JP5256521B2 - Evaluation method and evaluation apparatus for solar cell using LED - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device using a new LED for evaluating a solar battery, by which the output characteristic of the solar battery is easily performed. <P>SOLUTION: The solar battery 4 is irradiated with the light from a multi-wavelength LED light emitter 2 to measure the absolute spectral sensitivity (A/W) of the solar battery, from the irradiated light intensity (W) of each wavelength from the light emitter 2 and the output the short-circuit current (A) of the solar battery 4 of each wavelength. The absolute spectral sensitivity curve of the solar battery 4 can speedily be obtained from the fitting calculation of the absolute spectral sensitivity of the solar battery 4. Furthermore, the output short-circuit current in the case of irradiation of the solar battery 4 with the reference insolation can be calculated. Thus, the solar battery can speedily and inexpensively be evaluated also at the outdoor installing place of the sollar battery. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a solar cell evaluation method and an evaluation apparatus using LEDs.

The use of solar energy is progressing in order to preserve the global environment, and the installation of solar cell panels composed of solar cell modules in which a plurality of solar cells are connected to the roofs and walls of ordinary buildings and homes is also in progress. However, solar cells made of Si (silicon) or the like have not been spread as expected because of high cost. One of the reasons for the high cost of solar cells is an inspection process for output characteristics when the solar cells are irradiated with sunlight. The output characteristic evaluation of the solar cell is an important measurement item performed in the inspection after the solar cell is manufactured and in the research and development of the solar cell.
It is difficult to irradiate solar cells with solar light at any time because the intensity varies depending on the weather. For this purpose, instead of sunlight, a light source mainly using an Xe (xenon) lamp or a halogen lamp, a so-called solar simulator, is used as a light source for evaluating the output characteristics of a solar cell (see Patent Document 1). Here, the solar simulator adds a halogen lamp as a long-wavelength light source in addition to a normal xenon lamp, thereby suppressing the emission line spectrum of the xenon lamp and further approximating natural sunlight by using an optical filter. Light source.

          JP 2002-48704 A (page 2-3, FIG. 1)

Problems to be solved by the invention

There are only a few solar simulators that meet Grade A in the JIS standard, and in the inspection of many solar cells, comparative measurements are performed using solar cells (primary reference solar cells) that have been primarily calibrated by a Class A solar simulator. The measurement is equivalent to sunlight irradiation. In practice, secondary reference solar cells calibrated by primary reference solar cells are often used, so that there is a problem that the measurement error becomes large and accurate measurement is difficult.
Moreover, the evaluation of the output characteristics of a solar cell using a solar simulator has problems of spectrum mismatch with reference sunlight, a large facility, and a short lamp life and high power consumption.
In addition, when measuring the absolute spectral sensitivity curve in the wavelength range where the solar cell can receive light, the light of the solar simulator is dispersed with a spectroscope to obtain the absolute spectral sensitivity for each wavelength in the wavelength range of the light receiving range. Measuring. At this time, since the output of the spectral wavelength of the solar simulator is lowered, since the noise is large, the output short-circuit current of the solar cell is measured using a lock-in amplifier. For this reason, since the measuring device itself that measures the absolute spectral sensitivity curve of the solar cell is expensive and takes time to measure, there is a problem that the cost required for the inspection of the manufacturing cost of the solar cell does not decrease. is there.

  In view of the above problems, an object of the present invention is to provide a solar cell evaluation method using a novel LED and an evaluation device thereof that can easily evaluate the output characteristics of the solar cell.

Means for solving the problem

ここで、Ｉ_SCは太陽電池の出力短絡電流、Ｉ_hはｎ層の正孔電流、Ｉ_drは空乏層中の電流、Ｉ_eはｐ層の電子電流であり、下記（式１）（式２）（式３）を満たす。
【数２】

【数３】

【数４】

ただし、αは吸収係数であり、Ｌ_h ，Ｌ_e とＳ_h ，Ｓ_e とＤ_h ，Ｄ_e は、それぞれ、少数キャリアの拡散長、表面再結合速度、少数キャリアの拡散定数であり、添え字の_h と_e はそれぞれｎ層中における正孔とｐ層中の電子を示し、ｘ_j 、Ｗは空乏層の端、空乏層の厚さであり、Ｈ、Ｈ'は、空乏層末端の寸法である。
上記構成において、更に、第２ステップで求めた太陽電池の絶対分光感度曲線から、基準太陽光照射時の出力短絡電流を求めることが好ましい。
上記構成において、第１のステップでは、それぞれ短波長帯、中波長帯及び長波長帯の光を発光する複数のＬＥＤを用いて、各光の波長毎の絶対分光感度を求めることが好ましい。
上記構成において、第１のステップでは一色毎に変調をかけて太陽電池の出力短絡電流を得ることが好ましい。
上記構成において、ステップＤでは、ｎ層の正孔電流Ｉ_h及びＬ_eに関する偏微分導関数δＩ_h／δＳ_h及びδＩ_e／δＬ_eを用いて行うことが好ましい。
上記構成において、太陽電池が、Ｓｉ又は化合物半導体からなる結晶又はアモルファスを用いた太陽電池であることが好ましい。
[Means for Solving the Problems]
In order to achieve the above object, a solar cell evaluation method using an LED of the present invention has a pin structure in which discrete and different wavelengths of light are emitted from an LED light emitting unit having a plurality of LEDs that emit light of different wavelengths. A first step of irradiating the solar cell to measure an output short-circuit current of the solar cell and obtaining an absolute spectral sensitivity for each wavelength, and a current of the solar cell based on the absolute spectral sensitivity for each wavelength obtained in the first step A second step of performing a fitting calculation according to the following (Equation 4) derived from a semiconductor minority carrier continuity equation to obtain an absolute spectral sensitivity curve of the solar cell, in step, by setting the initial value surface reflectance R as a parameter, the surface recombination velocity S _h of the solar cell, the minority carrier diffusion length L _e, scan for obtaining the absolute spectral sensitivity curve And-up A, the fitting calculation using data of the measuring wavelengths, including the short wavelength side among the absolute spectral sensitivity for each wavelength obtained in the first step, a rough approximation of the surface recombination velocity S _h of the solar cell together determine the value, and step B of obtaining a correction value from the initial value of the absolute spectral sensitivity surface reflectance provides the curve R and the minority carrier diffusion length L _e, among the absolute spectral sensitivity for each wavelength obtained in the first step the fitting calculation using data of the measuring wavelengths, including the long wavelength side, fewer with obtaining a rough approximation of the carrier diffusion length L _e, surface reflectance R and the surface recombination velocity gives the absolute spectral sensitivity curve of the solar cell a step C for obtaining the correction value from the initial value of S _h, further steps B, and using a rough approximation and correction values of the parameters calculated in step C, the surface reflectance R, solar Characterized in that it comprises the surface recombination velocity S _h, Step D to obtain the optimum value of minority carrier diffusion length L _e, a.
[Expression 1]

Here, I _SC is the output short-circuit current of the solar cell, I _h is the hole current of the n layer, I _dr is the current in the depletion layer, I _e is the electron current of the p layer, and the following (formula 1) (formula 2) (Equation 3) is satisfied.
[Expression 2]

[Equation 3]

[Expression 4]

Where α is an absorption coefficient, L _h , _Le and S _h , _Se and D _h , and D _e are the minority carrier diffusion length, surface recombination velocity, and minority carrier diffusion constant, respectively. The letters _h and _e represent holes in the n layer and electrons in the p layer, respectively, x _j and W are the end of the depletion layer and the thickness of the depletion layer, and H and H ′ are the end of the depletion layer. Dimensions.
In the above configuration, it is further preferable to obtain an output short-circuit current at the time of reference sunlight irradiation from the absolute spectral sensitivity curve of the solar cell obtained in the second step.
In the above configuration, in the first step, it is preferable to obtain the absolute spectral sensitivity for each wavelength of each light by using a plurality of LEDs that emit light in the short wavelength band, medium wavelength band, and long wavelength band, respectively.
In the above configuration, it is preferable to obtain an output short-circuit current of the solar cell by modulating each color in the first step.
In the above configuration, in step D, it is preferably carried out using a partial differential derivative with respect to the hole current I _h and L _e of the n layer .delta.I _h / delta] S _h and δI _e / δL _e.
The said structure WHEREIN: It is preferable that a solar cell is a solar cell using the crystal | crystallization or amorphous which consists of Si or a compound semiconductor.

According to this configuration, the solar cell is irradiated with multi-wavelength LED light, and the solar light is output from the irradiation light intensity (W) for each wavelength of the multi-wavelength LED and the output short-circuit current (A) of the solar cell for each wavelength. The absolute spectral sensitivity (A / W) of the battery can be measured.
Further, by performing fitting calculation using the absolute spectral sensitivity of the solar cell, the absolute spectral sensitivity curve of the solar cell can be accurately obtained in a short time.
Furthermore, the output short circuit current at the time of reference sunlight irradiation can be calculated from the absolute spectral sensitivity curve of the solar cell.

ここで、Ｉ_SCは太陽電池の出力短絡電流、Ｉ_hはｎ層の正孔電流、Ｉ_drは空乏層中の電流、Ｉ_eはｐ層の電子電流であり、下記（式１）（式２）（式３）を満たす。

ただし、αは吸収係数であり、Ｌ_h ，Ｌ_e とＳ_h ，Ｓ_e とＤ_h ，Ｄ_e は、それぞれ、少数キャリアの拡散長、表面再結合速度、少数キャリアの拡散定数であり、添え字の_h と_e はそれぞれｎ層中における正孔とｐ層中の電子を示し、ｘ_j 、Ｗは空乏層の端、空乏層の厚さであり、Ｈ、Ｈ'は、空乏層末端の寸法である。
上記構成において、信号処理部は、得られた絶対分光感度曲線と基準太陽光放射照度分布との積を波長で積分して基準太陽光照射時の出力短絡電流を算出することが好ましい。
上記構成において、複数のＬＥＤとしてそれぞれ短波長帯、中波長帯及び長波長帯の光を発光するＬＥＤが配設されていることが好ましい。
上記構成において、ＬＥＤ発光部は、ＬＥＤ発光部は、正多角形の各頂点に各色のＬＥＤが配置されるブロックから成り、ブロックが複数配置されて所定の形状に構成されていることが好ましい。
上記構成において、ＬＥＤ発光部は正四角形のブロックが複数配置されて成り、各ブロックの各頂点に異なる色のＬＥＤが配設されていることが好ましい。
上記構成において、ＬＥＤ発光部は正六角形のブロックが複数配置され成り、各ブロックの各頂点に異なる色のＬＥＤが配設されていることが好ましい。
A solar cell evaluation apparatus using an LED according to the present invention is a sample holder on which an LED light emitting unit having a plurality of LEDs emitting discrete and different wavelengths of light, an LED driving unit, and a solar cell having a pin structure are placed. And a signal processing unit, and the LED light emitting unit is arranged to face the solar cell on the sample holder at a predetermined distance, and the signal processing unit controls the LED driving unit to change the light emitting unit to the solar cell. Each LED is made to emit light, the short-circuit current generated in the solar cell is input as a short-circuit current signal, the absolute spectral sensitivity of the solar cell for each wavelength is calculated, the program for obtaining the absolute spectral sensitivity curve is executed, and the wavelength is A formula that gives the current of a solar cell based on the absolute spectral sensitivity value of each solar cell, and is derived from the equation of continuity of minority carriers in a semiconductor. The absolute spectral sensitivity curve by performing the calculation, by the signal processing unit sets the surface reflectance R as a parameter, the surface recombination velocity S _h of the solar cell, the initial value of the minority carrier diffusion length L _e, absolute a step a of finding a spectral sensitivity curve by fitting calculation using data of the measuring wavelengths, including the short wavelength side among the values of the absolute spectral sensitivity for each wavelength, rough approximation of the surface recombination velocity S _h of the solar cell with seek, a step B of determining a correction value from the initial value of the absolute spectral sensitivity surface reflectance provides the curve R and the minority carrier diffusion length L _e, measured including the longer wavelength side of the value of the absolute spectral sensitivity for each wavelength the fitting calculation using data of wavelength, together with obtaining a rough approximation of the minority carrier diffusion length L _e of the solar cell, the surface reflectance R and surface recombination gives an absolute spectral sensitivity curve A step C for obtaining the correction value from the initial value of the speed S _h, further steps B, and using a rough approximation and correction values of the parameters calculated in step C, the surface reflectance R, surface recombination of the solar cell Step S for _obtaining the optimum value of the speed S _h and the minority carrier diffusion length Le is executed by the above program.

Here, I _SC is the output short-circuit current of the solar cell, I _h is the hole current of the n layer, I _dr is the current in the depletion layer, I _e is the electron current of the p layer, and the following (formula 1) (formula 2) (Equation 3) is satisfied.

Where α is an absorption coefficient, L _h , _Le and S _h , _Se and D _h , and D _e are the minority carrier diffusion length, surface recombination velocity, and minority carrier diffusion constant, respectively. The letters _h and _e represent holes in the n layer and electrons in the p layer, respectively, x _j and W are the end of the depletion layer and the thickness of the depletion layer, and H and H ′ are the end of the depletion layer. Dimensions.
In the above configuration, it is preferable that the signal processing unit calculates the output short-circuit current at the time of reference sunlight irradiation by integrating the product of the obtained absolute spectral sensitivity curve and the reference sunlight irradiance distribution with the wavelength.
In the above configuration, it is preferable that LEDs that emit light in a short wavelength band, a medium wavelength band, and a long wavelength band are disposed as the plurality of LEDs.
In the above configuration, it is preferable that the LED light emitting unit is composed of a block in which LEDs of each color are arranged at each vertex of a regular polygon, and a plurality of blocks are arranged to have a predetermined shape.
In the above configuration, it is preferable that the LED light emitting section is formed by arranging a plurality of regular square blocks, and LEDs of different colors are arranged at each vertex of each block.
In the above configuration, it is preferable that the LED light emitting section is formed by arranging a plurality of regular hexagonal blocks, and LEDs of different colors are arranged at the vertices of each block.

  According to the above configuration, the output short-circuit current of the solar cell can be measured by irradiation with a plurality of LED lights, and the absolute spectral sensitivity, the absolute spectral sensitivity curve, the absolute spectral sensitivity curve, etc. of the solar cell can be measured in a short time. it can. Thereby, various measurements, such as the absolute spectral sensitivity of the solar cell which conventionally required the measurement time and cost, can be performed in a short time and at low cost.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, a solar cell evaluation method using the LED according to the first embodiment of the present invention will be described.
FIG. 1 is a diagram showing a schematic configuration of a measurement system used in a solar cell evaluation method using the LED of the present invention. As shown in FIG. 1, the LED light emitting unit 2 irradiates light to the solar cell 4 to be measured. Here, the LED light emitting unit 2 has a plurality of wavelengths among the wavelengths included in sunlight, that is, a plurality of LEDs having a plurality of colors, faces the solar cell 4 at a predetermined distance, and has no uneven illuminance. Are arranged as follows. Here, the solar cell 4 may be a solar cell module in which a plurality of unit solar cells are connected.

FIG. 2 is a flowchart showing an absolute spectral sensitivity measurement of a solar cell using the measurement system of FIG. 1 and a procedure for obtaining an absolute spectral sensitivity curve from the measurement in the solar cell evaluation method using the LED of the present invention. FIG.
First, in step ST1, a plurality of LEDs having a plurality of colors are caused to emit light for each color, and the output short-circuit current I _SC (A) of the solar cell is measured. If the illuminance of each LED on the surface of the solar cell at this time, that is, the irradiation power (W) is measured in advance, the absolute spectrum for each LED color is calculated from the ratio of the output short-circuit current I _SC of the solar cell and the illuminance of each LED. Sensitivity (A / W) is obtained.
Here, since the irradiation light from the LED light emitting unit is irradiation of a discrete bright line spectrum unlike the reference sunlight, a plurality of LED emission colors are used in order to approximate the sunlight. For example, blue (short wavelength band), red (medium wavelength band), infrared (long wavelength band), and white (wide wavelength band) can be used as the emission color of these LEDs.
In addition, as described later, the light emission of each color from the LED is modulated for each certain color except white, and the other LEDs emit light, that is, when irradiated as bias light, The absolute spectral sensitivity for each color except for may be measured.

Next, in step ST2, the absolute spectral sensitivity curve of the solar cell is obtained from the absolute spectral sensitivity value of each color LED by fitting calculation described later.
Thus, in the solar cell evaluation method using the LED of the present invention, an absolute spectral sensitivity curve of the solar cell can be obtained.

Next, the measurement of absolute spectral sensitivity in step ST1 will be described in detail.
FIG. 3 is a flowchart showing a procedure for measuring the absolute spectral sensitivity of each LED irradiated to the solar cell in step ST1 in the evaluation method shown in FIG. 2 for the solar cell using the LED of the present invention. .
Here, the description will be made assuming that the emission colors of the LEDs are, for example, a plurality of n colors including four colors of infrared, red, blue, and white.
First, in step ST10, all the LEDs of each color of the LED light emitting section are made to emit light, and in step ST11, any one color LED except white is subjected to amplitude modulation (AM modulation), and an output short circuit of the solar cell by this modulation signal. The current I _SC (A) is measured. Here, out of the light emission of all LEDs, the light other than the modulated light is irradiated as bias light to bring the solar cell into an operating state.
Next, in step ST12, the absolute spectral sensitivity (A / W) of this irradiation wavelength from the output short-circuit current I _SC (A) of the solar cell with respect to the irradiation power (W) of the LED of any one color except white is applied to the solar cell. ).

  Next, in step ST13, it is determined whether or not all modulation signals of (n-1) colors excluding the white light emission color have been measured. If it is determined in step ST13 that the (n-1) color is not measured, the process returns to step ST11, the measurement of each color other than white is continued, and the absolute spectral sensitivity of each irradiation wavelength is calculated.

On the other hand, when it is determined in step ST13 that all modulation signals of (n-1) colors excluding white have been measured, the absolute spectral sensitivity measurement for each color is completed in step ST14.
In this way, in the solar cell evaluation method using the LED of the present invention, a plurality of different colors of LED irradiation, that is, a plurality of wavelengths, are measured with modulation for each color except white, thereby Absolute spectral sensitivity can be measured with high sensitivity and high accuracy.

Next, a method for obtaining an absolute spectral sensitivity curve based on the discrete absolute spectral sensitivity obtained by the above measurement will be described.
Here, it is assumed that the solar cell to be measured has a pin structure and the light receiving surface is an n layer.
The theoretical formula of the spectral sensitivity of the solar cell uses a model formula derived from the equation of semiconductor minority carrier continuity shown in the following formulas (1) to (3) (Makoto Konagai, “Semiconductor physical properties”, 1992, (See Shufukan, pp. 239-241).

I _h in Formula (1), I _dr in Formula (2), and I _{e in} Formula (3) indicate the hole current in the n layer, the current during depletion, and the electron current in the p layer, respectively. The sum of these formulas (1) to (3) is the formula (4) of the output short-circuit current I _SC of the solar cell.
In the above formula, alpha is the absorption coefficient, R is the surface reflectance, and L _h, L _e and _{S h, S e, D h} , D e , respectively, the diffusion length of minority carriers, surface recombination Velocity, minority carrier diffusion constant.
Here, the subscripts _h and _e indicate holes in the n layer and electrons in the p layer, respectively. X _j , W, H, and H ′ are the dimensions of the end of the depletion layer, the thickness of the depletion layer, and the end of the depletion layer, respectively.

FIG. 4 is a table showing variables (parameters), value ranges, units, and classifications of solar cells using crystalline Si. The parameters are classified into group A and group B according to the degree of influence on the spectral sensitivity curve, and the value range is based on the general value of crystalline Si (“Semiconductors And Semi-Metals Vol.11” by HJ Hovel) , 1975, Academic Press, p.26).
The parameter A group is a constant related to the material, and is a specific value depending on the type of solar cell, and the group B is a variable depending on individual differences in the same type of cells. In the A group, the absorption coefficient α is a wavelength-dependent value, and indicates that the shorter the wavelength, the easier the absorption.
In addition, for the number of incident photons I ₀ , the energy of one photon is expressed by E (eV) = 1239.5 / λ (nm), so that it can be seen that the longer the wavelength, the less the energy of the photon. These two parameters are functions depending on the wavelength, and are the parts that characterize the spectral sensitivity waveform.

As the parameter B, fig. 5 to FIG. And the surface reflectance R for determining the number of incident photons, and the surface recombination velocity S _h in the n layer, the effect in which the minority carrier diffusion length L _e in p layer on the output short-circuit current I _SC 7 shows. In the figure, the vertical axis represents absolute spectral sensitivity and the horizontal axis represents wavelength, and this data represents an absolute spectral sensitivity curve. As indicated by the arrows in the figure, each variable, that is, a parameter has a highly dependent wavelength band.
Here, as shown in FIGS. 5 to 7, the output short-circuit current I _SC of the short wavelength side and the long wavelength side of the solar cell is greater in the surface recombination velocity S _h and the minority carrier diffusion length L _e of each solar cell Influence, ie dependent. Since the absolute spectral sensitivity curve as a whole depends on the surface reflectance R of the solar cell, the dependence thereof may be examined using a wavelength band that is the center of spectral sensitivity. In this case, purple to blue, infrared, and red can be used as the emission colors of the LEDs that match the short wavelength, the long wavelength, and the wavelength that is the center of the spectral sensitivity, respectively. White light can be used as bias light.
Now, the surface recombination velocity S _h in the above formula (1) as a parameter minority carrier diffusion length L _e in (3), also with R, consistent with absolute spectral sensitivity obtained from the measured And fitting calculation of the absolute spectral sensitivity curve can be performed.

FIG. 8 is a flowchart showing a fitting calculation method for obtaining an absolute spectral sensitivity curve of a solar cell from discrete absolute spectral sensitivity in an evaluation method of a solar cell using LEDs.
First, in step ST20, R, enter the ideal parameter as an initial value of S _h, L _e, calculates the ideal absolute spectral sensitivity curve. Here, since the entire absolute spectral sensitivity curve depends on the surface reflectance R of the solar cell, the dependence thereof may be calculated using the wavelength band that is the center of the spectral sensitivity.
Next, in step ST21, it is determined whether or not the ideal absolute spectral sensitivity curve is within an allowable range as compared with the discrete absolute spectral sensitivity obtained by measurement. If it is determined in step ST21 that the obtained absolute spectral sensitivity curve is not valid, the process returns to step ST20 and the calculation is performed again. At this time, among the parameters in FIG. 3, A may be reviewed.

On the other hand, when it is determined in step S21 that the initial calculation is appropriate, the process proceeds to step ST22. We use in measuring wavelengths including short wavelength side to influence the surface recombination velocity S _h of the measured solar cell, the data of the absolute spectral sensitivity using LED of the solar cell, fitting calculation by the least square method I do. Thus, a rough approximation of S _h, R, which is modified from the initial _value, Le is obtained.

Next, in step ST23, using the measured wavelengths, including the long wavelength side that affect diffusion length L _e of the minority carriers of the measured solar cell, the data of the absolute spectral sensitivity using LED of the solar cell, the minimum Fitting calculation is performed by the square method. Thus, a rough approximation of L _e, R, which is modified from the initial _value, S _h is obtained.
In step ST22 and step ST23 of the above, it is possible to obtain _R which is modified from the initial value, S _h, and L _e, a rough absolute spectral sensitivity curve.

Next, in step ST24, R obtained in the above ST22 and ST23, by using the S _h, L _e, determine the optimum value by the nonlinear least squares method, performs fitting calculation of absolute spectral sensitivity curve. At this time, calculation of the nonlinear least squares method, convergence is likely deteriorated by particular S _h varies exponentially. For this, I _h and L _e about partial differential derivative _{(∂I h / ∂S h, ∂I} e / ∂L e) of formula (1) and (3) With the convergence good fit Calculations can be made. Note that R is a proportional coefficient in the equations of photocurrents of formulas (1) to (3), and the partial differential derivative is 1, so that the fitting calculation using the partial differential derivative can be omitted. .

  Subsequently, in step ST25, it is determined whether or not the obtained absolute spectral sensitivity curve is valid. When it is determined in step ST25 that the obtained absolute spectral sensitivity curve is not valid, the process returns to step ST22 and the calculation is performed again.

  On the other hand, when it is determined in step S25 that the fitting calculation is appropriate, an absolute spectral sensitivity curve of the solar cell to be measured is obtained in step ST26. In the determination of the fitting calculation, an absolute spectral sensitivity curve of the solar cell to be measured measured by an absolute spectral sensitivity curve measuring apparatus using a solar simulator can be used as calibration data.

In this way, in the solar cell evaluation method using the LED of the present invention, a photocurrent model equation is obtained by using a plurality of different colors of LED irradiation, that is, measured absolute spectral sensitivity of the solar cell at a plurality of wavelengths. By performing the fitting calculation, the absolute spectral sensitivity curve of the solar cell to be measured can be obtained.
In addition, although the photocurrent of the solar cell has been described with the Si pin structure, the fitting for obtaining an absolute spectral sensitivity curve by using an appropriate model formula also for solar cells using other compound semiconductors and solar cells having other structures. Calculations can be made. Parameters when performing the fitting calculation, R, S _h, shows the case of L _e, may be added that the S _e and L _p and the like.

Next, a calculation method for obtaining the output short-circuit current I _SC at the time of reference sunlight irradiation from the absolute spectral sensitivity curve of the solar cell will be described.
FIG. 9 is a calculation flow chart for obtaining the output short-circuit current I _SC at the time of reference solar light irradiation from the absolute spectral sensitivity curve of the solar cell in the solar cell evaluation method using the LED of the present invention. In the figure, in the same manner as described with reference to FIG. 8, in step ST20 to step ST24, calculation for obtaining an absolute spectral sensitivity curve of the solar cell is performed, and in step ST30, calculation of the output short-circuit current I _SC at the time of reference sunlight irradiation. Enter whether or not to perform.
And in step ST30, when not calculating the output short circuit current I _SC at the time of reference sunlight irradiation, the process ends in step ST25. On the other hand, if it is input in step S30 that the output short-circuit current I _SC at the time of reference sunlight irradiation is calculated, in step ST31, the output short-circuit current I at the time of reference sunlight irradiation of the solar cell to be measured. Calculate the _SC .

ここで、Ｑ（λ）（Ａ／Ｗｎｍ）、Ｅ_Ref （λ）（Ｗ／ｍ² ｎｍ）、λ（ｎｍ）、Ａ（ｍ² ）は、それぞれ、被測定太陽電池の絶対分光感度曲線、基準太陽光分光放射強度曲線、波長、被測定太陽電池の面積である。
このようにして、本発明のＬＥＤを用いた太陽電池の評価方法において、ＬＥＤ照射の複数の異なる色、即ち複数波長において測定した太陽電池の絶対分光感度から絶対分光感度曲線を得て、さらに、基準太陽光照射時の被測定太陽電池の出力短絡電流Ｉ_SCの計算を短時間で得ることができる。
At this time, the output short-circuit current I _SC at the time of reference solar light irradiation of the solar cell to be measured is the absolute spectral sensitivity curve of the solar cell to be measured and the reference solar spectral radiation intensity curve as shown in the following formula (5). It is obtained by integrating the product in the wavelength region.

Here, Q (λ) (A / Wnm), E _Ref (λ) (W / m ² nm), λ (nm), and A (m ² ) are respectively the absolute spectral sensitivity curves of the solar cells to be measured, Reference solar spectrum radiant intensity curve, wavelength, area of solar cell to be measured.
In this way, in the solar cell evaluation method using the LED of the present invention, the absolute spectral sensitivity curve is obtained from the absolute spectral sensitivity of the solar cell measured at a plurality of different colors of LED irradiation, that is, at a plurality of wavelengths, Calculation of the output short-circuit current I _SC of the solar cell to be measured at the time of reference sunlight irradiation can be obtained in a short time.

Next, a calculation example of the absolute spectral sensitivity curve by the solar cell evaluation method using the LED of the present invention described above will be described.
(Calculation Example 1)
FIG. 10 is a relative spectral sensitivity curve of a solar cell made of Si crystal (c-Si) used for calculation. In the figure, the vertical axis represents relative spectral sensitivity, and the horizontal axis represents wavelength (nm). As shown in the figure, the spectral sensitivity is measured at a plurality of wavelengths from 400 nm to 1100 nm. In calculating, the relative spectral sensitivity curve was converted to an absolute spectral sensitivity curve.

FIG. 11 is an absolute spectral sensitivity curve obtained by calculation from the data of the Si solar cell of FIG. In the figure, the vertical axis represents absolute spectral sensitivity (A / W), and the horizontal axis represents wavelength (nm). Assuming that absolute spectral sensitivity by LED is measured in blue (460 nm), green (570 nm), and infrared of two wavelengths (800 nm and 1000 nm) (+ in the figure), the absolute spectral sensitivity curve from the absolute spectral sensitivity of these four points It is the result of having performed fitting calculation of (thick line part).
Thus, it can be seen that the absolute spectral sensitivity curve can be fitted and calculated with higher accuracy than the absolute spectral sensitivity of the four wavelengths.

(Calculation Example 2)
FIG. 12 is a relative spectral sensitivity curve of a solar cell made of crystalline Si (c-Si) used for calculation. In the figure, the left vertical axis represents relative spectral sensitivity, and the horizontal axis represents wavelength (nm). In calculating, the relative spectral sensitivity curve was converted to an absolute spectral sensitivity curve.
FIG. 13 is an absolute spectral sensitivity curve obtained by calculation from the data of the a-Si solar cell of FIG. In the figure, the vertical axis represents absolute spectral sensitivity (A / W), and the horizontal axis represents wavelength (nm). This is a result of fitting calculation of the absolute spectral sensitivity curve (bold line portion) from the absolute spectral sensitivity at the four wavelengths, assuming that the absolute spectral sensitivity by the LED is measured at the same wavelength as that in FIG.
Thus, it can be seen that the absolute spectral sensitivity curve can be fitted and calculated with higher accuracy than the absolute spectral sensitivity of the four wavelengths.

(Calculation Example 3)
Next, calculation results in consideration of the influence of the light emission wavelength of the LED will be described.
When the absolute spectral sensitivity curve is calculated from the output short-circuit current I _SC of the solar cell to be measured, the fitting calculation using partial differential derivatives (微分 I _h / ∂S _h , ∂I _e / ∂L _e ) is performed. And the convergence of the calculation becomes faster. At this time, these partial differential derivatives further vary greatly depending on the irradiation wavelength.
14 and 15 are diagrams to calculate their size S _h and L _e and the wavelength dependence of the partial differential derivative ∂I _h / .differential.S _h and ∂I _e / ∂L _e. As shown in FIG. 14, ∂I _h / ∂S _h is greater in the vicinity of a wavelength lambda = 350 nm. From this, it can be seen that it is preferable to use an LED having a wavelength around 350 nm as the wavelength on the short wavelength side, which is greatly influenced by the surface recombination rate in the output short-circuit current I _SC of the solar cell. Further, as shown in FIG. 15, ∂I _h / ∂L _e increases near the wavelength λ = 800 nm. From this, it can be seen that it is preferable to use an LED having a wavelength in the vicinity of 800 nm as the wavelength on the long wavelength side where the influence of the minority carrier diffusion length in the output short-circuit current I _SC of the solar cell is large.

Due to the above wavelength dependence, the relative spectrum of the c-Si solar cell in FIG. 12 is used using four wavelengths of 350 nm (purple), 460 nm (blue), 640 nm (orange), and 800 nm (infrared) as the wavelength of the LED. Fitting calculation for obtaining an absolute spectral sensitivity curve was performed from the sensitivity curve data.
FIG. 16 is a graph of an absolute spectral sensitivity curve obtained by calculation from the value of the absolute spectral sensitivity of the four wavelengths whose wavelengths are optimized using the data of the c-Si solar cell of FIG. In the figure, the vertical axis represents absolute spectral sensitivity (A / W), and the horizontal axis represents wavelength (nm).
This is a result of fitting calculation of an absolute spectral sensitivity curve (thick line portion) from absolute spectral sensitivity at these four wavelengths, assuming that the absolute spectral sensitivity of the LED is measured at the above wavelength (+ mark in the figure). From the figure, it can be seen that the measured value and the fitting calculation are in good agreement.
Thus, in the L _e and S _h by the wavelength of the high impact long wavelength side and the short wavelength side to the output short-circuit current I _SC of the Si solar cell, partial differential derivative ∂I _h / .differential.S _h and ∂I _e / If absolute spectral sensitivity is obtained at multiple wavelengths including at least a wavelength at which ∂L _e increases, fitting calculation of the absolute spectral sensitivity curve can be obtained with better convergence.

Next, 2nd Embodiment which concerns on the evaluation apparatus of the solar cell using LED of this invention is shown.
FIG. 17 is a block diagram schematically showing a configuration of a solar cell evaluation apparatus using LEDs according to the second embodiment of the present invention. A solar cell evaluation apparatus 1 using an LED includes an LED light emitting unit 2, an LED driving unit 3, a sample holder 9 on which a solar cell 4 to be measured is placed, and a signal processing unit 5. The LED light emitting unit 2 includes a plurality of LEDs having a plurality of wavelengths among wavelengths included in sunlight, that is, a plurality of colors, and is disposed so as to face the measured solar cell 4 at a predetermined distance. .

  The LED driving unit 3 is controlled by the signal processing unit 5 to supply a voltage and a current necessary for light emission to the LEDs of the respective colors of the LED light emitting unit 2, and can apply a modulation signal in a superimposed manner as necessary. Here, the voltage and current supplied to the LED (hereinafter simply referred to as drive current) may be direct current or pulse. As the modulation method, AM modulation, pulse modulation, or the like can be used. The LED driving unit 3 outputs an LED driving current for each color of the LED light emitting unit 2 to the signal processing unit 5 as an output signal 6. Here, the LED driving current is measured by measuring the relationship between the LED driving current for each color of the LED light emitting unit 2 and the irradiation power (W) to the solar cell 4 to be measured, the so-called IL characteristic, in advance. The irradiation power to the solar cell is known from the value.

When the measured solar cell 4 is irradiated with LED light from the LED light emitting unit 2 to the measured solar cell 4, a short-circuit current I _SC is generated in the measured solar cell 4 and is output as a short-circuit current signal 7 to the evaluation device computer. Is done.

  The signal processing unit 5 demodulates a DC current or a modulation signal from a computer such as a personal computer, an output signal 6 from the LED driving unit 3 and a short-circuit current signal 7 generated in the solar cell 4 to be measured, and converts it into a current value. Interface circuit 8 and the like.

FIG. 18 is a time chart showing an operation when measuring the absolute spectral sensitivity in the solar cell evaluation apparatus 1. The time chart of FIG. 18 is a case where the LED light emission part demonstrated in FIG. 17 consists of four colors including white. The horizontal axis is the time axis t, and the vertical axis is the drive current of each color LED of the LED light emitting section and the output short-circuit current of the solar cell to be measured. 18A to 18D show drive currents from LED1 to LED4, and LED4 is white. (E) is the output short-circuit current I _SC of the solar cell to be measured.
As shown at time t1 in FIG. 18, AM modulation is applied to the LED 1 shown in (a), and the other LEDs 2 to 4 shown in (b) to (c) are driven by a direct current. . At this time, the output short-circuit current of the solar cell to be measured is the output short-circuit current component obtained by demodulating the AM modulation of the LED 1 above the dotted line, and the output short-circuit current component by the LEDs 2 to LED 4 is below the dotted line.
Thus, by measuring each color except the white color of the LED, the output short circuit current of the solar cell can be measured with high sensitivity and at high speed.

At this time, the signal processing unit 5 calculates the absolute spectral sensitivity of the solar cell at the wavelength of the LED 1 from the drive current and irradiation power intensity of the LED 1 stored in the memory in advance and the output short-circuit current component of the solar cell due to AM modulation of the LED 1. It is calculated and stored in the memory of the signal processing unit, and is output to a display device or a printer.
Similarly, after obtaining the absolute spectral sensitivity of the wavelength of the LED 1, AM modulation is applied to the LED 2 of (b) at t 2 after elapse of time ts, and the other (a), (c), LED1, LED3, and LED4 shown in (d) are driven by a direct current, and the absolute spectral sensitivity of the solar cell at the wavelength of LED2 is obtained from the output short-circuit current of LED2 at the output short-circuit current of the solar cell to be measured at that time. Further, the absolute spectral sensitivity of the solar cell at the wavelength of the LED 3 is measured at time t3.

Next, a program for obtaining an absolute spectral sensitivity curve by the solar cell evaluation method using the LED of the present invention is executed in the signal processing unit, so that the measured solar cell is obtained from the absolute spectral sensitivity obtained in the above measurement. The absolute spectral sensitivity curve is fitted and calculated.
Further, an integral calculation regarding the wavelength of the product of the obtained absolute spectral sensitivity curve and the reference solar irradiance distribution by IEC is executed in the signal processing unit, so that the reference solar radiation of the solar cell to be measured is obtained. The absolute spectral sensitivity curve by is calculated. Here, each parameter of the solar cell to be measured, an absolute spectral sensitivity curve for calibration previously measured by a solar simulator, and a standard solar irradiance distribution (IEC904-3 _, “Measurement principles for terrestrial photovoltaic (PV) by IEC) "Solar devices with reference spectral irradiance data") may be stored in advance in memory.

Next, since it is necessary for the LED light emitting unit to perform uniform light irradiation without uneven illuminance on the solar cell to be measured, the configuration will be described in more detail.
FIG. 19 is a plan view schematically showing the arrangement of the LEDs of the LED light emitting section when four colors of LEDs are used. The LED light emitting unit 2 shown in FIG. 19 includes a plurality of square blocks 2a each having a side L1 indicated by a dotted line in the drawing (this arrangement is referred to as a square arrangement). The outer shape of the LED light emitting unit 2 is a square having a side L2. Here, LEDs 11a, 11b, 11c, and 11d of four colors are arranged at each vertex of the block 2a.

  FIG. 20 is a plan view schematically showing the arrangement of the LEDs of the LED light emitting section when six colors of LEDs are used. The LED light emitting unit 2 shown in FIG. 20 includes a plurality of regular hexagonal blocks 2b each having a L3 side indicated by a dotted line in the drawing. The outer shape of the LED light emitting unit 2 is a square having a side L4. Here, six colors of LEDs 11e, 11f, 11g, 11h, 11i, and 11j are arranged at each vertex of the block 2b.

  In the above example, the case where the LED blocks are regular squares and regular hexagons is shown, but the LED blocks may be regular polygons in order to make the arrangement of the respective colors uniform. Moreover, infrared, red, orange, yellow, green, blue, purple, white, etc. can be used for the color of LED. At this time, since the LED can be approximated as a point light source, the illuminance on the surface of the solar cell to be measured changes in inverse proportion to the square of the distance to the LED light emitting unit, and the half-value width angle (front) of the light distribution curve. The dimensions L1 to L4 of the LED light emitting unit 2 may be determined in consideration of the angle at which the light intensity in the direction is half the power with respect to the central axis. For example, a chip type LED having a relatively wide angle giving a half width and a wide directivity angle may be used. By arrange | positioning in this way, since the number of each color LED is the same and arrange | positioned at equal intervals, the irradiation light intensity to a to-be-measured solar cell can be made uniform.

FIGS. 21 to 23 are tables and diagrams showing the results of calculating the illuminance unevenness on the solar cell to be measured by the LED light emitting unit of FIGS. 19 and 20.
FIG. 21 is a table showing the external dimensions of the LED light emitting unit 2 and the number of LEDs used per color. As shown in FIG. 21, when one side of the outer shape of the LED light emitting unit 2 is changed from 130 mm to 170 mm at intervals of 10 mm, the number of LEDs used per color in the square arrangement is 289 to 484. In addition, the number of LEDs used per color in the hexagonal arrangement is 133 to 243. Here, L1 and L3 which are the arrangement | positioning intervals of each LED are 4 mm.

22 and 23 are diagrams showing the results of calculating the illuminance unevenness to the measured element of the LED light emitting unit in the square arrangement and the hexagonal arrangement, respectively. In the figure, the vertical axis represents illuminance unevenness (%), and the horizontal axis represents the distance between the LED light emitting unit and the element to be measured, that is, the irradiation height (mm). Here, the irradiation unevenness was calculated by approximating the LED with a point light source, the illuminance being inversely proportional to the square of the distance from the point light source, and the directivity angle being 120 °. Moreover, the irradiation area to a to-be-measured element was 100 mm x 100 mm.
In the case of the square arrangement shown in FIG. 22, the illuminance unevenness decreases as the irradiation height is 11 mm to 17 mm and the area of the LED light emitting portion increases from 150 mm × 150 mm to 170 mm × 170 mm. The irradiation height at which the minimum illuminance unevenness is obtained varies depending on the area of the LED light emitting unit. When the area of the LED light emitting part is 160 mm × 160 mm and 170 mm × 170 mm, it can be seen that the illuminance unevenness is 5% or less.

  In the case of the hexagonal arrangement shown in FIG. 23, the illuminance unevenness decreases as the area of the LED light emitting portion increases from 150 mm × 150 mm to 170 mm × 170 mm, but the irradiation height at which the minimum value of the illuminance unevenness is obtained is shown in FIG. It turns out that it becomes 8 mm-12 mm lower than the square arrangement shown. When the area of the LED light emitting part is 150 mm × 150 mm and 160 mm × 160 mm, it can be seen that the illuminance unevenness is 5% or less.

Irradiation intensity of the above LED light-emitting section is about 10 mW / cm ² for continuous operation, is about 100 mW / cm ² at pulsed operation. In this way, the LED light-emitting part has a standard B of illuminance unevenness within 5%, which is a JIS standard of a solar simulator, by selecting an appropriate LED light-emitting part area and irradiation height with respect to the irradiation area to the element to be measured. Can be expected to be in the range.

The solar cell evaluation method and the evaluation apparatus using the LED of the present invention can be used for the following applications, for example.
When manufacturing solar cells, assuming that solar cells in the same lot have the same absolute spectral sensitivity, one representative solar cell is determined by the solar cell evaluation method using the LED of the present invention. Spectral sensitivity measurement is performed, and the output short circuit current I _SC of the solar cell to be measured at the time of reference sunlight irradiation is calculated. Other solar cells in the same lot irradiate light with a known spectral distribution, so that the absolute spectral sensitivity curve between the same lot and the output short-circuit current I _SC of the solar cell to be measured during reference solar irradiation Variations can be estimated in a short time.
In the solar cell evaluation apparatus using the LED of the present invention, each LED of the LED light-emitting unit can be controlled by current drive, so that the area that can be irradiated by the LED light-emitting unit is changed and the absolute spectral sensitivity for each minute region of the solar cell. Can be measured. Thereby, the measurement of the defective part of a solar cell, etc. can be performed in a short time.
Moreover, since the evaluation apparatus of the solar cell using LED of this invention is small and light, it can be used also in the installation place of an outdoor solar cell. Thereby, it can be easily used for on-site maintenance work of facilities where solar simulators could not be used conventionally, such as solar cell power plants.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Needless to say, the model formula and fitting calculation for obtaining the absolute spectral sensitivity curve from the absolute spectral sensitivity obtained by the irradiation of the LED can appropriately use an appropriate model formula or convergence calculation method according to the solar cell to be measured.

Effect of the invention

As understood from the above description, according to the present invention, by irradiating a solar cell or the like with an LED having a plurality of emission wavelengths, the absolute spectral sensitivity of the solar cell, the absolute spectral sensitivity curve, the reference of the solar cell to be measured The output short circuit current at the time of sunlight irradiation can be obtained in a short time.
Therefore, if the present invention is applied to the inspection after the manufacture of the current solar cell, the solar cell can be evaluated in a short time and at a low cost. Moreover, since the evaluation apparatus of this invention is small and light, it can be used also for the measurement and test | inspection of the solar cell installed outdoors.

  It is a figure which shows schematic structure of the measurement system used in the evaluation method of the solar cell using LED of this invention.   In the solar cell evaluation method using LED of this invention, it is a flowchart which shows the procedure for obtaining an absolute spectral sensitivity curve from the absolute spectral sensitivity measurement of a solar cell using the measurement system of FIG. 1, and the measurement.   In the evaluation method shown in FIG. 2 of the solar cell using the LED of the present invention, in step ST1, it is a flowchart showing a procedure for measuring the absolute spectral sensitivity for each LED irradiated to the solar cell.   It is a table | surface which shows the variable (parameter) of a solar cell using crystalline Si, a value range, a unit, and classification. Surface reflectance R for determining the number of incident photons is a diagram showing the effect on the output short-circuit current I _SC of the solar cell. surface recombination velocity S _h in the n layer is a diagram showing the effect on the output short-circuit current I _SC of the solar cell. minority carrier diffusion length L _e in p layer is a diagram showing the effect on the output short-circuit current I _SC of the solar cell.   In the solar cell evaluation method using LED of this invention, it is a flowchart which shows the method of the fitting calculation which calculates | requires the absolute spectral sensitivity curve of a to-be-measured solar cell from discrete absolute spectral sensitivity. In the evaluation method of the solar cell using the LED of the present invention, the absolute spectral sensitivity curve of the solar cell, a flow diagram of a calculation for obtaining the output short-circuit current I _SC during standard sunlight irradiation.   It is a figure which shows the relative spectral sensitivity curve of the solar cell by the Si crystal used for calculation.   It is a figure which shows the absolute spectral sensitivity curve calculated | required by calculation from the data of the Si solar cell of FIG.   It is a figure which shows the relative spectral sensitivity curve of the solar cell by crystal system Si (c-Si) used for calculation.   It is a figure which shows the absolute spectral sensitivity curve calculated | required by calculation from the data of the c-Si solar cell of FIG. Is a diagram showing the dependence of the calculation result of S _h and the wavelength for partial differential derivative ∂I _h / ∂S _h. It is a diagram showing the dependence of the calculation result between L _e and wavelength for partial differential derivative ∂I _e / ∂L _e.   It is a figure which shows the absolute spectral sensitivity curve calculated | required from the value of the absolute spectral sensitivity of 4 wavelengths which optimized the wavelength using the data of the c-Si solar cell of FIG.   It is a block diagram which shows typically the structure of the evaluation apparatus of the solar cell using LED by 2nd Embodiment which concerns on this invention.   It is a time chart which shows operation | movement when measuring the absolute spectral sensitivity in the evaluation apparatus of the solar cell using LED.   It is a top view which shows typically arrangement | positioning of LED of the LED light emission part when four colors of LED are used.   It is a top view which shows typically LED arrangement | positioning of the LED light emission part when six colors of LED are used.   It is a table | surface which shows the external dimension of a LED light emission part, and the number of use LED per color.   It is a figure which shows the result of having calculated the illumination intensity nonuniformity to the to-be-measured element of the LED light emission part in square arrangement | positioning.   It is a figure which shows the result of having calculated the illumination intensity nonuniformity to the to-be-measured element of the LED light emission part in hexagonal arrangement | positioning.

DESCRIPTION OF SYMBOLS 1 Evaluation apparatus of solar cell using LED 2 LED light emission part 2a Block 3 LED drive part 4 Solar cell 5 Signal processing part 6 Output signal 7 Short-circuit current signal 8 Interface circuit 9 Sample holder 11 LED

Claims (12)

A light emitting unit having a plurality of LEDs that emit light of different wavelengths is irradiated with light of discrete and different wavelengths to a solar cell having a pin structure to measure the output short-circuit current of the solar cell, and absolute spectroscopy for each wavelength. A first step for determining sensitivity;
A formula that gives the current of the solar cell based on the absolute spectral sensitivity for each wavelength obtained in the first step, and performs a fitting calculation according to the following (formula 4) derived by the equation of semiconductor minority carrier continuity: A second step of determining an absolute spectral sensitivity curve of the battery;
Have
In the second step,
Surface reflectance as the parameter R, the surface recombination velocity S _h of the solar cell, the minority carrier diffusion length L _e by setting the initial value, a step A for obtaining the absolute spectral sensitivity curve,
The fitting calculation using data of the measuring wavelengths, including the short wavelength side among the absolute spectral sensitivity for each wavelength determined in the first step, along with obtaining a rough approximation of the surface recombination velocity S _h of the solar cell a step B of obtaining a correction value from the initial value of the surface reflectance R and the minority carrier diffusion length L _e gives the absolute spectral sensitivity curve,
The fitting calculation using data of the measuring wavelengths, including the longer wavelength side of the absolute spectral sensitivity for each wavelength determined in the first step, along with obtaining a rough approximation of the minority carrier diffusion length L _e of the solar cell a step C for obtaining the correction value from the initial value of the surface reflectance R and the surface recombination velocity S _h gives the absolute spectral sensitivity curve,
Further, by using the rough approximate value and the corrected value of each parameter obtained in Step B and Step C, the optimum values of the surface reflectance R, the solar cell surface recombination velocity _Sh , and the minority carrier diffusion length _Le are used. Step D for obtaining
The solar cell evaluation method using LED including this.
[Expression 1]

Here, I _SC is the output short-circuit current of the solar cell, I _h is the hole current of the n layer, I _dr is the current in the depletion layer, I _e is the electron current of the p layer, and the following (formula 1) (formula 2) (Equation 3) is satisfied.
[Expression 2]

[Equation 3]

[Expression 4]

Where α is an absorption coefficient, L _h , _Le and S _h , _Se and D _h , and D _e are the minority carrier diffusion length, surface recombination velocity, and minority carrier diffusion constant, respectively. The letters _h and _e represent holes in the n layer and electrons in the p layer, respectively, x _j and W are the end of the depletion layer and the thickness of the depletion layer, and H and H ′ are the end of the depletion layer. Dimensions.
Furthermore, the solar cell evaluation method using LED of Claim 1 which calculates | requires the output short circuit current at the time of reference | standard sunlight irradiation from the absolute spectral sensitivity curve of the solar cell calculated | required by the said 2nd step.
3. The absolute spectral sensitivity for each wavelength of each light is obtained in the first step using a plurality of LEDs that emit light in a short wavelength band, a medium wavelength band, and a long wavelength band, respectively. Solar cell evaluation method using the LED.
The solar cell evaluation method using an LED according to claim 3, wherein in the first step, an output short circuit current of the solar cell is obtained by performing modulation for each color.
In the step D, performed using the partial differential derivative with respect to the hole current I _h and L _e of the n layer .delta.I _h / delta] S _h and δI _e / δL _e, the solar cell using an LED as claimed in claim 1 Evaluation method.
The solar cell evaluation method using an LED according to any one of claims 1 to 5, wherein the solar cell is a solar cell using a crystal or amorphous made of Si or a compound semiconductor.
An LED light emitting unit having a plurality of LEDs emitting discrete and different wavelengths of light, an LED driving unit, a sample holder on which a solar cell having a pin structure is placed, and a signal processing unit, the LED light emitting unit Is arranged to face the solar cell on the sample holder at a predetermined distance,
The signal processing unit controls the LED driving unit to cause each LED to emit light from the light emitting unit to the solar cell, inputs a short circuit current generated in the solar cell as a short circuit current signal, and the solar cell for each wavelength. The absolute spectral sensitivity is calculated and a program for obtaining an absolute spectral sensitivity curve is executed to give the solar cell current based on the absolute spectral sensitivity value of the solar cell for each wavelength. The absolute spectral sensitivity curve is obtained by performing the fitting calculation by the following (formula 4) derived from the equation,
The signal processing unit is
Surface reflectance as the parameter R, the surface recombination velocity S _h of the solar cell, by setting the initial value of the minority carrier diffusion length L _e, a step A for obtaining the absolute spectral sensitivity curve,
The fitting calculation using data of the measuring wavelengths, including the short wavelength side among the values of the absolute spectral sensitivity for each wavelength, with obtaining a rough approximation of the surface recombination velocity S _h of the solar cell, the absolute spectral sensitivity curve a step B of determining a correction value from the initial value of the surface reflectance R and the minority carrier diffusion length L _e give,
The fitting calculation using data of the measuring wavelengths, including the longer wavelength side of the value of the absolute spectral sensitivity for each wavelength, with obtaining a rough approximation of the minority carrier diffusion length L _e of the solar cell, the absolute spectral sensitivity curve a step C for obtaining the correction value from the initial value of the surface reflectance R and the surface recombination velocity S _h give,
Further, by using the rough approximate value and the corrected value of each parameter obtained in Step B and Step C, the optimum values of the surface reflectance R, the solar cell surface recombination velocity _Sh , and the minority carrier diffusion length _Le are used. Step D for obtaining
The evaluation apparatus of the solar cell using LED which performs this by the said program.
[Equation 5]

Here, I _SC is the output short-circuit current of the solar cell, I _h is the hole current of the n layer, I _dr is the current in the depletion layer, I _e is the electron current of the p layer, and the following (formula 1) (formula 2) (Equation 3) is satisfied.
[Formula 6]

[Expression 7]

[Equation 8]

Where α is an absorption coefficient, L _h , _Le and S _h , _Se and D _h , and D _e are the minority carrier diffusion length, surface recombination velocity, and minority carrier diffusion constant, respectively. The letters _h and _e represent holes in the n layer and electrons in the p layer, respectively, x _j and W are the end of the depletion layer and the thickness of the depletion layer, and H and H ′ are the end of the depletion layer. Dimensions.
The LED according to claim 7, wherein the signal processing unit calculates the output short-circuit current at the time of reference sunlight irradiation by integrating the product of the obtained absolute spectral sensitivity curve and the reference sunlight irradiance distribution with a wavelength. The solar cell evaluation device used.
The solar cell using the LED according to claim 7 or 9, wherein the LED light emitting unit is provided with LEDs that emit light in a short wavelength band, a medium wavelength band, and a long wavelength band, respectively, as the plurality of LEDs. Evaluation device.
9. The LED according to claim 7, wherein the LED light emitting unit includes a block in which LEDs of each color are arranged at each vertex of a regular polygon, and the plurality of blocks are arranged in a predetermined shape. The solar cell evaluation device used.
The solar cell evaluation apparatus using LEDs according to claim 7 or 8, wherein the LED light emitting unit is formed by arranging a plurality of regular square blocks, and LEDs of different colors are arranged at the vertices of the blocks. .
The said LED light emission part consists of a plurality of regular hexagonal blocks, and the evaluation device for solar cells using LEDs according to claim 7 or 8, wherein LEDs of different colors are arranged at each vertex of each block.

Images