Patent Publication Number: US-2023144536-A1

Title: Designable shingled photovoltaic module and manufacturing method therefor

Description:
TECHNICAL FIELD 
     The present invention relates to a designable shingled photovoltaic module in which an electrode structure is improved for variously designing the photovoltaic module and which is manufactured by connecting strings connected in a shingled manner using a flexible connecting wire, and a method of manufacturing the photovoltaic module. 
     BACKGROUND ART 
     Solar power generation involves generating power by converting light energy of the sun to electrical energy which is sustainable eco-friendly energy with low carbon and will not run out in the future unlike fossil fuels. 
     In conventional photovoltaic module manufacturing, cells are connected using metal ribbons, and thus spaces for electrically separating the cells are required when strings are manufactured. Accordingly, spaces in which a current is not generated are formed in the module, and thus output loss occurs. In addition, since the cells include front busbars, a current cannot be generated in these portions, and thus output loss is induced. 
     In another method, a photovoltaic module having a shingled array structure may be manufactured through an electrically conductive adhesive (ECA). For example, in a method of applying the ECA on front busbars of divided cells to connect the busbars to electrode pads (Ag) of other divided cells, since a busbarless structure in which a busbar is not present on a front surface is formed, there is an advantage that optical loss due to the busbar can be reduced, and since spaces for separating cells are not required unlike a conventional module, a larger number of cells can be occupied in the same area than the conventional module, and relatively high power can be output. For example, in patent document 1, as illustrated in  FIGS.  1  and  2   , a busbar electrode  61  of a lower divided cell  7  is disposed to overlap a busbar electrode  62  of a rear surface of an upper divided cell  7  and is electrically connected to the busbar electrode  62  using a conductive member  9 . 
     In Japanese Patent No. 10-6467549, a string is manufactured by forming busbar electrodes in straight lines adjacent to long sides of divided cells divided into rectangular shapes and arranging the long sides of the upper cells to overlap the long sides of the lower cells when the divided cells are connected. 
     According to the conventional technology, although a length of a string can be adjusted by connecting the larger number of divided cells to correspond to a size of a photovoltaic module, since a width of the string is limited due to a long side of the divided cell, there is a problem of difficulty in variously designing a shape of a photovoltaic module formed by variously combining strings. 
     The use of photovoltaic power generation facilities capable of generating electric power using solar energy is becoming more common. Since solar cells using solar energy do not use fossil fuels such as coal or petroleum but use sunlight which is a pollution-free and infinite energy source, the solar cells are spotlighted as new alternative energy sources in the future and are currently used to obtain power generated by solar power plants, buildings, vehicles, and the like. 
     Among various application fields of solar cells, a field of building integrated photovoltaic (BIPV) is a solar cell field of which rapid market growth is expected in the future, and particularly, a field of a window-type solar cells may be a next generation solar cell field in which not only a high power generation efficiency but also a high light transmittance are required. A dye-sensitized solar cell (DSSC) may be suitable for BIPV for a window because it allows light transmittance of a power generator to be controlled by adjusting dispersibility, and a film thickness of N-type semiconductor nanoparticles and a color or image thereof to be controlled. However, since a stability issue which is a most basic requirement for a solar cell is not solved yet, it is expected to take a long time for actual application. In addition, since a liquid electrolyte which is very toxic to the human body is used in the DSSC, a serious stability problem due to leakage of toxic substances may occur in case of damage. 
     According to the conventional technology, although a length of a string may be adjusted by connecting a larger number of divided cells to correspond to a size of a photovoltaic module, since a width of the string is limited due to a long side of the divided cell, there is a problem of a difficulty in variously designing a shape of a photovoltaic module formed by variously combining strings. 
     Accordingly, a BIPV solar cell for a window which secures light receiving performance and has superior stability using translucent high-efficiency silicon solar cells needs to be manufactured. In addition, a new solar cell structure capable of being applied to a window of a building and a vehicle to be rollable and receiving light through two surfaces and a manufacturing process therefor are required. 
     [Document 1] Japanese Patent No. 10-6467549 (registered on Jan. 18, 2019) 
     [Document 2] Korean Patent Publication No. 10-2019-0031995 (published on Mar. 27, 2019) 
     Technical Problem 
     The present invention is directed to providing a photovoltaic module having various types by improving an electrode structure of a solar cell to adjust a width and a length of a string in which unit cells are connected in a shingled manner. 
     Technical Solution 
     One aspect of the present invention provides a designable shingled photovoltaic module including electrode members each including a finger electrode and a busbar electrode on a front surface of a solar cell to correspond to the number of divided cells, wherein the finger electrode is disposed as a plurality of finger electrodes in a first direction parallel to a short side of a divided unit cell, and the busbar electrode includes a collection electrode line which extends in a second direction parallel to a long side of the divided unit cell and connects ends of the plurality of finger electrodes and a connecting electrode line which is branched off from an end of the collection electrode line and extends in the first direction to be electrically connected to another unit cell. 
     The connecting electrode line may be disposed adjacent to the short side of the unit cell to be divided, and the collection electrode line may be disposed adjacent to a cut line of the unit cell to be divided. 
     The connecting electrode line may be perpendicularly bent from the end of the collection electrode line so that the busbar electrode is formed in an “L” or “T” shape, and a length of the connecting electrode line in the “L” shape may be smaller than a length of the connecting electrode line in the “T” shape. 
     A line width of the busbar electrode may be in the range of 0.8 to 1.2 mm, and a line width of the finger electrode may be in the range of 0.08 to 0.12 mm. 
     The short side of the unit cell to be divided may be in the range of 13.3 to 66.6 mm. 
     Another aspect of the present invention provides a method of manufacturing a designable shingled photovoltaic module having a designable shingled string structure, the method including operation (a) of preparing a solar cell having a front surface on which a finger electrode and a busbar electrode are formed and a rear surface on which a rear surface electrode is formed, operation (b) of cutting the solar cell in a rectangular shape through a laser scribing process to divide the solar cell into a plurality of unit cells, and operation (c) of connecting the unit cells to have a shingled array structure in which a short side of any one divided unit cell overlaps a short side of another divided unit cell, wherein, in operation (a), the finger electrode is disposed as a plurality of finger electrodes in a first direction parallel to the short side of the divided unit cell, and the busbar electrode includes a collection electrode line which extends in a second direction parallel to a long side of the divided unit cell and connects ends of the plurality of finger electrodes and a connecting electrode line which is branched off from an end of the collection electrode line and extends in the first direction to be electrically connected to another unit cell to be connected. 
     In operation (c), a rear surface electrode of any one unit cell and the connecting electrode line of another unit cell may be bonded using an electrically conductive adhesive. 
     Still another aspect of the present invention provides a method of manufacturing a designable shingled photovoltaic module, the method including (a) forming a solar cell in which a front surface electrode, a finger electrode, and a rear surface electrode are formed on a semiconductor substrate and dividing the solar cell into a plurality of unit cells by cutting the solar cell along cut lines in a checkerboard shape, (b) forming strings by connecting the divided unit cells in a shingled manner, and (c) forming a photovoltaic module by connecting the plurality of strings using a conductive wire embedded in a flexible connecting wire, wherein the forming of the photovoltaic module includes applying an electrically conductive adhesive on electrodes of the unit cells formed at two sides of the strings and electrically connecting the electrodes and the conductive wire through a curing process performed as a thermal process in a state in which the conductive wire is disposed. 
     In the forming of the photovoltaic module, the number of strings connected by the conductive wire may be in the range of 2 to 200, and a separation distance between the strings may be in the range of 1 to 100 mm. 
     In the forming of the photovoltaic module, a thermal process temperature in the curing process may be in the range of 130 to 150° C., and a thermal process time may be 10 seconds or less. 
     In the forming of the photovoltaic module, when the conductive wire having an “E” type electrical connection pattern is applied, three first auxiliary conductive wires branched off from the conductive wire may be directly electrically connected to the electrodes of the unit cells, a diameter of the conductive wire may be 2 to 4 times a diameter of each of the electrodes of the unit cells to be connected, and a diameter of each of the first auxiliary conductive wires may be the same as the diameter of the electrode of the unit cell. 
     In the forming of the photovoltaic module, when the conductive wire having an “H” type electrical connection pattern is applied, a second auxiliary conductive wire connected to the conductive wire through three first auxiliary conductive wires branched off from the conductive wire and disposed parallel to the conductive wire may be electrically connected to the electrodes of the unit cells, a diameter of the conductive wire may be 2 to 4 times a diameter of the electrode of the unit cell to be connected, and a diameter of each of the first and second auxiliary conductive wires may be the same as the diameter of the electrode of the unit cell. 
     In the dividing of the unit cells, a horizontal width of each of the unit cells may be in the range of 3 to 50 mm, and a vertical width may be in the range of 3 to 50 mm. 
     In the forming of the strings, a length of each of the strings formed by connecting the unit cells may be in the range of 50 to 3,000 mm, a width of the string may be in the range of 3 to 25 mm, and an output voltage of the string may be proportional to the number of unit cells connected in series. 
     The conductive wire may be formed as a composite including a core of which a cross section has a circular shape and a passivation layer plated on the core, the core may be formed of copper (Cu), and the passivation layer may be formed of tin (Sn). 
     In the forming of the photovoltaic module, the number of strings connected in parallel to reduce shading loss in a string bundle may be set to 5 to 10, and when the photovoltaic module expands according to an installation area, string bundles may be connected in series using the conductive wire. 
     Yet another aspect of the present invention provides a designable shingled photovoltaic module formed through the method of manufacturing a designable shingled photovoltaic module. 
     Advantageous Effects 
     According to the present invention, since both a width and a length of each string used in a shingled array structure can be adjusted by connecting short sides of unit cells divided into a rectangular shape, a photovoltaic module formed by electrically connecting the strings can be implemented in one of various shapes, and thus the photovoltaic module is suitable for a building structure and a vehicle in which atypical installation of photovoltaic modules is required. 
     According to the present invention, since a busbar electrode can faithfully serve to move carriers collected by a finger electrode by applying a busbar electrode having an “L” shape when a short side of a unit cell with respect to a string width and applying a busbar electrode having a “T” shape when a short side of a unit cell is relatively large when an electrode structure is changed according to a size of a unit cell to be divided according to output characteristics of a solar cell, output power of the photovoltaic module having the shingled array structure can be improved. 
     According to the present invention, since shading loss can be reduced and the photovoltaic module can also be variously designed by adjusting a length and a width of each string by changing a horizontal width and a vertical width of each unit cell and connecting a plurality of strings formed by bonding the unit cells using a flexible connecting wire in parallel, a window-type photovoltaic module suitable for a building structure and a vehicle can be provided. 
     According to the present invention, since the photovoltaic module suitable for an installation environment can be manufactured by connecting string bundles in which many strings are bound in series, output power of the photovoltaic module can be easily set to correspond to the installation area. 
     According to the present invention, when wiring work is performed using a flexible connecting wire, since the string is electrically connected to a conductive wire having an “E” type electrical connection pattern or “H” type electrical connection pattern through a curing process in which a thermal process is simply performed on a conductive adhesive after applying the conductive adhesive on electrodes of the unit cell provided on both sides of the string, cost and working time can be reduced. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIGS.  1  and  2    are views showing cell connection according to a conventional technology. 
         FIG.  3    is a view illustrating a front surface of a solar cell according to an embodiment of the present invention. 
         FIG.  4    is a view illustrating a rear surface of the solar cell of  FIG.  3   . 
         FIG.  5    is a view showing connection of divided unit cells of  FIG.  3   . 
         FIG.  6    is a cross-sectional view along line A-A of  FIG.  5    showing a state in which the divided unit cells of  FIG.  3    are connected. 
         FIG.  7    is a view illustrating a front surface of a solar cell according to another embodiment of the present invention. 
         FIG.  8    is a view illustrating a rear surface of the solar cell of  FIG.  7   . 
         FIG.  9    is a view showing connection of divided unit cells of  FIG.  7   . 
         FIG.  10    is a cross-sectional view along line B-B of  FIG.  9    showing a state in which the divided unit cells of  FIG.  7    are connected. 
         FIG.  11    is a flowchart for manufacturing a photovoltaic module according to an embodiment of the present invention. 
         FIG.  12    is a cross-sectional view illustrating a photovoltaic module according to an embodiment of the present invention. 
         FIG.  13    is a view illustrating a front surface of a solar cell according to an embodiment of the present invention. 
         FIG.  14    is a view illustrating a rear surface of the solar cell of  FIG.  13   . 
         FIG.  15    is a view illustrating a string of a shingled array structure according to an embodiment of the present invention. 
         FIG.  16    is a view for describing a process of connecting divided unit cells for manufacturing the string of  FIG.  15   . 
         FIG.  17    is a cross-sectional view along line A-A of  FIG.  16   . 
         FIG.  18    is a view illustrating strings connected in parallel using a flexible connecting wire according to an embodiment of the present invention. 
         FIG.  19    is a view illustrating a conductive wire structure of  FIG.  18   . 
         FIG.  20    is a view illustrating strings connected in parallel using a conductive wire having an “E” type electrical connection pattern according to an embodiment of the present invention. 
         FIG.  21    is a view illustrating strings connected in parallel using a conductive wire having an “H” type electrical connection pattern according to another embodiment of the present invention. 
         FIGS.  22 A to  22 C  are views showing a series of process of connecting strings in parallel using the conductive wire having the “H” type electrical connection pattern of  FIG.  21   . 
         FIG.  23    is a view illustrating a window type flexible photovoltaic module including string bundles according to an embodiment of the present invention. 
         FIG.  24    is a flowchart for describing a manufacturing process of a photovoltaic module according to an embodiment of the present invention. 
     
    
    
     MODES OF THE INVENTION 
     Hereinafter, the present invention will be described by describing embodiments of the present invention with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements. In addition, in the description of the present invention, when it is determined that detailed descriptions of related well-known components and functions unnecessarily obscure the gist of the present invention, the detailed descriptions thereof will be omitted. In addition, when a certain part “includes” a certain component, this does not exclude other components unless explicitly described otherwise, and other components may in fact be included. 
     The term “shingled array structure” used in the present invention refers to a structure in which a solar cell in which front surface electrodes and rear surface electrodes are provided are cut to form a plurality of unit cells, and the front surface electrodes and the rear surface electrodes are bonded and connected using a conductive adhesive in order to improve a conversion efficiency and output power in units of photovoltaic modules. 
     In addition, a “photovoltaic module” is a module in which a plurality of solar cell strings having the shingled array structure are electrically connected, glass is positioned on a front surface, and an ethylene-vinyl acetate copolymer (EVA) sheet is formed on a rear surface to form a solar cell panel. 
     In addition, an “electrically conductive adhesive (ECA)” is an ECA used in wiring circuits or electrical and electronic products, and an epoxy resin mixed with silver particles is used as the ECA. A principle by which the electrically conductive adhesive has an electrically conductive property is that conductive fillers dispersed in an adhesive come in contact with each other to have the electrically conductive property in a curing or solidifying process. In addition, the ECA is applied using a micro dispenser, an amount of the ECA discharged from a needle should be constant, and the ECA should not flow down. A metal powder of gold, platinum, silver, copper, nickel, or the like, carbon fiber, graphite, a composite powder, or the like may be used as the conductive filler. 
     A solar cell used in an embodiment of the present invention includes a semiconductor substrate having a substantially rectangular shape and a plurality of finger electrodes and busbar electrodes formed on the semiconductor substrate. In  FIG.  3   , the solar cell has the semiconductor substrate having a quadrangular shape, and a semiconductor substrate having an octagonal shape formed by chamfering four corners may also be used as the solar cell. 
     Divided cells used in the present invention may be formed by dividing the semiconductor substrate into a plurality of cells, and may be formed as rectangular unit cells having the same shape according to the number of divided cells. For example, a size of the solar cell is 156.75 mm×156.75 mm. 
     In consideration of output power of the solar cell, the solar cell may be divided into 3 to 12 unit cells, and a short side of a divided unit cell  10  is in the range of 13.3 to 66.6 mm. 
     In one embodiment, as illustrated in  FIG.  3   , the solar cell is divided into four unit cells  10  and may be divided to have the same size along cut lines Ct through a laser scribing process. Electrode members including busbar electrodes  20  and finger electrodes  40  corresponding to the number of divided cells may be formed on a front surface of the solar cell. That is, the divided unit cells  10  may have the same size and the same shape, and the same electrode pattern may be formed on the divided unit cells  10 . 
     The plurality of finger electrodes  40  are disposed in a first direction parallel to a short side of the divided unit cell  10  and serve to collect photoelectrically converted carriers. A line width of each of the finger electrodes  40  is in the range of 0.08 to 0.12 mm. 
     Each of the busbar electrodes  20  serves to move the carriers collected through the finger electrodes  40  to an external storage battery or the like. The busbar electrodes  20  include collection electrode lines  21  for connecting ends of the plurality of finger electrodes  40  and connecting electrode lines  22  for being electrically connected to different unit cells. 
     Each of the collection electrode lines  21  extends in a second direction parallel to a long side of the divided unit cell  10 , and each of the connecting electrode lines  22  is branched off from an end of the collection electrode line  21  and extends in the first direction. 
     The collection electrode line  21  and the connecting electrode line  22  may be disposed along an edge of the divided unit cell  10 , the collection electrode line  21  is disposed adjacent to the cut line Ct of the unit cell  10  to be divided, and the connecting electrode line  22  is disposed adjacent to the short side of the unit cell  10  to be divided. 
     The connecting electrode line  22  is perpendicularly bent from an end of the collection electrode line  21 , and the entirety of the collection electrode line  21  and the connecting electrode line  22  may be formed in an “L” shape. A line width of the busbar electrode  20  is in the range of 0.8 to 1.2 mm. 
     Referring to  FIG.  4   , rear surface electrodes  30  may be formed on rear surfaces of the unit cells  10  to be divided to correspond to the number of cells to be divided. Each of the rear surface electrodes  30  may be formed to have the same electrode pattern as the busbar electrode  20  formed on front surfaces. The rear surface electrode  30  is electrically physically connected to the connecting electrode line  22  of another unit cell  10 . 
     As illustrated in  FIGS.  5  and  6   , the divided unit cells  10  may be connected by an ECA  50  through a thermal process in order to form a photovoltaic module having a shingled array structure. For example, a string array structure may be formed by overlapping a short side of any one unit cell  10  and a short side of another unit cell  10 , and by arranging the ECA  50  between the rear surface electrode  30  of the upper unit cell  10  and the connecting electrode line  22  of the busbar electrode  20  of the lower unit cell  10  and bonding the rear surface electrode  30  and the connecting electrode line  22  through the thermal process, two unit cells  10  are integrated, and a state in which a current collected through the finger electrodes  40  flows is implemented at the same time. 
     Unlike the previously described embodiment, when a size of a divided cell needs to be increased relatively, an electrode structure of a busbar electrode  20  may be changed. 
     As illustrated in  FIG.  7   , a plurality of divided cells used in an embodiment of the present invention may be formed by dividing a semiconductor substrate, and unit cells are formed in the same rectangular shape according to the number of divided unit cells. For example, a solar cell may be divided into two unit cells. For example, when a solar cell is divided into two unit cells  10 A, the two unit cells  10 A may be divided to have the same size along a cut line Ct through a laser scribing process. Electrode members including busbar electrodes  20  and finger electrodes  40  corresponding to the divided cells may be formed on a front surface of the solar cell. That is, the divided unit cells  10 A may have the same size and the same shape, and the same electrode pattern may be formed on the divided unit cells  10 A. 
     Each of the plurality of finger electrodes  40  is disposed in a first direction parallel to a short side of the divided unit cell  10 , and a line width of the finger electrode  40  is in the range of 0.08 to 0.12 mm. 
     Each of the busbar electrodes  20  serves to move carriers collected by the finger electrodes  40  to an external storage battery or the like. The busbar electrodes  20  include collection electrode lines  21  for connecting ends of the plurality of finger electrodes  40  and connecting electrode lines  22  for being electrically connected the other unit cells. 
     Each of the collection electrode lines  21  extends in a second direction parallel to a long side of the divided unit cell  1 , and each of the connecting electrode lines  22  is branched from an end of the collection electrode line  21  toward two sides and extends in the first direction. 
     The collection electrode line  21  and the connecting electrode line  22  may be disposed along an edge of the divided unit cell  10 , the collection electrode line  21  is disposed parallel to the cut line Ct of the unit cell  10  to be divided, and the connecting electrode line  22  is disposed adjacent to a short side of the unit cell  10 . 
     The connecting electrode line  22  is bent from the end of the collection electrode line  21  in both directions, and the entirety of the collection electrode line  21  and the connecting electrode line  22  may be formed in a “T” shape. A line width of the busbar electrode  20  is in the range of 0.8 to 1.2 mm. 
     Referring to  FIG.  8   , rear surface electrodes  30  corresponding to the number of the unit cells to be divided may be formed on rear surfaces of the unit cells  10 A to be divided. Each of the rear surface electrodes  30  may be formed to be the same as an electrode pattern of the busbar electrode  20  formed on front surfaces. The rear surface electrode  30  is electrically and physically connected to the connecting electrode line  22  of another unit cell  10 A. 
     As illustrated in  FIGS.  9  and  10   , the divided unit cells  10 A may be connected by an ECA  50  through a thermal process in order to form a photovoltaic module having a shingled array structure. For example, a string array structure may be formed by overlapping a short side of any one unit cell  10 A and a short side of another unit cell  10 A, and by arranging the ECA  50  between the rear surface electrode  30  of the upper unit cell  10 A and the connecting electrode line  22  of the busbar electrode  20  of the lower unit cell  10 A and bonding the rear surface electrode  30  and the connecting electrode line  22  through the thermal process, two unit cells  10 A are integrated, and a state in which a current collected through the finger electrodes  40  flows is implemented at the same time. 
     A method of manufacturing the photovoltaic module according to an embodiment will be described with reference to  FIG.  11   . 
     First, a solar cell in which finger electrodes  40  and busbar electrodes  20  are formed on a front surface and rear surface electrodes  30  are formed on a rear surface is prepared (S 10 ). In this case, the plurality of finger electrodes  40  are disposed in a first direction parallel to short sides of divided unit cells, and the busbar electrodes  20  include collection electrode lines  21  which extend in a second direction parallel to long sides of the divided unit cells and are connected to ends of the plurality of finger electrodes and connecting electrode lines  22  which are branched off from ends of the collection electrode lines  21  in the first direction to be electrically connected to other unit cells to be connected. 
     For example, the solar cell may include a semiconductor substrate, emitters formed on a front surface which is an incidence surface of the semiconductor substrate on which light is incident, an anti-reflection film formed on the emitters, a plurality of passivation layers formed on a rear surface opposite to the front surface of the semiconductor substrate, electrode members including the plurality of busbar electrodes  20  and finger electrodes  40  electrically connected to the emitters, the rear surface electrodes  30  formed between the plurality of passivation layers and the semiconductor substrate, and a plurality of rear surface electric field layers formed between the rear surface electrodes  30  and the semiconductor substrate. 
     The semiconductor substrate may be a semiconductor including a first conductive type, for example, a conductive n-type or p-type, silicon, and each of the emitters includes second conductive type, for example, conductive p-type or n-type, impurities of which the conductive type is opposite to that of the semiconductor substrate and forms a p-n junction with the semiconductor substrate. 
     The anti-reflection film may be formed by depositing a silicon nitride film (SiN x ) or silicon oxide film (SiO x ) on the emitters, and the plurality of passivation layers are formed on the rear surface of the semiconductor substrate and serve to reduce a recombination rate of charges near the rear surface of the semiconductor substrate. 
     The plurality of busbar electrodes  20  and finger electrodes  40  are formed on and electrically connected to the emitters and disposed apart from each other in a predetermined direction. The finger electrodes  40  serve to collect carriers, for example, holes/electrons, moved to the emitters, and the busbar electrodes  20  serve to output the carriers to an external apparatus (load). Each of the plurality of busbar electrodes  20  and finger electrodes  40  includes at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, and a combination thereof. In the present invention, each of the busbar electrode  20  and the finger electrode  40  includes Ag. 
     Each of the rear surface electrodes  30  may include a conductive material and may be integrally formed with the plurality of passivation layers on the rear surface of the semiconductor substrate. The rear surface electrode  30  includes at least one selected from Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, and a combination thereof. In the present invention, the rear surface electrode  30  includes Al in consideration of manufacturing costs and the like. 
     The rear surface electric field layer may be formed between the rear surface electrode  30  and the semiconductor substrate and serves to prevent a phenomenon in which the movement of the holes/electrons toward the rear surface of the substrate is hindered and electrons and holes are recombined to disappear on the rear surface of the semiconductor substrate. 
     Then, the solar cell prepared in operation S 10  is divided into a plurality of unit cells  10  or  10 A by cutting the solar cell in a rectangular shape (S 20 ). 
     The cutting in operation S 20  may be performed by, for example, a nanosecond laser (532 nm, 20 ns, 30 to 100 KHz from coherent). That is, the cutting in operation S 20  may be performed by the 20 ns laser which uses a wavelength of 532 nm and in which an average power is set to 10 W, a frequency is set to 50 KHz, and a scan speed is set to 1,300 mm/s. 
     Subsequently, an ECA  50  is applied on any one side among a short side of any one upper unit cell  10  or  10 A prepared in operation S 20  and a short side of another lower unit cell  10  or  10 A to bond any one upper unit cell  10  or  10 A and another lower unit cell  10  or  10 A in a shingled array structure (S 30 ). 
     Among ECAs on the market, a product that has a high conductivity and a suitable viscosity and is suitable for the present invention, for example, EL-3012, EL-3556, EL-3653, or EL-3655 of SKC Panacol or CE3103WLV or CA3556HF of Henkel, may be applied to the ECA  50 . For example, an adhesive having properties of a viscosity of 28,000 to 35,000 mPa·s(cP) at 25° C., a volume resistivity of 0.0025 Ω·cm as an electrical characteristic, a curing temperature of 130 to 150° C., and a curing time of 25 to 35 seconds is applied to the ECA  50 . In addition, a conductive filler in the ECA may include at least one material selected from the group consisting of Au, Pt, Pd, Ag, Cu, Ni, and carbon. 
     In operation S 30 , the application of the ECA is performed by controlling a discharge amount of the ECA discharged from a needle of a micro dispenser. The application of the ECA is performed using an ECA, which has properties of, for example, a viscosity of 28,000 to 35,000 mPa·s(cP) at a temperature of 25° C., a volume resistivity of 0.0025 Ω·cm as an electrical characteristic, a curing temperature of 130 to 150° C., and a curing time of 25 to 35 seconds, and by controlling revolutions per minute (RPM) to control a discharge amount of the needle of the micro dispenser, wherein the needle has a diameter of 250 μm. 
     The application of the ECA may be performed on any one side among the rear surface electrode  30  at the short side of the any one upper unit cell  10  or  10 A and the connecting electrode line  22  of the busbar electrode  20  at the short side of the other lower unit cell  10  or  10 A or on both sides among the rear surface electrode  30  and the connecting electrode line  22 . A position of the application may be determined according to properties and a discharge amount of the ECA. 
     The ECA is applied, and bonding is performed to implement the shingled array structure to form a solar cell string. In this case, the forming of the string may be performed under thermal process conditions of a time of 25 to 35 seconds and a temperature of 130 to 150° C. 
     As illustrated in  FIG.  12   , in a photovoltaic module  1  according to an embodiment of the present invention, a plurality of divided single cells  10 - 1  are connected using an ECA  7  to form a string having a shingled array structure. 
     In addition, an ECA  7  is an ECA used in wiring circuits or electrical and electronic products, and an epoxy resin mixed with silver particles is used as the ECA. A principle by which the electrically conductive adhesive has an electrically conductive property is that conductive fillers dispersed in an adhesive come in contact with each other to have the electrically conductive property in a curing or solidifying process. In addition, the ECA is applied using a micro dispenser, an amount of the ECA discharged from a needle should be constant, and the ECA should not flow down. A metal powder of gold, platinum, silver, copper, nickel, or the like, carbon fiber, graphite, a composite powder, or the like may be used as the conductive filler. 
     A first encapsulation material  4  and a front surface cover  2  are stacked on the string, a second encapsulation material  5  and a rear surface back sheet  3  are stacked under the string, and a lamination process for integrating all sequentially stacked module components (the front surface cover, the first encapsulation material, the string, the second encapsulation material, and the rear surface back sheet) is performed using a lamination apparatus. The lamination process may be performed at a low temperature of 140 to 160° C. 
     The front surface cover  2  serves to protect a solar cell from an external impact and the like. A transparent material such as ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polycarbonate (PC), acrylic, or the like may be used as a material of the front surface cover  2 . The front surface cover  2  may have waterproof, insulation, and ultraviolet protection functions and may be manufactured in one of various shapes such as a quadrangular or circular shape according to an installation environment or design. 
     A tedlar polyester tedlar (TPT) of a fluororesin series or polyethylene terephthalate (PET) type transparent synthetic resin may be used as the rear surface back sheet  3 , and the rear surface back sheet  3  serves waterproof, insulation, and ultraviolet protection functions, and the like. 
     A protection film may be formed at one side of each of the front surface cover  2  and the rear surface back sheet  3 . An ultraviolet protection film may be used as the protection film, and the protection film may block ultraviolet light and the like transferred to the solar cell through glass to help increase a lifetime of the solar cell. 
     The first and second encapsulation materials  4  and  5  are materials for increasing a lifetime of the photovoltaic module, are positioned on front and rear surfaces of the divided cell  10 - 1  to serve as buffers for preventing damage to the cell, and are adhered to the front surface cover  2  and the rear surface back sheet  3  for encapsulation. An ethylene-vinyl acetate copolymer (EVA), polyolefin (POE), ionomer, or the like may be used for each of the encapsulation materials. 
     As illustrated in  FIG.  13   , a solar cell is divided into a plurality of pieces in order to variously design a shape of a photovoltaic module. The solar cell may be cut and divided along cut lines Ct in a checkerboard shape through a laser scribing process into unit cells  10 - 1  having one of various shapes. For example, in each of the divided unit cells  10 - 1 , a horizontal width ml is in the range of 3 to 50 mm, and a vertical width n 1  is in the range of 25 to 170 mm. Front surface electrodes  20  and finger electrodes  40  may be formed on a front surface of the solar cell as electrode members, and the divided unit cells  10 - 1  may have substantially the same size and the same shape, and the same electrode pattern may be formed on the divided unit cells  10 - 1 . 
     The solar cell is formed on a semiconductor substrate. The semiconductor substrate may be a semiconductor including a first conductive type, for example, a conductive n-type or p-type, silicon, and each of emitters includes second conductive type, for example, conductive p-type or n-type, impurities of which the conductive type is opposite to that of the semiconductor substrate and forms a p-n junction with the semiconductor substrate. 
     The plurality of finger electrodes  40  are connected to the front surface electrodes  20  to collect photoelectrically converted carriers, and a line width of each of the finger electrodes  40  is in the range of 0.08 to 0.12 mm. 
     The front surface electrodes  20  serve as busbar electrodes which move the carriers collected through the finger electrodes  40  to an external storage battery or the like. A line width of each of the front surface electrodes  20  is in the range of 0.8 to 1.2 mm. Each of the front surface electrode  20  and the finger electrode  40  includes at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, and a combination thereof. In the embodiment, each of the front surface electrode  20  and the finger electrode  40  includes Ag. 
     Referring to  FIG.  14   , rear surface electrodes  30  corresponding to the number of divided cells may be formed on rear surfaces of the divided unit cells  10 - 1 . Each of the rear surface electrodes  30  may be formed to have the same electrode pattern as that formed on front surfaces. The rear surface electrode  30  is electrically and physically connected to the front surface electrode  20  of another unit cell  10 - 1 . A material of the rear surface electrode  30  includes at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, and a combination thereof. In the embodiment, the rear surface electrode  30  includes Al in consideration of manufacturing costs and the like. 
     As illustrated in  FIG.  15   , a string having a shingled array structure is formed by connecting a plurality of unit cells  10 - 1 , and a positive (−) electrode and a negative (+) electrode formed at two sides of the string are electrically connected to an external storage battery. In this case, a short side of any one unit cell  10 - 1  and a short side of another unit cell  10 - 1  partially overlap, and as a length of the string increases, the number of overlapping portions H 1  of the unit cells  10 - 1  increases. 
     As illustrated in  FIGS.  16  and  17   , the divided unit cells  10 - 1  may be connected by an ECA  7  through a thermal process in order to form the string having the shingled array structure. For example, the string may be formed by overlapping a short side of any one unit cell  10 - 1  and a short side of another unit cell  10 - 1 , and by arranging the ECA  7  between front surface electrodes  20  of the lower unit cell  10 - 1  and rear surface electrodes  30  of the upper unit cell  10 - 1  at the portions H 1  which face and overlap each other and bonding the front surface electrodes  20  and the rear surface electrodes  30  through a thermal process, two unit cells  10 - 1  are integrated, and an electrical connection state in which a current collected through finger electrodes  40  flows is formed at the same time. 
     A photovoltaic module according to an embodiment may be applied as a photovoltaic module for a window, which secures a light receiving property and has superior stability using a translucent high-efficiency silicon solar cells, and a double-sided light receiving photovoltaic module, which is rollable and is applied to a window of a building or vehicle, is proposed as illustrated in  FIG.  18   . 
     In  FIG.  18   , a window type photovoltaic module may be formed by connecting a plurality of strings S in parallel according to various sizes and shapes. Each of the strings S includes unit cells  10 - 1  which are connected as a shingled array structure. A length w 1  of the string S is in the range of 50 to 3,000 mm, and a width of the string S is in the range of 3 to 25 mm. In this case, an output voltage of the string S corresponds to the number of unit cells  10 - 1  connected in series. 
     Output voltage Vs of string S=0.6 V×the number of unit cells connected in series. 
     The plurality of strings S may be disposed in consideration of an installation environment of the window type photovoltaic module. A separation distance e 1  between the strings S is in the range of 1 to 100 mm. In addition, two sides of the strings S serve as negative (−) electrodes and positive (+) electrodes, and the electrodes are electrically connected to using connecting wires  100  in which conductive wires  110  are embedded. Each of the connecting wires  100  may be formed of a flexible material having an annular shape. The number of strings S connected in series or parallel by the flexible connecting wires  100  is in the range of 2 to 200. 
     Referring to  FIG.  19   , a conductor that has a superior electrical conductivity and of which a cross section has a circular shape may be used in the conductive wire  110 , and the conductive wire  110  may be formed as a composite including a core  111  and a passivation layer  120 . 
     Any one of Cu and Al may be selectively used as the core  111 . The passivation layer  112  is formed on a surface of the core  111 , and any one among Sn, highly pure In, and Ag may be selectively used as the passivation layer  112 . When Cu is used as the core  111  in the embodiment, Sn is plated as the passivation layer  112  to manufacture the conductive wire  110 . A diameter B 1  of the core  111  and a thickness C 1  of the passivation layer  112  may be changed according to a bonding area of the electrodes of the string and electrical properties. Unlike the embodiment, a conductive wire  110  may be formed of a single metal material as a conductor. 
     There are two forms in which the flexible connection wirings  100  are connected to the electrodes on two sides of the strings S, and the forms are classified according to a shape of an electrical connection pattern which connects the conductive wire  110  and an electrode of a single cell  10 - 1 . For example, as illustrated in  FIG.  20   , when the conductive wire  110  having an “E” type electrical connection pattern is used, first auxiliary conductive wires  101  branched off from the conductive wire  110  may be directly connected to a rear surface electrode  30  of the single cell  10 - 1 . In this case, each of three thin first auxiliary conductive wires  101  branched off from the thick conductive wire  110  may be connected to the rear surface electrode  30  of the single cell  10 - 1 . A diameter d 2  of the divided first auxiliary conductive wire  101  is the same as a width of the rear surface electrode  30 , and a diameter d 1  of the conductive wire  110  may be formed to be 2 to 4 times the width of the rear surface electrode  30 . 
     As another example, as illustrated in  FIG.  21   , when a conductive wire  110  having an “H” type electrical connection pattern is used, a second auxiliary conductive wire  102  may be connected to rear surface electrodes  30  of single cells  10 - 1  through first auxiliary conductive wires  101 . A conductive wire  110  and the second auxiliary conductive wire  102  are arranged in parallel, and the first auxiliary conductive wires  101  are disposed between and connected to the conductive wire  110  and the second auxiliary conductive wire  102 . In this case, a diameter d 2  of the first auxiliary conductive wire  101  and a diameter d 3  of the second auxiliary conductive wire  102  may be the same as a width of the rear surface electrode  30 , and a diameter d 1  of the conductive wire  110  may be formed to be 2 to 4 times the width of the rear surface electrode  30 . 
     A manufacturing process of connecting single cells of a string using a conductive wire having an “H” type electrical connection pattern will be described. First, as illustrated in  FIG.  22 A , single cells  10 - 1  forming a string are prepared, and an ECA  50  is applied on rear surface electrodes  30  of the single cells  10 - 1 . 
     Then, as illustrated in  FIG.  22 B , in a state in which a pre-manufactured second auxiliary conductive wire  102  of a conductive wire  110  having an “H” type electrical connection pattern is disposed on the ECA  50 , the ECA  50  is cured through a thermal process. The curing process may be performed at a temperature of 130 to 150° C. for a predetermined time (10 seconds or less). When the curing process is completed, as illustrated in  FIG.  22 C , the second auxiliary conductive wire  102  arranged parallel to the conductive wire  110  may electrically connect the single cells  10 - 1  forming a plurality of strings in parallel. 
     As illustrated in  FIG.  23   , in a window type flexible photovoltaic module according to an embodiment, a plurality of string bundles G 1 , G 2 , G 3 , and G 4  may be connected using flexible conductive wires  110 A and  110 B. 
     In order to reduce shading loss, each of the string bundles G 1 , G 2 , G 3 , and G 4  is formed by connecting a plurality of strings in parallel. In each of the string bundles G 1 , G 2 , G 3 , and G 4 , the number of the strings is set to correspond to an installation area to optimize an output current of the photovoltaic module, and 5 to 10 strings may be connected. 
     The string bundles G 1 , G 2 , G 3 , and G 4  are connected in series to implement the extended window type flexible photovoltaic module and may be connected using conductive wires having an “E” or “H” type electrical connection pattern described with reference to  FIGS.  20  and  21    so that damage to the strings and unit cells may be minimized. 
     Output power of the window type flexible photovoltaic module illustrated in  FIG.  23    may be changed according to an aperture ratio of a 1 m 2  window. The table below shows an expected output value according to the aperture ratio. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Photovoltaic module specification 
                 Aperture ratio 
                 Output power 
               
               
                   
               
             
            
               
                 1 m 2  window 
                 50% 
                 106.9 W 
               
               
                 Transmittance of suntan window: 
                 40% 
                 128.2 W 
               
               
                 20 to 30% 
               
               
                 Total power when unit cell of 
                 30% 
                 149.5 W 
               
               
                 5.2 W/sheet is applied: 213.6 W 
               
               
                   
               
            
           
         
       
     
     A method of manufacturing a photovoltaic module according to an embodiment will be described with reference to  FIG.  24   . First, a solar cell in which finger electrodes  40  and front surface electrodes  20  are formed on a front surface and rear surface electrodes  30  are formed on a rear surface is provided (S 100 ). Then, the solar cell provided in operation S 100  is cut in a rectangular shape to divide the solar cell in a plurality of unit cells  10 - 1  (S 200 ). The cutting in operation S 200  may be performed by a nanosecond laser (532 nm, 20 ns, 30 to 100 KHz from coherent). That is, the cutting in operation S 20  may be performed by the 20 ns laser which uses a wavelength of 532 nm and in which an average power is set to 10 W, a frequency is set to 50 KHz, and a scan speed is set to 1,300 mm/s. 
     The unit cells  10 - 1  provided in operation S 200  are disposed to partially overlap, and an ECA  7  is applied to any one side to connect the unit cells  10 - 1  as a shingled array structure to form strings (S 300 ). In this case, the application of the ECA may be performed on any one side among the rear surface electrode  30  of any one upper unit cell  10 - 1  and the front surface electrode  20  of another lower unit cell  10 - 1  or on both sides. An application position of the ECA may be determined according to properties and a discharge amount of the ECA. When the ECA is applied, the unit cells  10 - 1  are connected as the shingled array structure to form the strings through a thermal process (for 25 to 35 seconds at a temperature of 130 to 150° C.). 
     Then, the plurality of strings S are connected using a connecting wire  100  to form a window type flexible photovoltaic module (S 400 ). One side of a conductive wire  110  is electrically connected to negative (−) electrodes and positive (+) electrodes formed at two sides of each of the strings S. 
     For example, as illustrated in  FIG.  20   , when the conductive wire  110  having an “E” type electrical connection pattern is used, first auxiliary conductive wires  101  branched off from the conductive wire  110  may be directly connected to the rear surface electrodes  30  of the single cells  10 - 1 . In this case, three thin first auxiliary conductive wires  101  branched off from the thick conductive wire  110  may be connected to the rear surface electrodes  30  of the single cells  10 - 1 . A diameter d 2  of each of the branched first auxiliary conductive wires  101  may be the same as a width of each of the rear surface electrodes  30 , and a diameter d 1  of the conductive wire  110  may be formed to be 2 to 4 times the width of the rear surface electrode  30 . 
     As another example, as illustrated in  FIG.  21   , when the conductive wire  110  having an “H” type electrical connection pattern is used, a second auxiliary conductive wire  102  may be directly connected to the rear surface electrodes  30  of the single cells  10 - 1  through first auxiliary conductive wires  101 . The conductive wire  110  and the second auxiliary conductive wire  102  are arranged in parallel, and the first auxiliary conductive wires  101  are disposed between and connected to the conductive wire  110  and the second auxiliary conductive wire  102 . In this case, a diameter d 2  of each of the first auxiliary conductive wires  101  and a diameter d 3  of the second auxiliary conductive wire  102  may be the same as a width of the rear surface electrode  30 , and the diameter d 1  of the conductive wire  110  may be formed to be 2 to 4 times the width of the rear surface electrode  30 . 
     The above description of the present invention is only exemplary, and it will be understood by those skilled in the art that the present invention may be easily performed in other concrete forms without changing the technological scope and essential features. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to the field of manufacturing a photovoltaic module.