JP2012023070A - Solar cell, multilayer substrate for solar cell, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage to a substrate for integrated type thin-film solar cells caused by laser processing thereof.SOLUTION: In some embodiment of the present invention, a thin-film solar cell 100 is provided which includes, on one surface of a substrate 5, a ground layer 11 containing a material which exhibits a lower thermal decomposition temperature or evaporation start temperature than the thermal decomposition temperature of the substrate. Disposed above the ground layer 11 as conductive layers for connection or electrode purposes are connection wiring layers 7 and 10. To form an integrated type solar cell, a separation part 4 which has had the connection wiring layers 7 and 10 removed by laser processing is formed. If the ground layer 11 which has such properties is used, since the connection wiring layers 7 and 10 are removed by a weaker laser beam than otherwise, it is possible to reduce damage by a laser beam to the substrate 5 which is exposed to the separation part 4.

Description

  The present invention relates to a solar cell, a laminated substrate for solar cells, and a method for producing them. More specifically, the present invention relates to a solar cell using laser processing, a laminated substrate for the solar cell, and a method for manufacturing them.

  In recent years, thin film solar cells have attracted attention as solar cells with a low environmental load for production. A thin film solar cell is called an integrated thin film solar cell in which a plurality of photoelectric conversion elements are formed on one surface of a substrate, and each photoelectric conversion element is connected in series on the substrate and integrated. There is something. Integrated thin film solar cells are roughly classified into a super straight type and a substrate type. In a super straight type solar cell, light for power generation passes through a substrate and then enters a power generation layer, that is, a semiconductor layer. In contrast, in a substrate type solar cell, light for power generation enters the semiconductor layer without passing through the substrate. For this reason, the substrate in the substrate type solar cell is disposed on the side opposite to the light incident side (“front side”) (“back side”) for the semiconductor layer. In the solar cell using an amorphous silicon (a-Si) semiconductor layer in that case, the structure employed for the semiconductor layer is a nip structure in which an n layer, an i layer, and a p layer are stacked in this order from the substrate side. Patent Document 1 (Japanese Patent No. 4248351) proposes a technique for facilitating a patterning process for realizing a series connection structure of a substrate type nip structure.

  Looking at the configuration of the integrated thin-film solar cell in the above proposal in detail, a photoelectric conversion layer composed of a back electrode layer, a semiconductor layer, and a front transparent electrode layer is in each unit of the photoelectric conversion unit (hereinafter referred to as a unit photoelectric conversion unit). It is delimited. The unit photoelectric conversion units are connected in series by connecting adjacent unit photoelectric conversion units on the substrate. In this case, in series connection, among the two adjacent unit photoelectric conversion units, the front transparent electrode layer of one unit photoelectric conversion unit and the back electrode layer of the other unit photoelectric conversion unit are electrically connected to each other. Done. In such a configuration, each of the unit photoelectric conversion units is an element connected in series, so that the back electrode layer is also electrically separated and separated from the unit back electrode corresponding to each unit photoelectric conversion unit. Since the back electrode needs to have both light reflectivity and electrical conductivity, it is usually formed of a metal layer.

  In a substrate type integrated thin film solar cell, a thin film solar cell called a SCAF (Series Connection through Arts on Film) structure in which a unit photoelectric conversion unit is used as an element to form a serial connection has been proposed (for example, Patent Document 2). : JP 2002-57357 A). A flexible substrate is used in the thin film solar cell having the SCAF structure. In order to connect the unit photoelectric conversion units in series, a current collecting hole and a connection hole penetrating the substrate are used, and on the back surface of the substrate (the opposite surface as viewed from the surface on which the unit photoelectric conversion unit is formed) A conductor layer connected to the connection hole and the through hole is formed. This conductor layer is separated and separated between the unit connection wiring portions in order to serve as wiring for connecting the columns of the unit photoelectric conversion portions in series. The conductor layer is formed of a metal layer because it needs to have good electrical conductivity.

  In the substrate type thin film solar cell in each proposal mentioned above, a metal layer is utilized as either an electrode or a wiring, or both. This metal layer separation processing is usually performed by laser processing from the viewpoint of processing cost and accuracy. FIG. 1 is an explanatory view schematically showing the state of separation processing by the laser. In this separation process, laser light is irradiated toward the metal layer formed on the substrate 5, and the metal layer is removed by the action of the heat of the laser to form a separation portion. When the laser irradiation position is scanned, a linear separation portion is formed at the scanned position. The shape of the separation part is usually a straight line.

  As shown in FIG. 1, in this separation process, a galvano mirror 52 disposed in a space toward the substrate 5 is used. Laser light from a fixed laser light source 54 is incident on the galvanometer mirror 52, and the galvanometer mirror 52 is controlled so as to move the irradiation unit in the width direction of the substrate 5, for example. For example, the substrate 5 is sent in a longitudinal direction by a predetermined distance between one scan and the next scan, and a scan line 56 is formed on the substrate 5 as a laser irradiation trace. Each scan line 56 becomes a separation part from which the metal layer is removed.

Japanese Patent No. 4248351 (Japanese Patent Laid-Open No. 2005-93903) JP 2002-57357 A

"New edition physical constant table", Iida et al., 4 people, Asakura Shoten, 1979, p.172 "Method for thermogravimetric measurement of plastics" (JIS K 7120) "Measurement method of plastic transition temperature" (JIS K 7121)

  However, generally a metal layer shows a large light reflectance with respect to a laser beam. For this reason, the irradiation power of the laser beam necessary for removing the metal layer is set to a value that allows for the magnitude of the light reflectance. In particular, when a substrate made of a material that is easily affected by heat, such as a resin film, is employed as the flexible substrate of the substrate type solar cell, a particularly large problem is caused. The problem will be described below.

  First, in order to perform the separation process as intended, it is necessary to irradiate the metal layer on the substrate with a laser having an appropriate wavelength with a power sufficient to remove the metal layer. An example of a laser used for removing a metal layer on a flexible substrate is a second harmonic (SHG, wavelength 532 nm) of a pulsed Nd-YAG laser. The light of the Nd-YAG laser is repeatedly output at a repetition frequency of about 1 kHz to 100 kHz, for example, and scanned so as to draw a line while overlapping the irradiation positions. At this time, other conditions such as the beam diameter and irradiation power are determined so that the separation process can be performed appropriately while preventing adverse effects on the substrate as much as possible. Note that the irradiation power of the pulse laser is described as indicating the energy amount for one pulse.

FIG. 2 is a schematic perspective view (FIG. 2 (a)), a plan view (FIG. 2 (b)) showing a state in which a metal layer formed on a substrate is being removed by a pulsed laser, and each part It is explanatory drawing (FIG.2 (c)) which shows the intensity | strength by laser, and an enlarged plan view (FIG.2 (d)) which shows the relationship between the area | region removed by one laser pulse, and an irradiation area | region. When separation processing is performed by scanning the irradiation position by a pulsed laser, the irradiation range by each pulse forms a line so as to partially overlap each other. For the following explanation, an integer k is used to distinguish each pulse from a pulse k or the like, and the integer k is attached so as to increase in value such as 1, 2,... Over time. Then, the state in which the irradiation position is scanned while the pulse is oscillated is shown as a column of the range (irradiation range R _k ) to which each pulse k of the laser beam is irradiated, as schematically shown in FIG. be able to. Further time for explanation also distinguished by the same integer, a time point immediately after irradiation until a pulse k and the time t _k.

Figure 2 (b) shows a state of separating portions formed in the metal layer at time t _k. As shown in FIG. 2B, the irradiation range R _k overlaps with the irradiation range R _k−1 . As shown in FIG. 2 (c), the irradiation range R _k-1 by the pulse k _-1 and the irradiation range R _k by the pulse k are shifted from each other and each has a mountain-shaped intensity distribution. The overlapping portions are formed by overlapping the chevron-shaped hem portions with each other. Note that due to the intensity distribution, the metal layer is not removed at all positions included in each irradiation range. The intensity distribution indicated by each pulse can be prevented to some extent by devising the optical system of the laser beam, but it cannot be completely prevented. In the laser irradiation range, the metal layer is removed only at a position where the strength is strong.

The state of the separation part formed in the row of the irradiation range and the metal layer will be described with reference to FIG. FIG. 2 (d) is a diagram illustrating the stages in which the metal layer is removed at time t _k−1 and time t _k . When the pulse k-1 is compared with the irradiation region R _k-1 time t _k-1 after being irradiated, at the time t _k after the pulse k is irradiated to the irradiation region R _k are due to the scanning of the laser pulses The separation part extends by one pulse of k. Here, attention is paid to a region A _k indicated by hatching in FIG. 2D and an adjacent portion B _k . The region A _k is a portion where the metal layer remains at the time t _k−1 and the metal layer is removed only after the irradiation region R _k is irradiated with the pulse k. That is, the region _Ak is a separation part newly formed by one pulse k. However, the portion B _k close to the region A _k is a portion _{where the} metal layer has already been removed and the substrate surface is exposed at the time t _k−1 . Nevertheless, is set to the extent that can remove the metal layer in the region A _K, the pulse k of greater strength will also be irradiated to the portion B _k. Therefore, thus it extends adverse effects (damage) by laser in the portion B _k exposed substrate. Actually, since the laser irradiation position is scanned and the pulse is repeatedly irradiated, the substrate surface that is damaged in the inside thereof is linearly extended along with the formation of the separation portion.

  In order to cope with such a problem, a low reflective metal is used in the above-described SCAF structure. FIG. 3 is a sectional view showing a schematic layer structure of a thin film solar cell 700 in the case of the SCAF structure. In the thin film solar cell 700 having the SCAF structure, for example, a back electrode layer 76, a semiconductor layer 78, and a front transparent electrode layer 79 are disposed on the first surface 75A of the substrate 75. In the thin film solar cell 700, a first connection wiring layer 77 and a second connection wiring layer 80 are formed on the second surface 75B of the substrate 75 as metal layers used for wiring. Here, the second connection wiring layer 80 is a low reflection metal layer. That is, the first connection wiring layer 77 is a layer formed of, for example, silver (Ag), while the second connection wiring layer 80 is formed of, for example, nickel (Ni) and is a low-reflective layer. In addition, according to Non-Patent Document 1 ("New Edition Physical Constant Table", Iida et al., 4 people, Asakura Shoten, 1979, p. 172), the reflectance values of the silver and nickel thin films are 97.9%, respectively. (Wavelength 550 nm) and 54.9% (wavelength 546 nm).

  When such a low-reflectance metal layer (second connection wiring layer 80) is used, the irradiation power is reduced as compared with a case where a metal layer with high reflectivity (for example, the first connection wiring layer 77) is directly irradiated with a laser. Even in this case, the separation portion 74 can be formed. For this reason, the adverse effect on the substrate (damage D in FIG. 3) is reduced to some extent. However, the intensity of the laser pulse applied to the portion of the second surface 75B of the substrate 75 exposed at the separation portion 74 can remove both the first connection wiring layer 77 and the second connection wiring layer 80. It remains the same. For this reason, the damage D (FIG. 3) cannot be completely prevented only by using the second connection wiring layer 80 as a low reflection metal.

  A more effective method for reducing the influence of the laser irradiation on the substrate exposed portion described above has not been known so far, and a substrate and a metal layer that can form a separation portion even when the laser power is further reduced. The structure of the laminated body is required.

  The inventors of the present application have found that it is effective to further reduce the laser power by forming a certain base layer at a position where the metal layer is in contact with the position in the thickness direction of the substrate. This solution has been found by examining in detail the mechanism by which the metal layer is removed by the laser. This point will be described below.

  Conventionally, a mechanism for removing a metal layer by a laser pulse has been generally described as follows. That is, first, a laser is incident on the photometal layer. A certain amount of the amount of light incident on the metal layer is lost due to reflection, and the remaining light is transmitted to the metal layer. The metal layer at the irradiation position where the heat by the light is sufficient is removed in an instant. This explanation is consistent with the fact that the irradiation power can be reduced by adopting a low reflectance metal layer (nickel layer, hereinafter referred to as Ni layer) in the SCAF structure. In other words, when the Ni layer is employed, incident light that is absorbed and contributes to an increase in temperature is increased by the amount that the reflectance of the outermost surface is lowered. As a result, it can be understood that the same temperature is reached even when a laser pulse with less power is used than when the Ni layer is not formed, and the irradiation power required for removal is reduced.

  The inventor examined such a mechanism in more detail. A particular focus as a clue is the relationship between the Ag layer (first connection wiring layer 77, FIG. 3) and the Ni layer (second connection wiring layer 80) in the SCAF structure. This is because the boiling point and melting point of nickel are significantly higher than those of silver. In fact, the boiling point and melting point of nickel are about 2837 ° C. and about 1453 ° C., respectively, while that of silver is about 2150 ° C. and about 950 ° C., respectively. In spite of this relationship, in the configuration of FIG. 3 in which the Ni layer is stacked, the laser power (“minimum laser” required to form the separation portion by removing both the Ni layer and the Ag layer) "Power") is smaller than that without the Ni layer. From this, it can be said that the behavior of the layer below the Ni layer with respect to the heat is strongly related to the mechanism of removing the metal layer in which the Ni layer is laminated. Moreover, even if there is a layer that is more resistant to heat (here, the Ni layer) on the surface on which the laser is incident, the lower layer (here, the layer below the Ni layer including the Ag layer) that is more susceptible to heat. The effect of heat from the laser is increasing. That is, reducing the reflectance of the connection wiring layer is directly linked to reducing the minimum laser power accordingly.

  The inventor took this idea further. Further attention was paid to the fact that the silver is not completely sublimated or evaporated by the heat of the laser when the Ag layer is removed. To conclude the conclusion, the inventor suggested that the thin layer portion (interface portion) of the substrate in contact with the metal layer has some influence on the Ag layer, so that the Ag layer is removed. I guess. This point will be described below. First, for example, the Ag layer of the first connection wiring layer 77 (FIG. 3) is formed to a thickness set from the viewpoint of electrical conduction, for example, 200 nm. The thickness of this Ag layer can be said to be a very thin layer from the viewpoint of heat conduction for an Ag layer having a sufficiently large thermal conductivity. For this reason, the heat from the laser should be transmitted instantaneously through the Ag layer, and the heat should reach the substrate almost simultaneously with the irradiation of the laser pulse. In this case, it can be said that the material of the interface portion of the substrate has begun to be affected by heat in some form before reaching a temperature at which the Ag layer itself evaporates. For this reason, it is estimated that there is a high possibility that the interface portion in the vicinity of the Ag layer of the substrate has some influence on the removal of the Ag layer. Specifically, considering the above-described boiling point and melting point of silver, the interface portion of the substrate in contact with the Ag layer behaves such as releasing gas by the action of heat such as thermal decomposition, evaporation, or sublimation. It is natural to think that The Ag layer and the Ni layer are likely to be more directly affected by the behavior of the interface portion of the substrate, for example, blown away. Thus, the inventor presumes that the portion of the substrate in contact with the metal layer plays an important role in the removal of the Ag layer.

  Actually, the result of microscopic observation of the vicinity of the separation portion immediately after the separation processing also supports this assumption. In other words, while there is no metal layer residue in the separation part, the solid matter presumed to be due to the removed metal layer is scattered around the separation part as if it were scattered from the separation part. On the metal layer. From this, it is considered that some of the material of the metal layer to be removed is scattered as a solid. In addition, it has been experimentally observed that when the thickness of the substrate is changed, the influence of the laser on the substrate is great when a thin substrate is used. At present, the cause of this phenomenon is not always clear. Regardless of whether the substrate is thick or thin, the equivalent effect is exerted on the substrate and the effect of the effect is relatively large because the substrate is thin, or the effect is greater in the case of a thin substrate I have not been able to identify it. However, the inventor believes that the fact that the substrate is damaged at least depending on the thickness of the substrate itself is evidence that the substrate plays a certain role in the mechanism of the separation process.

  As a result of examination based on such experimental facts, the inventor of the present application can devise the base of the metal layer in order to achieve reduction in laser irradiation power that can reduce damage to the substrate. I thought it was useful. Specifically, in order to obtain a configuration effective for reducing the irradiation power by a laser in a laminate including a substrate and a metal layer, it was first considered that the position to be devised should be the base of the metal layer. Moreover, it should be good to positively form a material that is thermally weaker than the substrate at the base position. This is because a thermally weak layer, not a thermally strong material, helps protect the substrate.

  Next, an examination was made as to what attribute should be specified in the situation according to the problem of the present invention that the material used as the substrate is thermally “strong” or “weak”. There are three factors considered in this case. First, laser processing is thermal processing, and the portion irradiated by the laser is at a very high temperature. Second, when the temperature is transmitted to the underlayer, the laser is not directly incident on the underlayer, but the heat generated by the metal layer is conducted. Thirdly, after the irradiation with the laser, at least the underlayer in contact with the metal layer should be removed. Based on these factors, the inventor considers that a material suitable for the underlayer is a material that emits gas more easily than a substrate by a laser. That is, the material suitable for the underlayer is the temperature at which the gas begins to be released by thermal decomposition when the temperature is raised, or the temperature at which the gas starts to be released by the action of heat such as evaporation or sublimation is the thermal decomposition temperature of the substrate. It came to the conclusion that the material is lower. In particular, attention was paid to the thermal decomposition temperature and the vaporization start temperature of the underlayer as an index for the temperature at which the gas is emitted when the laser is irradiated.

  Therefore, in one aspect of the present invention, a substrate having a first surface and a second surface, a photoelectric conversion layer disposed on the first surface, and a substrate disposed on the second surface, A base layer containing a material exhibiting a thermal decomposition temperature or a vaporization start temperature lower than the thermal decomposition temperature of the material, and a connection wiring layer disposed on the base layer, and at least a part of the base layer, There is provided a thin film solar cell in which a separation portion from which the connection wiring layer is removed by laser light is formed on the second surface of the substrate.

  In this aspect, the photoelectric conversion layer is formed on the first surface of the substrate, and the connection wiring layer is formed on the second surface. A laser is used for the separation process of the connection wiring layer.

  Similarly, in one aspect of the present invention, a substrate having a first surface and a second surface, and a thermal decomposition temperature or vaporization start that is disposed on the first surface and is lower than the thermal decomposition temperature of the material of the substrate. A base layer containing a material indicating temperature; a back electrode layer; and a photoelectric conversion layer disposed in contact with the back electrode layer, wherein at least a part of the base layer and the back surface There is provided a thin film solar cell in which a separation portion from which an electrode layer is removed by a laser is formed on the first surface of the substrate.

  In this embodiment, the photoelectric conversion layer is formed on the first surface of the substrate, and the metal layer formed on the surface is separated by the laser. Particularly in this configuration, since the metal layer is a layer used as the back electrode of the photoelectric conversion layer, a metal layer having a low reflectance cannot be formed on the metal layer. Thus, this aspect of providing a technique for reducing the minimum laser power during the separation process is particularly useful.

  In each aspect of the present invention, a thermal decomposition temperature and a vaporization start temperature are used as indices for selecting an underlayer. Of these, the pyrolysis temperature can be determined based on several measurement methods and definitions. Therefore, in the determination by the pyrolysis temperature described in each aspect of the present invention, it is intended to use the pyrolysis temperature obtained in any of several measurement methods and definitions. Hereinafter, the thermal decomposition temperature will be exemplified and described.

  First, as the thermal decomposition temperature, a mass change temperature measured by thermogravimetry (TG) can be employed. Thermogravimetry is a technique prescribed in, for example, Non-Patent Document 2 (“Plastic Thermogravimetry Method” (JIS K 7120)), and the change in the mass of a sample is examined while the temperature is raised using a thermobalance. Is the method. There are an isothermal heating method and an isothermal temperature raising method, and any of them can be used in each aspect of the present invention. The substrate sample and the underlayer sample to be measured are both crushed samples or powders, and heated in an atmosphere such as dry air. The sample condition and the atmosphere condition are the same for the sample to be compared, for example, the substrate sample and the underlayer sample. Here, for example, as the above standards leave to the agreement between the parties, the conditions of the sample and the atmosphere are not limited to specific conditions, but are the same to the extent that they can be compared with the comparison target. It is optional if it is done. If the conditions according to each aspect of the present invention are enumerated, an inert gas atmosphere without oxygen is used in order to serve as an index for the separation process by laser at the position covered with the metal layer. However, measurement in other atmospheres or in vacuum is not excluded.

  The mass change temperature measured by thermogravimetry is any of the start temperature, the midpoint temperature, and the end temperature of the mass change calculated from the measured TG curve. Of these, the same type of temperature is used for the sample to be compared. For example, a 5% thermogravimetric decrease temperature can be used as the mass change start temperature. In the above standard, in order to indicate mass reduction in multiple stages, each stage is distinguished from primary, secondary, etc., and the start temperature, midpoint temperature, and end in each stage. It is prescribed to determine the temperature. In each aspect of the present invention, since it is used as an index of heat resistance during the separation process by laser, the first or lowest temperature is observed when multi-step pyrolysis is observed for both the substrate and the underlayer. The reduction in mass is taken as a comparison target.

  A second determination method of the thermal decomposition temperature that can be adopted is to measure the peak of thermal decomposition at the time of temperature rise of the material of the base layer and the material of the substrate by differential thermal analysis (DTA). For measurement by differential thermal analysis, a technique for the transition temperature is defined in, for example, Non-Patent Document 3 (“Method for Measuring Transition Temperature of Plastic” (JIS K 7121)). Here, what is defined by this standard is a general transition temperature (melting temperature, crystallization temperature, glass transition temperature, etc.), and is not a direct determination method of the thermal decomposition temperature. However, for example, when the temperature difference between the material of the substrate and the underlayer is compared while raising the temperature in a nitrogen atmosphere, the peak of thermal decomposition is observed as the peak on the endothermic side. For this reason, if the material in which the temperature at which such an endothermic peak appears is lower than that of the substrate is a base layer of the metal layer, it can be said that the base layer has a lower thermal decomposition temperature than that of the substrate. By such measurement, it is possible to compare the thermal decomposition temperatures of the materials of the substrate and the underlayer.

  A third method for determining the pyrolysis temperature is evolved gas analysis. The type of gas generated by pyrolysis depends on the substrate material. For this reason, indices that can be adopted as the thermal decomposition temperature for the material of the substrate and the underlayer include, for example, the temperature at which the gas generated by raising the temperature is the most abundant and the amount of decomposition product gas of the material of each sample. Various temperature indicators related to gas release, such as a peak temperature and a temperature at which gas generation starts, are included. A known method (for example, gas chromatography method) can be employed for the quantitative analysis of the gas.

  In addition to these determination methods, the use of a temperature index determined by another method as the thermal decomposition temperature is also included in each aspect of the present invention. Examples of the thermal decomposition temperature employed in each aspect of the present invention include a temperature at which volatilization occurs, which is determined based on the volatilization rate in a vacuum measured by raising the temperature, in a vacuum for a predetermined time (for example, 30 minutes). Includes the temperature at which the weight is halved when heated, as well as the differential and integral pyrolysis temperatures obtained by thermogravimetry (TG). Furthermore, you may perform the TG / DTA measurement which measures a differential heat and a thermogravimetry simultaneously. Also in these methods, the temperature index determined in the absence of oxygen is preferable as the thermal decomposition temperature of each aspect of the present invention.

  Furthermore, in each aspect of the present invention, it is also proposed to select the material of the underlayer based on another index, that is, the vaporization start temperature, instead of the thermal decomposition temperature. In this application, the vaporization start temperature means that a solid substance passes through a liquid or a liquid due to a change in a material phase including evaporation and sublimation (hereinafter collectively referred to as “vaporization phenomenon”). The lower limit of the temperature range in which the phase change that itself becomes a gas occurs. The gas may include not only a gas that has become a gas without changing the composition of the solid substance, but also a gas that is generated with some chemical change. In other words, the gasification phenomenon of the present application does not exclude the release of gas due to chemical changes such as thermal decomposition.

  This vaporization start temperature can be determined based on several measurement methods and definitions as well as the thermal decomposition temperature. Therefore, in the determination based on the vaporization start temperature described in each aspect of the present invention, it is intended to use the vaporization start temperature obtained in any of several measurement methods and definitions. For example, the measurement of the mass reduction accompanying vaporization can be adopted by the thermogravimetry (TG) described above as the first determination method of the thermal decomposition temperature. Moreover, the method of calculating | requiring the endothermic peak accompanying vaporization by the differential thermal analysis (DTA) mentioned above as a 2nd determination method of thermal decomposition temperature is employable. Furthermore, the temperature determined as the temperature at which gas generation starts by the generated gas analysis described above as the third method for determining the thermal decomposition temperature can be used as the vaporization start temperature.

  As in the case of the thermal decomposition temperature described above, a temperature index determined by a method other than these determination methods can also be employed as the vaporization start temperature. Among them, the temperature at which volatilization is determined based on the volatilization rate in vacuum measured by raising the temperature, the temperature at which the weight is reduced by half when heated in vacuum for a predetermined time (for example, 30 minutes), and the heat Differential pyrolysis temperature and integral pyrolysis temperature obtained by gravimetric measurement (TG) are included. As in the case of the pyrolysis temperature, TG / DTA measurement in which differential heat and thermogravimetry are simultaneously measured may be performed in order to determine the vaporization start temperature. The point that the temperature index determined in the absence of oxygen is preferable as the vaporization start temperature of each aspect of the present invention is the same as the thermal decomposition temperature.

  In each aspect of the present invention, it is presumed that gas release mainly due to thermal decomposition or vaporization phenomenon (evaporation or sublimation) of the underlayer acts on the removal of the metal layer by the material of the underlayer. A typical mode of removal caused by this thermal decomposition or vaporization phenomenon is as follows. When heat is transmitted to the base layer formed on the substrate, a certain thickness portion (interface portion) of the base layer is decomposed or vaporized by the heat. Along with this, the metal layer located immediately above the base layer loses adhesion to the substrate. Further, the gas contained in the decomposition product of the underlayer or the gas of the underlayer itself acts to lift or blow off the metal layer from below. Thus, the metal layer is removed by the heat of the laser. In order to realize such a removal mode, in each mode of the present invention, an underlayer showing a thermal decomposition temperature or a vaporization start temperature lower than the thermal decomposition temperature of the substrate is formed between the substrate and the metal layer. . Note that it is also assumed that only a part of the base layer is removed and the other part remains at the position where the metal layer is removed. Such a phenomenon is assumed mainly in two cases. One is when the underlayer is thick. In this case, the underlayer still remains under the portion of the underlayer that has been decomposed or vaporized to remove the metal layer. The other case is a case where the thermal decomposition or vaporization is a phenomenon of decomposition into a gas having a different composition and a solid (melt), that is, incongruent vaporization. In this thermal decomposition or vaporization mode, some solid component remains on the trace after the underlayer is removed. In any case, it is not essential in each aspect of the present invention that the underlayer is completely removed in the separation portion from which the metal layer has been removed.

  According to some aspects of the present invention, it is possible to reduce the minimum laser power when performing the separation process, and thus it is possible to produce a thin film solar cell in which the influence of the laser on the substrate is reduced. Become.

It is explanatory drawing which shows the mode of the separation process performed using a laser. It is explanatory drawing which shows a mode that a metal layer is removed in isolation | separation processing, the model perspective view (FIG. 2 (a)) which shows the mode, a top view (FIG. 2 (b)), and description which shows the intensity | strength by the laser of each part It is a figure (FIG.2 (c)) and an enlarged plan view (FIG.2 (d)) which shows the relationship between the area | region removed by a laser pulse, and an irradiation area | region. It is sectional drawing which shows the general | schematic layer structure of the thin film solar cell of the conventional SCAF structure. It is sectional drawing which shows the schematic structure of the thin film solar cell in one embodiment of this invention, the connection wiring layer contains the metal layer of two layers (FIG.4 (a)), and the connection wiring layer is one layer of metal. It is the structure (FIG.4 (b)) containing a layer. It is a top view (Drawing 5 (a)) and an enlarged plan view (Drawing 5 (b)) showing a schematic structure of a thin film solar cell which has a SCAF structure in an embodiment of the present invention. It is sectional drawing which shows schematic structure of the thin film solar cell which has a SCAF structure in one embodiment of this invention. It is a process flow figure explaining an outline of a process of manufacturing a thin film solar cell of SCAF structure in a certain embodiment of the present invention. It is sectional drawing which shows the schematic structure of the thin film solar cell of embodiment with this invention. It is a process flow figure explaining an outline of a process of manufacturing a thin film solar cell in an embodiment with the present invention.

  Hereinafter, embodiments of the present invention will be described. In the following description, unless otherwise specified, common parts or elements are denoted by common reference numerals throughout the drawings. In the drawings, each element of each embodiment is not necessarily shown in a scale ratio.

<First Embodiment>
FIG. 4 is a schematic cross-sectional view showing a schematic configuration of the thin-film solar cell 100 according to the first embodiment of the present invention. As shown to Fig.4 (a), the board | substrate 5 used for the thin film solar cell 100 has the 1st surface 5A and the 2nd surface 5B. In addition to the substrate 5, the thin-film solar cell 100 is disposed on the photoelectric conversion layer disposed on the first surface 5 </ b> A, the foundation layer 11 disposed on the second surface 5 </ b> B, and the foundation layer 11. And a connection wiring layer. Here, the photoelectric conversion layer includes a back electrode layer 6, a semiconductor layer 8, and a front transparent electrode layer 9, and the connection wiring layer includes a first connection wiring layer 7 and a second connection wiring layer 10. A typical configuration of the connection wiring layer is a stacked configuration in which the first connection wiring layer 7 is an Ag layer having a thickness of 200 nm and the second connection wiring layer 10 is an Ni layer having a thickness of 50 nm. The first connection wiring layer 7 and the second connection wiring layer 10 are directly stacked on each other. In this configuration, the second connection wiring layer 10 is electrically connected to the first connection wiring layer 7, and the light reflectance of the second connection wiring layer 10 is smaller than that of the first connection wiring layer 7. . Here, the light reflectance is a reflectance when light having a wavelength of a laser used for processing is perpendicularly incident on each layer from the air.

  The thin film solar cell of the present embodiment is not necessarily limited to one using two connection wiring layers, that is, both the first connection wiring layer and the second connection wiring layer. The thin film solar cell 110 shown in FIG. As described above, a configuration using only the first connection wiring layer 7 may be employed. Since the thin film solar cell 110 has the same configuration as the thin film solar cell 100 except for this point, the thin film solar cell 100 and the thin film solar cell 110 will be described below with the description of the thin film solar cell 100.

  The underlayer 11 employed in the thin film solar cell 100 is disposed on the surface of the paper 5 in FIG. 4A that faces the lower side of the substrate 5, that is, on the second surface 5 </ b> B of the substrate 5. The underlayer 11 includes a material exhibiting a thermal decomposition temperature or a vaporization start temperature lower than the thermal decomposition temperature of the material of the substrate 5. Details of the underlayer 11 will be described later. Further, the separation surface 4 from which the first connection wiring layer 7 and the second connection wiring layer 10 are removed and at least a part of the base layer 11 is removed is formed on the second surface 5B of the substrate 5. And the separation process which performs this removal is performed by the laser processing irradiated from the 2nd surface 5B side. Therefore, at the time of laser processing shown in FIG. 1, at least the base layer 11, the first connection wiring layer 7, and the second connection wiring layer 10 are formed on the second surface 5 </ b> B of the substrate 5.

  The details of the thin film solar cell 150 having the SCAF structure to which the same configuration as that of the thin film solar cell 100 is applied will be described with reference to FIGS. FIG. 5 is a plan view (FIG. 5 (a)) and an enlarged plan view (FIG. 5 (b)) showing a schematic configuration of the thin film solar cell 150 of the present embodiment adopting the SCAF structure, and FIG. It is sectional drawing which shows the structure of the thin film solar cell of this embodiment, and FIG. 7 is a process flow figure explaining the process of manufacturing a thin film solar cell in this embodiment.

  In the present embodiment, an integrated thin-film solar cell 150 having a SCAF (Series Connection through Arts on Film) structure is manufactured. When this thin-film solar cell 150 is actually used, for example, an additional member (such as a sealing member) is appropriately used to ensure weather resistance. These additional members are omitted from the illustration and illustration in order to clearly explain the present embodiment.

In the thin film solar cell 150 having the SCAF structure, as shown in FIG. 5A, on one surface (first surface 5A) of the substrate 5, the photoelectric conversion layer that converts light into electricity is a unit photoelectric conversion unit 120 _1. , 120 ₂ ,... 120 _N are separated by the separation unit 3 and electrically separated. Connection wiring layer disposed on the other side of the substrate (second surface 5B) also, the unit connection wiring portion _{140 1,} 140 2, are separated by the separating unit 4 so that the column of · · · 140 _N electrical Separated. Hereinafter, the symbols used for the unit photoelectric conversion unit and the unit connection wiring unit are indicated by symbols with abbreviations when collectively referred to, and suffixes are added when referring to these individual components. The first surface 5 </ b> A and the second surface 5 </ b> B of the substrate 5 are respectively selected from both surfaces forming the thickness of the substrate 5. Here, of both surfaces of the substrate, the surface on which the photoelectric conversion layer is disposed or formed is defined as the first surface 5A. Moreover, in each drawing explaining the thin film solar cell 150, in each drawing describing the cross section, a surface facing upward is drawn as the first surface 5A, and in each drawing describing the plane, the paper surface becomes the first surface 5A. It is drawn as follows. When distinguishing the directions in the plane of the substrate 5, the horizontal direction on the paper surface in FIGS. 5A and 5B is referred to as the longitudinal direction, and the vertical direction is referred to as the width direction.

In the thin film solar cell 150, as shown in FIG.5 (b), each of the isolation | separation part 3 and the isolation | separation part 4 has repeated the same thing several times, and was located in one direction. The respective positions of the substrate 5 are shifted so that their positions are different. Thus, the position of the partition that forms the unit photoelectric conversion unit 120 and the position of the partition that forms the unit connection wiring unit 140 are staggered. The unit connection wiring unit 140 is arranged in such a way that when each unit connection wiring unit, that is, the unit connection wiring unit 140 _i is viewed, two unit photoelectric conversion units 120 _i and 120 _{i + 1} adjacent to each other on the first surface 5A of the substrate 5 It overlaps with the area | region which can be connected through the board | substrate 5. FIG.

6 is a cross-sectional view taken along the line AA ′ (FIG. 6A) and a cross-sectional view taken along the line BB ′ (FIG. 6B) in the enlarged plan view of FIG. 5B. The current collecting holes 1 and the connection holes 2 formed as openings in the substrate 5 pass through the substrate 5, and each of the unit photoelectric conversion portions on the first surface 5 </ b> A passes through the current collection holes 1 and the connection holes 2. It is configured to be connected in series. That is, for example, when the central portion of the thin film solar cell 150 is viewed, the unit connection wiring part 140 _i partitioned by the separation unit 4 is in front of one unit photoelectric conversion unit 120 _i that overlaps the unit connection wiring part 140 _i. the transparent electrode layer 9, and is connected via current collection holes 1 (FIG. 6 (a), the reference a ₁ part near current collection holes 1). At the same time, the unit connection wiring part 140 _i is also connected through the connection hole 2 to the back electrode layer 6 of the other unit photoelectric conversion part 120 _{i + 1} overlapping the same unit connection wiring part (FIG. 6A). see _{a 3} parts near the connection hole 2). By repeating this connection configuration, unit photoelectric conversion units 120 ₁ , 120 _{2 on} the first surface 5A using the unit connection wiring portions 140 ₁ , 140 ₂ ,... 140 _N of the second surface 5B as wirings, respectively. ,... 120 _N are connected in series in the order of arrangement.

The unit photoelectric conversion unit 120 is obtained by dividing the photoelectric conversion layer by the separation unit 3. Here, the semiconductor layer 8 and the front transparent electrode layer 9 including the back electrode layer 6 and the nip junction structure are formed on the first surface 5A of the substrate 5 except for both ends in the width direction of the substrate 5 where the connection holes 2 are provided. Are arranged in this order. On the other hand, the opposite ends connection hole 2 is provided, the front transparent electrode layer 9 is not formed (see A ₃ parts near the connection hole 2 in FIG. 6 (a)). For this reason, the exposed semiconductor layer 8 and the back electrode layer 6 on the substrate side extend to the connection hole 2 at both ends where the connection hole 2 is provided.

  Next, a process for manufacturing the thin film solar cell 150 having such a structure will be described with reference to FIG. First, an insulating flexible substrate 5 (hereinafter referred to as “substrate 5”) is employed as a substrate for manufacturing the thin film solar cell 150. Specifically, for example, a polyimide resin film substrate is used. Other examples of the substrate material that can be used include other insulating plastic films such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PES (polyethersulfone), acrylic, and aramid. .

  First, the base layer 11 is formed on the second surface 5B which is one surface of the substrate 5 (base layer forming step S102). A specific example of the step of forming the base layer 11 will be described. First, the precursor solution of the base layer 11 is printed or applied to the substrate 5, and the layer of the precursor solution is applied to the second surface 5 </ b> B of the substrate 5. Form on top. Then, the layer of the precursor solution is dried, cured, polymerized, etc., and solidified to form the base layer 11. Solidification processing conditions such as drying, curing, and polymerization are appropriately determined according to the material used for the underlayer 11. The underlying layer 11 to be formed is adapted to satisfy several technical requirements. In the present embodiment, the thermal decomposition temperature or vaporization start temperature of the base layer 11 is made lower than the thermal decomposition temperature of the substrate. Other technical requirements for the underlying layer 11 are optional, for example, being able to withstand the temperature of each subsequent process, and in each process or use, the substrate 5 and a conductor layer thereon (for example, For example, sufficient adhesion with the first connection wiring layer 7) can be ensured, and flexibility of the substrate 5 is not disturbed. In addition to the above-described process examples, for example, the base layer forming step S102 is performed by laminating a layer that becomes the base layer 11 in the step of forming the substrate 5 into a belt-like film, and the base layer 11 is at least one of the substrates 5. You may perform the process which forms in the surface. Such a formation process of the underlayer 11 can employ various methods depending on a specific material employed as the underlayer 11. Hereinafter, the outline of the process will be further described for each material of the underlayer 11.

  First, a case where an acrylic resin is employed as the base layer 11 will be described. As a typical acrylic resin in this case, an acrylic resin used for paint or the like can be employed. More specifically, for example, an organic solvent-based, water-based, or solvent-free acrylic resin can be used. If the acrylic resin contained in each of these systems is exemplified, the organic solvent-based acrylic resin includes non-crosslinked acrylic lacquer and crosslinked aminoacrylic and acrylic urethane. The water-based acrylic resin includes water-soluble acrylic, acrylic hydrosol, and acrylic emulsion. The solventless acrylic resin includes powder acrylic, UV (ultraviolet ray) / EB (electron beam) cured acrylic. These various resins are formed as the base layer 11 by curing the precursor of the solution by a process corresponding to the curing method of each material. For example, amino acrylic and powder acrylic are thermally cured by heating, acrylic lacquer, acrylic urethane, acrylic emulsion, etc. are cured by volatilizing the solvent, and UV cured acrylic is cured by irradiating with ultraviolet rays, and EB curing. Acrylic is cured by irradiation with an electron beam.

  As the precursor of such an acrylic resin, for example, various acrylates (acrylic acid esters) and methacrylates (methacrylic acid esters) that become monomers and oligomers are used. The precursor is a solution in which an appropriate amount of a polymerization initiator is further mixed according to the need for curing, and the precursor solution is disposed so as to form a thin layer on the substrate 5. Then, the solidified underlayer 11 is formed by applying a stimulus (heat, light, electron beam, etc.) according to the polymerization initiator to the thin layer of the precursor solution. In the acrylic resin as described above, it is possible to adjust the thermal decomposition temperature or the vaporization start temperature by adjusting the chemical structure and solidification conditions. The inventor pays attention to the degree of polymerization as a particularly important parameter for adjusting the thermal decomposition temperature. Therefore, each element such as radical concentration, oxygen concentration, and temperature, which are factors affecting the degree of polymerization of the material of the base layer 11 after solidification, is appropriately controlled. Conditions appropriately controlled to influence the degree of polymerization include the influence of the precursor solution for the underlayer 11 and the underlayer 11 itself from the substrate 5, and just before the subsequent second surface patterning process S 122. The heat received by the base layer 11 in each process up to is included. Specifically, in curing by various polymerization reactions, it is not preferable that the degree of polymerization of the underlayer 11 is too high as a result of the reaction by heat. Therefore, for example, the base layer 11 is formed from a precursor solution that contains a photopolymerization initiator and is solidified by polymerization by light, without using a thermal polymerization initiator that causes a polymerization reaction by using heat. This is a preferable example of the technique for forming the underlayer of the present embodiment.

  Another material for the underlayer 11 may be a polyimide resin. In this case, as the precursor solution of the underlayer 11, a solution obtained by dissolving polyamic acid (polyamide acid) in an appropriate solvent (for example, N-methyl-2-pyrrolidone, xylene, gamma-butyrolactone) should be adopted. Can do. The substrate 5 on which such a precursor solution is formed in a layered form is heated and fired so as to have a temperature of, for example, about 300 ° C. to imidize it, whereby the base layer 11 containing a polyimide resin can be obtained. In addition, the polyimide resin base layer 11 can be obtained by applying a precursor of a photosensitive polyimide resin and exposing and curing it, or dissolving and applying a preliminarily-immobilized soluble polyimide in a solvent and drying. It is also possible to form In addition, when the substrate 5 itself is a polyimide film substrate, for example, it is preferable that the substrate 5 be a substrate that can withstand heat treatment with a substrate temperature of about 350 ° C., for example. Further, even when both the base layer 11 and the substrate 5 are formed of a polyimide resin, it is possible to prepare the material of the base layer 11 so as to exhibit a lower thermal decomposition temperature or vaporization start temperature than the material of the substrate 5. It is possible enough.

  In the case where the underlayer 11 is formed using the various precursor solutions described above, the underlayer 11 is also formed when the underlayer 11 is obtained by drying, curing, or polymerizing the precursor solution. Even when formed without the precursor solution, it is arranged or formed on the one surface of the substrate 5 so as to be a thin layer or a thin film by various methods. For this purpose, any method for printing or converting can be employed. That is, as a method for forming the precursor solution of the underlayer 11 on at least one surface of the substrate 5 as a layer of the precursor solution, a printing method such as screen printing, a slit coater, a roll coater, an air knife is used. Coating methods such as coater and bar coater can be employed. Furthermore, the layer of the precursor solution can be formed on the substrate 5 by spraying the precursor solution by spraying or by, for example, immersing and lifting the substrate 5 in the precursor solution. Further, the fine particles of the precursor solution of the underlayer 11 can be electrostatically formed in a thin layer on the substrate 5 as in powder coating, for example.

  Moreover, in each aspect of the present invention including this embodiment, the material of the underlayer 11 can also be selected from the various materials described above or a mixture including any of the materials described above. This mixture can be, for example, a mixture of a plurality of polymer materials to be phase-separated or a polymer layer mixed with some filler.

  As described above, the technical requirement considered for selecting the material of the underlayer 11 is that the thermal decomposition temperature (or vaporization start temperature) of the underlayer 11 is lower than the thermal decomposition temperature of the material of the substrate 5. Please include. The means for determining the thermal decomposition temperature (or vaporization start temperature) is determined for the material of the base layer 11 and the substrate 5 at any stage after the base layer formation step S102 is actually performed. Most typically, the thermal decomposition temperature (or vaporization start temperature) indicated by the underlayer 11 immediately before the second surface patterning step (S122, which will be described later), which is a separation process using a laser, is the heat of the material of the underlayer 11. The decomposition temperature (or vaporization start temperature) is used, and compared with the thermal decomposition temperature of the material of the substrate 5 at that stage. In this way, it is determined whether or not the material of the base layer 11 reflects the idea of each aspect of the present invention. However, the determination of the thermal decomposition temperature (or vaporization start temperature) of the material of the underlayer 11 and the substrate 5 is not necessarily limited to that stage, but a sample sample for measurement at another stage or using the same material. It is also possible to determine using The technical requirements for the base layer 11 include heat resistance that can withstand the temperature of the substrate reached in the process of manufacturing the solar cell. Therefore, for the underlayer 11, in addition to the above-mentioned acrylic resin and polyimide resin, other types of materials such as polystyrene, polypropylene, polyethylene, etc. whose thermal decomposition temperature or vaporization start temperature is lower than the thermal decomposition temperature of the substrate are used. It is possible to use.

  After the foundation layer 11 is formed, an opening for the connection hole 2 is formed (connection hole forming step S104). For this purpose, an opening is provided at a predetermined position of the substrate 5 by a punching die (punch). Next, by heating under reduced pressure, the gas released from the polyimide film or the base layer 11 made of the material of the substrate 5 is removed (degassing process S106). The degassing process S106 may be performed either before or after the connection hole forming step S104. In addition, since the degassing step S106 is a step in which not only the substrate 5 but also the underlayer 11 is heated, it is assumed that the material of the underlayer 11 has an effect of increasing the degree of polymerization, for example. It is also possible to leave.

  Thereafter, the back electrode layer 6 is formed on one surface (first surface 5A) of the substrate 5 (back electrode layer forming step S108), and then below the other surface (second surface 5B) of the substrate 5 surface. The first connection wiring layer 7 is formed on the ground layer 11 (first connection wiring layer forming step S110). The back electrode layer 6 is formed by sputtering, for example, so that an Ag layer has a thickness of 200 nm. Further, Ag is used as the material of the first connection wiring layer 7 in the same manner as the back electrode layer 6. As materials for the back electrode layer 6 and the first connection wiring layer 7, metals such as an Ag alloy, aluminum (Al), copper (Cu), and titanium (Ti) can be used in addition to these. The back electrode layer 6 may be a film having a multilayer structure of a metal layer and a transparent electrode layer. The film formation method for forming the back electrode layer 6 and the first connection wiring layer 7 is not limited to the sputtering method, and a vacuum deposition method, a spray film formation method, a printing method, a coating method, or a plating method can also be employed. .

  When the back electrode layer formation step S108 and the first connection wiring layer formation step S110 are finished, the back electrode layer 6 formed on the first surface of the substrate 5 and the first connection wiring layer 7 formed on the second surface of the substrate 5 Are directly overlapped in the vicinity of the inner wall of the connection hole 2 and are electrically connected to each other.

  When the first connection wiring layer formation step S110 is completed, the current collection holes 1 are formed in the substrate 5 using a punching die different from the case of the connection holes 2 (current collection hole formation step S112). At this time, the current collecting hole 1 is formed so as to penetrate not only the substrate 5 but also the back electrode layer 6, the base layer 11, and the first connection wiring layer 7 formed in the substrate 5 at that stage. The Further, the semiconductor layer 8 is formed on the first surface side of the substrate 5 (semiconductor layer forming step S114). The semiconductor layer 8 is a silicon (Si) layer having a nip structure in which, for example, an amorphous silicon n-layer, i-layer, and p-layer are arranged from the substrate 5 side. For this formation, for example, a high frequency capacitively coupled plasma CVD (Chemical Vapor Deposition) method is used. In the present embodiment, the film forming method for forming the semiconductor layer 8 is not particularly limited. As described above, it is a preferable example of the film forming method to use the high frequency capacitively coupled plasma CVD method, and further to use a device having a parallel plate type showerhead electrode as a discharge electrode as a film forming device therefor. Other configurations of the semiconductor layer 8 may be a photoelectric conversion layer using microcrystalline Si as an i layer, or a multi-junction type in which an amorphous Si nip structure and a microcrystalline Si nip structure are stacked. A (tandem type) photoelectric conversion layer may be used.

  Further, when the semiconductor layer 8 is formed in the present embodiment, another device for increasing the processing efficiency of the film forming process is also useful. For example, a roll-to-roll method of continuously forming a film while continuously transporting the substrate 5 can be adopted as a preferable process for this embodiment. In addition to this, there is also a method (stepping roll method) that operates so as to repeat the transfer mode and the film formation mode and advances the film formation process so that the substrate is stopped in the film formation mode. It can be employed as a preferred process of the embodiment.

After the semiconductor layer is formed in the semiconductor layer forming step S114, a transparent conductive material is further deposited on the first surface 5A side of the substrate 5 as the front transparent electrode layer 9 (transparent conductive layer forming step S116). At this time, the transparent conductive material is not deposited by applying a mask to both side end portions of the photoelectric conversion layer, that is, the portions where the connection holes 2 are provided (in the vicinity of A ₂ and A _{3 in} FIG. 5B). . As a result, the semiconductor layer 8 is exposed in this portion (FIG. 6A). Even when the unit photoelectric conversion units 120 connected in series are provided so as to form a plurality of columns (not shown), the transparent conductive material is not deposited between the columns. Thus, the transparent conductive layer 9 is prevented from being formed in the region of the connection hole 2.

Various transparent conductive materials can be used as the transparent conductive material for the front transparent electrode layer 9 of the present embodiment, and the material is not particularly limited. This transparent conductive material is typically any one or combination of transparent conductive materials of metal oxides such as ITO, SnO ₂ , TiO ₂ , ZnO, IZO (In ₂ O ₃ —ZnO, registered trademark). (Laminate or mixture) is selected. Furthermore, RF sputtering, DC sputtering, printing method, coating method, etc. can be employed as the film forming method in the transparent conductive layer forming step S116.

  Next, the second connection wiring layer 10 is formed on the entire second surface side of the substrate 5 (second connection wiring layer forming step S118). When the second connection wiring layer forming step S118 is completed, the front transparent electrode layer 9 formed on the first surface of the substrate 5 and the second connection wiring layer 10 formed on the second surface 5B of the substrate 5 They overlap directly near the inner wall and are electrically connected to each other. Since the second connection wiring layer 10 is formed on the second surface 5B of the substrate 5 so as to be in contact with the first connection wiring layer 7, these connection wiring layers on the second surface 5B are connected to each other and electrically connected. The connection wiring layer is integrated with the wiring.

  After the second connection wiring layer forming step S118, patterning for forming the separation portion 3 on the first surface 5A side of the substrate 5 is performed (first surface patterning process S120). By this patterning, the semiconductor layer 8 is separated by the separation part 3 together with the back electrode layer 6. The front transparent electrode layer 9 is not formed in the vicinity of the connection hole 2, but the vicinity of the separation portion 3 is partitioned at the same position as the back electrode layer 6. As a result, the unit photoelectric conversion unit 120 in which the back electrode layer 6, the semiconductor layer 8, and the front transparent electrode layer 9 are stacked in this order except for the vicinity of the connection hole 2 at the end of the shape surrounded by the separation unit 3. It is formed.

  In addition, in order to perform the process of forming the unit photoelectric conversion part 120 more reliably, it is also preferable to perform a preliminary patterning process in addition to the first surface patterning process S120 shown here. This preliminary patterning process is performed, for example, at any stage after the back electrode layer forming step S108 and before the semiconductor layer forming step S114. Also in this preliminary patterning process, it is the position of the separation portion 3 that is patterned so as to divide the back electrode layer 6.

  Finally, laser processing is performed on the second surface 5B side of the substrate 5 at the position of the separation portion 4 (second surface patterning process S122). In the second surface patterning process S122, the second connection wiring layer 10 and the first connection wiring layer 7 are simultaneously separated, and the separation portion 4 is formed. That is, in this process, the second connection wiring layer 10 and the first connection wiring layer 7 are removed from the separation portion 4. At this time, with respect to the base layer 11, a part or all of the thickness on the first connection wiring layer 7 side is removed. Here, for the laser processing in the second surface patterning process S122, patterning is performed using, for example, a SHG wave (wavelength: 532 nm) of a YAG laser. As long as the laser power required for processing can be secured, YAG-THG wave (355 nm), YAG-FHG wave (266 nm), KrF excimer laser (248 nm), etc. can be used. . The irradiation conditions at this time are determined by adjusting the conditions when the base layer 11 is not employed as a starting point. The conditions include various conditions. For example, circular pulses or rectangular pulses, conditions related to the beam shape such as irradiation range, conditions related to scanning such as pulse frequency, overlap, scanning speed, and irradiation power. Conditions can be subject to adjustment. Thus, the unit connection wiring part 140 is formed on the second surface 5B of the substrate 5.

  In the second surface patterning process S122, the power extraction electrode (not shown) is simultaneously electrically separated, that is, individualized, so that the peripheral portion of the substrate 5 overlaps with the separation portion on the first surface side. A separation part is drawn by laser processing (none is shown). Looking at the separation part of the formed second surface 5B, it is separated at the periphery that encloses all the thin-film solar cell elements at once and the adjacent boundary (inside of the peripheral conductive part) of the two series-connected solar cell elements. There is a department. In the separation part including the separation part 4, at least the second connection wiring layer 10 and the first connection wiring layer 7 are not left, and at least a part of the thickness of the base layer 11 is removed. .

The fact that the unit photoelectric conversion units formed in this way form a series-connected column becomes clear by following the electrical path sequentially from the left side of the sheet of FIG. 5 (a). First, the electrical path is from the first unit photoelectric conversion unit 120 ₁ (front transparent electrode layer 9, semiconductor layer 8, back electrode 6) on the left side of FIG. It is connected to the first unit connection wiring portion 140 _1. The coupled first from the unit connection wiring portion 140 ₁ to the connection hole 2 through the second unit photoelectric conversion unit 120 _2. Hereinafter, this repetition has led is connected to a unit photoelectric conversion unit 120 _N of the N to the unit connection wiring portion 140 _N of the N. Here, in order to take out the output from the overall unit photoelectric conversion layer 120 which are connected in series, for example, the unit connection wiring portion 140 _N of the N also be used as an electrode for taking out the power, first unit Photoelectric It connected to the wiring portion on the back surface electrode 6 or the back electrode 6 that the conversion unit 120 ₁ is also used as an electrode for taking out electric power.

  In order to further enhance the practicality of the thin film solar cell 150 as a thin film solar cell module, a sealing material, a back sheet and the like are further laminated as an exterior. As the sealing material and the back sheet, various resin materials such as EVA (ethylene vinyl acetate), PE (polyethylene), PET, ETFE (ethylene tetrafluoroethylene) are employed. Here, these materials are not shown.

  The effect of the thin film solar cell 150 of the present embodiment is that the first connection wiring layer 7 and the second connection wiring layer 10 of the same material are employed as compared with the case of the conventional SCAF structure in which the base layer 11 is not employed. Even if it does, it will become possible to form the isolation | separation part 4 with the laser beam of smaller irradiation power. For this reason, the possibility that the portion of the substrate 5 exposed in the separation portion 4 is damaged by the laser is reduced.

  In the thin film solar cell 150 of this embodiment, an additional effect is also brought about. That is, by providing the base layer 11, it is possible to employ a kind of metal that has been difficult to employ in the connection wiring layer. Specifically, it is possible to employ, for example, a metal having a high light reflectivity as the second connection wiring layer 10 such that when the separation process by laser processing for the separation portion is performed, it is difficult to employ the damage to the substrate. It becomes. For example, in a solar cell having a SCAF structure, if the thickness of the Ag layer of the first connection wiring layer 7 is reduced and aluminum is used as the second connection wiring layer 10, the conductivity and It is possible to realize a thin film solar cell that is further excellent in balance between performance such as durability and cost. This is because, even if it is a kind of metal that has been difficult to adopt in the past due to its high reflectance, it can be employed as the second connection wiring layer 10 by using the base layer 11.

<Second Embodiment>
Next, 2nd Embodiment is described as embodiment of the thin film solar cell which implement | achieves serial connection only in one side of a board | substrate. The description of the same configuration as that of the first embodiment is omitted.

  FIG. 8 is a cross-sectional view of a thin-film solar cell 200 having a schematic configuration according to the second embodiment of the present invention. As shown in FIG. 8, the substrate 5 used in the thin film solar cell 200 also has a first surface 5A and a second surface 5B. In addition, the thin-film solar cell 200 includes a base layer 11 disposed on the first surface 5 </ b> A of the substrate 5 and a photoelectric conversion layer disposed on the base layer 11. Here, the photoelectric conversion layer has the back electrode layer 6, the semiconductor layer 8, and the front transparent electrode layer 9, and is arranged so that the back electrode layer 6 is in contact with the base layer 11.

  Among the above elements, at least a part of the base layer 11 and the back electrode layer 6 are removed at the separation portion (P1 portion) 23 on the first surface 5A. The underlayer 11 employed in the thin film solar cell 200 is disposed on the first surface 5A of the substrate 5, that is, on the surface of the substrate 5 facing upward on the paper surface of FIG. Also in the second embodiment, the underlying layer 11 includes a material having a thermal decomposition temperature (or vaporization start temperature) lower than the thermal decomposition temperature of the material of the substrate 5 as in the first embodiment. The material and forming method of the underlayer 11 are the same as those described in the first embodiment.

  The solar cell 200 manufactured in the present embodiment is a substrate type solar cell. That is, the solar cell 200 is configured to use light incident from above in FIG. 8 for power generation. When this thin-film solar cell 200 is actually used, for example, an additional member (such as a sealing member) is used as appropriate in order to ensure weather resistance. However, the additional member is the same as in the first embodiment. Are omitted from the illustration and illustration to clearly describe the present embodiment.

This thin-film solar cell 200 is an integrated solar cell in which electrical elements are produced only on the first surface 5A of the substrate 5 and connected in series. Specifically, the unit photoelectric conversion units 220 ₁ , 220 ₂ ,... 220 _N formed by dividing the photoelectric conversion units are connected in series to each other. FIG. 8 shows unit photoelectric conversion units 220 _i−1 , 220 _{i, and} 220 _{i + 1} (i is an integer of 2 to N−1) among them. The front transparent electrode layer 9 of the unit photoelectric conversion part 220 _i-1 is connected to the back electrode layer 6 in the unit photoelectric conversion part 220 _{i at} the contact part (P2 part) 24. The connection configuration is the same as in between the back electrode layer 6 of the front transparent electrode layer 9 and the unit photoelectric conversion unit 220 i + ₁ in the unit photoelectric conversion unit 220 _i. In the separation unit 23, so as not to the back electrode layer 6 corresponding to the back electrode layer 6 and the unit photoelectric conversion unit 220 i + ₁ corresponding to the unit photoelectric conversion unit 220 _i is electrically short-circuited to each other, the back electrode layer 6 and at least a part of the base layer 11 are removed. In this way, series connection of the unit photoelectric conversion units 220 ₁ , 220 ₂ ,... 220 _N is realized on the first surface 5 A of the substrate 5. In order to realize such a series connection, in the contact portion (P2 portion) 24, the semiconductor layer 8 is removed while leaving the back electrode layer 6 and the base layer 11, and then the front transparent electrode layer 9 is formed. ing. Similarly, in the separation part (P3 part) 25, the front transparent electrode layer 9 and the semiconductor layer 8 are removed, leaving the back electrode layer 6 and the base layer 11. In addition, since the separation part 23, the contact part 24, and the separation part 25 are also called P1 (Pattern 1), P2 (Pattern 2), and P3 (Pattern 3) conventionally, they are written together as appropriate.

  A process for manufacturing the thin film solar cell 200 employing such an underlayer 11 will be described below. FIG. 9 is a process flow diagram illustrating a process of manufacturing the thin-film solar cell 200 in the present embodiment. First, the substrate 5 on which the thin-film solar cell 200 is manufactured is an insulating flexible substrate. Typically, for example, a polyimide film is used as in the first embodiment. Other insulating plastic films such as PET, PEN, PES, acrylic, and aramid can also be used as in the first embodiment.

  First, the base layer 11 is formed on the first surface 5A, which is one surface, of the substrate 5 (base layer forming step S202). Except that the surface to be formed is the first surface 5A on which the photoelectric conversion layer is formed, the detailed steps for forming the foundation layer 11 are the same as in the first embodiment.

  After the foundation layer 11 is formed, the gas emitted from the polyimide film or the foundation layer 11 of the material of the substrate 5 is removed (degassing process S204). Note that it is possible to set the degassing process S204 as a condition assuming the influence of heat on the underlayer 11 as in the first embodiment.

  Next, the back electrode layer 6 is formed on the base layer 11 on the one surface (first surface 5A) of the substrate 5 (back electrode layer forming step S206). The back electrode layer 6 is formed by sputtering, for example, so that a silver layer (Ag layer) has a thickness of 200 nm. In addition, as a material for the back electrode layer 6, metals such as an Ag alloy, aluminum (Al), copper (Cu), and titanium (Ti) can be used. The back electrode layer 6 may be a film having a multilayer structure of a metal layer and a transparent electrode layer. The film formation method for forming the back electrode layer 6 is not limited to the sputtering method, and a vacuum deposition method, a spray film formation method, a printing method, a coating method, or a plating method can also be employed.

  When the back electrode layer forming step S206 is completed, a pattern 1 forming step S208 is performed. This pattern 1 forming step S208 is a step of forming the separation part 23. In order to form the separation part 23, a patterning process using a laser as shown in FIG. 1 is performed. In this case, the power of the laser beam is adjusted for irradiation. The laser and wavelength used are, for example, YAG laser SHG waves, and the wavelength is 532 nm.

  Next, the semiconductor layer 8 is formed on the back electrode layer 6 on the first surface 5A side of the substrate 5 (semiconductor layer forming step S210). The semiconductor layer 8 is a silicon (Si) layer having a nip structure in which, for example, an n layer, an i layer, and a p layer of amorphous silicon are arranged from the substrate 5 side, as in the first embodiment. For this formation, for example, a high frequency capacitively coupled plasma CVD (Chemical Vapor Deposition) method is used. Also in the present embodiment, the film forming method for forming the semiconductor layer 8 is not particularly limited, can be a photoelectric conversion layer using microcrystalline Si as an i layer, a nip structure of amorphous Si and a nip of microcrystalline Si. As in the first embodiment, a multi-junction type (tandem type) photoelectric conversion layer can be formed by laminating the structure, and a roll-to-roll method or a stepping roll method can be adopted.

  After the semiconductor layer 8 is formed by the semiconductor layer forming step S210, the pattern 2 forming step S212 is performed. This pattern 2 formation step S212 is a process for forming the contact portion 24 in the semiconductor layer 8. For this treatment, a laser having a wavelength that is easily absorbed by the semiconductor 8 and the back electrode 6 has high reflectivity, for example, a SHG wave (532 nm) of a YAG laser can be employed. When the SAG wave of the YAG laser is employed, the patterning process for forming the contact portion 24 can be performed even if the laser power is smaller than the laser power necessary for processing the back electrode 6. Further, when the underlying layer 11 cannot withstand the patterning process and the back electrode layer 6 is removed, for example, a mechanical scribing method of mechanically removing the semiconductor layer 8 with a metal needle is employed. Is also possible.

  Next, a transparent conductive material is deposited as the front transparent electrode layer 9 on the semiconductor layer 8 on which the contact portion 24 is formed (transparent conductive layer forming step S214). The front transparent electrode layer 9 fills the contact portion 24 and is electrically connected to the back electrode layer 6. Also in the present embodiment, various transparent conductive materials can be used as the transparent conductive material for the front transparent electrode layer 9 as in the first embodiment, and various film forming methods can be used. It becomes possible to adopt.

  Finally, pattern 3 formation step S216 is performed. This pattern 3 formation step S216 is a process of forming the separation portion 25. Similarly to the pattern 2 formation step S212, this treatment is also preferably patterning using a laser beam having a wavelength (532 nm) at which the absorbance of the semiconductor layer 8 is large and the back electrode 6 is strongly reflected, and mechanical scribing is used. It is also possible to adopt.

  Also in this embodiment, in order to further enhance the practicality of the thin-film solar cell module as in the first embodiment, a sealing material, a back sheet, and the like are laminated as an exterior. As the sealing material and the back sheet, various resin materials such as EVA, PE, PET, and ETFE are employed. Here, these materials are not shown.

  Also in this embodiment, there is an advantage that the power of the laser can be lowered in the pattern 1 formation step S208 as in the first embodiment. This advantage leads to a reduction in damage to the portion of the substrate 5 exposed in the separation portion 23 during the pattern 1 formation step S208. Moreover, the point which the selection range of a metal spreads is the same as that of 1st Embodiment.

  Next, a sample for actually measuring how much the minimum laser power during the separation process is reduced in the first embodiment and the second embodiment described above was produced. First, in order to confirm the effect of the underlayer 11 in the SCAF structure of the first embodiment, the example sample 1 manufactured using the underlayer 11 as described in the first embodiment and the underlayer 11 are adopted. Comparative Example Sample 1 produced without comparison was compared. At this time, the minimum laser power capable of appropriately performing the separation process (second surface patterning process S122) was investigated. Next, the minimum laser power was similarly investigated in order to confirm the effect of the foundation layer 11 on the separation process (pattern 3 formation step S216) in the second embodiment. That is, the example sample 2 manufactured as described in the second embodiment using the base layer 11 and the comparative example manufactured as described in the second embodiment except that the base layer 11 is not used. Sample 2 was targeted. Hereinafter, conditions for producing each sample and comparison results thereof will be described. In addition, the name of the temperature index described as “thermal decomposition temperature” in the examples and comparative examples and the value thereof are not used to limit that the phenomenon actually occurring is thermal decomposition. Rather, the phenomenon actually occurring includes a vaporization phenomenon (evaporation or sublimation) as a possibility. For this reason, in the description of the following examples and comparative examples, the description part referred to as “thermal decomposition temperature” should be understood as the vaporization start temperature.

[Example Sample 1]
As Example Sample 1, a thin-film solar battery cell having the configuration of the thin-film solar battery 150 was produced. A single-junction amorphous Si solar cell was produced. The manufactured process is as described based on FIG. Specific conditions were as follows. First, a polyimide film having a thickness of 50 μm was used as the substrate 5. Further, UV curable acrylic was adopted as the base layer 11 of acrylic resin. For this reason, in the underlayer forming step S102, first, a thin layer of a precursor solution obtained by mixing a photopolymerization initiator in acrylate was applied to the second surface 5B of the substrate 5 by a slit coater. Then, the precursor solution was polymerized and cured with ultraviolet rays to form the base layer 11. The thermal decomposition temperature in the stage immediately before the second surface patterning process S122 of the base layer 11 was approximately 280 to 320 ° C. On the other hand, the thermal decomposition temperature of the polyimide resin of the substrate 5 at the same stage was approximately 500 to 550 ° C. These thermal decomposition temperatures are the start temperatures of mass changes based on TG curves measured for the measurement samples of the underlayer and the substrate that have undergone the same thermal history as those immediately before the second surface patterning process S122 in FIG. Adopted.

  The connection hole 2 is opened using a punch in the connection hole forming step S104, and the substrate 5 and the base layer 11 are degassed by heating the substrate 5 to 250 ° C. under a reduced pressure of 10 Pa or less as a degassing process S106. Processed. As the back electrode layer in the back electrode layer forming step S108, an Ag layer was formed by sputtering so as to have a film thickness of 200 nm.

  In the first connection wiring layer formation step S110, Ag was formed to 200 nm on the second surface of the substrate 5 by Ar gas sputtering at a pressure of 2 Pa to form the first connection wiring layer 7. In the current collecting hole forming step S112, a large number of current collecting holes 1 were formed by punching so as to obtain a 5 mm pitch with a diameter of 1 mm.

Next, the semiconductor layer 8 was formed by plasma CVD method as semiconductor layer formation process S114. Each layer of the semiconductor layer 8 was formed using a capacitive coupling plasma method so that the layer thicknesses were 20 nm (n layer), 300 nm (i layer), and 20 nm (p layer). Specifically, a parallel plate type shower head electrode was used as the discharge electrode of the plasma CVD apparatus, and the semiconductor layer 8 was formed with a discharge frequency of 27.12 MHz at an electrode distance of 20 mm. Note that the substrate 5 was kept stationary when the semiconductor layer 8 was formed. Regarding conditions such as the gas used, an n-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas, H ₂ gas, and PH ₃ gas. The discharge power at this time was 5 W, and the film formation temperature (set temperature of the substrate) was 250 ° C. Next, an i-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas and H ₂ gas. The discharge power at this time was 20 W, and the film formation temperature was 250 ° C. Further, a p-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas, H ₂ gas, and B ₂ H ₆ gas. The discharge power at this time was 5 W and the film formation temperature was 160 ° C.

  Thereafter, as the transparent conductive layer forming step S116, the front transparent electrode layer 9 was formed on the nip single junction structure made of amorphous Si formed on the first surface side of the substrate 5. ITO was adopted as the transparent conductive material for the front transparent electrode layer 9. In this embodiment, the formation conditions are set to 0.7 Pa by an RF sputtering method using Ar gas, and the layer thickness is set to 70 nm. At this time, the vicinity of the connection hole 2 was masked so that the front transparent electrode layer 9 was not formed in the connection hole 2.

  Next, as a second connection wiring layer formation step S118, a Ni layer to be the second connection wiring layer 10 was formed on the entire second surface. The Ni layer was formed by sputtering with Ar gas at a pressure of 2 Pa. The thickness of the Ni layer was 50 nm. Finally, the first surface patterning step S120 and the second surface patterning process S122 were performed. In the second surface patterning process S122, conditions are set so that the separation portion 4 is formed in which at least a part of the base layer 11 is removed together with the first connection wiring layer 7 and the second connection wiring layer 10 thereon. Were determined.

[Conventional sample 1]
A comparative example sample 1 of a thin-film solar cell was produced in the same manner as the example sample 1 except that the base layer forming step S102 for forming the base layer 11 on the second surface 5B of the substrate 5 was not performed. In this case, during the second surface patterning process S122, the YAG laser irradiation conditions were determined so that the separation portion 4 removed together with the first connection wiring layer 7 and the second connection wiring layer 10 was formed. . The irradiation conditions were changed from the irradiation conditions of Example Sample 1 only in irradiation power.

[Comparison between Example Sample 1 and Conventional Sample 1]
The minimum value (minimum laser power) of irradiation power that can form a good separation portion 4 during the second surface patterning process S122 was 1.0 mJ for each pulse in Example Sample 1, whereas In Comparative Example Sample 1, it was 2.1 mJ. As described above, in the thin film solar cell having the SCAF structure described in the first embodiment, the laser power necessary for the separation process is reduced to half or less by employing the base layer 11. At this time, the other laser irradiation conditions were a processing width of 400 μm, a repetition frequency of 5 kHz, and a processing speed of 900 mm / s.

[Example Sample 2]
The example sample 2 was produced by the structure of the thin film solar cell 200 (FIG. 8) of 2nd Embodiment. The manufactured steps are as described based on FIG. Specific conditions were as follows. First, a polyimide film having a thickness of 50 μm was used as the substrate 5. In the underlayer forming step S202, the underlayer 11 was formed by the same material and method as in the example sample 1. In addition, the thermal decomposition temperature in the stage immediately before pattern 1 formation process S208 of this base layer 11 was about 280-320 degreeC, and the thermal decomposition temperature of the polyimide resin of the board | substrate 5 was about 500-550 degreeC. These thermal decomposition temperature values are values of the onset temperature of mass change measured from the TG curve.

  Next, as the degassing process S204, the substrate 5 and the base layer 11 were degassed by heating so that the substrate temperature became 350 ° C. under a reduced pressure of 10 Pa or less. As the back electrode layer 6 in the back electrode layer forming step S206, an Ag layer was formed by sputtering so as to have a film thickness of 200 nm. The pressure at this time was 1 Pa.

  Next, pattern 1 formation process S208 was performed. At that time, the conditions were determined so that the separation part 23 in which at least a part of the base layer 11 was removed together with the back electrode layer 6 thereon was formed.

  Next, as a semiconductor layer forming step S210, a single-junction amorphous Si solar cell was formed with the semiconductor layer 8 by plasma CVD. The layer thickness of each layer of the semiconductor layer 8 was the same as that of Example Sample 1. Similarly, when the semiconductor layer 8 is formed, the substrate 5 is stationary.

  Then, pattern 2 formation process S212 was performed. At that time, using a pulse of a SHG wave (532 nm) of a YAG laser, conditions were determined so that the back electrode layer 6 would not be removed due to the presence of the base layer 11. Subsequently, transparent conductive layer formation process S214 was performed. Finally, pattern 3 formation step S216 was performed. Also in the pattern 3 formation step S216, the condition was determined using the pulse of the SHG wave (532 nm) of the YAG laser as in the pattern 2 formation step S212. Example sample 2 was produced as described above.

[Conventional sample 2]
A comparative sample 2 of a thin-film solar cell was produced in the same manner as the example sample 2 except that the base layer forming step S202 for forming the base layer 11 on the first surface 5A of the substrate 5 was not performed. In the pattern 1 formation step S208 of the conventional sample 2, the YAG laser irradiation conditions were determined so that the separation part 23 from which the back electrode layer 6 was removed was formed. The irradiation conditions were changed from the irradiation conditions of the example sump 21 only in the irradiation power.

[Comparison between Example Sample 2 and Conventional Sample 2]
The minimum laser power capable of forming a good separation portion 23 was 1.8 mJ for each pulse in the example sample 2, and 3.6 mJ in the comparative sample 2. As described above, in the substrate-type thin film solar cell described in the second embodiment, the minimum laser power of the separation process is reduced to one half by employing the base layer 11.

<Modification of each embodiment>
The first embodiment and the second embodiment have been described above as the embodiments of the present invention. These embodiments can be variously modified while maintaining the advantages. For example, in the configuration of the SCAF structure related to the first embodiment, the configuration in which the base layer 11 is formed only on the second surface 5B of the substrate 5 has been described. In this configuration, a similar underlayer can also be formed on the first surface 5A, for example. In this case, a base layer is formed on both surfaces of the substrate 5 in the base layer forming step S102. If it does in this way, it will become possible to also reduce the damage with respect to the 1st surface 5B at the time of performing the patterning process of 1st surface patterning process S120. Furthermore, since the substrate is less likely to warp than when the base layer is formed only on one side of the substrate, for example, the substrate can be easily handled in the process of manufacturing the solar cell.

  The first embodiment and the second embodiment described above have been described through the entire process for producing a thin film solar cell. However, in another aspect of the present invention, a laminated substrate for a solar cell and its substrate are produced. A method is also provided. That is, an electrically insulating substrate, and an underlayer containing a material that is formed on at least one surface of the substrate and exhibits a thermal decomposition temperature (or vaporization start temperature) lower than the thermal decomposition temperature of the material of the substrate; A laminated substrate for the above-described thin film solar cell including the above is also included in the embodiment of the present invention. And a step of forming a base layer including a material having a thermal decomposition temperature (or vaporization start temperature) lower than a thermal decomposition temperature of the material of the substrate on at least one surface of the electrically insulating substrate. A method for manufacturing a laminated substrate for any of the thin film solar cells is also included in the embodiment of the present invention. In any of these cases, since a substrate for a solar cell that can obtain at least one of the advantages described above when a solar cell is manufactured later is produced, the laminated substrate itself on which an underlayer is formed Becomes a substrate suitable for the manufacture of solar cells involving laser processing.

  The embodiments of the present invention have been specifically described above. The above-described embodiments and examples are described for explaining the invention, and the scope of the invention of the present application should be determined based on the description of the claims. Moreover, the modification which exists in the scope of the present invention including other combinations of each embodiment is also included in a claim.

  The present invention provides a solar cell in which the influence on the substrate when performing laser processing is reduced, thereby spreading or improving the performance of any power device or electric device partially including such a solar cell. Contribute greatly.

100, 110, 150, 200, 700 Thin film solar cell 1 Current collecting hole 2 Connection hole 3, 4, 74 Separating part 5, 75 Substrate 5A, 75A First surface 5B, 75B Second surface 6, 76 Back electrode layer 7, 77 First connection wiring layer 8, 76 Semiconductor layer 9, 79 Front transparent electrode layer 10, 80 Second connection wiring layer 11 Underlayer 12 Position 120, 220 Unit photoelectric conversion unit 140 Unit connection wiring unit 23 Separating unit (P1 unit)
24 Contact part (P2 part)
25 Separation part (P3 part)
52 Galvano mirror 54 Laser light source 56 Scan line

Claims (13)

A substrate having a first surface and a second surface;
A photoelectric conversion layer disposed on the first surface;
An underlayer including a material disposed on the second surface and exhibiting a thermal decomposition temperature or a vaporization start temperature lower than a thermal decomposition temperature of the material of the substrate;
A connection wiring layer disposed on the base layer,
A thin film solar cell, wherein a separation portion from which at least a part of the base layer and the connection wiring layer are removed by laser light is formed on the second surface of the substrate. The connection wiring layer partitioned by the separation part forms a row of unit connection wiring parts including several unit connection wiring parts;
The photoelectric conversion layer forms a row of unit photoelectric conversion units,
The thin film solar cell according to claim 1, wherein the unit photoelectric conversion units are connected in series by being electrically connected to each other through the connection wiring unit. Both of the material of the substrate and the material of the base layer are flexible materials that exhibit electrical insulation,
In the photoelectric conversion layer, a back electrode layer, a semiconductor layer, and a front transparent electrode layer are disposed in this order from the first surface side on the first surface of the substrate,
The unit photoelectric conversion unit is obtained by dividing the photoelectric conversion layer,
Any one of the two unit photoelectric conversion units adjacent to each other on the first surface of the substrate is one of the second surfaces through a current collecting hole through which the front transparent electrode layer of one unit photoelectric conversion unit penetrates the substrate. Are electrically connected to the unit connection wiring part, and the back electrode layer of the other unit photoelectric conversion part is electrically connected to the unit connection wiring part through the connection hole penetrating the substrate, so that The thin film solar cell according to claim 2 connected. A first connection wiring layer disposed on the base layer;
A second connection wiring layer disposed on the first connection wiring layer and electrically connected to the first connection wiring layer;
The thin film solar cell according to any one of claims 1 to 3, wherein the second connection wiring layer exhibits a light reflectance that is smaller than that of the first connection wiring layer. A substrate having a first surface and a second surface;
An underlayer containing a material disposed on the first surface and exhibiting a thermal decomposition temperature or a vaporization start temperature lower than a thermal decomposition temperature of the material of the substrate;
A backside electrode layer, and a photoelectric conversion layer disposed in contact with the backside electrode layer,
A thin film solar cell, wherein a separation portion from which at least a part of the base layer and the back electrode layer are removed by laser light is formed on the first surface of the substrate. The photoelectric conversion layer forms a row of unit photoelectric conversion units,
The unit photoelectric conversion unit includes a unit front transparent electrode unit corresponding to each unit photoelectric conversion unit,
The back electrode layer is divided by the separation part, and forms a column of unit back electrode parts in which unit back electrode parts are arranged corresponding to each of the unit photoelectric conversion parts,
Each of the unit back electrode parts is electrically connected to a unit front transparent electrode part belonging to another unit photoelectric conversion part adjacent to one side of the unit photoelectric conversion part to which each unit back electrode part belongs. The thin film solar cell according to claim 5, wherein the columns of the unit photoelectric conversion units are connected in series by being connected. The thin film solar cell according to claim 5, wherein both the material of the substrate and the material of the base layer are flexible materials. The thin film solar cell according to any one of claims 1 to 7, wherein a material of the base layer includes a component that is applied in a solution state on at least one surface of the substrate and then cured. . The thin film solar cell according to claim 8, wherein the material of the underlayer is a material that is cured from a precursor that includes a photocurable component or a photopolymerization initiator and does not include a thermal polymerization initiator. The substrate material is polyimide resin,
The material of the said foundation | substrate layer contains at least 1 or more types of resin chosen from the group which consists of an acrylic resin, a polyimide resin, a polystyrene resin, a polyethylene resin, and a polypropylene resin. Thin film solar cell. An electrically insulating substrate;
The underlayer including a material formed on at least one surface of the substrate and exhibiting a thermal decomposition temperature or a vaporization start temperature lower than a thermal decomposition temperature of the material of the substrate. A laminated substrate for the thin film solar cell according to claim 1. Forming a base layer including a material having a thermal decomposition temperature or a vaporization start temperature lower than a thermal decomposition temperature of the material of the substrate on at least one surface of the electrically insulating substrate;
Forming a conductor layer on the underlayer;
Irradiating a laser beam toward the conductor layer from the space on the one surface side of the substrate to partially remove at least a part of the base layer and the conductor layer. A method for manufacturing a solar cell. Forming a base layer containing a material having a thermal decomposition temperature or a vaporization start temperature lower than a thermal decomposition temperature of the material of the substrate on at least one surface of the electrically insulating substrate; Item 11. A method for manufacturing a laminated substrate for a thin film solar cell according to any one of Items 10 to 10.

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