JP4617141B2 - Judgment method of characteristic limiting element cell of multi-junction photoelectric conversion element - Google Patents

Description

  The present invention relates to a method for determining an element cell having the smallest characteristic, for example, current among photoelectric conversion elements composed of a plurality of element cells under a specific spectrum condition of interest.

  In recent years, thin film solar cells have also diversified, and crystalline thin film solar cells have been developed in addition to conventional amorphous thin film solar cells. As a method for improving the conversion efficiency of a thin film solar cell, there is a method in which two or more photoelectric conversion units (hereinafter referred to as element cells) are stacked to form a multi-junction type (or also called a tandem type). In this method, a front element cell including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the thin film solar cell, and a rear element cell including a photoelectric conversion layer having a small band gap is sequentially disposed behind the cell. This enables photoelectric conversion over a wide wavelength range of incident light, thereby improving the conversion efficiency of the entire solar cell.

Such a multi-junction photoelectric conversion element has a structure in which element cells composed of a plurality of semiconductor junctions are stacked. The stacked element cells are formed in series connection or parallel connection. Examples of the multi-junction photoelectric conversion element include a solar cell, a photodiode, and a sensor. Examples of the semiconductor junction include a pn junction, a pin junction, and a MIS junction. Examples of semiconductor materials include crystalline, polycrystalline, microcrystalline, and amorphous materials. Further, examples of semiconductor materials include group 4 compounds such as Si, SiGe, Ge, SiC, and C, group 3-5 compounds such as GaAs, GaAlAs, and InP, CdTe, CdS, and Cu2S (precisely Cu ₂ S sulfide). copper), Cu2 O (exactly Cu ₂ O copper oxide), ZnO, 2-6 group compound such as ZnSe, CuIn (S, Se) 2 ( to be precise _{CuIn (S, Se) 2)} , Cu (Ga, In) (S, Se) 2 (precisely Cu (Ga, In) (S, Se) ₂ ), a compound such as InGaN, an organic semiconductor, or the above compound.

  However, it is technically difficult to accurately measure the output characteristics of a multi-junction photoelectric conversion element. The main reason is that the output current and the maximum output power of the multi-junction solar cell are limited by a photoelectric conversion unit (hereinafter simply referred to as an element cell) in which the output current is the smallest. For example, in a tandem solar cell in which two element cells are stacked and connected in series, the wavelength sensitivity band of each element cell is different. Change.

  The output characteristics of the solar cell vary depending on the degree of current limitation. Since the degree of current limitation is directly affected by the change in the spectral emission spectrum of the light source, this appears as the spectral dependence of the output characteristics of the multijunction solar cell. It is difficult to verify the output current that should be obtained from each element cell under the spectral conditions of interest and the output characteristics of the tandem solar cell based on the output current using the spectral mismatch correction used in conventional single-junction solar cells. It is. This is synonymous with the difficulty in confirming which element cell is subject to current limitation under the spectral conditions of interest simultaneously.

  On the other hand, it is very important to determine the element cell that receives the current limitation of the multi-junction photoelectric conversion element for the following reason.

  For example, depending on the difference in the degree of current limitation of the element cells of the multi-junction solar cell, a difference occurs in the dependence of the output characteristics on the change of the light source spectrum. Since the spectral emission spectrum of outdoor sunlight changes under the influence of air mass, atmospheric turbidity, and precipitable water, it is known that the spectral conditions change periodically during one day or one year. The degree of current limiting of the element cell of the multi-junction solar cell should be designed to obtain a high output under outdoor sunlight. Since the degree of current limit between element cells changes due to fluctuations in manufacturing conditions, when the multi-junction solar cell is inspected at the time of shipment, if the current limit is not within the range of the shipping standard, it must be regarded as a non-standard product. Don't be. However, if the degree of current limitation is not accurately determined, it will be difficult to ensure outdoor standard output. In addition, if the influence of changes in the manufacturing process on the degree of current limitation is unclear, it becomes difficult to stabilize the manufacturing process in order to keep the product quality constant.

(Standard condition)
In the photoelectric conversion device, it is common to use the characteristics of the reference state as the sunlight irradiation condition for the standard as described above. The reference state is a state defined by the following conditions.
(1) Cell temperature 25 degrees Celsius (° C)
(2) Spectral distribution AM1.5 global solar radiation standard sunlight (3) Irradiance 100mW / cm2 (milliwatt per square centimeter)
However, it is very difficult to obtain a spectral radiation spectrum that matches the reference spectrum even when outdoor sunlight or approximate solar light source is used as the measurement light source. The reference spectrum is defined as a spectrum in the case where the air mass, atmospheric turbidity, precipitable water amount, etc. are constant, and the opportunity to obtain the reference spectrum from outdoor sunlight is very limited. Furthermore, since the spectrum of the approximate solar light source is merely approximated to the reference spectrum by correcting the spectral radiation spectrum of an available lamp with an optical filter, it is impossible to obtain the reference spectrum itself.

  As described above, it is difficult to obtain not only the reference spectrum but also the output characteristics under a specific spectral emission spectrum that is a target, and the output current of each element cell and the current limiting state between element cells. It is synonymous with the difficulty of accurately predicting the degree of the above.

  Furthermore, even when trying to determine the element cell subject to current limitation by changing the spectral emission spectrum of the light source so as to increase the current of a specific element cell under an approximate solar light source, the spectral conditions of the approximate solar light source If is not specified, the condition of the light source when determining the element cell subject to current limitation becomes ambiguous. That is, in order to accurately determine the element cell subject to current limitation, it is necessary to quantify the spectral conditions of the light source and to accurately evaluate the output current of each element cell under such spectral conditions. The technical problem that is substantially equivalent to the output measurement under the standard condition must be solved.

Non-Patent Document 1 proposes a method of using, as a pseudo-element cell, a single-junction photoelectric conversion element whose relative spectral sensitivity matches that of an element cell as a method for estimating the output current of the element cell of a multi-junction solar cell. Yes. As the pseudo element cell, a combination of a plurality of optical filters and photoelectric conversion elements is used in order to simulate relative spectral sensitivity. By measuring the short-circuit current value of the pseudo-element cell under an approximate solar light source and correcting it with the calibration value of the pseudo-element cell, the irradiance of the light source is obtained, and as a result, the current value of the sample element cell should be estimated. is there.
R. Shimokawa, F. Nagamine, M. Nakata, K. Fujisawa and Y. Hamakawa: Jpn. J. Appl. Phys. 28 (1989) L845

  The present invention is intended to solve the above-mentioned problems individually or comprehensively, regardless of the type and number of junctions of the multi-junction solar cell to be measured and the light receiving area of the photoelectric conversion element. An object of the present invention is to make it possible to accurately determine element cells that limit characteristics such as current, such as large-area solar cell modules under spectral conditions.

The invention according to claim 1 is a method of determining a characteristic limiting element cell that is an element cell having a minimum output current in a specific spectrum state of a test cell including a multi-junction photoelectric conversion element in which a plurality of element cells are stacked. Then, under a test light source having two spectral states close to the specific spectral condition, the current as the output characteristic of the test cell is obtained, the spectral condition is changed slightly, and the output characteristic of the test cell is determined from the obtained current . the gradient of the change is calculated, and a method of determining characteristics limiting element cell of the photoelectric conversion element test cells and judging a characteristic limiting element cell of the photoelectric conversion element test cells by positive and negative of the gradient.
The invention according to claim 2 uses a pseudo element cell having a spectral sensitivity equivalent to each element cell of the test cell, and a ratio between the element cells of the short-circuit current obtained from the pseudo element cell in two spectral states. Is the current ratio between the element cells of the test cell, and the test cell is determined from the change in the current ratio between the element cells of the test cell between the two spectral states and the change in current as the output characteristics of the test cell. The characteristic limiting element cell determination method according to claim 1, wherein a gradient of a change in the output characteristic is calculated .

According to the third aspect of the present invention, the currents that are output characteristics in the two spectral states are P1 and P2, and the current ratio between the pseudo element cells in the two spectral states is (Ib / It) 1 and (Ib / It). ) 2, and a method of determining characteristics limiting element cell below (photoelectric conversion element testing cell according to claim 1 or 2, characterized in that said calculating the slope B from equation 1).
In other words, a multijunction photoelectric conversion element test cell comprising: a step of calculating a gradient that is a rate of change of characteristics between two spectral states; and a step of determining a characteristic limiting element cell based on the value of the gradient. This is a method of determining a characteristic limiting element cell.

前記特性としては電流であることが好ましい。

The characteristic is preferably a current.

  Further, if the two spectral states close to the specific spectral condition are two spectral states obtained depending on whether or not an optical filter is sandwiched between the test light source and the test cell, a simple multi-spectrum state is obtained. This is a method for determining the characteristic limiting element cell of the junction photoelectric conversion element test cell.

  Furthermore, the change of the spectrum condition can be realized by adjusting at least one selected from an air mass filter, an optical filter, an auxiliary light source, a plurality of light sources, and a light source pulse width using an approximate solar light source as a test light source. it can.

  According to the determination method of the present invention, it is possible to accurately and easily determine the characteristic limiting element cell in a specific spectrum state of a test cell including a multi-junction photoelectric conversion element in which a plurality of element cells are stacked.

  Further, the determination method of the present invention is to estimate the effective spectral conditions of light sources having different divergence angles, using the spectral dependence of the output characteristics of a multi-junction solar cell having the same optical structure as the sample, It is possible to accurately determine the element cell having the smallest current under the spectral conditions of interest.

  As a result of trying to apply the above-described prior art to the determination of the current limiting element cell of the multi-junction photoelectric conversion element, the present inventor discovered that there is a problem described below and came to devise the present invention.

  That is, even when trying to obtain a spectral condition close to the reference state by using a single-junction photoelectric conversion element whose relative spectral sensitivity matches that of the element cell of Non-Patent Document 1 as a pseudo-element cell and correcting with the calibration value, In this case, the irradiance received by the sample differs depending on the spread angle of the light source and the difference between the pseudo element cell and the sample structure. In particular, a solar cell module having an effective area of about 1 m 2 (square meter) as a sample is provided with a glass substrate of about 4 mm thickness in front of the solar cell in order to ensure mechanical strength, so that the light source is not strictly parallel light Found that the effective spectral radiation spectrum received by the module differs from that received by the pseudo-element cell due to the difference in refraction of light of each wavelength.

  Hereinafter, the present invention will be described in more detail by showing the best mode as an example of the determination method of the present invention.

(Measuring method)
In the determination method of the current limiting element cell of the multijunction photoelectric conversion element of the present invention, the rate of change of the output characteristic with respect to the change of the current ratio indicating the state of the two irradiation light source spectra in the vicinity of the target specific spectral condition is calculated. It is used to determine the element cell constituting the multi-junction solar cell that has the smallest output current.

  Specifically, the short-circuit current obtained from the pseudo-element cell measured at the same time for the output characteristics of the multi-junction solar cell measured under two different conditions by changing the spectral condition slightly in the vicinity of the target spectral condition. The ratio to the change in the ratio between the element cells is obtained. In order to explain the method, the spectral dependence of the multijunction photoelectric conversion element will be described below.

(Spectral dependence)
Here, first, the spectral dependence of the multijunction solar cell will be specifically described based on an actual example. When the element cells are connected in series, the output characteristics of the multi-junction solar cell are limited by the element cell that limits the current. FIG. 2 is an example of the spectral dependence of the tandem solar cell having the relative spectral sensitivity shown in FIG.

  FIG. 2 is a measurement result (vertical axis) of each output of the solar cell when the radiation spectrum is changed by adjusting the lamp light quantity under an approximate solar light source including a xenon lamp, a halogen lamp, an optical filter, and the like. . The horizontal axis shows the short-circuit current under each radiation spectrum condition of each pseudo-element cell having a spectral sensitivity relatively matched to the spectral sensitivity of the top layer and the bottom layer, which are each element cell of the tandem solar cell. This is the value to be obtained.

  Here, as a pseudo-element cell for the top, a single-junction amorphous silicon solar cell provided with a plurality of colored glass filters is used, and substantially matched with the relative spectral sensitivity of the top layer of the tandem solar cell. Yes. In addition, as a pseudo element cell for the bottom, a colored glass filter is applied to a single-junction microcrystalline silicon solar cell, which substantially matches the relative spectral sensitivity of the bottom layer of the tandem solar cell.

  In addition, Ib / It on the horizontal axis in FIG. 2 corresponds to the current mismatch ratio of a tandem solar cell in which the photocurrent of each element cell is balanced as an example of a reference state as a specific spectral state, It represents a deviation from the reference state, and when it is 1, it is the reference state. That is, for a tandem solar cell in which the photocurrents of the respective element cells are balanced in the reference state, the top layer current is excessive due to the spectrum when it is smaller than 1, due to the difference from the reference state of the light source spectrum. Is a state reflecting a state of excessive bottom current due to the spectrum.

  Here, as specific values of It and Ib, the short-circuit current value output by each pseudo-element cell under the approximate solar light source is the short-circuit current value (calibration value) of each pseudo-element cell under the reference state. ), And the lamp illuminance is adjusted in the spectrum of the approximate solar light source so that the following (Equation 2) holds for Itm and Ibm as specific short-circuit current values.

つまり、ＩｔｍとＩｂｍは基準状態に近い但し青赤比があっていない状態の近似太陽光光源下でのトップ擬似要素セルとボトム擬似要素セルの短絡電流値。Ｉｔ０とＩｂ０は基準状態に近く青赤比があっている状態のトップ擬似要素セルとボトム擬似要素セルの短絡電流値であって一般に校正値と呼ばれる。δ（デルタ）は基準状態からの変化率を表す。

That is, Itm and Ibm are short circuit current values of the top pseudo element cell and the bottom pseudo element cell under an approximate solar light source that is close to the reference state but does not have a blue-red ratio. It0 and Ib0 are short-circuit current values of the top pseudo-element cell and the bottom pseudo-element cell in a state where the blue-red ratio is close to the reference state and are generally called calibration values. δ (delta) represents the rate of change from the reference state.

  The spectral dependency evaluation method based on the above equation is a method for evaluating the spectral dependency of output characteristics as the rate of change from the reference state of a multi-junction solar cell. It is.

(Judgment method of current limiting element cell)
Now, in a two-stage tandem solar cell composed of a top cell and a bottom cell, which is an example of a multi-junction photoelectric conversion element, the short-circuit current is maximized under spectral conditions where the currents of the top cell and the bottom cell match. When the current between the element cells is different, the current of the multijunction solar cell is limited by the smaller output current. More specifically, the maximum output Pmax is limited by the minimum value of the output current of the element cell obtained at the maximum output point voltage Vmax. The spectrum dependence of Pmax becomes the maximum value when the currents between the element cells coincide with each other, similarly to the spectrum dependence of the short circuit current. For example, the short circuit current and the maximum output of the tandem solar cell illustrated in FIG. 2 are limited by the top cell current (It) in the range where the current ratio (Ib / It) between the element cells is greater than 1.05. Hereinafter, the gradient rate B expressed by (Equation 1) is negative.

ここで、Ｐ１とＰ２は、それぞれ対象となるスペクトル条件近傍での異なる２つのスペクトル条件で測定した出力特性を表す。（Ｉｂ／Ｉｔ）１と（Ｉｂ／Ｉｔ）２はそれぞれ異なる２つのスペクトル条件に相当する擬似要素セル間の電流比を表す。

Here, P1 and P2 represent output characteristics measured under two different spectral conditions in the vicinity of the target spectral condition. (Ib / It) 1 and (Ib / It) 2 represent current ratios between pseudo-element cells corresponding to two different spectral conditions.

  On the other hand, in the range where the current ratio (Ib / It) is smaller than 0.95, the gradient rate B obtained by the above equation is limited by the current (Ib) of the bottom cell and becomes positive. Although the short-circuit current and the current ratio at which the maximum output reaches a peak are different, the gradient rate B substantially approaches zero under conditions where a peak is obtained. Therefore, it is possible to determine the element cell subject to the current limitation under the target spectrum condition by determining the sign by obtaining the gradient rate of the output characteristic with respect to the current ratio of the two sets of element cells contributing to the current limitation. I can do it.

  Here, the currents It and Ib representing the spectral state of the irradiation light source are values measured using a pseudo-element cell having a spectral sensitivity that matches the element cell relatively.

(Pseudo element cell)
Next, the pseudo element cell will be described. The pseudo element cell in the present invention has a relative spectral sensitivity substantially equivalent to that of the element cell constituting the multi-junction solar cell. This is one of the reference cells fabricated by simulating spectral sensitivity by stacking an optical filter or the like on a single junction solar cell. More preferably, in order to suppress the influence of non-linearity on the irradiance of the element cell, the material of the single junction solar cell constituting the pseudo element cell may be the same as that of the element cell.

  The calibration value under the reference state of the pseudo-element cell must be obtained by measurement under the condition in which the reference state is confirmed. By adjusting the irradiance of the light source so as to reproduce the calibration value, it is possible to check the reference spectrum condition of the element cell. Furthermore, the current value under any spectral condition of interest can be corrected using a spectral mismatch factor with respect to the reference spectrum, and correction is performed for each pseudo-element cell, and the current ratio between the pseudo-element cells is corrected. It is possible to determine the current ratio corresponding to the target spectral condition by using the pseudo element cell.

  A method for determining an element cell that is current-limited in a multi-junction solar cell will be described with reference to FIG. What is needed in the method of the present invention is a test cell, a quasi-element cell calibrated and a test light source having a variable spectral state. First, the pseudo element cell will be described.

(Production of pseudo element cell)
A tandem solar cell having a laminated structure of a top layer (amorphous silicon cell) and a bottom layer (thin film microcrystalline silicon cell) on a glass substrate was produced. The obtained tandem solar cell was irradiated with monochromatic light while taking responsibility for color bias light, thereby obtaining the relative spectral sensitivity characteristics of the top layer and the bottom layer shown by the solid line in FIG.

  In order to produce a pseudo-element cell that relatively matches the spectral sensitivity of the top layer, a single-junction amorphous silicon solar battery was produced on a glass substrate, and a glass filter of CAW500 (made by HOYA) was attached to the upper surface of the cell. In order to improve the degree of coincidence of the relative spectral sensitivities, the film thickness of the amorphous silicon i layer was changed around 3000A.

  In addition, in order to produce a pseudo element cell that relatively matches the spectral sensitivity of the bottom layer, a single-junction thin-film microcrystalline silicon solar cell is produced on a glass substrate, and A71 (manufactured by ATG) and M30 (manufactured by HOYA). A glass filter was attached to the upper surface of the cell. In order to improve the degree of coincidence of the relative spectral sensitivity, the film thickness of the thin film microcrystalline silicon i layer was changed around 2 μm (micrometer).

(Pseudo element cell pricing)
The pseudo-element cells of the top layer and the bottom layer were stabilized by light irradiation, and then the short-circuit current was calibrated as a calibration value in the reference state by the Japan Quality Organization (JQA).

(Measurement of spectrum dependence of test cell)
Next, in order to confirm that the current-limiting element cell can be determined by the measurement method of the present invention, the spectrum dependence of the three test cells (tandem solar cells 1, 2, and 3) is previously determined. Measurements were made to ascertain the correct conditions of the spectral conditions and the current limiting element cell.

  Specifically, the spectral dependence of three types of tandem solar cells having different top layer and bottom layer thicknesses was examined. In order to evaluate the spectral dependence of the IV characteristics of the tandem solar cell, the illuminance of the xenon lamp and the halogen lamp of the two-lamp light source was changed.

  The short-circuit current 1.1 times the calibration value from the top layer pseudo-element cell is 0.9 times the calibration value from the bottom layer pseudo-element cell so that the irradiance condition is such that the current ratio is 0.818. It adjusted so that a short circuit current might be obtained simultaneously, and measured the IV characteristic of the tandem solar cell.

  Similarly, by changing the spectral condition of the two-lamp light source in the current ratio range of 0.8 to 1.2, the spectral dependence on the short-circuit current Isc indicated by the solid line in FIG. 3 was obtained. Here, the range of the current ratio is based on the premise that the range of change in the current value of each element cell is about ± 10% (plus or minus 10 percent). This is because when the current ratio is less than 0.8 or greater than 1.2, the output current of the element cell changes by more than 10% (percent) with respect to the current value obtained in the reference state. This is because linearity with respect to irradiance is not guaranteed.

  The current ratio at which the Isc peak of each element cell was obtained was different. The difference in the current ratio of the pseudo element cell in which the currents of the top layer and the bottom layer coincide with each other is due to the difference in the current ratio of the top layer and the bottom layer of the three types of tandem solar cells.

(Example)
For the above-described three types of tandem solar cells 1, 2, and 3, the slope ratio with respect to the current ratio of the short-circuit current was determined in order to determine the element cells that are subject to current limitation under the reference spectral conditions.

First, using the tandem solar cell having the spectrum dependency shown in FIG. 2, IV measurement was performed using a single-lamp short pulse type xenon diffusion light source used in the production line.
At that time, when the top pseudo-element cell with the calibration value of 44.9 mA and the bottom pseudo-element cell with the calibration value of 24.4 mA are arranged on the irradiated surface and the short-circuit current is measured, 37.5 mA and 18.9 mA are obtained, respectively. Obtained. Moreover, when the short circuit current was measured about the tandem solar cells 1, 2, and 3, they were 0.499 A, 0.503 A, and 0.478 A, respectively.

  Next, as a result of changing the irradiance distribution of the light source received by the solar cell by placing a film having a large refractive index dispersion between the multi-junction solar cell and the light source as an optical filter, The short circuit currents of the element cell and the bottom pseudo element cell were changed to 34.4 mA and 17.8 mA, respectively. In that state, the short-circuit currents of the tandem solar cells 1, 2, and 3 were measured to be 0.475A, 0.449A, and 0.454A, respectively.

  Here, since the output currents of all the element cells are reduced by the film transmittance after the film is installed, in order to obtain a current value substantially equivalent to the spectrum dependence of FIG. It is necessary to obtain an illuminance correction value G, which is a geometric mean of the ratios of the short-circuit currents of the element cells, by the following (Equation 3), and further to obtain a short-circuit current after film installation using G.

この場合には、照度補正値Ｇとして１．０９２の値が得られた。

In this case, a value of 1.092 was obtained as the illuminance correction value G.

  Finally, the gradient rate B was determined using (Equation 4) below. This (Formula 4) corresponds to the case where P1 and P2, which are output characteristics measured under two different spectral conditions in the above (Formula 1), are short-circuit currents.

ここで、Ｉ０とＩｆはそれぞれフィルム設置前とフィルム設置後のタンデム型太陽電池の短絡電流を表す。また、（Ｉｂ／Ｉｔ）０と（Ｉｂ／Ｉｔ）ｆは、それぞれフィルム設置前後のトップ用擬似要素セルの短絡電流に対するボトム用擬似要素セルの短絡電流の電流比を表す。また、ＩｔｃａｌとＩｂｃａｌはそれぞれトップ用擬似要素セルとボトム用擬似要素セルの校正値を表す。タンデム型太陽電池１及び２、３について、フィルムを配置する前後での短絡電流の変化から、前記電流比の変化を用いて勾配率を計算するとそれぞれ、０．００（接線６の勾配）及び−０．２２（マイナス０．２２）（接線７の勾配）、０．３１（接線８の勾配）が得られた。

Here, I0 and If represent short-circuit currents of the tandem solar cell before and after the film installation, respectively. Further, (Ib / It) 0 and (Ib / It) f represent current ratios of the short-circuit current of the bottom pseudo-element cell to the short-circuit current of the top pseudo-element cell before and after the film installation, respectively. Itcal and Ibcal represent calibration values of the top pseudo element cell and the bottom pseudo element cell, respectively. For the tandem solar cells 1, 2, and 3, when the gradient rate is calculated using the change in the current ratio from the change in the short-circuit current before and after placing the film, 0.00 (gradient of the tangent line 6) and − 0.22 (minus 0.22) (gradient of tangent line 7) and 0.31 (gradient of tangent line 8) were obtained.

  The element cells that are subjected to current limitation under the reference spectrum condition determined from the gradient rate are substantially equal in current because the gradient rate of the tandem solar cell 1 is close to zero, and the gradient rate of the tandem solar cell 2 is negative. Therefore, it was found that the top layer was restricted, and the tandem solar cell 3 was restricted by the bottom layer because the gradient rate was positive. The above results were consistent with the spectral dependence results for each module shown in FIG.

  With the determination method according to the present invention, it is possible to accurately determine the element cell subject to the current limitation using the gradient rate with respect to the output characteristics under the target spectral condition.

It is an example of the relative spectral sensitivity of a tandem type solar cell. It is an example of the spectrum dependence of a tandem type solar cell. It is the schematic explaining the rule determination method of this invention.

1 Relative spectral sensitivity of the top cell of a tandem solar cell 2 Relative spectral sensitivity of the bottom cell of a tandem solar cell 3 Spectral dependence of the tandem solar cell 1 in which the short-circuit current is current matching under the standard spectral condition 4 Reference spectral condition The spectral dependence of the tandem solar cell 2 in which the short-circuit current is restricted by the top cell 5 The spectral dependence of the tandem solar cell 3 in which the short-circuit current is restricted by the bottom cell under the standard spectral conditions 6 The standard of the tandem solar cell 1 Tangent to current ratio in spectral condition 7 Tangent to current ratio in standard spectral condition of tandem solar cell 2 8 Tangent to current ratio in standard spectral condition of tandem solar cell 3

Claims (4)

A method of determining a characteristic limiting element cell that is an element cell having a minimum output current in a specific spectrum state of a test cell composed of a multi-junction photoelectric conversion element in which a plurality of element cells are stacked,
Under a test light source with two spectral states close to the specific spectral condition, the current as the output characteristic of the test cell is obtained, the spectral condition is changed slightly, and the change in the output characteristic of the test cell is determined from the obtained current . Calculate the slope,
Method of determining characteristics limiting element cell of the photoelectric conversion element test cells and judging a characteristic limiting element cell of the photoelectric conversion element test cells by positive and negative of the gradient. Using a pseudo-element cell having the same spectral sensitivity as each element cell of the test cell, the change in the ratio between the element cells of the short-circuit current obtained from the pseudo-element cell in the two-point spectral state is changed between the element cells of the test cell. The gradient of the change in the output characteristics of the test cell is calculated from the change in the current ratio between the element cells of the test cell between the two spectral states and the change in the current as the output characteristic of the test cell. The method of determining a characteristic limiting element cell according to claim 1. The currents that are output characteristics in the two-point spectral state are P1 and P2, and the current ratio between the pseudo-element cells in the two-point spectral state is (Ib / It) 1 and (Ib / It) 2, and the following (formula 1) method of determining characteristics limiting element cell of the photoelectric conversion element testing cell according to claim 1 or 2, characterized in that said calculating the slope B from.

The two spectral states near the specific spectral condition are two spectral states obtained depending on whether or not an optical filter is sandwiched between a test light source and the test cell. 4. A method for determining a characteristic limiting element cell of a multi-junction photoelectric conversion element test cell according to any one of 1 to 3 .

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