JP2006229063A - Method for correcting and predicting measured result of current/voltage characteristic of photoelectric conversion element, method and device for measuring and for manufacturing photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a correction accuracy when the current/voltage characteristic of a photoelectric conversion element is corrected to a reference state. <P>SOLUTION: Data (V<SB>1</SB>, I<SB>1</SB>) about a set of current/voltage characteristics measured in a state other than a reference state are corrected to data (V<SB>2</SB>, I<SB>2</SB>) about the current/voltage characteristic in the reference state, according to a correction equation, I<SB>2</SB>=I<SB>1</SB>+ΔI<SB>1</SB>+α×ΔTV<SB>2</SB>=(V<SB>1</SB>-Rs×ΔI<SB>1</SB>)(1+β/Voc'×ΔT)-Ka×I<SB>2</SB>×ΔT. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for correcting a current-voltage characteristic of a photoelectric conversion element, and more particularly to a method for correcting a current-voltage characteristic of a photoelectric conversion element to a reference state or an arbitrary irradiance and element temperature state.

  It is very important to accurately measure the current-voltage characteristics of the photoelectric conversion element for the following reasons.

  The output characteristics of the photoelectric conversion element such as maximum output, open circuit voltage, short circuit current, and fill factor are obtained from the current voltage characteristics. For example, when manufacturing and shipping a photoelectric conversion element in which the maximum output is important, if the maximum output is less than the rated value in the inspection, it is considered a defective product, but if the current / voltage characteristics cannot be measured accurately, it will be shipped. The maximum output of the photoelectric conversion element cannot be guaranteed. In addition, the measurement error of the current-voltage characteristics is large. For example, if the measured value changes depending on the state of the measuring device, the inspection threshold value changes even if a photoelectric conversion element of the same quality is manufactured. Yield becomes unstable. Furthermore, if the error in measurement of the current-voltage characteristics is added to the inspection threshold value in order to guarantee the quality of the shipped product, the manufacturing yield will be reduced. Further, when constructing a photovoltaic power generation system using the photoelectric conversion element, if the output of the photoelectric conversion element cannot be accurately predicted, an error in the entire photovoltaic power generation system may increase or the efficiency of the photovoltaic power generation system may increase. Or drop.

Here, as the current-voltage characteristics of the photoelectric conversion element, use of values in a reference state is standardized as a standard in Non-Patent Document 1 and Non-Patent Document 2 described later, and is also adopted in international standards such as IEC. Has been.
Here, the reference state is a state that satisfies the following conditions.
Solar cell temperature: 25 ° C
Spectral distribution: AM1.5 global solar standard sunlight (Spectrum of standard sunlight is defined in JIS C 8911.)
Irradiance: 1000 W / m ²

  When comparing the measured current-voltage characteristics of the photoelectric conversion elements, it is essential to compare them under the same conditions. Therefore, the reference state is very important. However, it is actually very difficult to measure the current-voltage characteristics of the photoelectric conversion element under conditions that satisfy all of the reference states.

  Therefore, it is essential and important to correct the current-voltage characteristics of the photoelectric conversion element measured under conditions other than the reference state to values in the reference state. At this time, it is necessary to correct the current-voltage characteristics using at least the temperature of the photoelectric conversion element and the irradiance of the irradiation light as parameters.

By the way, the current-voltage characteristic of a photoelectric conversion element is represented by a current-voltage characteristic curve. The current-voltage characteristic curve is represented by connecting a plurality of current-voltage data (hereinafter abbreviated as IV data). For example, when n pieces of IV data are measured to represent one current-voltage characteristic curve, the first IV data is (V _1-1 , I _1-1 ) and the nth IV data is (V _{1− n} , I _1-n ), a set of IV data {(V _1-1 , I _1-1 ), (V _1-2 , I _1-2 ),. . . , (V _1-n , I _1-n )} (hereinafter referred to as a set of current-voltage characteristics or a set of IV data sets) are arranged in the order of voltage or current, A current-voltage characteristic curve is obtained by creating a graph of the axial current and connecting each IV data on the graph with a straight line or a curve.

Here, by correcting the IV data of each point constituting the measured IV data set to the values in the reference state by the method described later using the element temperature and irradiance as parameters, A set of IV data sets {(V _2-1 , I _2-1 ), (V _2-2 , I _2-2 ),. . . , (V _2-n , I _2-n )}. By connecting this IV data set with a straight line or a curve as described above, a current-voltage characteristic curve in the reference state can be obtained.

If the IV data obtained by measuring a certain photoelectric conversion element under certain conditions is (V ₁ , I ₁ ) and the IV data in the reference state is (V ₂ , I ₂ ), for example, in the case of a crystalline photoelectric conversion element, As described in Patent Document 2, (V ₂ , I ₂ ) can be obtained from (V ₁ , I ₁ ) by the following equation (3). In this way, the formula for converting to the value in the reference state is called a correction formula.
I ₂ = I ₁ + Isc · (E ₂ / E ₁ −1) + α (T ₂ −T ₁ )
_{V 2 = V 1 + β (} T 2 -T 1) -Rs · (I 2 -I 1) -K · I 2 · (T 2 -T 1)
... (3)
Here, E ₁ : Irradiance at the time of measurement (W / m ² )
E ₂ : Irradiance in the standard state (1000 W / m ² )
T ₁ : Temperature of photoelectric conversion element during measurement (° C.)
T ₂ : Temperature of the photoelectric conversion element in the standard state (25 ° C.)
α: Fluctuation value of short-circuit current when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (A / ° C.)
β: fluctuation value of open-circuit voltage when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (V / ° C.)
Rs: series resistance of photoelectric conversion element (Ω)
K: Curve correction factor (Ω / ° C)

The above correction formula is for a crystalline photoelectric conversion element. When the semiconductor junction is made of an amorphous semiconductor, accurate correction is difficult. Therefore, when the photoelectric conversion element is made of a single-junction amorphous semiconductor, IV data (V ₁ , I ₁ ) and (V ₃ , I ₃ ) measured under two different irradiances E ₁ and E _3. Using IV, the IV data (V ₂ , I ₂ ) in the reference state is obtained by the following correction formula (4), which is described in the appendix of Non-Patent Document 1 as a corrected linear interpolation method.
I ₂ = I ₁ + ΔI ₁ + α (T ₂ −T ₁ )
V ₂ = (V ₁ −Rs · ΔI ₁ ) {1 + β / Voc · (T ₂ −T ₁ )}
... (4)
Here, ΔI ₁ = (E ₂ −E ₁ ) / (E ₁ −E ₃ ) · (I ₁ −I ₃ ^* )
E ₁ , E ₃ : Irradiance during measurement (W / m ² )
E ₂ : Irradiance in the standard state (1000 W / m ² )
T ₁ , T ₃ : Temperature of photoelectric conversion element during measurement (° C.)
(However, T ₁ −2 ≦ T ₃ ≦ T ₁ +2 must be satisfied.)
T ₂ : Temperature of the photoelectric conversion element in the standard state (25 ° C.)
α: Variation value of short-circuit current when the temperature of the photoelectric conversion element varies by 1 ° C. when the irradiance is 1000 W / m ² (A / ° C.)
β: Fluctuation value of open-circuit voltage when the temperature of the photoelectric conversion element fluctuates by 1 ° C. at irradiance of 1000 W / m ² (V / ° C.)
Rs: series resistance of photoelectric conversion element (Ω)
On the curve drawn by I ₃ ^* : (V ₃ + Rs · I ₃ , I ₃ ), current value Voc: (V ₁ −Rs · ΔI ₁ , I ₂ ) when voltage = V ₁ + Rs · I ₁ is drawn Open-circuit voltage obtained from the curve

  However, the correction method using the amorphous correction formula (4) has the following problems.

That is, firstly, since two sets of IV data measured under two different irradiances E ₁ and E ₃ are used, a process for measuring current-voltage characteristics for two times and a process for changing irradiance are required. This is a problem that it takes two times or more measurement time compared to the case where the correction formula (3) for the crystalline photoelectric conversion element is used. For example, when using a correction method using the correction formula (4) as an inspection method for manufacturing a photoelectric conversion element, this problem delays production tact, and thus increases the manufacturing cost. Serious.

  Second, correction is inaccurate unless the irradiance is changed while maintaining the wavelength relative value (the shape of the spectrum graph in the wavelength direction) of the spectral irradiance (hereinafter abbreviated as spectrum) of the irradiation light. It is a problem. Although it is not impossible to change the irradiance while maintaining the wavelength relative value of the irradiation light spectrum, it is practically difficult because the measurement apparatus becomes large. This problem is particularly serious when the photoelectric conversion element is a multi-junction type because its output characteristics change sensitively with respect to the irradiation light spectrum.

  Third, since there is no term for correcting the temperature change of the fill factor (FF) of the photoelectric conversion element in the correction formula (4), the correction result of the maximum output (Pmax) and the fill factor (FF) is inaccurate. It is a problem.

JIS C 8934 (Amorphous Solar Cell Output Measurement Method) JIS C 8913 (Measurement method of crystalline solar cell output)

  The present invention solves the inaccuracy of the correction by the conventional correction formula and the problem of the measurement process as described above, and a high-precision correction method and a quick measurement process of the current-voltage characteristics of the photoelectric conversion element by the new correction formula. The purpose is to provide. It is another object of the present invention to provide a highly accurate and efficient measurement program and a measurement apparatus.

In order to achieve the above object, according to the present invention, in a method for correcting the current-voltage characteristics of a photoelectric conversion element, a set of current-voltage characteristics data (V ₁ , I ₁ ) measured in a state other than the reference state is corrected as follows. According to the equation (1), the current-voltage characteristic data (V ₂ , I ₂ ) in the reference state is corrected.
I ₂ = I ₁ + ΔI ₁ + α · ΔT
V ₂ = (V ₁ −Rs · ΔI ₁ ) (1 + β / Voc ′ · ΔT) −Ka · I ₂ · ΔT
... (1)
here,
ΔI ₁ = Isc ₁ · (E ₂ / E ₁ −1)
ΔT = T ₂ −T ₁
However,
E ₁ : Irradiance during measurement (W / m ² )
E ₂ : Irradiance in the standard state (1000 W / m ² )
T ₁ : Temperature of photoelectric conversion element during measurement (° C.)
T ₂ : Temperature of the photoelectric conversion element in the standard state (25 ° C.)
α: Fluctuation value of short-circuit current when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (A / ° C.)
β: fluctuation value of open-circuit voltage when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (V / ° C.)
Rs: series resistance of photoelectric conversion element (Ω)
Ka: Curve correction factor (Ω / ° C)
Voc ′: open circuit voltage obtained from a curve drawn by (V ₁ −Rs · ΔI ₁ , I ₂ ) Isc ₁ : short circuit current during measurement

  In the correction equation (1), Ka is a function of ΔT.

In the correction equation (1), Ka is a linear function of ΔT as in the following equation (2).
Ka = ak · ΔT + bk (2)
Here, ak and bk are constants.

  In the current-voltage characteristic correction method for a photoelectric conversion element, the correction method using the correction formula (1) is applied to a photoelectric conversion element having at least one non-single-crystal semiconductor.

  Moreover, in the current-voltage characteristic correction method of a photoelectric conversion element, the correction method using the correction formula (1) is applied to a multi-junction photoelectric conversion element having a plurality of semiconductor junctions.

  In the computer program for correcting the current-voltage characteristics of the photoelectric conversion element, the correction program is a program for realizing a correction method using the correction formula (1).

  Further, in the method for measuring the current-voltage characteristics in the reference state of the photoelectric conversion element, a correction method using the correction formula (1) is used.

  In addition, the current-voltage characteristic measuring apparatus for the photoelectric conversion element includes a computer program for realizing the correction method using the correction formula (1), and measures the current-voltage characteristic in the reference state of the photoelectric conversion element. To do.

  Further, a method for producing a photoelectric conversion element, comprising: a step of forming at least one photoelectric conversion portion on a substrate; and a step of measuring a current-voltage characteristic of the photoelectric conversion element formed by the step, The step of measuring the current-voltage characteristic is a step using a correction method using the correction formula (1).

  The step of measuring the current-voltage characteristics of the photoelectric conversion element is in an intermediate stage of a plurality of steps for manufacturing the photoelectric conversion element.

  Further, based on the measurement value in the step of measuring the current-voltage characteristics of the photoelectric conversion element, any one of the steps for forming the photoelectric conversion element is adjusted so that the measurement value falls within a predetermined range. It is characterized by.

  Moreover, it is a manufacturing apparatus of a photoelectric conversion element having at least a photoelectric conversion part forming unit and a current-voltage characteristic measuring unit, and the current-voltage characteristic measuring unit uses a correction method using the correction formula (1). It is characterized by being.

In the correction equation (1), the current voltage characteristics data (V ₁ , I ₁ ) is a value in the reference state, and the current voltage characteristics data (V ₂ , I ₂ ) is an arbitrary irradiance and element temperature. By redefining the value in the above, the current voltage characteristic of the photoelectric conversion element at an arbitrary irradiance and element temperature can be calculated from the data of the current voltage characteristic in the reference state using the correction formula (1). Features.

According to the present invention, in the method for correcting the current-voltage characteristic of the photoelectric conversion element, the measured current-voltage characteristic data (V ₁ , I ₁ ) is converted into the current-voltage characteristic in the reference state by the correction equation (1). By correcting the data (V ₂ , I ₂ ), it is possible to improve the accuracy of the obtained current-voltage characteristic data in the reference state. That is, the current-voltage characteristic of the photoelectric conversion element that exhibits a behavior different from the irradiance dependency or the element temperature dependency of the crystalline photoelectric conversion element can be accurately corrected to the characteristic in the reference state. Furthermore, even when the curve factor of the photoelectric conversion element has temperature dependency, the current-voltage characteristic can be accurately corrected to the characteristic in the reference state.

  Furthermore, in the correction equation (1), by using Ka as a function of ΔT, even if the temperature dependence of the fill factor of the photoelectric conversion element is nonlinear, it is accurately corrected to the current-voltage characteristic data in the reference state. can do.

  Furthermore, in the correction equation (1), by making Ka a linear function of ΔT as in the equation (2), the temperature dependence of the curve factor of the photoelectric conversion element can be approximated by a quadratic curve. Accurate correction can be realized while maintaining the simplicity of parameter fitting.

  Further, by applying the correction method of the present invention to a photoelectric conversion element having at least one non-single-crystal semiconductor, the illuminance characteristics and temperature characteristics of current-voltage characteristics of the photoelectric conversion element using the non-single-crystal semiconductor are obtained. When expressed appropriately, the correction of the data of the current-voltage characteristic to the reference state can be made more accurate.

  Further, by applying the correction method of the present invention to a multi-junction photoelectric conversion element having a plurality of semiconductor junctions, errors due to characteristic changes with respect to changes in the irradiation light spectrum of the multi-junction photoelectric conversion element are eliminated. Thus, the correction of the current-voltage characteristic data to the reference state can be made more accurate.

  Further, by inputting a correction parameter by a computer program describing the correction method of the present invention, current-voltage characteristic data in a reference state can be obtained quickly and accurately. In addition, output characteristics such as open-circuit voltage, short-circuit current, fill factor, maximum output, and conversion efficiency can be calculated quickly and accurately from the current-voltage characteristics data.

  Moreover, the current-voltage characteristic data in the reference state of the photoelectric conversion element can be accurately measured by the method for measuring the current-voltage characteristic of the photoelectric conversion element using the correction method of the present invention. Further, output characteristics such as open-circuit voltage, short-circuit current, fill factor, maximum output, and conversion efficiency can be accurately calculated from the data of current-voltage characteristics. In addition, since only one set of current-voltage characteristic data necessary for correction is required, the measurement time of the current-voltage characteristic of the photoelectric conversion element can be shortened and the measurement process can be simplified. In addition, since two sets of current-voltage characteristics are not measured at different irradiances, errors due to the difference in the spectrum of the irradiated light between the two sets of data are eliminated, and the current-voltage characteristics measurement results are accurate. become.

  Further, a method for producing a photoelectric conversion element, comprising: a step of forming at least one photoelectric conversion portion on a substrate; and a step of measuring a current-voltage characteristic of the photoelectric conversion element formed by the step, The step of measuring the current-voltage characteristics is based on the measurement method using the correction method of the present invention, thereby suppressing variations due to the measurement of the characteristics of the photoelectric conversion element to be manufactured and improving the stability of quality. Can do. Furthermore, for example, by appropriately adjusting the formation conditions of the photoelectric conversion element based on the measured value, the manufacturing yield can be improved. Moreover, since the measurement time of the current-voltage characteristic of a photoelectric conversion element can be shortened as mentioned above, the production speed of a photoelectric conversion element can be improved, the production amount per unit time can be increased, and the manufacturing cost can be reduced.

In the correction equation (1), the current voltage characteristics data (V ₁ , I ₁ ) is a value in the reference state, and the current voltage characteristics data (V ₂ , I ₂ ) is an arbitrary irradiance and element temperature. By redefining the value in the above, the current-voltage characteristic of the photoelectric conversion element at an arbitrary irradiance and element temperature can be calculated from the data of the current-voltage characteristic in the reference state using the correction equation (1). Therefore, the power generation amount of the photoelectric conversion element at an arbitrary irradiance and element temperature when the photoelectric conversion element is installed outdoors can be predicted with higher accuracy than before. In addition, the design of the power generation system using the photoelectric conversion element can be optimized, and the system efficiency can be improved.

(Correction formula)
First, the feature of the correction equation (1), which is the key of the method for correcting the current-voltage characteristics of the photoelectric conversion element of the present invention, will be described in more detail.

First, according to the correction formula (1), the current-voltage characteristic of the photoelectric conversion element that exhibits behavior different from the irradiance dependency or temperature dependency of the crystalline photoelectric conversion element is accurately corrected to the characteristic in the reference state. can do. This is because the first term on the right side of the voltage correction formula of the correction formula (1) is different from the voltage correction formula of the crystal-type photoelectric conversion element correction formula (3). According to the correction formula (1), not only a photoelectric conversion element using an amorphous semiconductor as a photoelectric conversion layer but also a current-voltage characteristic of a photoelectric conversion element using a microcrystalline semiconductor or a polycrystalline semiconductor as a photoelectric conversion layer can be accurately corrected. That is, the correction formula (1) can be suitably applied to the correction of the current-voltage characteristics of the photoelectric conversion element using a non-single crystal semiconductor other than the single crystal semiconductor as at least a part of the photoelectric conversion layer. Further, when the temperature dependence of the curve factor of the photoelectric conversion element is recognized by the second term (−Ka · I ₂ · ΔT) on the right side of the correction equation of the voltage of the correction equation (1), The characteristic can be corrected. Since the photoelectric conversion element using a non-single crystal semiconductor as the photoelectric conversion layer in which the shape of the first term on the right side of the voltage correction formula of the correction formula (1) is suitable, temperature dependence is often recognized in the curve factor. This term is important. If the curve factor has no temperature dependence, Ka = 0 may be set.

Further, according to the correction equation (1), a set of data (V ₁ , I ₁ ) is sufficient for the data of current-voltage characteristics necessary for correcting the current-voltage characteristics in the reference state. As in the conventional amorphous correction equation (4), two sets of IV data (V ₁ , I ₁ ) and (V ₃ , I ₃ ) measured at different illuminances are not required. Time is shortened. In addition, there is no problem of error due to a change in the irradiance spectrum that tends to occur when the irradiance is changed, and the measurement result becomes accurate. The fact that there is no problem of spectrum change is particularly effective for multi-junction photoelectric conversion elements.

When correcting to the current-voltage characteristic in the reference state by the correction formula (1) using a set of IV data, the linearity of the short-circuit current with respect to the irradiance of the photoelectric conversion element is poor, and the current-voltage characteristic is measured. When the irradiance is far from 1000 W / m ² , there is a concern that an error occurs in the correction result, but this can be solved by the following method. That is, as a detector for measuring irradiance, a photoelectric conversion element using the same material as the photoelectric conversion element for measuring current-voltage characteristics is prepared as a reference device, and the reference device is used to measure the irradiance. The change of the short-circuit current with respect to the light intensity of the device and the change of the short-circuit current with respect to the light intensity of the measured photoelectric conversion element have a proportional relationship, and the linearity of the short-circuit current of the measured photoelectric conversion element with respect to the detected irradiance is maintained. Even if an amorphous semiconductor is used, the linearity of the short-circuit current with respect to the irradiance of the photoelectric conversion element is rarely lost unless the fill factor of the photoelectric conversion element is less than 0.5. .

  In addition, when the value of Ka is a constant, the change of the fill factor with respect to the temperature can be accurately corrected only when it is linear, but by making Ka a function of ΔT instead of a constant, the temperature of the fill factor can be corrected. Even when the change to is non-linear, it can be corrected accurately. The function form of ΔT may be appropriately selected according to the change of the fill factor with respect to the temperature.

  For example, when the change of the curve factor with respect to the temperature is a graph with the temperature as the horizontal axis and the curve factor as the vertical axis, the curve is convex upward or convex downward, Ka is expressed by the equation (2). By using a linear function of ΔT, correction can be performed with high accuracy. In that case, the accuracy of correction can be further improved by optimizing ak and bk in Equation (2) so that the curve of the graph near 25 ° C. is best reproduced.

  At this time, in the determination of the constants ak and bk in the formula (2), the temperature dependence of the current-voltage characteristics of the photoelectric conversion element centered on 25 ° C. is at least 10 ° C. or less, preferably 5 ° C. or less. It is preferable that the measurement is performed in a range including the actual measurement temperature region, and the correction result by the correction formula (1) is best matched with the measurement result at 25 ° C. For example, constants ak (t) and bk (t) are calculated such that the curve factor calculated from the result of correcting the current-voltage characteristic measured at the temperature t ° C. by the equation (1) matches the curve factor at 25 ° C. Then, there is a method of determining ak and bk from the obtained constants ak (t) and bk (t) by the method of least squares. In this case, if the constants ak and bk are determined so that the deviation between ak (t) and bk (t) near 25 ° C. becomes small, the accuracy of temperature correction of the current-voltage characteristics measured near 25 ° C. can be improved. Can be improved.

Further, when the change of the fill factor with respect to the temperature does not become a relatively simple curve as described above, Ka is set to a higher-order function of ΔT or higher, or, for example, the temperature T _{1 of the} photoelectric conversion element. (Absolute temperature) can be accurately corrected by using a function form including an exponent and a logarithm.

For example, Ka can be a function form of ΔT as follows. (In the following formula, ck, dk, ek, fk, gk, hk, ik are constants)
Ka = ck · ΔT ² + dk · ΔT + ek (5)
Ka = fk · log (T ₁ ) + gk (6)
Ka = hk · exp (T ₁ ) + ik (7)

  The functional form of ΔT of Ka is, for example, that the temperature dependence of the current-voltage characteristics of the photoelectric conversion element is measured at a certain temperature interval around 25 ° C. as described above, and the current-voltage characteristics measured at the temperature t ° C. If the correction result is calculated by using Ka as the constant and Ka (t) closest to the current-voltage characteristic at 25 ° C., the horizontal axis temperature t and the vertical axis Ka (t) are graphed, and Ka (t ) As a higher-order function of ΔT or higher, and an approximate expression that can best approximate the graph is obtained by a method such as a least square method. However, if Ka (t) is too complex in function of ΔT, the number of correction parameters increases and the correction becomes complicated.

  Also, when measuring a large number of photoelectric conversion elements of the same type, such as when producing photoelectric conversion elements, measure the irradiance dependence and temperature dependence of the current-voltage characteristics of photoelectric conversion elements with average characteristics. Each correction parameter of the correction formula (1) is determined, and the current-voltage characteristics of a large number of photoelectric conversion elements can be corrected to the reference state using the same correction parameter.

(Measuring method)
The method for measuring current-voltage characteristics of a photoelectric conversion element of the present invention is characterized by using the correction formula of the present invention. As a method for obtaining the current-voltage characteristics, a known method may be used. Further, when measuring the current-voltage characteristics of the photoelectric conversion element, it is desirable to adjust the temperature of the photoelectric conversion element to be 25 ± 2 ° C. if possible. Even when it is difficult to adjust the temperature, it is desirable to measure at a temperature as close as possible to 25 ° C. Moreover, it is desirable that the irradiance when measuring is close to 1000 W / m ² .

(measuring device)
The photoelectric conversion element current-voltage characteristic measuring apparatus of the present invention includes a correction program using the correction formula of the present invention, and measures the current-voltage characteristic of the photoelectric conversion element in the reference state.

  A known device such as a light irradiation device, a current-voltage characteristic measuring unit, or a voltage varying unit may be used as a device necessary for acquiring current-voltage characteristic data. The current-voltage characteristic measuring unit includes a voltage detection unit and a current detection unit.

  As the voltage detection means and the current detection means, a known means such as a digital multimeter or a combination of an analog-digital conversion board (A / D board) and a resistor may be used.

  As a means for varying the voltage of the photoelectric conversion element to be measured (voltage varying means), a known means such as a bipolar power source, an electronic load, or discharge of charges accumulated in a capacitor may be used. Further, the voltage of the photoelectric conversion element may be measured by changing the current flowing through the photoelectric conversion element while controlling it.

  In order to obtain a current-voltage characteristic measurement when the voltage or current is controlled and changed, the voltage or current must be swept. Although this sweep may be a continuous change or a step change, the IV data is measured at a measurement interval sufficiently longer than the charge / discharge time constant in consideration of the charge / discharge time constant of the photoelectric conversion element to be measured. It is desirable to do. This is particularly important when measuring a photoelectric conversion element having a large capacitance.

  As means for controlling the measuring instrument and means for processing the measured data, it is desirable to provide a data processing means capable of exchanging data with a measuring instrument such as a personal computer. Further, it is desirable that the data processing means has a function capable of controlling the measuring instrument, and it is more desirable that the data processing means can program the control of the measuring instrument.

  Further, there is a need for a data processing means that incorporates a correction program that can correct the measured current-voltage characteristic to the current-voltage characteristic in the reference state using the correction formula of the present invention. This data processing means can also serve as the measurement control / data processing means. It is desirable to incorporate a program for calculating various characteristics such as open-circuit voltage, short-circuit current, fill factor, maximum output, photoelectric conversion efficiency, series resistance, and parallel resistance from the current-voltage characteristics corrected to the reference state. Further, it is desirable to provide a storage medium for storing current-voltage characteristic data before correction, current-voltage characteristic data after correction, and calculation results of the various characteristics.

(Photoelectric conversion element)
Examples of the types of photoelectric conversion elements measured by the correction method of the present invention include photovoltaic elements such as solar cells and photodiodes, photosensors, electrophotographic photoreceptors, and the like.

  The semiconductor junction mainly has a photoelectric conversion function. Examples of the semiconductor junction include a pn junction, a pin junction, a Schottky junction, and an MIS type junction. In addition, as other types of photoelectric conversion elements, for example, wet solar cells such as dye-sensitized solar cells are also included.

Examples of the semiconductor material include crystalline, polycrystalline, microcrystalline, and amorphous materials. Examples of the material include group IV or group IV compounds such as Si, SiC, SiGe, C, and Ge, GaAs, and AlGaAs. III-V group compounds such as InP and InSb, II-VI group compounds such as ZnSe, ZnO, CdS, CdTe and Cu ₂ S, I-III-VI ₂ group compounds such as CuInSe ₂ and CuInS ₂ , organic semiconductors, etc. Or a mixture of the above-mentioned compounds.

  In addition, the photoelectric conversion device created by connecting the photoelectric conversion elements in series or in parallel or encapsulating them in an environmentally resistant container is also measured by the measuring method using the correction method of the present invention, as with the photoelectric conversion elements. Measured.

  In addition, the correction method of the present invention is particularly preferably applied to the photoelectric conversion element using at least a part of a non-single crystal semiconductor such as polycrystalline, microcrystalline, or amorphous. The photoelectric conversion element using a non-single-crystal semiconductor in part is often different from the conventional correction formula (3) in the dependence of the characteristics on the irradiance and the element temperature. In the conventional correction formula (3), This is because there are many things that cannot be corrected accurately.

  Furthermore, the correction method of the present invention is particularly preferably applied to a multi-junction photoelectric conversion element in which a plurality of semiconductor junctions are stacked among the photoelectric conversion elements described above. As described above, this is because the multi-junction photoelectric conversion element is sensitive to changes in characteristics with respect to the spectrum of irradiation light.

  In addition, the photoelectric conversion element to be measured to which the measurement method of the present invention is applied needs to know the dependency of the current-voltage characteristics (illuminance dependency) on the irradiance of the irradiated light. It is necessary that at least the series resistance component Rs of the element used for illuminance correction is known or can be estimated from an equivalent photoelectric conversion element.

  Further, the photoelectric conversion element to be measured needs to have a known temperature coefficient of current-voltage characteristics. Specifically, it is necessary to know the temperature coefficients of the open circuit voltage and the short circuit current. When it is difficult to measure the temperature coefficient of the photoelectric conversion element itself that measures the current-voltage characteristics, a representative value of the temperature coefficient of the equivalent photoelectric conversion element may be used.

(Irradiation light)
The light used in the measurement method of the present invention may be sunlight or light from an artificial light source. In the case of an artificial light source, a pseudo solar light source described later is desirable.

Irradiance of the irradiating light is preferably, 500~1500W / m ^2, more preferably 800~1200W / m ^2, and optimally it is desirable to measure the range of 950~1050W / m ^2. The closer the irradiance is to 1000 W / m ² , the smaller the amount of correction for illuminance correction, so the error due to illuminance correction is preferably smaller.

  When sunlight is used as the irradiating light, it is desirable to have a clear day when the irradiance of sunlight is stable. When using a pseudo solar light source, a known solar simulator is suitable. As the light source lamp, a xenon lamp, a metal halide lamp or the like is preferably used. The lighting method may be continuous lighting (steady light) or pulse lighting (pulse light).

(Reference device)
The reference device is used for detecting the irradiance of the irradiation light in the measurement method of the present invention. The detection of irradiance is done by comparing the measured value of the short circuit current of the reference device with the short circuit current value in the reference state (this is commonly referred to as the calibration value of the reference device). The short-circuit current of the reference device is approximately determined by measuring the voltage across the shunt resistor connected between the electrodes of the reference device. At this time, the resistance value of the shunt resistor is desirably a small resistance value such that the forward bias to the reference device by the shunt resistor is sufficiently small as an error given to the detection of the short-circuit current of the reference device. The calibration value of the reference device is measured by a public calibration authority by a known method. If there are circumstances that cannot be calibrated by a public proofreading organization, the operator may proofread it. The reference device includes a reference cell, a reference submodule, a reference module, and the like depending on the size thereof, and is appropriately selected depending on the application. The reference device basically desirably uses an element having the same configuration as the photoelectric conversion element to be measured, but may be composed of a different material.

  For example, as described above, when the linearity with respect to the light intensity of the photoelectric conversion element to be measured is poor, an element having the same configuration and the same material as the photoelectric conversion element to be measured as a reference device (the areas may be different) It is desirable to use Thereby, the linearity with respect to the detected irradiance of the photoelectric conversion element is maintained.

  When a different material is used as the reference device, it is desirable to adjust the spectral sensitivity with a filter or the like so that the spectral sensitivity of the reference device approximates that of the photoelectric conversion element. As a result, when measuring the irradiance of the irradiated light using a reference device, errors due to the spectrum of the irradiated light and the spectral sensitivity of the photoelectric conversion element are reduced, and the measurement result of the current-voltage characteristics of the photoelectric conversion element is accurate. become.

  Further, it is desirable that the reference device is processed so that the characteristics are stable over time. By stabilizing the reference device against light, heat, humidity, etc., the reliability of the calibration value of the reference device is increased, and the measurement of the current-voltage characteristics of the photoelectric conversion element becomes accurate. Further, the time interval for re-measurement of the calibration value in the reference state can be widened.

  Further, it is desirable that the reference device has previously measured a short circuit current (calibration value) in the reference state. The measurement method of the calibration value is, for example, JIS C 8911: Secondary reference crystal solar cell, IEC 60904-2: Photovoltaic devices Part 2 Requirements for reference solar cells, or IEC 60904-6: Petovolt 6 What is necessary is just to take the well-known method described in standards, such as for reference solar modules. A value measured by a public institution according to a defined standard is called a calibration value. The short-circuit current in the reference state of the reference device is desirably priced as a calibration value by a public institution. If multiple reference devices are used, and these are used as primary primary reference devices and secondary secondary reference devices, the primary primary reference device is calibrated by a public institution, and the secondary secondary reference device is the primary primary The value may be transferred from the reference device.

  In addition, it is desirable to use a reference device whose temperature coefficient of short circuit current is known. When it is difficult to measure the temperature coefficient of the reference device itself, the value of the temperature coefficient of the photoelectric conversion element having the same configuration may be used. Moreover, when measuring a photoelectric conversion element using a reference device, it is desirable to adjust the temperature of the reference device to be 25 ± 2 ° C. When it is difficult to adjust the temperature, it is necessary to obtain a short-circuit current at 25 ° C. by performing temperature correction by the known temperature correction method described in the standard using the temperature coefficient described above.

Moreover, as for the relationship between the spectral sensitivity of the reference device and the photoelectric conversion element, it is desirable that the mismatch coefficient Mn calculated by Expression (8) is 0.98 or more and 1.02 or less.
Mn = ∫Eo (λ) Qr (λ) dλ / ∫Et (λ) Qr (λ) dλ
× ∫Et (λ) Qs (λ) dλ / ∫Eo (λ) Qs (λ) dλ
... (8)
here,
Eo (λ): Spectral irradiance of reference sunlight Et (λ): Spectral irradiance of irradiated light Qr (λ): Spectral sensitivity of reference device Qs (λ): Spectral sensitivity of measured photoelectric conversion element

  When there is unevenness in the irradiance of the irradiation light as in the case of using an artificial light source, the power generation unit area of the reference device is preferably ± 20% or less, more preferably the power generation unit area of the photoelectric conversion element to be measured. Preferably, it is desirable to approximate within a range of ± 10% or less, optimally ± 5% or less. This is because the error due to the uneven location of the irradiated light is greatly reduced by approximating the power generation area of the reference device and the photoelectric conversion element. In the case of measurement using sunlight with almost no uneven irradiance, or when the above-mentioned secondary reference device is used to monitor the irradiance of irradiated light during measurement of the current-voltage characteristics of the photoelectric conversion element. May not approximate the power generation area. However, it is desirable to fix in which part of the irradiation area the common secondary reference device is installed. In addition, when the irradiance of the irradiation light or the spectral location variation changes, it is necessary to transfer the value from the regular primary reference device to the regular secondary reference device again.

(Manufacture of photoelectric conversion elements)
Further, in the present invention, by incorporating the method for measuring current-voltage characteristics of the photoelectric conversion element into a part of the manufacturing process of the photoelectric conversion element, variation in characteristics of the photoelectric conversion element to be manufactured is suppressed, and quality stability is improved. Can be increased. Furthermore, the yield can be further improved by appropriately adjusting, for example, the formation conditions of the photoelectric conversion elements based on the measured values.

  For example, in a manufacturing process of a solar cell module which is an example of a photoelectric conversion element disclosed in JP-A-2002-252362, unit elements (so-called solar cells) before being connected in series or in parallel before the resin sealing step As the step of measuring the current-voltage characteristics of the cell), a step of measuring the current-voltage characteristics of the photoelectric conversion element by the correction method of the present invention can be incorporated.

  By incorporating the current-voltage characteristics measurement process of the photoelectric conversion element of the present invention into the photoelectric conversion element manufacturing process in this way, it is possible to accurately grasp the element characteristics at an intermediate stage until the photoelectric conversion element is completed. It becomes possible to sort out defective products at an early stage of the manufacturing process. As a result, only non-defective products selected in the intermediate stage can be flowed to the subsequent processes, and materials or processes spent on defective products can be reduced, and the manufacturing cost of the photoelectric conversion element can be reduced. In addition, since current-voltage characteristics that cannot always be measured accurately by conventional measurement methods can be measured more accurately, fluctuations in photoelectric conversion element manufacturing yield due to measurement errors can be suppressed, and manufacturing yield can be stabilized. it can. In addition, the accurate measurement of current-voltage characteristics by the measurement method of the present invention can suppress variations in characteristics of the photoelectric conversion elements to be manufactured, and can improve the stability of quality. Furthermore, the yield can be further improved by appropriately adjusting, for example, the formation conditions of the photoelectric conversion elements based on the measured values as necessary. For example, even if an abnormality occurs in the characteristics of the photoelectric conversion element due to some cause (for example, lack of high-frequency power in the plasma CVD process), the current-voltage characteristic measurement process of the photoelectric conversion element of the present invention is an intermediate stage. This is because it is possible to quickly detect an abnormality and to deal with it early, and to reduce the amount of defective products created during the handling.

  In addition, for example, in the manufacturing process of the solar cell module, the current-voltage characteristic measurement step of the photoelectric conversion element of the present invention can be incorporated as a final inspection step for measuring the current-voltage characteristic of the completed solar cell module.

  By incorporating the current-voltage characteristics measurement process of the photoelectric conversion element of the present invention as the final inspection process of the photoelectric conversion element manufacturing process, the current-voltage characteristics can be measured more accurately than before, so the fluctuation in the manufacturing yield can be reduced. Therefore, the production yield can be stabilized and the stability of the quality of the photoelectric conversion element to be shipped can be improved.

  Furthermore, in addition to the above-described effects, the photoelectric conversion element current / voltage characteristic measurement method of the photoelectric conversion element of the present invention is incorporated as an inspection process in both the intermediate stage and the final stage of the photoelectric conversion element manufacturing process. It is easy to analyze the influence of the manufacturing process on the characteristics of the photoelectric conversion element or the influence on the manufacturing yield, and the manufacturing yield or the quality of the photoelectric conversion element to be shipped can be further improved.

  Although the Example of this invention is shown below, the content of this invention is not limited by the following Example.

Example 1
As a photoelectric conversion element to be measured (sample), a pin junction using amorphous silicon as an i layer (hereinafter abbreviated as a top cell) and a pin junction using amorphous silicon germanium as an i layer (hereinafter abbreviated as a middle cell) from the light incident side. The current-voltage characteristics of a triple solar cell module having a structure in which pin junctions (hereinafter abbreviated as bottom cells) using amorphous silicon germanium for the i layer are stacked in this order were measured outdoors with sunlight as follows. .

  In the triple solar cell module, a cell having a size of 35 cm × 24 cm formed on one stainless steel substrate is connected in series while inserting a bypass diode on a support plate, and a surface protective layer is formed. The size of the outer shape is about 140 cm × 42 cm.

Also, the triple type solar cell module, while keeping the module temperature at 50 ° C., by a solar simulator, 900 W / m ² in irradiated for 200 hours light is light degradation, was used as the stabilized current-voltage characteristic.

The current-voltage characteristics of the module were measured as follows.
The module's current-voltage characteristics are measured by selecting a clear day with almost no clouds, and a module that automatically tracks the sun so that the incident angle of sunlight on the module surface is constant (hereinafter referred to as “automatic”). It was mounted on a tracking base) so that direct sunlight was always incident substantially perpendicular to the module plane. Since it is difficult to adjust the module temperature outdoors, quickly remove the module with the light-shielding plate attached from the air-conditioned room, place it on the automatic tracking stand, remove the light-shielding plate, and The current-voltage characteristics were measured.

As the voltage variable means, a known programmable bipolar power supply (R6246 manufactured by Advantest Co., Ltd.) was used, and the bipolar power supply was controlled by a personal computer, and the voltage was swept stepwise. Also, as the voltage detection means and current detection means, the above-described R6246 has a measurement function, so that it is also used. At this time, in measuring the current, a delay time was set between the voltage setting and the current measurement in consideration of the voltage rise time and the capacitance of the sample cell. Here, the set voltage was set at 128 points while the sweep voltage interval was narrowed as the voltage was closer to the open circuit voltage of the module. As a result, even when the number of voltage setting points is the same, data near the maximum output can be measured more finely than when the voltage is swept at equal intervals, and the measurement accuracy is improved. The current-voltage characteristics of the module to be measured were obtained by the above procedure. In addition, by measuring the data set of the sweep voltage stored in the memory of the bipolar power source in advance, 128 points could be measured in 0.5 seconds or less. The temperature rise of the module immediately after removing the light shielding plate was about 0.15 ° C./sec when the irradiance of sunlight was 1000 W / m ² (1 sun). The error could be reduced sufficiently.

  In addition, after removing the light shielding plate, the temperature of the module rises due to sunlight, but by repeating the measurement of the current-voltage characteristics several times in the course of the temperature rise, A set of IV data sets (first, second, third) was acquired.

  Here, the module temperature was measured by two methods: a method in which a sheet-type thermocouple was attached to the back surface of the module, and a method in which the module temperature was calculated from the open-circuit voltage obtained from the current-voltage characteristics. The method for calculating the module temperature from the open circuit voltage is to calculate the open circuit voltage in the reference state of the module and the temperature coefficient of the open circuit voltage in advance, and compare the open circuit voltage after illuminance correction with the open circuit voltage in the reference state. A known method was used. The latter temperature was adopted on the assumption that the temperature obtained by the latter method is closer to the temperature of the semiconductor junction portion of the module. The temperature on the back of the module by the former thermocouple was used as a reference. As an open circuit voltage in the reference state of the module, an indoor measurement value measured using a pulse type solar simulator in a state where the temperature of the module was adjusted to 25 ° C. ± 2 ° C. was used.

  The former method is preferable when the open-circuit voltage in the reference state is unknown and difficult to estimate, and the latter method is more effective when the open-circuit voltage in the reference state can be estimated. It is desirable because it can be measured accurately. In the present embodiment, the latter method was used because the open circuit voltage in the reference state could be estimated by performing indoor measurement with a solar simulator in advance. The temperature determined by the latter method was 1st: 20.4 ° C, 2nd: 25.7 ° C, 3rd: 43.1 ° C.

  Here, as a reference cell, three reference cells (reference cells 1, 2, and 3) are attached by attaching the following three combinations of optical filters to the light incident side of a crystalline silicon solar cell having the same size of 1 cm × 1 cm. It was created.

  As the reference cell 1, a combination of a filter that transmits blue light, which is a wavelength with high sensitivity of the top cell, and a filter that absorbs infrared light is used. As the filter, for example, HA30 and B460 manufactured by HOYA Corporation can be used. Thereby, the reference cell 1 having a spectral sensitivity approximate to the spectral sensitivity of the top cell of the solar cell module to be measured was created.

  For the reference cell 2, in order to approximate the spectral sensitivity of the middle cell, HA30 manufactured by HOYA and LB-A8 manufactured by Toshiba Glass were used as filters. As a result, the spectral sensitivity approximated to the spectral sensitivity of the middle cell of the solar cell module to be measured was obtained.

  In order to approximate the spectral sensitivity of the bottom cell, the reference cell 3 uses a CF870 manufactured by HOYA (an interference filter called a cold filter that cuts the long wave side) and an A-73B manufactured by Toshiba Glass Co., Ltd. It was. As a result, the spectral sensitivity approximated to the spectral sensitivity of the bottom cell of the solar cell module to be measured was obtained.

  In addition, each reference cell requested a public institution to perform calibration as a primary reference solar cell in advance, and obtained a short-circuit current value (calibration value) in a reference state. As a result, the calibration values of the respective reference cells were 5.17 mA for the reference cell 1, 7.56 mA for the reference cell 2, and 7.29 mA for the reference cell 3.

  In addition, the standard cell package is a well-known one (for example, shown in JIS C 8911) using a black anodized aluminum block on the surface, and a Peltier element is attached to the outside of the package, The temperature was adjusted to 25 ° C. ± 2 ° C.

  As the irradiance detecting means, the reference cell 1 was used because the rate-limiting cell (semiconductor junction that controls the short-circuit current of the multi-junction solar cell) of the solar cell module to be measured was the top cell. The reference cell was installed on the automatic tracking platform, that is, on the same plane as the module to be measured.

The irradiance when the three IV data sets were acquired was 1st: 998 W / m ² , 2nd: 996 W / m ² , 3rd: 983 W / m ² , respectively.

  As described above, since the conditions under which the three sets of IV curves are measured are different from the reference state, it is necessary to correct the values in the reference state.

  Therefore, the three IV data sets were corrected to the values in the reference state by the correction method of the present invention using the correction formula (1). FIG. 1 shows three IV data sets before correction, and FIG. 2 shows three IV data sets after correction. The numbers in the legends of FIGS. 1 and 2 indicate the temperature of the solar cell module when the IV data set is acquired.

  The open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and maximum output (Pmax) before correction were determined from the three IV data sets before correction, and are summarized in Table 1.

  Further, Voc, Isc, FF, and Pmax were similarly obtained from the three corrected IV data sets corrected by the correction method of the present invention, and are summarized in Table 2. Further, Table 3 summarizes the first and third corrected Voc, Isc, FF, and Pmax divided by the second value.

  From FIG. 2, since the current-voltage characteristic curves of the three corrected IV data sets are almost overlapped, the three IV data sets are converted to the values in the reference state by the correction method of the present invention. It can be seen that the correction was made with high accuracy.

  Also, from Table 3, since the characteristic values from the first measurement and the third measurement are close to the characteristic values from the second measurement when the measurement conditions are closest to the reference state, the three IV data sets are It can be seen that the value in the reference state was accurately corrected by the correction method of the invention.

  At this time, the parameters, α, β, Rs, and Ka of the correction formula (1) were obtained as follows.

  First, the temperature coefficient α of Isc and the temperature coefficient β of Voc are selected from several cells having the same configuration as the 35 cm × 24 cm cell used in the triple solar cell module, and the temperature coefficient is set to a known temperature. Obtained by a coefficient measurement method, normalized temperature coefficients α / Isc and β / Voc are calculated, and average values of α / Isc and β / Voc (0.000682, −0.00373) are obtained, and then the measured sun It was obtained by multiplying Isc and Voc obtained from the indoor measurement value of the battery module.

  Next, as the series resistance Rs, a value (Rs = 0.35Ω) measured in advance by a known method obtained by measuring the current-voltage characteristics by changing the illuminance of the module indoors was used.

  Furthermore, Ka used a fixed value (Ka = −0.0006) such that the curve factor after the correction of the third IV data set almost coincides with the curve factor after the correction of the second IV data set. .

(Comparative Example 1)
In Example 1, the obtained three IV data sets were tried to be corrected by the modified linear interpolation method using Expression (4) described in the appendix of Non-Patent Document 1. However, the difference between the irradiance E ₁ and E ₃ when measuring two sets of IV data sets used for correction was too small, and the temperature T ₁ and T of the solar cell module when measuring the two sets of IV data sets _Since the difference of ₃ exceeded 2 ° C., this correction method could not be used and the reference state could not be corrected.

The difference between the irradiances E ₁ and E ₃ can be obtained by intentionally shifting the incident angle of sunlight with respect to the solar cell module, but the incident between the reference cell for detecting the irradiance and the measured solar cell module. Unless the angular dependence is consistent, the error due to the incident angle becomes large, which is difficult.

It is also possible to shift the measurement time to make the difference between the irradiance E ₁ and E ₃ , but the conditions such as air mass change, and the spectral irradiance of sunlight incident on the solar cell module changes. Then, since the fill factor of the solar cell module to be measured is changed, it is inappropriate to use these two IV data sets for correction.

  Thus, the corrected linear interpolation method described in the appendix of Non-Patent Document 1 cannot be used as a correction method.

(Comparative Example 2)
In Example 1, the obtained three IV data sets were corrected by a method using Equation (3) described in Non-Patent Document 2. Three corrected IV data sets are shown in FIG. Similarly to Example 1, Voc, Isc, FF, and Pmax were obtained from three corrected IV data sets and are summarized in Table 4. In addition, Table 5 shows Voc, Isc, FF, and Pmax after the first and third corrections divided by the second value.

  At this time, the same values as in Example 1 were used for α, β, and Rs in Equation (3). In Equation (3), the value of K is a fixed value (K =) such that the curve factor after correction of the third IV data set substantially matches the curve factor after correction of the second IV data set. -0.0025) was used.

  Comparing Table 3 and Table 5, it can be seen that the correction method of Example 1 was corrected with higher accuracy than the correction method of Comparative Example 2.

Here, in order to clarify the difference between the correction method of Example 1 and the correction method of Comparative Example 2, FIG. 4 and FIG. 4 are enlarged views of FIG. 2 of Example 1 and FIG. As shown in FIG. From FIG. 4 and FIG. 5, it can be seen that the three IV curves are closer to each other in Example 1 (FIG. 4) than in Comparative Example 2 (FIG. 5). This means that the corrected IV curve is close to the IV curve in the reference state (1000 W / m ² , 25 ° C.), and indicates that the correction is appropriately performed with high accuracy.

  Next, in order to further clarify the difference between the corrections, a voltage with a current of 5.2 A was obtained in the corrected IV curve and shown in Tables 6 and 7. Table 6 is obtained from the corrected IV curve of Example 1, and Table 7 is obtained from the corrected IV curve of Comparative Example 2. Tables 6 and 7 show values obtained by dividing the obtained voltage by the corrected voltage value of the second measurement in which the measurement conditions are closest to the reference state. The closer this value is to 1, the more accurate correction is performed.

  From Tables 6 and 7, the first and third relative values obtained by dividing the corrected voltage by the second value are 0.993 and 1.040 in Example 1, while In the cases 0.982 and 1.071, it can be seen that the first embodiment using the correction method of the present invention is closer to 1, and the correction is performed more accurately than the second comparative example using the conventional correction method.

(Example 2)
In Example 1, when the three acquired IV data sets were corrected using the correction formula (1), Ka was corrected as a linear function of ΔT as in the formula (2).

At this time, the parameters, α, β, and Rs of the correction formula (1) use the same values as in the first embodiment, and for Ka, ak and bk in the formula (2) are each 4.66 × 10 ^−5. , −0.00148. That is,
Ka = 4.66 × 10 ⁻⁵ × ΔT−0.00148
As a correction.

  Table 8 shows the calculation results of Voc, Isc, FF, and Pmax from the corrected IV data set according to this example. Table 9 summarizes the first and third corrected Voc, Isc, FF, and Pmax divided by the second value after correction.

  As is apparent from Table 9, by making Ka a linear function of ΔT as shown in equation (2), the temperature dependence of the fill factor can be accurately corrected, and after the first and third corrections. The value of the curve factor was in the range of less than ± 0.05%, and coincided with the value after the second correction. As a result, the deviation of the first and third Pmax after correction relative to the second time could be suppressed to 0.1%. Thus, by making Ka a linear function of ΔT, a more accurate correction result than the correction result of the IV data set of Example 1 could be obtained.

(Example 3)
From the light incident side, a pin junction (top a-Si cell) using amorphous silicon as the i layer, a pin junction (middle μc-Si cell) using microcrystalline silicon as the i layer, and microcrystalline silicon as the i layer The output of the a-Si / μc-Si / μc-Si triple solar cell having a structure in which the used pin junction (bottom μc-Si cell) is laminated in this order is used for the production line for manufacturing the solar cell as follows. Measured in an output inspection device.

  The triple solar cell has a size of 35 cm × 24 cm formed on a single stainless steel substrate.

  The measurement of the current-voltage characteristics of the cell is performed in the same manner as in Example 1 except that the probe is used to make electrical contact with the electrode, and an effective irradiation area of 40 cm is used instead of sunlight as the light source. A pseudo solar light source (solar simulator) of × 40 cm, grade A was used.

In addition, solar cells that have no light irradiation history are originally measured on the production line. In this example, in order to clarify the effect of the correction method, the solar cells to be measured are kept at a temperature of 50 ° C. Using a simulator, the light voltage was deteriorated by irradiating light at 900 W / m ² for 200 hours to stabilize the current-voltage characteristics. In addition, while keeping the shutter of the solar simulator for current-voltage characteristics measurement longer than usual, the temperature of the solar cell to be measured is intentionally increased, and three sets of IV data sets at three different temperatures ( 1st time, 2nd time, 3rd time) were obtained. The temperature of the solar cell to be measured was 1st: 26.1 ° C, 2nd: 29.4 ° C, 3rd: 31.5 ° C.

  Here, the irradiance of the simulated sunlight by the solar simulator was measured by the reference cell in the same manner as in Example 1. The reference cell has a spectral sensitivity that approximates the spectral sensitivity of each of the top a-Si cell, the middle μc-Si cell, and the bottom μc-Si cell, as in Example 1, except that the type and combination of the filters are different. Reference cell 4, reference cell 5, and reference cell 6 were prepared. Here, since the measured solar cell was the middle μc-Si cell, the irradiance was measured using the reference cell 5.

The irradiance when the three IV data sets were acquired was 1st: 994 W / m ² , 2nd: 992 W / m ² , 3rd: 994 W / m ² , respectively.

The three IV data sets were corrected to the values in the reference state by the correction method of the present invention using the correction formula (1). Here, the temperature coefficient α of Isc and the temperature coefficient β of Voc are average values of standardized temperature coefficients α / Isc and β / Voc (0.00047, from several cells having the same configuration, as in the first embodiment. -0.00363), and then obtained by multiplying Isc and Voc obtained from the indoor measurement value of the solar cell having a production number close to that of the solar cell to be measured. Also, Rs is 0.025Ω, Ka is a quadratic function of ΔT as shown in Equation (5), and each coefficient is
ck = −2.46 × 10 ⁻⁶
dk = 2.96 × 10 ⁻⁵
ek = 7.16 × 10 ⁻⁵
It was.

  Voc, Isc, FF, and Pmax were obtained from three sets of IV data before and after correction, and are summarized in Tables 10 and 11. Further, Tables 12 and 13 are obtained by dividing the second and third times Voc, Isc, FF, and Pmax in Tables 10 and 11 by the first value.

  From Table 12 and Table 13, it can be seen that the measurement results after the second correction and the third correction are in good agreement with the first measurement result under the condition closest to the reference state among the three corrections according to the correction of the present invention. . That is, the value of the curve factor after the second correction and the third correction matched the value after the first correction within a range of less than ± 0.05%. As a result, the deviation of the second and third Pmax after the correction from the value after the first correction could be suppressed to 0.2%. Thus, it can be seen that the three IV data sets were accurately corrected to the values in the reference state by the correction method of the present invention.

  Using the current-voltage characteristic correction method of the present invention described above, the current-voltage characteristic in the reference state of the solar cell being manufactured was measured in the output inspection device of the production line for manufacturing the solar cell. The current-voltage characteristic of the solar battery cell was measured by the output inspection apparatus including a current-voltage characteristic measuring apparatus using a control device incorporating a measurement program including the correction program of the present invention. Based on the measured current-voltage characteristics, in addition to the Voc, Isc, FF, and Pmax, the maximum output operating voltage (Vpm), the maximum output operating current (Ipm), the photoelectric conversion efficiency (η), the shunt resistance (Rsh), Various characteristic values in the reference state of the solar battery cell such as series resistance (Rs) were calculated. The calculation of these various characteristic values is also included in the measurement program. The calculated various characteristic values were stored in a storage device of a control device attached to the inspection device. Of these various characteristics, for example, η and Rsh were appropriately selected and compared with a reference value to determine whether the solar cell passed or failed. Solar cells that did not pass the standard value were discharged as defective and were not allowed to flow into subsequent production processes.

  By using such a method for measuring current-voltage characteristics of the present invention, the current-voltage characteristics of solar cells can be measured more accurately, so that fluctuation in photoelectric conversion element manufacturing yield due to measurement errors can be suppressed, and manufacturing can be performed. Yield was stabilized. Moreover, the variation by the measurement of the characteristic of the photoelectric conversion element to manufacture was suppressed, and the stability of quality could be improved. Furthermore, the yield could be improved by appropriately adjusting the formation conditions of the solar cells based on the measured characteristic values.

  In the present embodiment, the subsequent production process (referred to as modularization process) is, for example, a process of appropriately serially paralleling the solar cells while incorporating the bypass diode, on the front and back of the solar cells that are serially parallelized There is a process of attaching a covering material and the like, and finally the solar cell module is completed. As described above, by preventing the solar cells that have not passed the reference value from flowing into the modularization process, it is possible to improve the production yield of the solar battery module, and in the modularization process. Materials or processes spent on defective products could be reduced, and the manufacturing cost of the solar cell module could be reduced. In addition, the quality of the solar cell module could be stabilized.

Example 4
The current-voltage characteristics of the a-Si / [mu] c-Si / [mu] c-Si triple solar cell similar to that in Example 3 were measured using a solar simulator in the same manner as in Example 3, and a book using the correction formula (1) The current-voltage characteristics in the reference state were obtained by the correction method of the invention.
At this time,
α = 0.00354A / ° C
β = −0.00668V / ° C
Rs = 0.024Ω,
Ka = 5.0 × 10 ⁻⁶ × ΔT−1.0 × 10 ⁻⁵
It was.

Next, the current-voltage characteristics corrected to the reference state are (V ₁ , I ₁ ), E ₁ = 1000 W / m ² , T ₁ = 25 ° C., and any state (irradiance E ₂ , solar cell temperature T ₂ ) Current-voltage characteristics (V ₂ , I ₂ ) were calculated using the correction formula (1) and predicted. The parameter values used were the same as those in the above-described correction to the reference state.

6, at a temperature 25 ° C. of the solar cell, showing a current-voltage characteristic estimation results when the irradiance was varied ^{500W / m 2, 800W / m} 2, 1100W / m 2. (1000 W / m ² indicates current-voltage characteristics in the reference state.)
FIG. 7 shows the current-voltage characteristic prediction results when the solar cell temperature is changed to 15 ° C., 35 ° C., and 55 ° C. with an irradiance of 1000 W / m ² . (25 ° C. indicates current-voltage characteristics in the reference state.)

  As described above, the current-voltage characteristic prediction method of the present invention was able to predict the current-voltage characteristic of the solar battery cell at an arbitrary irradiance and an arbitrary temperature.

(Example 5)
The current of the amorphous silicon (a-Si) sub-module having a layer configuration having one amorphous silicon pin junction by the indoor measurement method using the solar simulator similar to that of Example 3 except that it is not a production line inspection apparatus. The voltage characteristics were measured, and the current-voltage characteristics in the reference state were obtained by the correction method of the present invention as in Example 3. The amorphous silicon submodule has a size of 10 cm × 10 cm, and is formed by serially connecting 10 amorphous silicon cells on a glass substrate.

  The current-voltage characteristics were measured twice, and two IV data sets were acquired. For the second time, the temperature of the sub-module was intentionally increased while keeping the solar simulator shutter open. As a result, the temperature of the submodule was 25.0 ° C. for the first time and 26.4 ° C. for the second time.

  Here, the irradiance of the simulated sunlight by the solar simulator was measured by the reference cell in the same manner as in Example 1. The reference cell is an amorphous silicon cell of 2cm x 2cm size (not serially parallelized) that is made of the same material as the submodule and manufactured by the same manufacturing method and has an approximate spectral sensitivity. The one with the calibration value attached was used. By measuring the irradiance with this reference cell, the linearity of the amorphous silicon sub-module with respect to the irradiance of Isc was improved.

The irradiance when the two IV data sets were acquired was 1st: 991 W / m ² and 2nd: 990 W / m ² , respectively.

  The two IV data sets were corrected to the values in the reference state by the correction method of the present invention using the correction formula (1). FIG. 8 shows two IV data sets after correction. In FIG. 8, the current value and the voltage value are normalized by Isc and Voc, respectively, obtained from the first current-voltage characteristic measurement correction result that is substantially close to the reference state. It can be seen from FIG. 8 that the second current-voltage characteristic correction result is corrected to be in good agreement with the first current-voltage characteristic correction result that is almost close to the reference state.

  Similarly to Example 1, various characteristic values of Voc, Isc, FF, and Pmax were obtained from the IV data set before and after correction, and divided by the characteristic value after the first correction are summarized in Table 14. From Table 14, it can be seen that the characteristic value after the second correction substantially matches the characteristic value after the first correction close to the reference state by the correction method of the present invention. Therefore, it can be seen that the two IV data sets are accurately corrected to the values in the reference state by the correction method of the present invention.

  Here, the temperature coefficient α of Isc and the temperature coefficient β of Voc are the average values of normalized temperature coefficients α / Isc and β / Voc (0.0007, -0.003), and then obtained by multiplying Isc and Voc obtained from the first current-voltage characteristic measurement result almost close to the reference state. Further, Rs was 1.1Ω / A, and Ka was −0.036Ω / A / ° C. Here, Rs and Ka are normalized to a value of Isc = 1A.

It is the graph which showed an example of the result acquired on three different conditions by the current-voltage characteristic of an example of a photoelectric conversion element. It is the graph which showed the current voltage characteristic which correct | amended the said 3 sets of current voltage characteristics to the value in a reference | standard state by the correction method of this invention. It is the graph which showed the current voltage characteristic which correct | amended the said 3 sets of current voltage characteristics to the value in a reference | standard state by the conventional correction method. It is the enlarged view to which a part of FIG. 2 was expanded. It is the enlarged view to which a part of FIG. 3 was expanded. It is the graph which showed an example of the result of having predicted the current voltage characteristic of the photoelectric conversion element in arbitrary irradiance by the current voltage characteristic prediction method of this invention. It is the graph which showed an example of the result of having predicted the current voltage characteristic of the photoelectric conversion element in arbitrary element temperature by the current voltage characteristic prediction method of this invention. It is the graph which showed the current-voltage characteristic which corrected the result acquired on two different conditions by the correction method of this invention into the value in a reference state by the current-voltage characteristic of another example of a photoelectric conversion element.

Claims (13)

In the correction method of the current-voltage characteristics of the photoelectric conversion element, a set of current-voltage characteristics data (V ₁ , I ₁ ) measured in a state other than the reference state is obtained by using the following correction equation (1), A method of correcting a current-voltage characteristic of a photoelectric conversion element, wherein the characteristic data (V ₂ , I ₂ ) is corrected.
I ₂ = I ₁ + ΔI ₁ + α · ΔT
V ₂ = (V ₁ −Rs · ΔI ₁ ) (1 + β / Voc ′ · ΔT) −Ka · I ₂ · ΔT
... (1)
here,
ΔI ₁ = Isc ₁ · (E ₂ / E ₁ −1)
ΔT = T ₂ −T ₁
However,
E ₁ : Irradiance during measurement (W / m ² )
E ₂ : Irradiance in the standard state (1000 W / m ² )
T ₁ : Temperature of photoelectric conversion element during measurement (° C.)
T ₂ : Temperature of the photoelectric conversion element in the standard state (25 ° C.)
α: Fluctuation value of short-circuit current when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (A / ° C.)
β: fluctuation value of open-circuit voltage when the temperature of the photoelectric conversion element fluctuates by 1 ° C. (V / ° C.)
Rs: series resistance of photoelectric conversion element (Ω)
Ka: Curve correction factor (Ω / ° C)
Voc ′: open circuit voltage obtained from a curve drawn by (V ₁ −Rs · ΔI ₁ , I ₂ ) Isc ₁ : short circuit current during measurement   2. The method of correcting a current-voltage characteristic of a photoelectric conversion element according to claim 1, wherein Ka is a function of ΔT in the correction equation (1). 2. The method of correcting a current-voltage characteristic of a photoelectric conversion element according to claim 1, wherein Ka is a linear function of [Delta] T in the correction formula (1) as shown in the following formula (2).
Ka = ak · ΔT + bk (2)
(Here, ak and bk are constants.)   The method for correcting a current-voltage characteristic of a photoelectric conversion element according to claim 1, wherein the photoelectric conversion element includes at least one non-single-crystal semiconductor.   The method for correcting a current-voltage characteristic of a photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a multi-junction photoelectric conversion element having a plurality of semiconductor junctions.   A computer program for correcting a current-voltage characteristic of a photoelectric conversion element, wherein the correction program is a program for realizing the correction method according to claim 1.   A method for measuring current-voltage characteristics of a photoelectric conversion element, wherein the correction method according to claim 1 is used in the method for measuring current-voltage characteristics in a reference state of the photoelectric conversion element.   An apparatus for measuring current-voltage characteristics of a photoelectric conversion element, comprising the computer program according to claim 6 and measuring current-voltage characteristics in a reference state of the photoelectric conversion element. .   A method for producing a photoelectric conversion element, comprising: a step of forming at least one photoelectric conversion portion on a substrate; and a step of measuring a current-voltage characteristic of the photoelectric conversion element formed by the step, wherein the current voltage The process for measuring characteristics is a process based on the measurement method according to claim 7.   The method for manufacturing a photoelectric conversion element according to claim 9, wherein the step of measuring the current-voltage characteristics of the photoelectric conversion element is in an intermediate stage of a plurality of steps for manufacturing the photoelectric conversion element.   Based on the measurement value in the step of measuring the current-voltage characteristics of the photoelectric conversion element, any one of the steps for forming the photoelectric conversion element is adjusted so that the measurement value falls within a predetermined range. The manufacturing method of the photoelectric conversion element of Claim 9 or 10.   An apparatus for manufacturing a photoelectric conversion element having at least a photoelectric conversion part forming unit and a current-voltage characteristic measurement unit, wherein the current-voltage characteristic measurement unit uses the current-voltage characteristic measurement device according to claim 8. An apparatus for manufacturing a photoelectric conversion element, comprising: In the correction formula (1), the current-voltage characteristic data (V ₁ , I ₁ ) is a value in the reference state, and the current-voltage characteristic data (V ₂ , I ₂ ) is a value at an arbitrary irradiance and element temperature. The current-voltage characteristics of the photoelectric conversion element at an arbitrary irradiance and element temperature are calculated from the data of the current-voltage characteristics in the reference state by using the correction equation (1). To predict the current-voltage characteristics of a photoelectric conversion element.

Images