Patent ID: 12218259

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals. Further, for the sake of simplicity, illustration of members, reference numerals, and the like may be omitted, but in such a case, other drawings are referred to. In addition, the shapes and dimensions of various members in the drawings are adjusted so as to be easy to see for convenience.

<Solar Cell>

FIG.1is a rear view showing a solar cell1according to an embodiment of the present disclosure.FIG.2is a cross-sectional view of the solar cell1. The solar cell1includes a semiconductor substrate10having a first conductivity type; a first semiconductor layer20having a conductivity type different from that of the semiconductor substrate10; a second semiconductor layer30having the same conductivity type as that of the semiconductor substrate10; a first electrode pattern40laminated on the first semiconductor layer20; and a second electrode pattern50laminated on the second semiconductor layer30.

The semiconductor substrate10can be formed of a crystalline silicon material such as monocrystalline silicon or polycrystalline silicon. The semiconductor substrate10may be formed of another semiconductor material such as gallium arsenide (GaAs). The semiconductor substrate10is, for example, an n-type semiconductor substrate in which an n-type dopant is doped in a crystalline silicon material. Examples of the n-type dopant include phosphorus (P). The semiconductor substrate10functions as a photoelectric conversion substrate that absorbs incident light from the light receiving surface side to generate photocarriers (electrons and holes). Since crystalline silicon is used as the material of the semiconductor substrate10, a relatively high output (a stable output regardless of illuminance) can be obtained even when the dark current is relatively small and the intensity of incident light is low.

The first semiconductor layer20and the second semiconductor layer30attract carriers having different polarity from each other from the inside of the semiconductor substrate10, thereby collecting charges having different polarity. Specifically, when the semiconductor substrate10is of an n-type, the first semiconductor layer20is formed of a p-type semiconductor, and the second semiconductor layer30is formed of an n-type semiconductor. The first semiconductor layer20and the second semiconductor layer30can be formed of, for example, an amorphous silicon material containing a dopant imparting a desired conductivity type. Examples of the p-type dopant include boron (B), and examples of the n-type dopant include phosphorus (P).

The first semiconductor layer20and the second semiconductor layer30are formed in a substantially complementary shape on the rear surface of the semiconductor substrate10. That is, substantially all regions of the back surface of the semiconductor substrate10are covered with either the first semiconductor layer20or the second semiconductor layer30.

The first semiconductor layer20includes a main functional portion21on which the first electrode pattern40is laminated, and an isolation portion22isolated from the main functional portion21and not stacked with the first electrode pattern40. The main functional portion21includes a first base end portion23formed at an end portion of the semiconductor substrate10on one side in the first direction over substantially the entire length in the second direction intersecting the first direction, and a plurality of first collecting portions24extending from the first base end portion23to the other side in the first direction. The isolation portion22is formed linearly over the entire length of the semiconductor substrate10in the second direction at the other end in the first direction.

The second semiconductor layer30has a second base end portion31adjacent to one side in the first direction of the isolation portion22and extending in the second direction, and a plurality of second collecting portions32extending from the second base end portion31to the one side in the first direction.

It is preferable that the first collector24and the second collector32are alternately formed with a relatively small constant width that allows the first electrode pattern40or the second electrode pattern50, which will be described later, to be laminated, in order to reduce the carrier transfer distance in the semiconductor substrate10to improve the photoelectric conversion efficiency. The first base end portion23and the second base end portion31preferably have a width larger than that of the first collector portion24and the second collector portion32in order to reduce electric resistance because charges extracted by the first collector portion24and the second collector portion32flow into the first base end portion23and the second base end portion31. Since the isolation portion22does not contribute to photoelectric conversion, the average width of the isolation portion22in the second direction is preferably a minimum width that can be continuously formed in the first direction. Therefore, the average width of the isolation portion22in the first direction is preferably smaller than the average width of the first collection portion24in the second direction, and the average width of the first collection portion24in the second direction is preferably smaller than the average width of the first base end portion23in the first direction. Specifically, the lower limit of the average width of the isolation portion in the first direction is preferably 100 μm, and more preferably 200 μm. On the other hand, the upper limit of the average width of the isolation portion in the first direction is preferably 2000 μm, and more preferably 1000 μm.

The first electrode pattern40and the second electrode pattern50are formed of a material having high conductivity such as metal. Further, the first electrode pattern40and the second electrode pattern50may be a laminate of a transparent electrode layer made of, for example, indium tin oxide (ITO), zinc oxide (ZnO), or the like laminated on the first semiconductor layer20and the second semiconductor layer30, and a metal electrode layer mainly made of a metal.

The first electrode pattern40is provided to extract charges from the first semiconductor layer20, and the second electrode pattern50is provided to extract charges from the second semiconductor layer30. The first electrode pattern40and the second electrode pattern50are laminated so as to leave a margin at the outer edge portions of the first semiconductor layer20(the main functional portion21) and the second semiconductor layer30in order to prevent a short circuit.

More specifically, the first electrode pattern40includes a first bus bar electrode41stacked on the first base end portion23and extending in the second direction, and a plurality of first finger electrodes42extending from the first bus bar electrode41toward the other side in the first direction and stacked on the respective first collecting portions24. The second electrode pattern50includes a second bus bar electrode51stacked on the second base end portion31and extending in the second direction, and a plurality of second finger electrodes52extending from the second bus bar electrode51toward one side in the first direction and stacked on the respective second collecting portions32.

As described above, in the solar cell1, the first semiconductor layer20(the first base end portion23and the isolation portion22) having a conductivity type different from that of the semiconductor substrate10exists over the entire length in the first direction at both ends in the first direction. Therefore, when a plurality of solar cells1are singularly connected in the first direction, even when the semiconductor substrate10comes into contact with the first semiconductor layer20of the adjacent solar cell1, the semiconductor substrate10does not come into contact with the second semiconductor layer30. Therefore, the solar cell1is not short-circuited during the shingling connection. In the figure, it is seen that the semiconductor substrate10of the solar cell1on the back side and the first semiconductor layer20and the second semiconductor layer30of the solar cell1on the front side do not contact each other due to the thicknesses of the first electrode pattern40and the second electrode pattern50. However, since the actual thicknesses of the first electrode pattern40and the second electrode pattern50are small, the semiconductor substrate10of the solar cell1on the back side can be easily brought into contact with the isolation portion22by a slight inclination or deformation.

<Photovoltaic Cell Manufacturing Method>

The solar cell1can be manufactured by a solar cell manufacturing method according to an embodiment of the present disclosure shown inFIG.3.

The solar cell manufacturing method of the present embodiment includes a step of forming a plurality of cell structures C on the back surface of the semiconductor wafer W (step S1: cell structure forming step), and a step of cutting the semiconductor wafer W at the boundary of the cell structures C (step S2: cutting step). The semiconductor wafer W is a large plate-shaped semiconductor that can cut out a plurality of semiconductor substrates10by cutting. The cell structure C is a concept in which components other than the semiconductor substrate10of each solar cell, that is, the first semiconductor layer20, the second semiconductor layer30, the first electrode pattern40, and the second electrode pattern50are combined.

In the cell structure forming step of step S1, as shown inFIG.4, a plurality of cell structures C are formed on the semiconductor wafer W, aligned in the first direction, and oriented in the same direction.FIG.4shows a cross section at the same position asFIG.2, that is, a cross section taken along the line A-A ofFIG.1. As is apparent from the description of the solar cell1, the first semiconductor layer20includes a first base end portion23formed at an end portion on one side in the first direction of each cell structure C over an entire length in the second direction intersecting the first direction; a plurality of first collecting portions24extending from the first base end portion23toward the other side in the first direction; a main functional portion21on which the first electrode patterns40are laminated; and a separation portion22formed linearly over an entire length in the second direction at an end portion on the other side in the first direction of each cell structure and on which the first electrode patterns40are not laminated.

In the cell structure forming step, the main functional portion21of the cell structure C on the other side in the first direction and the isolation portion22of the cell structure C adjacent to the other side in the first direction are continuously formed. That is, by forming the first semiconductor layer20so as to extend across the boundary (shown by the one-dot chain line) of the cell structure C, the main functional portion21of the cell structure C on the other side in the first direction and the isolation portion22of the cell structure C on the one side in the first direction are integrally formed. That is, inFIG.4, the first semiconductor layer20of the right cell structure C extends slightly beyond the boundary of the cell structure C to the left cell structure C, and a portion beyond the boundary of the cell structure C constitutes the isolation portion22of the left cell structure C.

The first semiconductor layer20and the second semiconductor layer30can be formed by forming a resist pattern and selectively laminating a semiconductor material by a film forming technique such as CVD. The first electrode pattern40and the second electrode pattern50can be formed by, for example, etching of a metal layer formed by plating using a seed layer formed by sputtering or the like as an adherend, printing and firing of a conductive paste, or the like.

In the cutting step of step S2, by cutting the semiconductor wafer W along the boundary of the cell structure C, the main functional portion21of the cell structure C on the other side in the first direction and the isolation portion22of the cell structure C adjacent to the other side in the first direction are separated, and the solar cell1is cut out.

The semiconductor wafer W can be cut by forming a scribed groove by, for example, laser irradiation, milling, or the like, and cutting the semiconductor wafer W by bending the semiconductor wafer W.

<Solar Cell Modules>

FIG.5is a cross-sectional view of a solar cell module M having a plurality of solar cells1. The solar cell module M includes a plurality of solar cell strings100formed by connecting a plurality of solar cell cells1in a line, a plate-shaped surface protection material200covering the front side of the plurality of solar cell strings100, a plate-shaped or sheet-shaped back surface protection material300covering the back side of the plurality of solar cell strings100, and a sealing material400filled between the surface protection material200and the back surface protection material300.

The solar cell string100includes a plurality of solar cells1arranged in a line in the first direction, and an interconnector2connecting adjacent solar cells. In the solar cell string100, one end portion of the solar cell1in the first direction is arranged to overlap the back side of the other end portion of the adjacent solar cell1in the first direction. The interconnector2is formed of a conductor such as a metal foil or a metal net wire, and connects the first bus bar electrode41of the solar cell1stacked on the front side and the second bus bar electrode51of the solar cell1stacked on the back side.

In the solar cell string, as shown in the figure, the interconnector2can abut on the isolation portion22of the first semiconductor layer20, but since the isolation portion22is isolated from the main functional portion21that contributes to photoelectric conversion, there is no disadvantage even when the interconnector2comes into contact with the main functional portion21.

The surface protection material200protects the solar cell string100by covering the surface of the solar cell string100with the sealing material400interposed therebetween. The surface protection material200is preferably formed of a transparent and scratch-resistant material such as glass, polycarbonate, or acrylic resin, and is excellent in weatherability. Specifically, examples of the material of the surface protection material200include a transparent resin such as an acrylic resin or a polycarbonate resin, and glass. Further, the surface of the surface protection material200may be processed into an uneven shape or may be covered with an antireflection coating layer in order to suppress reflection of light. The surface protection material200may have a light shielding region in the outer peripheral portion.

The surface protection material200preferably has a sufficient thickness to provide a strength capable of maintaining the shape of the solar cell module M. The solar cell module M having a desired shape can be obtained by using the surface protection material200formed in advance into a desired shape.

The solar cell string100may be formed to have a length substantially equal to the length in the first direction of the light-transmitting region inside the light-shielding region of the surface protective material200. Thus, the effective area of the solar cell string100received by the solar cell string100is increased, and the photoelectric conversion efficiency can be prevented from being lowered due to the fact that light does not enter a part of the solar cell1at the end portion of the solar cell string100. The plurality of solar cell strings100may be connected to each other by a wiring material (not shown).

The back surface protection material300is a layer for protecting the back surface side of the solar cell string100. The material of the back surface protective material300is not particularly limited, but is preferably a material that prevents water or the like from entering (a material having high water barrier properties). Specifically, the back surface protective material300can be formed of, for example, a resin such as glass, polyethylene terephthalate (PET), acrylic resin, polyethylene (PE), olefinic resin, fluororesin, or silicone-containing resin. The back surface protection material300may be a laminate of a resin layer and a metal layer such as aluminum foil. In addition, it is preferable that the color (light reflection characteristic) when viewed from the front surface side of the back surface protection material300is similar to the color of the front surface side of the solar cell1in order to improve the aesthetics of the solar cell module M by making the gaps between the solar cell strings100less conspicuous.

The sealing material400seals the solar cell string100in the space between the front surface protective material200and the rear surface protective material300, and suppresses deterioration of the solar cell string100due to moisture or the like. The sealing material400is formed of a material having transparency and adhesiveness to the surface protective material200and the solar cell string100. The material forming the sealing material400preferably has thermoplastic properties so that the gap between the surface protection material200and the solar cell string100can be sealed by hot pressing. Specifically, as a material forming the sealing material400, for example, a resin composition mainly containing ethylene/vinyl acetate copolymer (EVA), ethylene/α-olefin copolymer, ethylene/vinyl acetate/triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), acrylic resin, urethane resin, silicone resin, or the like can be used.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various changes and modifications are possible. The solar cell according to the present disclosure may include components other than those described in the above embodiment. By way of example, a solar cell according to the present disclosure may have an intrinsic semiconductor layer separating a first semiconductor layer and a second semiconductor layer. The planar shape of the main functional portion of the first semiconductor layer, the planar shape of the second semiconductor layer, and the planar shape of the first electrode pattern and the second electrode pattern can be appropriately changed.