TWI470815B - Silicon-based solar cell and method of fabricating the same - Google Patents

Description

Silicon-based solar cell and method of manufacturing same

The present invention relates to a silicon-based solar cell and a method of fabricating the same, and in particular, to a germanium-based solar cell having a special back electrode structure and a method of fabricating the same.

Photovoltaic devices have been widely used because they convert energy that is easily obtained from a light source (for example, sunlight) into electricity to manipulate electronic devices such as computers, computers, heaters, and the like. Use. The most common photovoltaic component is a germanium based solar cell.

A ruthenium-based solar cell refers to a solar cell fabricated using a crystalline ruthenium substrate obtained from a single crystal twin rod or a polycrystalline tantalum ingot. The widespread use of germanium-based solar cells is mainly due to three major breakthroughs in technology: (1) surface passivation technology; (2) wire-cutting technology for cutting crystalline germanium substrates; and (3) silver positive electrodes ( Front electrode) Co-firing with an aluminum back electrode.

The surface atoms of the crystalline germanium substrate are not covalently bonded like internal atoms, but have many empty floating bonds. The surface passivation technology utilizes, for example, hydrogen atom passivation thermal oxidation or annealing to passivate the surface and reduce the probability of carrier recombination on the surface to improve the photoelectric conversion efficiency of the germanium-based solar cell.

The wire-cutting technique of cutting a crystalline germanium substrate can reduce the thickness of the crystalline germanium substrate, thereby reducing the manufacturing cost of the germanium-based solar cell. Wire-cutting technology reduces the thickness of commercial crystalline germanium substrates from the original 200μm to 180μm, even to 160μm and 150μm.

In the prior art for forming electrodes on a ruthenium-based solar cell, after the metal paste was applied on the front and back surfaces of the ruthenium-based solar cell, two sintering procedures were required to form a metal electrode having good ohmic contact. A typical bismuth-based solar cell is coated with a conductive silver paste on its front surface and a conductive aluminum paste and a conductive silver paste (or conductive silver-aluminum paste) on its back surface. The co-firing technique only needs to perform a sintering process, that is, simultaneously forming a positive electrode having a good ohmic contact, a bus bar for soldering, a back electrode formed of aluminum, and a bus bar electrode for soldering. The aluminum partially diffuses into the back surface of the germanium-based solar cell to form a back surface filed (BSF). The back surface electric field reflects minority carriers and increases the collection of majority carriers and transports them to the back electrode formed of silver or silver-aluminum, thereby improving the overall efficiency of the germanium-based solar cell.

The thickness of the back electrode also affects the overall performance of the germanium based solar cell. In the past, a solar cell manufactured by using a 200 μm thick crystalline germanium substrate has a back electrode thickness of about 60 μm, which does not affect the overall performance of the germanium-based solar cell, and does not reduce the manufacturing yield of the germanium-based solar cell. However, as the thickness of the crystalline germanium substrate is reduced to 180 μm, the metal paste forming the back electrode (for example, a conductive aluminum paste) is almost completely covered on the back surface of the germanium-based solar cell, and due to the conductive paste during the sintering process The difference in thermal expansion coefficient of the crystalline germanium substrate, the metal paste having a thickness of about 60 μm causes warpage of the germanium-based solar cell in the process of forming the back electrode, thereby causing the warped germanium-based solar cell to rupture in subsequent packaging. Therefore, at present, a ruthenium-based solar cell having a crystal ruthenium substrate having a thickness of 180 μm has a thickness of the back electrode which has been reduced to 40 μm to avoid warpage of the ruthenium-based solar cell in the co-firing process. However, this practice of reducing the thickness of the back electrode also somewhat reduces the overall efficiency of the germanium-based solar cell.

In addition, the premise of co-firing to complete the positive electrode, the back electrode, and the bus bar electrode is that the thermal expansion caused by the positive electrode, the back electrode, and the bus bar electrode does not cause warpage of the bismuth-based solar cell during the co-firing process. Therefore, in practice, when the co-firing technology is used, if the metal paste (for example, conductive aluminum paste) originally formed by the back electrode is replaced by factors such as cost or efficiency, the other metal pastes must be replaced. This is a work that requires multiple attempts, time consuming, and reduced productivity, which is often prohibitive.

Therefore, the technical problem to be solved by the present invention is to provide a germanium-based solar cell and a method of manufacturing the same. Moreover, the ruthenium-based solar cell according to the present invention has a special back electrode structure to avoid warpage of the ruthenium-based solar cell in the co-firing process.

Accordingly, another aspect of the present invention is to provide a germanium-based solar cell and a method of fabricating the same. Moreover, the bismuth-based solar cell according to the present invention has a crystalline germanium substrate which can be reduced to a thickness of about 170 μm or less, and a back electrode having a thickness of about 40 μm or more to improve the overall efficiency of the germanium-based solar cell and reduce the sulfhydryl group. The manufacturing cost of solar cells.

A bismuth-based solar cell according to a preferred embodiment of the present invention comprises a semiconductor structure combination, a positive electrode, at least one backside bus electrode, and a back electrode. The semiconductor structure combination includes at least one p-n junction and has a front surface and a back surface. The positive electrode is formed on the front surface of the semiconductor structure combination. The at least one backside busbar electrode is formed on the back surface of the semiconductor structure combination. The back electrode is formed on the back surface of the semiconductor structure combination and covers a region on the back surface other than the at least one back bus bar electrode. In particular, the back electrode also has at least one first trench.

In one embodiment, the back electrode in each of the first trenches may have a first residual thickness or may have no residual thickness.

In one embodiment, each of the first trenches is substantially perpendicular to the at least one backside bus electrode.

In one embodiment, the back electrode has at least one second trench, each second trench being substantially parallel to the at least one backside bus electrode.

In one embodiment, the back electrode in each of the second trenches may have a second residual thickness or may have no residual thickness.

In one embodiment, the semiconductor structure combination comprises a crystalline germanium substrate. The crystalline germanium substrate has a thickness of less than about 170 [mu]m and the back electrode has a thickness greater than about 40 [mu]m.

In one embodiment, the at least one backside bus electrode is substantially aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. Formed.

In one embodiment, the at least one positive electrode is substantially formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. .

In one embodiment, the back electrode is formed substantially of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy, or a mixture thereof.

In accordance with a preferred embodiment of the present invention, a method of fabricating a germanium-based solar cell, first, forms a semiconductor structure combination. The semiconductor structure combination includes at least one p-n junction and has a front surface and a back surface. Next, the method applies a first conductive paste having a first pattern on the front surface of the semiconductor structure assembly. The first pattern corresponds to a positive electrode. Next, the method applies a second conductive paste having a second pattern on the back surface of the semiconductor structure assembly. The second pattern corresponds to a back electrode. Next, the method applies a third conductive paste having a third pattern on the back surface of the semiconductor structure combination. The third pattern corresponds to at least one back bus bar electrode. Finally, the method performs a co-firing process on the structure of the previous step, the first conductive paste having the first pattern is sintered into the positive electrode, and the second conductive paste having the second pattern is sintered into the back And the third conductive paste having the third pattern is sintered into the at least one back bus bar electrode. In particular, the back electrode has at least one first trench. The back electrode in each of the first trenches may have a first residual thickness.

In one embodiment, the first conductive paste is a mixture of particles formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. A conductive paste.

In one embodiment, the second conductive paste is a mixture of particles formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. A conductive paste.

In one embodiment, the third conductive paste is a mixture of particles formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. A conductive paste.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

The present invention provides a bismuth based solar cell and a method of fabricating the same. Moreover, the ruthenium-based solar cell according to the present invention has a special back electrode structure to avoid warpage of the ruthenium-based solar cell in the co-firing process. Moreover, the bismuth-based solar cell according to the present invention has a crystalline germanium substrate which can be reduced to a thickness of about 170 μm or less, and a back electrode having a thickness of about 40 μm or more to improve the overall efficiency of the germanium-based solar cell and reduce the sulfhydryl group. The manufacturing cost of solar cells. Further, the ruthenium-based solar cell according to the present invention facilitates replacement of the originally used metal paste based on factors such as cost or efficiency.

Please refer to FIG. 1, FIG. 2, FIG. 3 and FIG. 4, and FIG. 1 is a bottom view of a bismuth-based solar cell 1 according to a preferred embodiment of the present invention. Figure 2 is a top plan view of a germanium-based solar cell 1 in accordance with a preferred embodiment of the present invention. Fig. 3 is a cross-sectional view taken along line A-A of Fig. 1 and Fig. 2; Fig. 4 is a cross-sectional view taken along line B-B of Fig. 1 and Fig. 2;

As shown in FIG. 1, FIG. 2, FIG. 3 and FIG. 4, the bismuth-based solar cell 1 of the present invention comprises a semiconductor structure 10, a positive electrode 12, a back electrode 14, and at least one back bus electrode. (16a, 16b). The semiconductor structure assembly 10 includes at least one p-n junction 106 and has a front surface 102 and a back surface 104. The front surface 102 faces upwards and will face the sun. In order to reduce the reflectance of incident sunlight, as shown in Figs. 3 and 4, the front surface 102 is preferably roughened to a rough surface.

The positive electrode 12 is formed on the front surface 102 of the semiconductor structure assembly 10. As shown in FIG. 2, the positive electrode 12 includes a grid electrode 122 having a thin line width and at least one front bus bar electrode 124 having a relatively large line width. The at least one front bus bar electrode 124 is arranged along the Y direction in FIG. 1 and is used for soldering the bismuth-based solar cell 1 in series. Generally, the bismuth-based solar cell 1 has two or three front bus bar electrodes 124.

In one embodiment, the grid electrode 122 and the at least one front bus bar electrode 124 are substantially aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum. Alloys, palladium alloys, mixtures thereof or other metals that form good ohmic contact with tantalum. Preferably, the grid electrode 122 and the at least one front bus bar electrode 124 are formed of silver.

The at least one back bus bar electrode (16a, 16b) is formed on the back surface 104 of the semiconductor structure assembly 10 and is used for soldering the germanium-based solar cell 1 in series. In the case shown in Fig. 1, three rear side bus bar electrodes 16a arranged in a line are arranged symmetrically with three rear side bus bar electrodes 16b arranged in a row, and are arranged in the Y direction in Fig. 1.

The back electrode 14 is formed on the back surface 104 of the semiconductor structure assembly 10 and covers a region of the back surface 104 other than the at least one back surface bus electrode (16a, 16b). In practice, the positive electrode 12, the back electrode 14, and the at least one back bus electrode (16a, 16b) are formed by a co-firing process.

In one embodiment, the back electrode 14 is substantially made of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy, mixture thereof or other energy. Formed by a metal that forms a good ohmic contact with the crucible. The back electrode 14 is preferably formed of aluminum. In the co-firing process, the aluminum forming the back electrode 14 is partially diffused into the back surface 104 of the semiconductor structure assembly 10 to form a back surface electric field. The back surface electric field reflects minority carriers and increases the collection of majority carriers and transmits them to the at least one back bus bar electrode (16a, 16b), thereby improving the overall efficiency of the germanium based solar cell 1. As shown in FIG. 1, the three back bus bar electrodes 16a are arranged symmetrically with the back bus bar electrode 16b, and the three back bus bar electrodes 16a are responsible for collecting a majority carrier of the left half of the first drawing, the back bus bar electrode 16b is responsible for collecting the majority of the carriers on the right half of the first picture. The three back bus bar electrodes 16a and the back bus bar electrodes 16b are arranged in a dashed line to increase the area of the aluminum surface forming the back surface electric field to improve the overall performance of the germanium-based solar cell 1. The back side bus electrode of the bismuth-based solar cell 1 of the present invention may also be two or three electrodes extending from the edge of the bismuth-based solar cell 1 to the opposite edge, like the back bus bar electrode of the conventional bismuth-based solar cell. .

In one embodiment, the at least one backside busbar electrode (16a, 16b) is substantially formed of a mixture of aluminum, silver, silver, and aluminum or other metal capable of forming good ohmic contact with the crucible. Preferably, the at least one back bus bar electrode (16a, 16b) is formed of silver/aluminum or silver.

In particular, the back electrode 14 also has at least one first trench 142. The back electrode 14 in each of the first trenches 142 may have no residual thickness. The back electrode 14 in each of the first trenches 142 may also have a first residual thickness, as shown in FIG. 3, to reduce the formation of an electric field on the back surface of the first trench 142 and the influence of conduction of majority carriers.

In one embodiment, each of the first trenches 142 is substantially perpendicular to the at least one backside bus bar electrode (16a, 16b). As shown in FIG. 1 , the three back bus bar electrodes 16 a and the three back bus bar electrodes 16 b are arranged along the Y direction in FIG. 1 , and each of the first trenches 142 is arranged along the X direction in FIG. 1 . The continuity of the block of the back electrode 14 in the Y direction is interrupted, thereby allowing the back electrode 14 to shrink its thermal expansion within the block interrupted by the first trench 142 during co-firing. In practical applications, the first trench 142 may have a gap between the first trench 142 and the back bus bar electrode (16a, 6b) as shown in FIG. 1 and the edge of the germanium-based solar cell 1. The first trench 142 may also be a continuous trench extending from the back bus bar electrode 16a to the back bus bar electrode 16b, and continuing from the back bus bar electrode 16a or the back bus bar electrode 16b to the edge of the germanium-based solar cell 1.

In one embodiment, the back electrode 14 also has at least one second trench 144. The back electrode 14 may have no residual thickness in each of the second trenches 144. The back electrode 14 in each of the second trenches 144 may also have a second residual thickness as shown in FIG. Each of the second trenches 144 is substantially parallel to the at least one back bus bar electrode (16a, 16b). As shown in FIG. 1 , the three back bus bar electrodes 16 a and the three back bus bar electrodes 16 b are arranged along the Y direction in FIG. 1 , and each of the second trenches 144 is arranged along the Y direction in FIG. 1 . The thermal expansion of the back electrode 14 during co-firing is slowed down. In the case shown in FIG. 1, the three back bus bar electrodes 16a are symmetrically arranged with the three back bus bar electrodes 16b. Therefore, the second trenches 144 are preferably arranged symmetrically so as not to affect the back bus bar electrodes. 16a is responsible for collecting the majority carriers of the left half of the first drawing, and the back bus electrode 16b is responsible for collecting the majority carriers of the right half of the first drawing. In a practical application, the second trench 144 may be a gap between the edge of the germanium-based solar cell 1 and the adjacent second trench 144 as shown in FIG. 1 . The second trench 144 may also be a continuous trench extending from the edge of the germanium based solar cell 1 to the opposite edge.

In one embodiment, the semiconductor structure assembly 10 comprises a crystalline germanium substrate 101. The thickness of the crystalline germanium substrate 101 may be less than about 170 μm, or even less than 160 μm and 150 μm, to reduce the manufacturing cost of the germanium-based solar cell 1. Moreover, the thickness of the back electrode 14 may be greater than about 40 μm, or even as thick as 60 μm, to enhance the overall performance of the germanium-based solar cell 1.

In one embodiment, the semiconductor structure assembly 10 comprises a p-type crystalline germanium substrate 101, and an n-type doped region is implanted on the surface of the p-type crystalline germanium substrate 101 to form an n-type region. The semiconductor structure assembly 10 includes a passivation layer 108 overlying the n-type region and providing the front surface 102. The ruthenium-based solar cell 1 according to the present invention further includes an anti-reflection layer 18 which covers the passivation layer 108 as shown in FIGS. 3 and 4.

In another embodiment, the semiconductor structure assembly 10 includes an n-type crystalline germanium substrate 101, and a p-type doping is implanted on the surface of the n-type crystalline germanium substrate 101 to form a p-type region. The semiconductor structure assembly 10 includes a passivation layer 108 overlying the p-type region and provides the front surface 102. The ruthenium-based solar cell 1 according to the present invention further includes an anti-reflection layer 18 which covers the passivation layer 108 as shown in FIGS. 3 and 4.

In another embodiment, the semiconductor structure assembly 10 is a structure of a silicon heterojunction solar cell as disclosed in U.S. Patent No. 5,935,344. For the structure of the heterojunction solar cell, please refer to U.S. Patent No. 5,935,344, which is not described here.

Referring to FIGS. 5A to 5D, a method of manufacturing a bismuth-based solar cell 1 as shown in the cross-sectional view taken along line A-A of FIG. 1 according to a second preferred embodiment of the present invention is a cross-sectional view.

As shown in FIG. 5A, in accordance with a preferred embodiment of the present invention, first, a semiconductor structure combination 10 is formed. The semiconductor structure assembly 10 includes at least one p-n junction 106 and has a front surface 102 and a back surface 104. The front surface 102 faces upwards and will face the sun. In order to reduce the reflectance of the incident sunlight, as shown in Fig. 5A, the front surface 102 is roughened to a rough surface. In one embodiment, the semiconductor structure assembly 10 comprises a crystalline germanium substrate 101, and the crystalline germanium substrate 101 has a thickness of less than about 170 μm, even down to 160 μm, less than 150 μm.

Next, as shown in FIG. 5B, the method of the present invention applies a first conductive paste 12 ' having a first pattern on the front surface 102 of the semiconductor structure assembly 10. The first pattern corresponds to a positive electrode 12, and includes a grid electrode 122 having a thin line width and at least one front bus bar electrode 124 having a relatively large line width.

In a specific embodiment, the first conductive paste 12 ' is formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. A conductive paste in which the particles are mixed, or other commercially available conductive metal paste. The first conductive paste 12 ' is preferably a conductive paste in which silver particles are mixed.

Next, as shown in FIG. 5B, the method of the present invention applies a second conductive paste 14 ' having a second pattern on the back surface 104 of the semiconductor structure assembly 10. The second pattern corresponds to a back electrode 14.

In a specific embodiment, the second conductive paste 14 ' is formed of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy or a mixture thereof. A conductive paste in which the particles are mixed, or other commercially available conductive metal paste. The second conductive paste 14 ' is preferably a conductive paste in which aluminum particles are mixed.

Next, as shown in FIG. 5B, the method of the present invention applies a third conductive paste (16a ' , 16b ' ) having a third pattern on the back surface 104 of the semiconductor structure assembly 10. The third pattern corresponds to at least one back bus bar electrode (16a, 16b).

In a specific embodiment, the third conductive paste (16a ' , 16b ' ) is made of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy. Or a conductive paste formed by mixing particles formed by the mixture thereof, or other commercially available conductive metal paste. The third conductive paste (16a ' , 16b ' ) is preferably a conductive paste in which silver particles and aluminum particles are mixed.

Finally, as shown in FIG. 5C, the method of the present invention performs a co-firing process on the structure of the previous step, and the first conductive paste 12 ' having the first pattern is sintered into the positive electrode 12 (including the line width). a thin grid electrode 122 and at least one front bus bar electrode 124 having a thicker line width, the second conductive paste 14 ' having the second pattern is sintered into the back electrode 14, and having the third pattern The third conductive paste (16a ' , 16b ' ) is sintered into the at least one back bus bar electrode (16a, 16b). In particular, the back electrode 14 has at least one first trench 142. The back electrode 14 in each of the first trenches 142 may have a first residual thickness that does not affect the formation of the back surface electric field and the conduction of the majority of the carriers.

In one embodiment, the back electrode 14 also has at least one second trench 144. The functions, structures, and arrangements of the at least one first trench 142 and the at least one second trench 144 are detailed above, and are not described herein again.

In one embodiment, the semiconductor structure assembly 10 comprises a p-type crystalline germanium substrate 101, and an n-type doped region is implanted on the surface of the p-type crystalline germanium substrate 101 to form an n-type region. As shown in FIG. 5A, the method of the present invention forms a passivation layer 108 overlying the n-type region, the passivation layer 108 providing the front surface 102. As shown in FIG. 5D, the method of the present invention further forms an anti-reflective layer 18 that covers the passivation layer 108.

In another embodiment, the semiconductor structure assembly 10 includes an n-type crystalline germanium substrate 101, and a p-type doping is implanted on the surface of the n-type crystalline germanium substrate 101 to form a p-type region. As shown in FIG. 5A, the method of the present invention forms a passivation layer 108 overlying the p-type region, and the passivation layer 108 provides the positive surface 102. As shown in FIG. 5D, the method of the present invention further forms an anti-reflective layer 18 that covers the passivation layer 108.

In another embodiment, the semiconductor structure assembly 10 is a structure of a silicon heterojunction solar cell as disclosed in U.S. Patent No. 5,935,344. For the structure of the heterojunction solar cell, please refer to U.S. Patent No. 5,935,344, which is not described here.

In one embodiment, the semiconductor structure assembly 10 comprises a crystalline germanium substrate 101. The thickness of the crystalline germanium substrate 101 may be less than about 170 μm, or even less than 160 μm and 150 μm, to reduce the manufacturing cost of the germanium-based solar cell 1. Moreover, the thickness of the back electrode 14 may be greater than about 40 μm, or even as thick as 60 μm, to enhance the overall performance of the germanium-based solar cell 1.

As is apparent from the above detailed description, by the introduction of the at least one first trench 142 and the at least one second trench 144, the amount of thermal expansion of the back electrode 14 during the co-firing process is limited or reduced. Therefore, the ruthenium-based solar cell 1 of the present invention facilitates replacement of the original metal paste based on factors such as cost or efficiency.

In summary, the bismuth-based solar cell according to the present invention has a special back electrode structure, which can avoid warpage of the bismuth-based solar cell in the co-firing process. The ruthenium-based solar cell according to the present invention has a crystalline ruthenium substrate which can be reduced to a thickness of about 170 μm or less to reduce its overall manufacturing cost. Further, the ruthenium-based solar cell according to the present invention has a back electrode having a thickness of about 40 μm or more to enhance the conductivity of the back electrode.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

1. . . Silicon-based solar cell

10. . . Semiconductor structure combination

101. . . Crystalline ruthenium substrate

102. . . Positive surface

104. . . Back surface

106. . . P-n junction

108. . . Passivation layer

12. . . Positive electrode

122. . . Grid electrode

124. . . Positive bus bar electrode

14. . . Back electrode

142. . . First groove

144. . . Second groove

16a, 16b. . . Back bus bar electrode

18‧‧‧Anti-reflective layer

12 ' ‧‧‧First conductive paste

14 ' ‧‧‧Second conductive paste

16a ' , 16b ' ‧‧‧ third conductive paste

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a bottom plan view of a germanium based solar cell in accordance with a preferred embodiment of the present invention.

Figure 2 is a top plan view of a germanium based solar cell in accordance with a preferred embodiment of the present invention.

Fig. 3 is a cross-sectional view of the bismuth-based solar cell of Figs. 1 and 2 taken along line A-A of Figs. 1 and 2;

Fig. 4 is a cross-sectional view of the bismuth-based solar cell of Figs. 1 and 2 taken along line B-B of Figs. 1 and 2;

5A through 5D are schematic views showing a method of fabricating a germanium-based solar cell as shown in the cross-sectional view taken along line A-A of Fig. 1 in accordance with a preferred embodiment of the present invention.

1. . . Silicon-based solar cell

10. . . Semiconductor structure combination

101. . . Crystalline ruthenium substrate

102. . . Positive surface

104. . . Back surface

106. . . P-n junction

108. . . Passivation layer

12. . . Positive electrode

122. . . Grid electrode

124. . . Positive bus bar electrode

14. . . Back electrode

142. . . First groove

16a, 16b. . . Back bus bar electrode

18. . . Antireflection layer

Claims (10)

A germanium-based solar cell comprising: a semiconductor structure combination comprising at least one pn junction and having a front surface and a back surface; a positive electrode formed on the front surface of the semiconductor structure combination; at least one back surface a bus bar electrode formed on the back surface of the semiconductor structure combination; and a back electrode formed on the back surface of the semiconductor structure combination and covering the back surface to form the at least one back surface bus electrode a region and having at least one first trench. The bismuth-based solar cell of claim 1, wherein each of the first trenches is substantially perpendicular to the at least one backside bus electrode. The bismuth-based solar cell of claim 2, wherein the back electrode further has at least one second trench, each second trench being substantially parallel to the at least one backside bus electrode. The bismuth-based solar cell according to claim 2, wherein the semiconductor structure combination comprises a crystalline germanium substrate having a thickness of less than 170 μm and a thickness of the back electrode of greater than 40 μm. The bismuth-based solar cell of claim 2, wherein the at least one backside bus electrode comprises a layer selected from the group consisting of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, One of a group of palladium alloys and mixtures thereof, the back electrode comprising selected from the group consisting of aluminum, silver, copper, gold, platinum, palladium, aluminum alloys, silver alloys, copper alloys, gold alloys, platinum alloys, palladium alloys. And one of the groups in which the mixture is grouped. A method of forming a germanium-based solar cell, comprising the steps of: (a) forming a semiconductor structure combination, wherein the semiconductor structure combination comprises at least one pn junction and having a front surface and a back surface; (b) on the front surface of the semiconductor structure combination, the coating has a first a pattern of a first conductive paste, the first pattern corresponding to a positive electrode; and (c) coating a second conductive paste having a second pattern on the back surface of the semiconductor structure combination, the second The pattern corresponds to a back electrode; and (d) coating, on the back surface of the semiconductor structure, a third conductive paste having a third pattern corresponding to at least one back bus electrode; and (e) Performing a co-firing process on the structure of the step (d), the first conductive paste having the first pattern is sintered into the positive electrode, and the second conductive paste having the second pattern is sintered into the back electrode, and The third conductive paste having the third pattern is sintered into the at least one back bus bar electrode, wherein the back electrode has at least one first trench. The method of claim 6, wherein each of the first trenches is substantially perpendicular to the at least one backside bus electrode. The method of claim 7, wherein the back electrode further has at least one second trench, each second trench being substantially parallel to the at least one backside bus electrode. The method of claim 7, wherein the semiconductor structure combination comprises a crystalline germanium substrate having a thickness of less than 170 μm and the back electrode having a thickness greater than 40 μm. The method of claim 7, wherein the second conductive paste comprises a material selected from the group consisting of aluminum, silver, copper, gold, platinum, palladium, aluminum alloys, silver alloys, copper alloys, gold alloys, platinum alloys, palladium alloys, and mixtures thereof. One of the group consisting of aluminum, silver, copper, gold, platinum, palladium, aluminum alloy, silver alloy, copper alloy, gold alloy, platinum alloy, palladium alloy, and mixtures thereof One of the groups in the group.