TWM505701U - Solar cell - Google Patents

Abstract

A solar cell includes a semiconductor substrate, a backside busbar and a conductive layer. The backside busbar is disposed on the back surface of the semiconductor substrate and includes two opposite sides. The conductive layer is disposed on the back surface of the semiconductor substrate and covers portions of the backside busbar. The two sides of the backside busbar are exposed from the conductive layer.

Description

Solar battery

This creation is about the field of solar cells, especially regarding the structural improvement of a solar cell backside bus electrode and a peripheral conductive layer design layout.

With the depletion of consumable energy, the development of alternative energy sources such as solar energy has long been an important development direction. Solar cells work by using the radiant energy of sunlight and semiconductor materials to generate electricity. The main material of the solar cell includes a semiconductor substrate and a conductive paste. The semiconductor substrate mainly includes a germanium substrate and a III-V compound semiconductor substrate, and the conductive paste includes silver paste or aluminum paste. Silver glue is mainly used to form the front and back bus electrodes of the solar cell, and the aluminum glue is placed on the periphery of the back side.

In general, after forming the back side bus electrode of the solar cell, a layer of aluminum glue is further printed on the back side of the solar cell, and the aluminum glue slightly overlaps the edge of the back side bus electrode. Thereafter, a sintering process may be further performed to sinter the aluminum paste into a conductive layer, and react the semiconductor substrate with the aluminum paste to form a eutectic metal layer. For the finished product of the solar cell, the eutectic metal layer can generate a back side field (BSF) in the adjacent semiconductor substrate to reduce the surface composite probability of a minority carrier on the back surface of the semiconductor substrate. Thereafter, the desired solar module can be obtained by soldering using a continuous strip of solder ribbon to connect the solar cells in a series.

However, the structure of the above solar cell still has a problem to be improved. For example, since the overlap between the backside bus electrode and the conductive layer and the non-overlap between the two have a relative relationship with each other The height difference is such that during the subsequent soldering of the solar cell, the height difference causes the semiconductor substrate outside the overlap and the overlap to withstand different soldering down pressures, thereby causing fragmentation of the solar cell.

Accordingly, there is still a need to provide an improved solar cell structure that addresses the deficiencies and shortcomings of the prior art described above.

In view of this, the present invention proposes an improved solar cell to solve the shortcomings and disadvantages of the above-mentioned conventional solar cells.

According to an embodiment of the present invention, a solar cell is provided. The solar cell includes a semiconductor substrate, a back side bus electrode, and a conductive layer. Wherein, the back side bus electrode is disposed on the back surface of the semiconductor substrate and includes two opposite sides. The conductive layer is disposed on the back surface of the semiconductor substrate and covers a portion of the back surface bus electrode such that oppositely disposed sides of the back side bus electrode are exposed outside the conductive layer.

The above described objects, features and advantages of the present invention will become more apparent from the following description. However, the following preferred embodiments and drawings are for illustrative purposes only and are not intended to limit the present invention.

100, 100’‧‧‧ solar cells

102‧‧‧Semiconductor substrate

102a‧‧‧Received back

102b‧‧‧lighted front

104‧‧‧ Conductive layer

106‧‧‧Backside bus electrode

106’‧‧‧th sink electrodes

108‧‧‧Overlapping areas

110‧‧‧Doped area

112‧‧‧ Positive Convergence Electrode

114‧‧‧Protective dielectric layer

120‧‧‧ soldering tape

122‧‧‧Welding materials

1061, 1062, 1063, 1064‧‧‧ side

1061’, 1062’‧‧‧ side

△H‧‧‧ height difference

X‧‧‧ long axis direction

Y‧‧‧Short axis direction

Fig. 1 is a schematic view showing the structure of the back surface of the solar cell of the first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing the solar cell of the first embodiment of the present invention taken along the line A-A' of Fig. 1.

Fig. 3 is a schematic view showing the back structure of a solar cell provided with a solder ribbon in the first embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view showing the solar cell of the first embodiment of the present invention taken along the line B-B' of Fig. 3.

Fig. 5 is a schematic view showing the structure of the back surface of the solar cell of the second embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view showing the solar cell of the second embodiment of the present invention taken along line C-C' of Fig. 5.

In the following, the solar cell structure of the present invention is set forth so that those skilled in the art can implement the present invention. The specific embodiments may be referred to the corresponding drawings, and the drawings may form part of the embodiments. Although the embodiments of the present invention are disclosed as follows, they are not intended to limit the present invention, and those skilled in the art can make some changes and refinements without departing from the spirit and scope of the present invention.

Fig. 1 is a schematic view showing the structure of the back surface of the solar cell of the first embodiment of the present invention. The solar cell 100 includes a semiconductor substrate 102, a back side bus electrode 106, and a conductive layer 104. The back surface bus electrodes 106 may be disposed in parallel on the light receiving back surface 102a of the semiconductor substrate 102 in pairs. Each of the backside bus electrodes 106 may have a strip shape, which may include two side edges 1061, 1062 disposed opposite each other along the major axis direction X, and two side edges 1063, 1064 disposed opposite each other along the minor axis direction Y. In other words, the sides 1061, 1062 will be perpendicular to the major axis direction X, while the sides 1063, 10642 will be perpendicular to the minor axis direction Y. The conductive layer 104 is disposed on the back surface of the semiconductor substrate 102 and covers a portion of the back surface bus electrode 106 such that the oppositely disposed side edges 1061, 1062 of the back surface bus electrode 106 are exposed outside the conductive layer 104. In contrast, the other sides 1063, 1064 of the backside bus electrode 106 are covered by the conductive layer 104 such that there will be an overlap region 108 between the backside bus electrode 106 and the conductive layer 104, the overlap region 108 and the adjacent backside bus electrode. There will be a height difference between the conductive layers 104 covered by 106.

Figure 2 is a schematic cross-sectional view of the solar cell taken along the line A-A' of Figure 1 Figure. The side 1064 of the backside bus electrode 106 is covered by the conductive layer 104 and thus has an overlap region 108, and the conductive layer 104 located in the overlap region 108 and the adjacent conductive layer 104 outside the region have a height difference ΔH. . In contrast, the side 1061 of the backside bus electrode 106 is not covered by the conductive layer 104, such that the side 1061 can be exposed to the conductive layer 104, and both have substantially equal heights. Alternatively, the side 1061 of the backside bus electrode 106 and the conductive layer 104 may be further separated such that there may be a gap therebetween.

In addition to the components described above, the solar cell 100 may further include a doping region 110, a front side bus electrode 112, a protective dielectric layer 114, and a eutectic alloy layer (not shown). The doped region 110 is disposed in the semiconductor substrate 102 of the solar cell 100, and its conductivity type is different from that of the semiconductor substrate 102 to generate a PN junction therebetween. The front bus electrode 112 is disposed on the light receiving front surface 102b of the solar cell 100. The protective dielectric layer 114 is disposed on the light receiving front surface 102b and disposed between the front surface bus electrode 112 and the semiconductor substrate 102. The eutectic alloy layer can be positioned within the semiconductor substrate 102 directly beneath the conductive layer 104 to provide a back surface electric field. Preferably, the metal atoms in the eutectic alloy layer are the same as the metal atoms in the conductive layer 104, such as aluminum atoms, but are not limited thereto.

The semiconductor substrate 102 may include a germanium substrate or a III-V compound semiconductor substrate, for example. The composition of the bus electrodes 106, 112 includes a low-resistance conductive material, such as an element or a compound of copper, silver, aluminum, etc., preferably silver is used as an electrode, and the bus electrodes 106, 112 can be screen printed, inkjet printed, It is formed by processes such as decal transfer, plating, and electroless plating, and is preferably formed by screen printing, but is not limited thereto. The composition of the conductive layer 104 includes a low resistance metal, and preferably includes aluminum, and the manner of forming the conductive layer 104 may include screen printing, inkjet printing, printing transfer, electroplating, electroless plating, but is not limited thereto. The composition of the protective dielectric layer 114 includes hafnium oxide, tantalum nitride or titanium dioxide, and the process of forming the protective dielectric layer 114 may include chemical vapor deposition (CVD), low pressure chemical vapor. Low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), spray pyrolysis, spin coating, screen printing or other deposition techniques.

Fig. 3 is a schematic view showing the back structure of a solar cell provided with a solder ribbon in the first embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing the solar cell taken along the line B-B' of Fig. 3. The solder ribbon 120 is disposed parallel to the major axis direction X of each of the back surface bus electrodes 106 and spans the side edges 1061, 1062 of the back surface bus electrode 106. Each solder ribbon 120 can be soldered to each of the backside bus electrodes 106 through the solder material 122, so that two adjacent solar cells 100 can be electrically connected to form a part of the subsequent solar cell module. The solder ribbon 120 may be a solder ribbon of other low-resistance materials such as aluminum, and the solder material 122 may be a solder ball.

Further, since the side edges 1061, 1062 of the back surface bus electrode 106 do not overlap with the conductive layer 104, the solder ribbon 120 extending along the long-axis direction X is not soldered to the back surface bus electrode 106. A section of the conductive layer 104 that bulges or swells. In this case, the magnitude of the downforce that the semiconductor substrate 102 is subjected to during the soldering process can be stabilized, thereby reducing the probability of solar cell breakage.

This creation may include, in addition to the first preferred embodiment described above, other embodiments of solar cells. In order to simplify the description, the following description mainly refers to the differences of the second embodiment, and the details are not repeated. In addition, the same elements in the embodiments of the present invention are denoted by the same reference numerals to facilitate the comparison between the embodiments.

Fig. 5 is a schematic view showing the structure of the back surface of the solar cell of the second embodiment of the present invention. Fig. 6 is a schematic cross-sectional view of the solar cell taken along the line C-C' of Fig. 5. The main difference between this embodiment and the above-mentioned first and second embodiments is that each of the back surface bus electrodes of the solar cell 100' is a discontinuous layer, which includes a plurality of secondary bus electrodes distributed along the long axis direction X. 106'. its The two side edges 1061', 1062' of the respective secondary bus electrodes 106' are disposed along the long axis direction X such that the side edges 1061', 1062' are perpendicular to the long axis direction X. Similarly, the sides 1061', 1062' of each of the bus electrodes 106' will be exposed outside of the conductive layer 104.

In a subsequent process, the ribbon extending along the major axis direction X can be soldered to the respective secondary bus electrodes 106' such that the ribbon can span the sides 1061', 1062' of each of the bus electrodes 106'. Since the sides 1061', 1062' of the secondary bus electrode 106' do not overlap the conductive layer 104, the solder ribbon does not pass through the section of the conductive layer 104 that protrudes or collapses during soldering. In this case, the downforce that the semiconductor substrate 102 is subjected to during the soldering process can be stabilized, thereby reducing the probability of solar cell breakage. The solar cell of the present embodiment has similar features, arrangement positions, and material characteristics to those of the first embodiment except that the arrangement of the back side bus electrodes is changed, and therefore will not be described herein.

The above descriptions are only preferred embodiments of the present invention, and all changes and modifications made by the scope of the patent application of the present invention should be covered by the present invention.

100‧‧‧ solar cells

102‧‧‧Semiconductor substrate

104‧‧‧ Conductive layer

106‧‧‧Backside bus electrode

110‧‧‧Doped area

112‧‧‧ Positive Convergence Electrode

114‧‧‧Protective dielectric layer

120‧‧‧ soldering tape

122‧‧‧Welding materials

1061, 1062‧‧‧ side

X‧‧‧ long axis direction

Claims (10)

A solar cell comprising: a semiconductor substrate having a back surface; a back side bus electrode disposed on the back surface, wherein the back side bus electrode includes opposite side edges; and a conductive layer disposed on the back surface, wherein The conductive layer covers a portion of the backside bus electrode, and the sides of the backside bus electrode are exposed outside the conductive layer. The solar cell of claim 1, wherein the backside bus electrode is a continuous layer of strips. The solar cell of claim 1, wherein the backside bus electrode is a discontinuous layer. The solar cell of claim 3, wherein the backside bus electrode further comprises a plurality of secondary bus electrodes, each of the busbar electrodes includes two opposite sides, and the sides of each of the busbar electrodes Will be exposed to the conductive layer. The solar cell of claim 4, wherein each of the current collecting electrodes and the conductive layer has a gap. The solar cell of claim 4, wherein the solar cell further comprises a solder ribbon that spans the opposite sides of the plurality of bus electrodes. The solar cell of claim 1, wherein the backside bus electrode further comprises The longitudinal direction of the vertical axis and the direction of the short axis, the opposite sides of the back side bus electrode are perpendicular to the long axis direction. The solar cell of claim 1, wherein the backside bus electrode has a gap between the conductive layer and the conductive layer. The solar cell of claim 1, wherein the solar cell further comprises a solder ribbon that spans the sides of the backside bus electrode. The solar cell of claim 1, wherein the semiconductor substrate further has a light receiving front surface, the solar cell further comprising: a front side bus electrode disposed on the light receiving front surface; and a protective dielectric layer disposed on the The front side bus electrode and the semiconductor substrate.