KR20170136806A - Solar cell module and manufacturing method threof - Google Patents

Abstract

The present invention relates to a solar cell module, and a manufacturing method thereof. According to an embodiment of the present invention, the solar cell module comprises: first and second solar cells separately having a semiconductor substrate, and first and second electrodes which are spaced apart from each other on a rear surface of the semiconductor substrate, and arranged in a first direction; and an insulating substrate on which a plurality of metal foils are elongated and patterned in the first direction. The metal foils patterned on the insulating substrate are commonly connected to the first electrode of the first solar cell and the second electrode of the second solar cell. Furthermore, according to an embodiment of the present invention, the manufacturing method of a solar cell module comprises: a cell array step of arranging first and second solar cells in a first direction; an insulating substrate aligning step of allowing the insulating substrate having a plurality of metal foils patterned thereon to be arranged to cross partial areas of rear surfaces of the first and second solar cells; and a metal foil connecting step of performing heat treatment for areas where the metal foils overlap the first electrode of the first solar cell, and overlap the second electrode of the second solar cell.

Description

SOLAR CELL MODULE AND MANUFACTURING METHOD THREOF BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a solar cell module and a manufacturing method thereof.

Recently, as energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing, and solar cells that produce electric energy from solar energy are attracting attention.

Typical solar cells have a semiconductor portion that forms a p-n junction by different conductive types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types, respectively.

When light is incident on such a solar cell, a plurality of electron-hole pairs are generated in the semiconductor portion, and the generated electron-hole pairs are separated into electrons and holes, respectively, so that the electrons move toward the n- Type semiconductor portion. The transferred electrons and holes are collected by different electrodes connected to the n-type semiconductor portion and the p-type semiconductor portion, respectively, and electric power is obtained by connecting these electrodes with electric wires.

The present invention provides a solar cell module and a manufacturing method thereof.

A solar cell module according to an exemplary embodiment of the present invention includes first and second solar cells each having first and second electrodes spaced apart from each other on a rear surface of a semiconductor substrate and a semiconductor substrate, the first and second solar cells being arranged in a first direction; And a plurality of metal foils patterned on the insulating substrate, the plurality of metal foils patterned in common in the first electrode of the first solar cell and the second electrode of the second solar cell, Respectively.

The metal foil may be any one of a metal foil in which a layer of aluminum (Al), copper (Cu), or aluminum (Al) and a layer of copper (Cu) are laminated.

For example, the metal foil may be formed by sequentially stacking an aluminum layer and a copper layer, and a copper layer may be connected to the first electrode of the first solar cell and the second electrode of the second solar cell.

Further, the insulating substrate is located over a part of the rear surface area of the first solar cell and a part of the rear surface part of the second solar cell, and can be transparent.

The insulating substrate may be formed of at least one of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).

In addition, the first and second electrodes may be elongated in the first direction.

A method of manufacturing a solar cell module according to an embodiment of the present invention includes arranging first and second solar cells each having first and second electrodes extending in a long direction on a rear surface of a semiconductor substrate and a semiconductor substrate in a first direction ; An insulating substrate having a plurality of metal foils patterned in a long direction in a first direction is disposed over a rear partial area of the first solar cell and a rear partial area of the second solar cell, An insulating substrate aligning step of overlapping the electrode with the second electrode of the second solar cell; And a metal foil connecting step of heat treating a region where the metal foil overlaps with the first electrode of the first solar cell and a region overlapping with the second electrode of the second solar cell.

The metal foil may be any one of a metal foil in which a layer of aluminum (Al), copper (Cu), or aluminum (Al) and a layer of copper (Cu) are laminated.

For example, the metal foil may be formed by sequentially stacking an aluminum layer and a copper layer, and the copper layer of the metal foil may be arranged to face the at least one electrode in the aligning step.

In addition, the first and second electrodes are elongated in the first direction, and the metal foil patterned in the first direction in the insulating substrate alignment step, the first electrode of the first solar cell, and the first electrode of the first solar cell, The second electrodes of the two solar cells can overlap and be aligned with each other.

In addition, in the metal foil connecting step, the metal foil patterned on the entire surface of the insulating substrate may be thermally treated by irradiating a laser beam to the back surface of the insulating substrate to connect the first and second electrodes.

More specifically, the metal foil connecting step may selectively irradiate a region where the metal foil overlaps with the first electrode of the first solar cell and a region where the metal foil overlaps with the second electrode of the second solar cell, have.

A solar cell module and a manufacturing method thereof according to an exemplary embodiment of the present invention use an insulating substrate having a plurality of metal foils patterned to electrically connect a plurality of solar cells to one another, .

1 to 6 are views for explaining a solar cell module according to a first embodiment of the present invention.
7 to 9 are views for explaining a method of manufacturing a solar cell module according to an example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above another portion but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. Further, when a certain portion is formed as "whole" on another portion, it means not only that it is formed on the entire surface of the other portion but also that it is not formed on the edge portion.

Hereinafter, the front surface may be one surface of the semiconductor substrate 110 to which the direct light is incident, and the rear surface may be the opposite surface of the semiconductor substrate in which direct light is not incident, or reflected light other than direct light may be incident.

1 to 6 are views for explaining a solar cell module according to a first embodiment of the present invention.

Here, FIG. 1 is an example of a shape of the solar cell module according to the first embodiment of the present invention viewed from the front side.

As shown in FIG. 1, the solar cell module according to the first embodiment of the present invention may include first and second solar cells C1 and C2 and an insulating substrate 400.

The first and second solar cells C1 and C2 are arranged along the first direction x and are arranged on the rear surface of the semiconductor substrate 110 and the semiconductor substrate 110, Electrodes 141 and 142 may be provided. The specific structure of the first and second solar cells C1 and C2 will be described with reference to Figs. 2 and 3. Fig.

The insulating substrate 400 includes a plurality of metal foils 300 patterned in a long direction in a first direction x and is electrically connected to the first metal foil 300 through a plurality of metal foils 300 patterned on the insulating substrate 400. [ The first electrode 141 of the solar cell C1 and the second electrode 142 of the second solar cell C2 may be connected in series with each other.

Hereinafter, a specific structure of the solar cell applied to the solar cell module according to the first embodiment of the present invention will be described in more detail with reference to FIGS. 2 and 3. FIG.

FIG. 2 is a partial perspective view of a solar cell applied to the solar cell module of the present invention, and FIG. 3 is an example of patterns of the first and second electrodes 141 and 142 provided on the rear surface of the solar cell shown in FIG.

2 and 3, an example of a solar cell according to the present invention includes an antireflection film 130, a semiconductor substrate 110, a tunnel layer 180, a first semiconductor portion 121, The passivation layer 190, the plurality of first electrodes 141, and the plurality of second electrodes 142. The first electrode 141 and the second electrode 142 may be formed of the same material.

Here, the antireflection film 130, the tunnel layer 180, the intrinsic semiconductor part 200, and the passivation layer 190 may be omitted. However, since the efficiency of the solar cell is improved when provided, As an example.

The semiconductor substrate 110 may be formed of at least one of monocrystalline silicon and polycrystalline silicon doped with impurities of the first conductivity type or the second conductivity type. In one example, the semiconductor substrate 110 may be formed of a single crystal silicon wafer.

Here, the impurity of the first conductive type contained in the semiconductor substrate 110 or the impurity of the second conductive type may be any of n-type and p-type conductive types.

When the semiconductor substrate 110 has a p-type conductivity type, impurity of a trivalent element such as boron (B), gallium, indium, or the like is doped in the semiconductor substrate 110. However, when the semiconductor substrate 110 has an n-type conductivity type, impurities of pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb) may be doped into the semiconductor substrate 110.

Hereinafter, the case where the impurity contained in the semiconductor substrate 110 is an impurity of the second conductivity type and is n-type will be described as an example. However, the present invention is not limited thereto.

The semiconductor substrate 110 may have a plurality of uneven surfaces on the entire surface thereof. Accordingly, the first semiconductor part 121 located on the front surface of the semiconductor substrate 110 may also have an uneven surface.

Accordingly, the amount of light reflected from the front surface of the semiconductor substrate 110 decreases, and the amount of light incident into the semiconductor substrate 110 increases.

The antireflection film 130 is formed on the front surface of the semiconductor substrate 110 to minimize the reflection of light incident from the outside to the front surface of the semiconductor substrate 110. The antireflection film 130 is formed of an aluminum oxide film (AlOx), a silicon nitride film (SiNx) An oxide film (SiOx), and a silicon oxynitride film (SiOxNy).

The tunnel layer 180 is disposed in direct contact with the entire rear surface of the semiconductor substrate 110 as shown in FIG. 2, and may include a dielectric material. Accordingly, the tunnel layer 180 can pass carriers generated in the semiconductor substrate 110, and can perform a passivation function with respect to the rear surface of the semiconductor substrate 110.

In addition, the tunnel layer 180 may be formed of a dielectric material formed of SiCx or SiOx having high durability even at a high temperature process of 600 DEG C or more.

2, the first semiconductor section 121 may be disposed on the rear surface of the semiconductor substrate 110, for example, in direct contact with a part of the rear surface of the tunnel layer 180.

The first semiconductor section 121 is disposed on the rear surface of the semiconductor substrate 110 and is extended in a first direction x as shown in FIG. And may be formed of a polycrystalline silicon material having a second conductivity type.

Here, the first semiconductor section 121 may be doped with an impurity of the first conductivity type, and when the impurity contained in the semiconductor substrate 110 is an impurity of the second conductivity type, The pn junction with the semiconductor substrate 110 can be formed with the layer 180 therebetween.

The first semiconductor section 121 may have a p-type conductivity type and the plurality of first semiconductor sections 121 may be formed of p Impurity of the trivalent element can be doped in the first semiconductor portion 121. [0157]

The second semiconductor section 172 is disposed on the rear surface of the semiconductor substrate 110 and is in direct contact with a part of the rear surface of the tunnel layer 180 spaced apart from each of the first semiconductor sections 121, (X) in a direction parallel to the first semiconductor portion 121. In the present embodiment,

The second semiconductor section 172 may be formed of a polycrystalline silicon material doped with impurities of the second conductivity type at a higher concentration than the semiconductor substrate 110. Therefore, for example, when the semiconductor substrate 110 is doped with an n-type impurity which is an impurity of the second conductivity type, the plurality of second semiconductor regions 172 may be an n + impurity region.

The second semiconductor section 172 prevents the hole movement toward the second semiconductor section 172, which is the direction of electron movement, by the potential barrier due to the difference in impurity concentration between the semiconductor substrate 110 and the second semiconductor section 172 (E. G., Electrons) to the second semiconductor portion 172 can be facilitated.

Therefore, the amount of charges lost by recombination of electrons and holes in the second semiconductor section 172 and the vicinity thereof or the first and second electrodes 141 and 142 is reduced and the electron movement is accelerated, Can be increased.

2, the case where the semiconductor substrate 110 is the impurity of the second conductivity type is described as an example and the first semiconductor portion 121 serves as the emitter portion and the second semiconductor portion 172 serves as the back surface As an example, a case in which it functions as a frontier.

Alternatively, when the semiconductor substrate 110 contains impurities of the first conductivity type, the first semiconductor portion 121 serves as a rear electric field portion and the second semiconductor portion 172 serves as an emitter portion .

2, the first semiconductor section 121 and the second semiconductor section 172 are formed of polycrystalline silicon on the back surface of the tunnel layer 180. Alternatively, the tunnel layer 180 The first semiconductor section 121 and the second semiconductor section 172 may be doped with impurities diffused in the rear surface of the semiconductor substrate 110. [ In this case, the first semiconductor section 121 and the second semiconductor section 172 may be formed of the same single-crystal silicon material as the semiconductor substrate 110.

As shown in FIG. 2, the intrinsic semiconductor part 200 may be formed on the rear surface of the tunnel layer exposed between the first semiconductor part 121 and the second semiconductor part 172, 200 may be formed of an intrinsic polycrystalline silicon layer that is not doped with an impurity of the first conductivity type or an impurity of the second conductivity type unlike the first semiconductor portion 121 and the second semiconductor portion 172.

2, each of the opposite side surfaces of the intrinsic semiconductor part 200 may have a structure in which the side surfaces of the first semiconductor part 121 and the side surfaces of the second semiconductor part 172 are in direct contact with each other.

The passivation layer 190 is formed on the back surface of the polycrystalline silicon layer formed on the first semiconductor section 121, the second semiconductor section 172, and the intrinsic semiconductor section 200. The passivation layer 190 may include a defect caused by a dangling bond So that carriers generated from the semiconductor substrate 110 can be prevented from being recombined by the dangling bonds and disappearing.

The plurality of first electrodes 141 may be connected to the first semiconductor section 121 and extended in a first direction x. The first electrode 141 may collect carriers, for example, holes, which have migrated toward the first semiconductor section 121.

The plurality of second electrodes 142 may be connected to the second semiconductor portion 172 and extend in the first direction x in parallel with the plurality of first electrodes 141. As such, the second electrode 142 can collect carriers, for example, electrons, which have migrated toward the second semiconductor section 172.

As shown in FIG. 1, the first electrode 141 and the second electrode 142 may be alternately arranged in the second direction y.

The holes collected through the first electrode 141 and the electrons collected through the second electrode 142 in the solar cell according to the present invention are used as electric power of the external device through the external circuit device .

The solar cell applied to the solar cell module according to the present invention is not necessarily limited to FIG. 2 except that the first and second electrodes 141 and 142 provided in the solar cell are formed only on the rear surface of the semiconductor substrate 110 Any other component can be changed.

For example, in the solar cell module of the present invention, a part of the first electrode 141 and the first semiconductor part 121 are located on the front surface of the semiconductor substrate 110, and a part of the first electrode 141 is disposed on the semiconductor substrate 110 The MWT type solar cell may be connected to the remaining part of the first electrode 141 formed on the rear surface of the semiconductor substrate 110 through the hole formed in the semiconductor substrate 110. [

The insulating substrate 400 connected to the rear surface of the solar cell will be described in more detail with reference to FIG.

4 is a view for explaining the insulating substrate 400 and the metal foil 300 of the solar cell module according to the first embodiment, FIG. 4 (a) is a view from the front of the insulating substrate 400 , And FIG. 4 (b) is a sectional view of the insulating substrate 400.

As shown in FIG. 4 (a), the insulating substrate 400 applied to the solar cell module of the present invention may be formed by patterning a plurality of metal foils 300 on the entire surface.

Here, the insulating substrate 400 may be formed of at least one of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), and may be transparent for convenience of the process.

In addition, the plurality of metal foils 300 may be formed to extend in a first direction (x). However, the planar pattern of the metal foil 300 is not necessarily limited to that shown in FIG. 4 (a), but may be a pattern of the first and second electrodes 141 and 142 of the solar cell or a pattern of the first and second electrodes 141 and 142 It may be patterned differently as shown in Fig. 4 (a), considering the position.

The line width of the metal foil 300 may be substantially the same as the line width of the first and second electrodes 141 and 142. The interval between the metal foils 300 may be equal to the line width of the first electrode 141 and the second electrode 142 ). ≪ / RTI >

The metal foil 300 may be formed of any one of aluminum (Al), copper (Cu), aluminum (Al), and copper (Cu).

For example, when the aluminum foil 300 is formed by sequentially stacking the aluminum layer 303 and the copper layer 301, as shown in FIG. 4B, the aluminum foil 300 is formed on the insulating substrate And the copper layer 301 may be formed on the aluminum layer 303. When the insulating substrate 400 is connected to the rear surfaces of the first and second solar cells C1 and C2, The solar cell 301 can be connected to the first electrode 141 of the first solar cell C1 and the second electrode 142 of the second solar cell C2.

The insulating substrate 400 on which the metal foil 300 is patterned as described above can be connected to the rear surfaces of the first and second solar cells C1 and C2 as described above. More specifically, it is as follows.

FIG. 5 is a rear view of the solar cell module according to the first embodiment of the present invention, and FIG. 6 is a cross-sectional view taken along the line C6-C6 in FIG.

5, the insulating substrate 400 is divided into first and second solar cells C1 and C2 (see FIG. 5) over a rear area of the first solar cell C1 and a rear area of the second solar cell C2. Respectively.

5 and 6, a plurality of metal foils 300 patterned on the insulating substrate 400 are electrically connected to the first electrode 141 of the first solar cell C1 and the second solar cell C2 The first electrode 142 and the second electrode 142 may be connected in common.

When the metal foil 300 is formed to include the aluminum layer 303 and the copper layer 301, as shown in FIG. 6, the copper layer 301 is electrically connected to the first And may be connected to the electrode 141 and the second electrode 142 of the second solar cell C2.

A plurality of solar cells are connected in series by using the insulating substrate 400 on which the metal foil 300 is previously patterned, so that the solar cell module having such a structure can be easily manufactured.

Hereinafter, a method of manufacturing such a solar cell module will be described.

FIGS. 7 to 9 are diagrams for explaining a manufacturing method of a solar cell module according to an example of the present invention, FIG. 7 is a flowchart of a manufacturing method of a solar cell module according to an example of the present invention, 7 is a view for explaining a cell array step S1 and an insulating substrate aligning step S2, and FIG. 9 is a view for explaining the metal foil connecting step S3 in FIG.

As shown in Fig. 7, a method of manufacturing a solar cell module according to an example of the present invention includes a cell array step S1, an insulating substrate align step S2, and a metal foil connection step S3.

Here, in the cell arrangement step S1, the first, second, and third semiconductor layers 110 and 120 are separated from each other on the back surface of the solar cell, that is, the semiconductor substrate 110 and the semiconductor substrate 110 described above with reference to FIGS. 2 and 3, The first and second solar cells C1 and C2 having the two electrodes 141 and 142 can be arranged in the first direction x as shown in Fig.

In the insulating substrate aligning step S2, the insulating substrate 400, in which the plurality of metal foils 300 described in FIG. 4 are patterned in the first direction x, is patterned as shown in FIG. A plurality of metal foils 300 are disposed over the first electrode 141 of the first solar cell C1 and the second electrode of the second solar cell C2, 2 solar cell C2 of the first embodiment.

At this time, the plurality of metal foils 300 and the first electrodes 141 of the first solar cell C1 are opposed to each other, and the plurality of metal foils 300 and the second electrodes 142 of the second solar cell C2 May also be facing each other.

At this time, the metal foil 300 may be any one of a metal foil 300 in which a layer of aluminum (Al), copper (Cu), or aluminum (Al) and a layer of copper (Cu)

For example, in the case where the metal foil 300 is formed by sequentially stacking the aluminum layer 303 and the copper layer 301, the copper layer 300 of the metal foil 300 in the aligning step 301 may be arranged to face the electrode.

In this case, when the transparent insulating substrate 400 is used as described above, the first and second electrodes 141 and 142 of the first and second solar cells C1 and C2 and the metal foil patterned on the insulating substrate 400 It is possible to align the antenna 300 more easily.

Thereby, the insulating substrate 400 is disposed on the first and second solar cells C1 and C2 in which the first and second electrodes 141 and 142 are extended in the first direction x, The first electrode 141 of the first solar cell C1 and the first electrode 141 of the first solar cell C1 are formed on the insulating substrate 400 in such a manner that the metal foil 300 is elongated in the first direction x, The metal foil 300 and the second electrode 142 of the second solar cell C2 can be overlapped and aligned with each other.

As described above, in the state where the first and second solar cells C1 and C2 and the insulating substrate 400 are aligned, the metal foil connecting step S3 can be performed.

9, the metal foil connecting step S3 is performed in a region where the metal foil 300 overlaps with the first electrode 141 of the first solar cell C1 and the region where the metal foil 300 overlaps with the first electrode 141 of the second solar cell C2 And the region AL1 overlapping with the two-electrode 142 may be heat-treated.

 9, the metal foil 300 patterned on the entire surface of the insulating substrate 400 is subjected to heat treatment by irradiating a laser L1 on the back surface of the insulating substrate 400, The first and second electrodes 141 and 142 can be connected.

The region irradiated with the laser L1 is divided into a region AL1 where the metal foil 300 overlaps with the first electrode 141 of the first solar cell C1 in the back surface of the insulating substrate 400, And may be an area AL1 overlapping with the second electrode 142 of the battery C2.

In this case, when the transparent insulating substrate 400 is used as described above, the metal foil 300 on the back surface of the insulating substrate 400 is divided into the regions AL1 (AL1) And the area overlapping with the second electrode 142 of the second solar cell C2 can be visually easily distinguished, so that the metal foil connecting step S3 can be performed much more easily.

In FIG. 9, for example, a region AL1 overlapping the metal foil 300 and the first electrode 141 of the first solar cell C1 among the back surface of the insulating substrate 400 is shown.

As described above, the solar cell module according to the present invention can simplify the manufacturing process of the solar cell module by electrically connecting a plurality of solar cells using the insulating substrate 400 on which the metal foil 300 has been previously patterned have.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (13)

First and second solar cells each having a semiconductor substrate and first and second electrodes spaced apart from each other on a rear surface of the semiconductor substrate, the first and second solar cells being arranged in a first direction; And
And an insulating substrate on which a plurality of metal foils are patterned in a long direction in the first direction,
Wherein a plurality of metal foils patterned on the insulating substrate are commonly connected to a first electrode of the first solar cell and a second electrode of the second solar cell. The method according to claim 1,
Wherein the metal foil is any one of a metal foil in which a layer of aluminum (Al), copper (Cu), or aluminum (Al) and a layer of copper (Cu) are stacked. 3. The method of claim 2,
Wherein the metal foil is formed by sequentially stacking the aluminum layer and the copper layer, and the copper layer is connected to the first electrode of the first solar cell and the second electrode of the second solar cell. The method according to claim 1,
Wherein the insulating substrate is located over a partial rear region of the first solar cell and a partial rear region of the second solar cell. The method according to claim 1,
Wherein the insulating substrate is transparent. The method according to claim 1,
Wherein the insulating substrate is formed of at least one of polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). The method according to claim 1,
Wherein the first and second electrodes are elongated in the first direction. Arranging first and second solar cells in the first direction, the first and second solar cells having a first substrate and a second substrate, the first and second electrodes being spaced apart from each other on a rear surface of the semiconductor substrate;
An insulating substrate having a plurality of metal foils patterned in a long direction in the first direction is disposed over a rear area of the first solar cell and a rear area of the second solar cell, An insulating substrate aligning step of overlapping the first electrode of the solar cell and the second electrode of the second solar cell; And
And a metal foil connecting step of heat treating a region where the metal foil overlaps with the first electrode of the first solar cell and a region overlapping with the second electrode of the second solar cell. 9. The method of claim 8,
Wherein the metal foil is any one of a metal foil in which a layer of aluminum (Al), copper (Cu), or aluminum (Al) and a layer of copper (Cu) are laminated. 10. The method of claim 9,
Wherein the metal foil is formed by sequentially stacking the aluminum layer and the copper layer,
And a copper layer of the metal foil is disposed facing the at least one electrode in the aligning step. 9. The method of claim 8,
Wherein the first and second electrodes are elongated in the first direction,
The metal foil patterned in the first direction and the first electrode of the first solar cell, and the metal foil and the second electrode of the second solar cell are overlapped with each other in the first direction in the insulating substrate aligning step A method of manufacturing a solar cell module to be aligned. 9. The method of claim 8,
Wherein the step of connecting the metal foil irradiates a laser beam on the back surface of the insulating substrate to heat the patterned metal foil on the front surface of the insulating substrate to connect the first and second electrodes. 13. The method of claim 12,
The metal foil connecting step may include a step of selectively irradiating a region where the metal foil overlaps with the first electrode of the first solar cell and a region where the metal foil overlaps with the second electrode of the second solar cell, Wherein the method comprises the steps of:

Images