JP4523333B2 - Method for evaluating characteristics of chalcopyrite solar cells - Google Patents

Description

  The present invention relates to a characteristic evaluation method for evaluating output characteristics of a chalcopyrite solar cell.

  A chalcopyrite solar cell is a solar cell comprising a chalcopyrite compound (hereinafter also referred to as CIGS) expressed as Cu (InGa) Se as a light absorption layer, and has high energy conversion efficiency, and is hardly deteriorated by aging. It has attracted particular attention because it has various advantages such as non-occurrence, excellent radiation resistance, wide light absorption wavelength region, and large light absorption coefficient, and various studies have been made for mass production.

This type of chalcopyrite solar cell is manufactured by electrically connecting a plurality of cells to each other and then sealing the cells with a resin material to form a module. Each cell is incident on, for example, a first electrode made of Mo, a light absorption layer made of CIGS, a buffer layer, a high resistance layer (semi-insulating layer), a transparent second electrode made of ZnO / Al, and a light absorption layer. The antireflection layer 26 for preventing the reflected light from being reflected and leaking to the outside is formed by providing the glass substrate in this order. Here, each of the buffer layer, the high resistance layer, and the antireflection layer is made of, for example, CdS, ZnO, or MgF ₂ . As the material of the buffer layer, ZnO or InS may be selected.

  When the chalcopyrite solar cell thus configured is irradiated with light such as sunlight, a pair of electrons and holes is generated in the light absorption layer. Then, at the junction interface between the light absorption layer made of CIGS, which is a P-type semiconductor, and the second electrode, which is an N-type semiconductor, electrons gather at the interface of the second electrode (N-type side), and holes are light. Aggregates at the interface of the absorption layer (P-type side). When this phenomenon occurs, an electromotive force is generated between the light absorption layer and the second electrode. The electric energy generated by the electromotive force is taken out as current from the first lead portion and the second lead portion connected to the first electrode and the second electrode, respectively.

  By the way, when the buffer layer is formed of a material other than CdS, such as ZnO or InS, when the chalcopyrite solar cell is stored in a dark place for a long time, a phenomenon that the battery performance deteriorates, that is, a so-called light irradiation effect occurs. For this reason, it becomes difficult to accurately evaluate whether or not the manufactured chalcopyrite solar cell has predetermined characteristics.

From such a viewpoint, in Patent Document 1 and Patent Document 2, in order to accurately evaluate the characteristics of a chalcopyrite solar cell having a buffer layer made of ZnSe, a solar simulator is used to manufacture the chalcopyrite solar cell. air mass (AM) 1.5, the artificial light irradiation intensity 100 mW / cm ² to eliminate the light irradiation effect was irradiated for 30-60 minutes, then, AM 1.5, similarly artificial light irradiation intensity 100 mW / cm ² It has been proposed to evaluate the output characteristics while irradiating.

Non-Patent Document 1 reports that it is effective to reduce the light irradiation effect by providing a buffer layer made of In (OH) ₃ : Zn ²⁺ with a high concentration of ZnCl _2. ing. According to Non-Patent Document 1, since the Zn ions are diffused in the CIGS light absorption layer and the pn homojunction is buried in the CIGS light absorption layer, the pn homojunction is separated from the defect that causes the light irradiation effect. As a result, the light irradiation effect is considered to be reduced.

JP-A-9-36401 JP-A-9-36402 Fiscal 2001 New Energy and Industrial Technology Development Organization Commissioned Business Results Report Photovoltaic Power Generation Technology Research and Development Advanced Solar Cell Technology Research and Development Advanced Solar Cell Practical Research Study “Analysis of Buffer Layer and Junction Interface Properties” Union, Tokyo Institute of Technology March 2002

  However, as described in Patent Document 1 and Patent Document 2, when chalcopyrite solar cells are preliminarily irradiated with artificial light, and then the characteristic evaluation is performed while irradiating artificial light, the chalcopyrite type over time There is a problem that the output characteristics of the solar cell deteriorate.

As described in Non-Patent Document 1, even when a buffer layer made of In (OH) ₃ : Zn ²⁺ is provided, it is difficult to eliminate all the light irradiation effects. In particular, when selenization is performed in the gas phase when the light absorption layer is provided, a light irradiation effect having a larger scale than that in the case where the buffer layer is provided from CdS is recognized.

  The present invention has been made to solve the above-described problems, and avoids as much as possible the occurrence of light irradiation effects on the chalcopyrite solar cell, thereby making it possible to more accurately characterize the chalcopyrite solar cell. It is an object of the present invention to provide a method for evaluating the characteristics of a chalcopyrite solar cell that can be evaluated in a simple manner.

  In the techniques described in Patent Literature 1 and Patent Literature 2, it is known that the performance of the chalcopyrite solar cell is preliminarily irradiated to the chalcopyrite solar cell before performing the characteristic evaluation. It is assumed that this is because In spite of such knowledge being obtained, in the process of repeatedly studying the reason why the battery characteristics of chalcopyrite solar cells deteriorate over time, the present inventors I guessed that the temperature of the chalcopyrite solar cell would rise.

  However, when it is left until the temperature of the chalcopyrite solar cell drops, the light irradiation effect appears again. Eventually, this makes it difficult to accurately evaluate the output characteristics of the chalcopyrite solar cell.

  In view of this point, the present inventors have conducted further intensive studies and have come to the present invention.

That is, the present invention relates to a chalcopyrite solar cell for evaluating the characteristics of a chalcopyrite solar cell modularized by electrically connecting a plurality of cells exhibiting light irradiation effects and sealing with a resin material. Characterization method,
A preliminary light irradiation step of irradiating the chalcopyrite solar cell with the first light;
An output measuring step of measuring the output of the chalcopyrite solar cell while irradiating the chalcopyrite solar cell with pseudo-sunlight,
Have
The first light is irradiated with light that can pass through the resin material and has a maximum peak in a wavelength region up to 480 nm.

  By irradiating the first light, the light irradiation effect of the chalcopyrite solar cell is eliminated. Moreover, in this case, the first light is irradiated with light having a maximum peak in the wavelength region up to 480 nm, in other words, short-wavelength light, and thus the temperature of the chalcopyrite solar cell is increased by the light preliminary irradiation process. Is suppressed. For the reasons as described above, it is avoided that the output value of the chalcopyrite solar cell becomes small even immediately after the start of measurement in the output measurement step. That is, the output characteristics of the chalcopyrite solar cell can be accurately evaluated immediately after the start of measurement.

  In order to sufficiently eliminate the light irradiation effect of the chalcopyrite solar cell, it is preferable that the integrated irradiation amount of the first light is 0.1 kWh or more.

  The first light is not particularly limited as long as it is light that can pass through the resin material encapsulating the cell and has a maximum peak in a wavelength region of 480 nm or less. As the resin material, ethylene vinyl acetate copolymer resin (EVA) is generally used. In this case, as the first light, light having a maximum peak in a wavelength region of 370 nm or more is selected so as to transmit EVA.

  Here, during the output measuring step, the temperature of the chalcopyrite solar cell rises as the pseudo-sunlight is irradiated to the chalcopyrite solar cell for a long time, and as a result, the chalcopyrite type solar cell The output of the solar cell may decrease. Therefore, it is preferable to investigate in advance the correlation between the temperature of the chalcopyrite solar cell and the output value, and to perform temperature correction on the output value of the chalcopyrite solar cell in the output measurement step. Thereby, even if it is a case where output fall arises, the output characteristic of a chalcopyrite type | mold solar cell can be evaluated correctly.

  According to the present invention, the chalcopyrite solar cell before the output measurement is performed is preliminarily irradiated with the short wavelength light. For this reason, the light irradiation effect of a chalcopyrite solar cell is eliminated. And when irradiating short wavelength light, it is suppressed that the temperature of a chalcopyrite solar cell rises. Accordingly, since the chalcopyrite solar cell exhibits a high output value immediately after the output measurement is started, the output characteristics of the chalcopyrite solar cell can be evaluated relatively accurately.

  Hereinafter, preferred embodiments of the method for evaluating characteristics of a chalcopyrite solar cell according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic longitudinal sectional view of a cell 10 of a chalcopyrite solar cell. The cell 10 is provided by laminating a laminated body 14 on a glass substrate 12. Here, the laminated body 14 includes, from the glass substrate 12 side, a first electrode 16 made of Mo, a light absorption layer 18 made of CIGS, and a transparent second electrode 20 made of ZnO / Al, and absorbs light. Between the layer 18 and the second electrode 20, a buffer layer 22 and a high resistance layer (semi-insulating layer) 24 for relaxing the difference in thermal expansion coefficient between the light absorption layer 18 and the second electrode 20 are interposed. Has been. Furthermore, an antireflection layer 26 is provided on the second electrode 20 to prevent light incident upon light absorption from being reflected and leaking outside. In the present embodiment, the buffer layer 22, the high resistance layer 24, and the antireflection layer 26 are made of InS, ZnO, and MgF ₂ , respectively.

  A part of the first electrode 16 is exposed from the laminated body 14, and the first lead portion 28 is provided in the exposed portion. On the other hand, a part of the second electrode 20 is also exposed from the antireflection layer 26, and the second lead portion 30 is provided in the exposed portion.

  A chalcopyrite solar cell is constructed by electrically connecting a plurality of cells 10 configured in this manner and then sealing them with a resin material (not shown) to form a module. Generally, EVA is selected as the resin material.

  When evaluating the output characteristics of the chalcopyrite solar cell configured as described above, the characteristic evaluation method whose flowchart is shown in FIG. 2 is performed. This characteristic evaluation method includes a light preliminary irradiation step S1 for irradiating the chalcopyrite solar cell with the first light, and an output measurement for measuring the output while irradiating the chalcopyrite solar cell with simulated sunlight. Step S2.

  First, the chalcopyrite solar cell is irradiated with short wavelength light in the preliminary light irradiation step S1. Here, short wavelength light refers to light having a maximum peak in a wavelength region of 480 nm or less. In addition, the short wavelength light is selected such that the maximum peak appears at a wavelength capable of transmitting the resin material. For example, when EVA is selected as the resin material, a material having a maximum peak at a wavelength of 370 nm or more is irradiated.

  By irradiating the short wavelength light, the light irradiation effect of the chalcopyrite solar cell is eliminated, and the battery performance is restored. In order to sufficiently eliminate the light irradiation effect, it is preferable to set the irradiation time and irradiation intensity of the short wavelength light so that the integrated irradiation amount as a product thereof is 0.1 kWh or more.

  In this case, since the short wavelength light having the maximum peak at a wavelength of 480 nm or less is irradiated, it is possible to suppress the temperature of each cell 10 and thus the chalcopyrite solar cell from rising.

Next, in the output measurement step S2, the chalcopyrite solar cell is irradiated with pseudo-sunlight, that is, artificial light having an AM of 1.5 and an irradiation intensity of 100 mW / cm ² while irradiating the chalcopyrite solar cell. Measure.

  The output change of the chalcopyrite solar cell thus measured is shown in FIG. 3 together with the output change of the chalcopyrite solar cell measured without performing the light preliminary irradiation step S1. From FIG. 3, the output of the chalcopyrite solar cell immediately after the start of the output measurement is small due to the light irradiation effect when the short wavelength light is not irradiated, whereas when the short wavelength light is irradiated in advance. It can be understood that the size becomes sufficiently large by eliminating the light irradiation effect.

  Thus, in the present embodiment, the chalcopyrite solar cell is first irradiated with short-wavelength light, thereby recovering the light irradiation effect of the chalcopyrite solar cell. For this reason, even immediately after the output measurement is started, the output of the chalcopyrite solar cell can be accurately measured.

  In addition, according to the present embodiment, since the irradiated light is short-wavelength light, as described above, an increase in the temperature of the chalcopyrite solar cell in the light preliminary irradiation step S1 is suppressed. For this reason, it is possible to avoid the temperature of the chalcopyrite solar cell from dropping during the output measurement, and thus to avoid the change in output due to the temperature drop, so that the output of the chalcopyrite solar cell can be further increased. It can be measured accurately.

  In addition, when the output measurement is performed for a long time, the temperature of the chalcopyrite solar cell may rise as the pseudo-sunlight is continuously irradiated. In this case, the output of the chalcopyrite solar cell is lowered, and as a result, it is not easy to measure accurate output characteristics.

  In order to avoid such a situation, temperature correction may be applied to the output value in the output measurement step S2. Specifically, the output at various temperatures in the chalcopyrite solar cell is measured, and the correlation between the temperature and the output of the chalcopyrite solar cell is obtained in advance. In the output measurement step S2, the temperature of the chalcopyrite solar cell is also measured at the same time and compared with the temperature at the start of measurement.

  When the temperature is rising, the output difference from the case where the temperature is not rising is obtained from the correlation between the temperature and the output examined in advance. By adding the output difference to the actual output value, the output characteristics can be evaluated more accurately.

  In the above-described embodiment, the case where the light irradiation effect occurs due to the buffer layer 22 made of a material other than CdS has been described as an example. However, the present invention is particularly limited to this case. However, any chalcopyrite solar cell that produces a light irradiation effect can be applied.

It is a schematic longitudinal cross-sectional view of a chalcopyrite solar cell. It is a flowchart of the characteristic evaluation method of the chalcopyrite solar cell according to the present embodiment. It is a graph which shows the relationship between the irradiation time and output change in a chalcopyrite solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Cell 12 ... Glass substrate 14 ... Laminated body 16, 20 ... Electrode 18 ... Light absorption layer 22 ... Buffer layer 24 ... High resistance layer 26 ... Antireflection layer 28, 30 ... Lead part

Claims (4)

This is a method for evaluating the characteristics of a chalcopyrite solar cell, in which a plurality of cells showing the light irradiation effect are electrically connected and sealed with a resin material to evaluate the characteristics of the chalcopyrite solar cell modularized. And
A preliminary light irradiation step of irradiating the chalcopyrite solar cell with the first light;
An output measurement step of measuring the output of the chalcopyrite solar cell while irradiating the standardized sunlight against the chalcopyrite solar cell,
Have
A method for evaluating characteristics of a chalcopyrite solar cell, characterized in that the first light is irradiated with light that can pass through the resin material and has a maximum peak in a wavelength region up to 480 nm.   The method for evaluating characteristics of a chalcopyrite solar cell according to claim 1, wherein an integrated dose of the first light is 0.1 kWh or more.   3. The property evaluation method according to claim 1, wherein the cell is sealed with an ethylene vinyl acetate copolymer resin as the resin material, and the first light has a maximum peak in a wavelength region of 370 nm or more. A method for evaluating the characteristics of a chalcopyrite solar cell characterized by   4. The chalcopyrite type according to claim 1, wherein temperature correction is performed on an output value of the chalcopyrite solar cell in the output measurement step. Method for evaluating characteristics of solar cell.

Images