficiency of the solar cell and the photoluminescence emission intensity at the target photon flux density, and is a photon flux density of the IV measurement light such that an open circuit voltage when IV characteristics are measured while irradiating the solar cell with IV measurement light coincides with a maximum power point voltage of the IV measurement light at the target photon flux density.

2. 2. The method for measuring photoelectric conversion efficiency according to claim 1, wherein the luminous intensity at the corresponding photon flux density is estimated as a logarithm of the luminous intensity expressed as a quadratic function of the logarithm of the photon flux density.

3. 3. The method for measuring photoelectric conversion efficiency according to claim 1, wherein the relational expression is a sum of a peak function and a linear function or a logarithmic function.

4. The photoelectric conversion efficiency measuring method according to claim 3 , wherein the peak function is a Gaussian function or a Lorentzian function.

5. 5. The photoelectric conversion efficiency measuring method according to claim 3, wherein coefficients of the relational expression are determined by a least squares method to approximate the relational expression for a combination of a light emission intensity when the solar cell is irradiated with PL measurement light of the corresponding photon flux density, the light emission intensity being obtained in advance for a plurality of the solar cells, and a photoelectric conversion efficiency calculated based on IV characteristics measured by irradiating the solar cell with IV measurement light of the target photon flux density.

6. 6. The photoelectric conversion efficiency measurement method according to claim 5, wherein in determining the coefficients of the relational expression, from among the actual measured values ​​of the luminous intensity and the actual measured values ​​of the photoelectric conversion efficiency, values ​​having relatively small and large ratios of the actual measured values ​​of the photoelectric conversion efficiency to the actual measured values ​​of the luminous intensity are excluded for each category of the actual measured values ​​of the luminous intensity.

7. forming a solar cell structure on a semiconductor substrate; measuring the photoelectric conversion efficiency of the solar cell structure by the photoelectric conversion efficiency measurement method according to any one of claims 1 to 6; sorting the semiconductor substrates based on the measured photoelectric conversion efficiency; A solar cell manufacturing method comprising:

8. a light source that sequentially irradiates a solar cell with PL measurement light having a plurality of measurement photon flux densities higher than a corresponding photon flux density corresponding to a desired target photon flux density; an imaging device that captures photoluminescence images of the solar cell after the plurality of PL measurement light beams are irradiated from the light source; an image processing device that calculates a photoelectric conversion efficiency of the solar cell at the target photon flux density from the photoluminescence images at the plurality of measured photon flux densities; Equipped with The image processing device includes: a light emission intensity calculation unit that calculates light emission intensities at the plurality of measured photon flux densities of the solar cell from the photoluminescence images at the plurality of measured photon flux densities; an emission intensity estimation unit that estimates an emission intensity when a PL measurement light of the corresponding photon flux density is irradiated from the emission intensities at the plurality of measurement photon flux densities calculated by the emission intensity calculation unit; an efficiency calculation unit that calculates a photoelectric conversion efficiency at the target photon flux density by substituting the emission intensity at the corresponding photon flux density estimated by the emission intensity estimation unit into a predetermined relational expression, The corresponding photon flux density is a photon flux density of PL measurement light that has a high correlation between the photoelectric conversion efficiency of the solar cell and the photoluminescence emission intensity at the target photon flux density, and is a photon flux density of the IV measurement light such that an open circuit voltage when IV characteristics are measured while irradiating the solar cell with IV measurement light coincides with a maximum power point voltage of the IV measurement light at the target photon flux density.

Images