TW201813115A - Silicon-based photovoltaic device and manufacture thereof - Google Patents

Abstract

The invention discloses a silicon-based photovoltaic device and method of fabricating the same. The method of the invention is to form a back passivation layer to overlay a back surface of a p-type silicon wafer. In particular, during a heat treatment process, the method of the invention is to form a silicon oxide layer on a textured front surface of the p-type silicon wafer, and simultaneously to anneal the back passivation layer to improve the quality of the back passivation layer. Compared to the conventional PERC (Passivated Emitter and Rear Cell) silicon-based photovoltaic device, the silicon-based photovoltaic fabricated according to the method of the invention has higher photoelectric conversion efficiency.

Description

 Silicon-based photovoltaic element and method of manufacturing same  

The present invention relates to a Silicon-based Photovoltaic Device and a method of fabricating the same, and in particular, to a Passivated Emitter Rear Cell (PERC) structure and photoelectric conversion efficiency. A more improved bismuth-based photovoltaic element and its method of manufacture.

Photovoltaic Device is a photovoltaic component because it converts 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. It is widely used. The most common photovoltaic component is a germanium-based photovoltaic component that uses a germanium wafer as a substrate.

Although bismuth-based photovoltaic components rely on silicon wafers, conductive paste technology improvement and process optimization, photoelectric conversion efficiency continues to improve year by year, but with the rise of distributed systems, the market needs products with high cost performance and high photoelectric conversion efficiency. At the right time, manufacturers have successfully mass-produced PERC-based photovoltaic components, opening up a whirlwind with PERC technology to improve efficiency.

The PERC technology uses a material such as Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _x or SiOxNy/SiN _x to form a passivation layer on the back surface of the germanium-based photovoltaic element as a back reflector to increase the absorption of long-wave light while The potential difference between the pn junctions is maximized, and the electron recombination is reduced, thereby improving the photoelectric conversion efficiency of the bismuth-based photovoltaic element.

Referring to Figure 1, there is shown a cross-sectional view of a typical PERC germanium-based photovoltaic element 1 to reveal the various layers of a typical PERC germanium-based photovoltaic element 1.

As shown in FIG. 1, a typical PERC germanium-based photovoltaic element 1 comprises a p-type germanium wafer 10. The p-type germanium wafer 10 has a roughened front surface 102 and a back surface 104. After the roughened front surface 102 of the p-type germanium wafer 10 is subjected to a phosphorus diffusion process, a p-n junction 106 is formed in the p-type germanium wafer 10 near one of the roughened front surfaces 102.

A typical PERC germanium-based photovoltaic element 1 and includes a back passivation layer 14. The back passivation layer 14 is formed to coat the back surface 104 of the p-type germanium wafer 10. In particular, a plurality of microstructures 142 are formed on the back passivation layer 14, and within each of the microstructures 142, the back surface 104 is exposed. Typically, the plurality of microstructures 142 are trench-type microstructures that even penetrate the back surface 104.

A typical PERC germanium-based photovoltaic element 1 and comprises an anti-reflective layer 17. The anti-reflective layer 17 is formed to coat the roughened front surface 102.

A typical PERC germanium-based photovoltaic element 1 also includes a front side electrode 16 and a back side electrode 18. The front electrode 16 is formed on the anti-reflective layer 17 and is in ohmic contact with the roughened front surface shape 102. The back electrode 18 is formed on the back passivation layer 14 and fills a plurality of microstructures 142. Generally, the back surface electrode 18 is formed by sintering with an aluminum paste. During the sintering process, aluminum locally diffuses into the back surface 104 of a typical PERC bismuth-based photovoltaic element 1 to form a Back Surface Filed (BSF) 182, as shown in FIG. The back surface electric field 182 reflects minority carriers and increases the collection of majority carriers and transports them to busbar electrodes formed of silver or silver-aluminum, thereby improving the overall performance of a typical PERC-based photovoltaic component 1.

However, there is still room for improvement in the performance of PERC-based photovoltaic components.

Therefore, the technical problem to be solved by the present invention is to provide a bismuth-based photovoltaic element having a PERC structure and having improved photoelectric conversion efficiency and a method of manufacturing the same.

According to a first preferred embodiment of the present invention, a method of fabricating a germanium-based photovoltaic device, first, a p-type germanium wafer is prepared, wherein the p-type germanium wafer has a front surface and a back surface. Next, the method according to the first preferred embodiment of the present invention performs a roughening process on the front surface of the p-type germanium wafer. Next, the method according to the first preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface to form a pn junction in one of the roughened front surfaces in the p-type germanium wafer. And forming a phosphor glass layer on the roughened front surface. Next, the method according to the first preferred embodiment of the present invention removes the phosphorous glass layer on the roughened front surface. Next, the method according to the first preferred embodiment of the present invention forms a back passivation layer to be coated on the back surface of the p-type germanium wafer. Next, the method according to the first preferred embodiment of the present invention performs a heat treatment process to form a ruthenium oxide layer on the roughened front surface and simultaneously anneal the back passivation layer. Next, the method according to the first preferred embodiment of the present invention forms an antireflection layer to coat the ruthenium oxide layer. Next, the method according to the first preferred embodiment of the present invention partially removes the back passivation layer, thereby forming a plurality of microstructures on the back passivation layer, wherein the back surface is exposed in each of the microstructures. Next, the method according to the first preferred embodiment of the present invention is to form a front electrode on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface. Finally, the method according to the first preferred embodiment of the present invention is to form a back electrode on the back passivation layer, wherein the back electrode is filled with a plurality of microstructures.

According to a second preferred embodiment of the present invention, a method of fabricating a germanium-based photovoltaic device, first, a p-type germanium wafer is prepared, wherein the p-type germanium wafer has a front surface and a back surface. Next, the method according to the second preferred embodiment of the present invention performs a roughening process on the front surface of the p-type germanium wafer. Next, a method according to a second preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface to form a pn junction in one of the roughened front surfaces in the p-type germanium wafer. And forming a phosphor glass layer on the roughened front surface. Next, the method according to the second preferred embodiment of the present invention removes the phosphor glass layer on the roughened front surface. Next, the method according to the second preferred embodiment of the present invention performs a heat treatment process to form a front ruthenium oxide layer on the roughened front surface and simultaneously form a back ruthenium oxide layer on the back surface. Next, a method according to a second preferred embodiment of the present invention forms a back passivation layer to coat the back ruthenium oxide layer. Next, a method according to a second preferred embodiment of the present invention forms an anti-reflective layer to coat the front yttrium oxide layer. Next, the method according to the second preferred embodiment of the present invention partially removes the back passivation layer and the back ruthenium oxide layer, thereby forming a plurality of microstructures on the back passivation layer, wherein in each of the microstructures, the back surface Exposed. Next, a method according to a second preferred embodiment of the present invention is to form a front electrode on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface. Finally, the method according to the second preferred embodiment of the present invention is to form a back electrode on the back passivation layer, wherein the back electrode is filled with a plurality of microstructures.

According to a third preferred embodiment of the present invention for fabricating a germanium-based photovoltaic device, first, a p-type germanium wafer is prepared, wherein the p-type germanium wafer has a front surface and a back surface. Next, the method according to the third preferred embodiment of the present invention performs a roughening process on the front surface of the p-type germanium wafer. Next, the method according to the third preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface to form a pn junction in one of the roughened front surfaces in the p-type germanium wafer. And forming a phosphor glass layer on the roughened front surface. Next, the method according to the third preferred embodiment of the present invention removes the phosphor glass layer on the roughened front surface. Next, a method according to a third preferred embodiment of the present invention forms an anti-reflective layer to coat the roughened front surface. Next, a method according to a third preferred embodiment of the present invention forms a back passivation layer to coat the back surface of the p-type germanium wafer. Next, the method according to the third preferred embodiment of the present invention performs a heat treatment process to simultaneously heat-treat the back passivation layer and the anti-reflection layer. Next, the method according to the third preferred embodiment of the present invention partially removes the back passivation layer to form a plurality of microstructures on the back passivation layer, wherein the back surface is exposed in each of the microstructures. Next, a method according to a third preferred embodiment of the present invention is to form a front electrode on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface. Finally, the method according to the third preferred embodiment of the present invention is to form a back electrode on the back passivation layer, wherein the back electrode is filled with a plurality of microstructures.

In practical applications, the microstructure may be a recess, a trench, or a hybrid structure of the above structure.

In a specific embodiment, the composition of the back passivation layer may be Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _x or SiO _x N _y /SiN _x , or a mixture of the above compounds.

In a specific embodiment, the composition of the antireflection layer may be SiN _x , SiO ₂ /SiN _x or SiN _x /SiO _x N _y , or a mixture of the above compounds.

In one embodiment, the p-type germanium wafer may be a p-type single crystal germanium wafer or a p-type poly germanium wafer.

Unlike the prior art, the bismuth-based photovoltaic element fabricated according to the method of the present invention not only has a PERC structure, but also has a higher photoelectric conversion efficiency than a typical PERC-based photovoltaic element.

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

1, 2, 3, 4‧‧‧ 矽 based photovoltaic components

10, 20, 30, 40‧‧‧p-type wafers

102, 202, 302, 402‧‧‧ front surface

104, 204, 304, 404‧‧‧ back surface

106, 206, 306, 406‧‧‧p-n junction

14, 24, 34, 44‧‧‧ back passivation layer

142, 242, 342, 442‧‧‧ microstructures

16, 26, 36, 46‧‧‧ front electrodes

17, 27, 37, 47‧‧‧ anti-reflection layer

18, 28, 38, 48‧‧‧ back electrode

182, 282, 382, 482‧‧‧ back surface electric field

21, 31, 41‧‧ ‧ phosphorus glass layer

22‧‧‧Oxide layer

32‧‧‧Positive oxidized ruthenium layer

33‧‧‧Back ruthenium oxide layer

Figure 1 is a cross-sectional view of a typical PERC germanium based photovoltaic component.

2 through 7 are cross-sectional views showing a method of fabricating a germanium-based photovoltaic device in accordance with a first preferred embodiment of the present invention.

8 through 13 are cross-sectional views showing a method of fabricating a germanium-based photovoltaic element in accordance with a second preferred embodiment of the present invention.

14 through 18 are cross-sectional views showing a method of fabricating a germanium-based photovoltaic element in accordance with a third preferred embodiment of the present invention.

Referring to FIGS. 2-7, the drawings depict a method of fabricating a germanium-based solar cell 2 as shown in the cross-sectional view of FIG. 7 in accordance with a first preferred embodiment of the present invention in a cross-sectional view.

As shown in FIG. 2, in a method of fabricating a germanium-based photovoltaic device 2 according to a first preferred embodiment of the present invention, first, a p-type germanium wafer 20 is prepared, wherein the p-type germanium wafer 20 has a front surface 202. And a back surface 204.

In one embodiment, the p-type germanium wafer 20 can be a p-type single crystal germanium wafer or a p-type poly germanium wafer.

Also shown in FIG. 2, the method according to the first preferred embodiment of the present invention roughens the front surface 202 of the p-type germanium wafer 20 to allow the front surface 202 of the p-type germanium wafer 20 to pass through. The roughened front surface 202 further reduces the reflectivity of the p-type germanium wafer 20 to incident light. The roughening process can be etched using an alkaline liquid such as KOH or NaOH, but is not limited thereto.

As shown in FIG. 3, next, the method according to the first preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface 202, thereby approaching the roughened positive in the p-type germanium wafer 20. A pn junction 206 is formed at one of the surfaces 202, and a phosphor glass layer 21 is formed on the roughened front surface 202.

As shown in FIG. 4, next, the method according to the first preferred embodiment of the present invention removes the phosphorous glass layer 21 on the roughened front surface 202.

As shown in FIG. 5, a method of forming a back passivation layer 24 to cover the back surface 204 of the p-type germanium wafer 20 is then performed in accordance with the method of the first preferred embodiment of the present invention.

In one embodiment, the composition of the back passivation layer 24 may be Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _x or SiO _x N _y /SiN _x , or a mixture of the above compounds.

Also shown in Fig. 5, and in particular, the method according to the first preferred embodiment of the present invention performs a heat treatment process to form a ruthenium oxide layer 22 on the roughened front surface 202 and simultaneously to the back passivation layer. 24 is annealed. In one embodiment, the temperature range of the heat treatment process ranges from 300 ° C to 900 ° C, and the process time ranges from 1 minute to 120 minutes. The furnace atmosphere uses air, nitrogen (N ₂ ), and oxygen (O ₂ ). Or a mixture of the above gases, whereby the defect density of the back passivation layer 24 can be lowered, and the surface morphology of the back passivation layer 24 can be improved.

As shown in FIG. 6, then, in accordance with the method of the first preferred embodiment of the present invention, an anti-reflective layer 27 is formed to coat the yttria layer 22.

In one embodiment, the composition of the anti-reflective layer 27 may be SiN _x , SiN _x /SiO _x N _y or SiO ₂ /SiN _x , or a mixture of the above compounds.

As shown in FIG. 7, next, the method according to the first preferred embodiment of the present invention partially removes the back passivation layer 24, thereby forming a plurality of microstructures 242 on the back passivation layer 24, wherein each of the microstructures Within 242, the back surface 204 is exposed. In one embodiment, the plurality of microstructures 242 may be formed by laser engraving the back passivation layer 24, and the plurality of microstructures 242 may even penetrate the back surface 204, but are not limited thereto.

In practical applications, the microstructures 242 can be recesses, trenches, or a hybrid structure of the above structure.

Also shown in Fig. 7, then, in accordance with a first preferred embodiment of the present invention, a front side electrode 26 is formed on the anti-reflective layer 27, wherein the front side electrode 26 forms an ohmic contact with the roughened front surface 202.

Also shown in Fig. 7, finally, the method according to the first preferred embodiment of the present invention is such that the back surface electrode 28 is formed on the back passivation layer 24, i.e., the germanium based solar cell 2 is completed. In particular, the back electrode 28 is filled with a plurality of microstructures 242. The germanium-based solar cell 2 shown in Fig. 7 has a PERC structure.

In a specific embodiment, the front electrode 26 can be formed by partially coating a silver paste on the anti-reflective layer 27, and the back electrode 28 can be formed by coating an aluminum paste on the back passivation layer 24, and then co-firing. The process is formed together. During the sintering process, aluminum partially diffuses into the back surface 204, forming a back surface electric field 282, as shown in FIG.

Referring to FIG. 7, the germanium-based photovoltaic device 2 manufactured according to the method of the first preferred embodiment of the present invention comprises a p-type germanium wafer 20, a back passivation layer 24, a hafnium oxide layer 22, an anti-reflection layer 27, Front electrode 26 and back electrode 28.

The p-type germanium wafer 20 has a roughened front surface 202 and a back surface 204 and includes a p-n junction 206 adjacent the roughened front surface 202. A back passivation layer 24 is formed to coat the back surface 204 of the p-type germanium wafer 20. In particular, a plurality of microstructures 242 are formed on the back passivation layer 24, and within each microstructure 242, the back surface 204 is exposed.

The hafnium oxide layer 22 is formed on the roughened front surface 202 of the p-type germanium wafer 20. In particular, during the formation of the hafnium oxide layer 22, the back passivation layer 24 is simultaneously annealed, whereby the defect density of the back passivation layer 24 can be lowered, and the surface morphology of the back passivation layer 24 can be improved.

The anti-reflection layer 27 is formed to cover the ruthenium oxide layer 22. The front electrode 26 is formed on the anti-reflective layer 27 and forms an ohmic contact with the roughened front surface 202. The back electrode 28 is formed on the back passivation layer 24, and in particular, the back electrode 28 fills the plurality of microstructures 242. The aluminum partially diffuses into the back surface 204, forming a back surface electric field 282.

Referring to Table 1, the battery characteristics obtained by the ruthenium-based photovoltaic element 2 manufactured according to the method of the first preferred embodiment of the present invention include photoelectric conversion efficiency (Efficiency), open circuit voltage (V _oc ), and short circuit. Current (I _sc ) and fill factor (FF). Table 1 also lists a typical PERC-based photovoltaic component as a reference group 1 test result, as a comparison.

From the test data of Table 1, it can be clearly seen that the bismuth-based photovoltaic element 2 manufactured according to the method of the first preferred embodiment of the present invention has superior battery characteristics to typical PERC bismuth-based photovoltaic elements (reference group). 1) Various battery characteristics.

Referring to Figures 8 through 13, the drawings depict a method of fabricating a germanium-based solar cell 3 as shown in the cross-sectional view of Figure 13 in accordance with a second preferred embodiment of the present invention in a cross-sectional view.

As shown in FIG. 8, a method of manufacturing a germanium-based photovoltaic device 3 according to a second preferred embodiment of the present invention, first, a p-type germanium wafer 30 is prepared, wherein the p-type germanium wafer 30 has a front surface 302. And a back surface 304.

In one embodiment, the p-type germanium wafer 30 can be a p-type single crystal germanium wafer or a p-type poly germanium wafer.

Also shown in FIG. 8, a method according to a second preferred embodiment of the present invention roughens the front surface 302 of the p-type germanium wafer 30 to allow the front surface 302 of the p-type germanium wafer 30 to pass through. The roughened front surface 302 further reduces the reflectivity of the p-type germanium wafer 30 to incident light.

As shown in FIG. 9, next, the method according to the second preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface 302, thereby approaching the roughened positive in the p-type germanium wafer 30. A pn junction 306 is formed at one of the surfaces 302, and a phosphor glass layer 31 is formed on the roughened front surface 302.

As shown in FIG. 10, next, the method according to the second preferred embodiment of the present invention removes the phosphorous glass layer 31 on the roughened front surface 302.

As shown in FIG. 11, then, the method according to the second preferred embodiment of the present invention performs an annealing process to form a front oxide layer 32 on the roughened front surface 302 of the p-type germanium wafer 30, and At the same time, a back yttrium oxide layer 33 is formed on the back surface 304 of the p-type germanium wafer 30.

In one embodiment, the temperature range of the heat treatment process ranges from 300 ° C to 900 ° C, and the process time ranges from 1 minute to 120 minutes. The furnace atmosphere uses air, nitrogen (N ₂ ), and oxygen (O ₂ ). Or a mixture of the above gases, as shown in Fig. 12, followed by forming a back passivation layer 34 to coat the back yttria layer 33 in accordance with the method of the second preferred embodiment of the present invention.

In one embodiment, the composition of the back passivation layer 34 may be Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _x or SiO _x N _y /SiN _x , or a mixture of the above compounds.

Also shown in Fig. 12, then, in accordance with a second preferred embodiment of the present invention, an anti-reflective layer 37 is formed to coat the front ruthenium oxide layer 32.

In one embodiment, the composition of the anti-reflective layer 37 may be SiN _x , SiO _x N _y /SiN _x or SiO ₂ /SiN _x , or a mixture of the above compounds.

As shown in FIG. 13, the method according to the second preferred embodiment of the present invention partially removes the back passivation layer 34 and the back ruthenium oxide layer 33, thereby forming a plurality of microstructures 342 on the back passivation layer 34. Within each of the microstructures 342, the back surface 304 is exposed. In a specific embodiment, the plurality of microstructures 342 may be formed by laser engraving the back passivation layer 34, and the plurality of microstructures 342 may even penetrate the back surface 304, but not limited thereto.

In practical applications, the microstructure 342 can be a recess, a trench, or a hybrid structure of the above structure.

Also shown in Fig. 13, then, in accordance with a second preferred embodiment of the present invention, a front side electrode 36 is formed on the anti-reflective layer 37, wherein the front side electrode 36 forms an ohmic contact with the roughened front surface 302.

Also shown in Fig. 13, finally, the method of the second preferred embodiment of the present invention is formed on the back passivation layer 34 to form the back electrode 38. In particular, the back electrode 38 is filled with a plurality of microstructures 342. The germanium-based solar cell 3 shown in Fig. 13 has a PERC structure.

In one embodiment, the front electrode 36 can be formed by partially coating a silver paste on the anti-reflective layer 37. The back electrode 38 can be formed by coating an aluminum paste on the back passivation layer 34 and co-firing. The process is formed together. During the sintering process, aluminum partially diffuses into the back surface 304, forming a back surface electric field 382, as shown in FIG.

Referring to FIG. 13, a bismuth-based photovoltaic device 3 fabricated according to the method of the second preferred embodiment of the present invention comprises a p-type germanium wafer 30, a front yttrium oxide layer 32, a back yttria layer 33, and a back passivation layer. 34. Antireflection layer 37, front electrode 36, and back electrode 38.

The p-type germanium wafer 30 has a roughened front surface 302 and a back surface 304 and includes a p-n junction 306 near the roughened front surface 302. The front yttrium oxide layer 32 is formed on the roughened front surface 302 of the p-type germanium wafer 30. A back yttrium oxide layer 33 is formed on the back surface 304 of the p-type germanium wafer 30. In particular, the front ruthenium oxide layer 32 is formed simultaneously with the back ruthenium oxide layer 33.

The back passivation layer 34 is formed to coat the back yttria layer 33. In particular, a plurality of microstructures 342 are formed on the back passivation layer 34, and within each of the microstructures 342, the back surface 304 is exposed.

The anti-reflective layer 37 is formed to coat the front yttrium oxide layer 32. The front electrode 36 is formed on the anti-reflective layer 37 and forms an ohmic contact with the roughened front surface 302. The back electrode 38 is formed on the back passivation layer 24, and in particular, the back electrode 38 fills the plurality of microstructures 342. The aluminum partially diffuses into the back surface 304, forming a back surface electric field 382.

Referring to Table 2, the average battery characteristics of a plurality of test pieces of the bismuth-based photovoltaic element manufactured by the method according to the second preferred embodiment of the present invention, including photoelectric conversion efficiency (Efficiency, Eff), open circuit Voltage (V _oc ), short circuit current (I _sc ), and fill factor (Fill Factor, FF). Table 2 also lists a typical PERC-based photovoltaic component as a reference group 2 test result, for comparison.

From the test data of Table 2, it can be clearly seen that the bismuth-based photovoltaic element 3 manufactured according to the method of the second preferred embodiment of the present invention has better battery characteristics than the typical PERC bismuth-based photovoltaic element (reference group) 2) Various battery characteristics.

Referring to Figures 14 through 19, the drawings depict a method of fabricating a germanium-based solar cell 4 as shown in the cross-sectional view of Figure 19 in accordance with a third preferred embodiment of the present invention in a cross-sectional view.

As shown in FIG. 14, a method of fabricating a germanium-based photovoltaic device 4 according to a third preferred embodiment of the present invention, first, a p-type germanium wafer 40 is prepared, wherein the p-type germanium wafer 40 has a front surface 402. And a back surface 404.

In one embodiment, the p-type germanium wafer 40 can be a p-type single crystal germanium wafer or a p-type poly germanium wafer.

Also shown in FIG. 14, a method according to a third preferred embodiment of the present invention roughens the front surface 402 of the p-type germanium wafer 40 to allow the front surface 402 of the p-type germanium wafer 40 to pass through. The roughened front surface 402 further reduces the reflectivity of the p-type germanium wafer 40 to incident light. The roughening process may be performed by using an alkaline liquid such as KOH or NaOH, but is not limited thereto.

As shown in FIG. 15, next, the method according to the third preferred embodiment of the present invention performs a phosphorus diffusion process on the roughened front surface 402, thereby approaching the roughened positive in the p-type germanium wafer 40. A pn junction 406 is formed at one of the surfaces 402, and a phosphor glass layer 41 is formed on the roughened front surface 402.

As shown in FIG. 16, then, the method according to the third preferred embodiment of the present invention removes the phosphor glass layer 41 on the roughened front surface 402.

As shown in FIG. 17, then, in accordance with a third preferred embodiment of the present invention, an anti-reflective layer 47 is formed to coat the roughened front surface 402 of the p-type germanium wafer 40.

In one embodiment, the composition of the anti-reflective layer 47 may be SiN _x , SiN _x /SiO _x N _y or SiO ₂ /SiN _x , or a mixture of the above compounds.

Also shown in FIG. 17, then, a method according to a third preferred embodiment of the present invention forms a back passivation layer 44 to be coated over the back surface 404 of the p-type germanium wafer 40.

In one embodiment, the composition of the back passivation layer 44 may be Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _x or SiO _x N _y /SiN _x , or a mixture of the above compounds.

Also shown in Fig. 17, then, in particular, the method according to the third preferred embodiment of the present invention performs a heat treatment process to simultaneously anneal the back passivation layer 44 and the anti-reflective layer 47. In one embodiment, the temperature range of the heat treatment process ranges from 300 ° C to 900 ° C, and the process time ranges from 1 minute to 120 minutes. The furnace atmosphere uses air, nitrogen (N ₂ ), and oxygen (O ₂ ). Hydrogen (H ₂ ), argon (Ar) or a mixture of the above gases, whereby the defect density of the back passivation layer 44 and the anti-reflective layer 47 can be lowered, and the surface morphology of the back passivation layer 44 and the anti-reflective layer 47 can be improved.

As shown in FIG. 18, next, the method according to the third preferred embodiment of the present invention partially removes the back passivation layer 44, thereby forming a plurality of microstructures 442 on the back passivation layer 44, wherein each of the microstructures In 442, the back surface 404 is exposed. In one embodiment, the plurality of microstructures 442 may be formed by laser engraving the back passivation layer 44, but is not limited thereto.

In practical applications, the microstructure may be a recess, a trench, or a hybrid structure of the above structure.

Also shown in Fig. 18, a method according to a third preferred embodiment of the present invention is followed by forming a front side electrode 46 on the anti-reflective layer 47, wherein the front side electrode 46 forms an ohmic contact with the roughened front surface 402.

Also shown in Fig. 18, finally, the method according to the third preferred embodiment of the present invention is such that the back surface electrode 48 is formed on the back passivation layer 44, i.e., the germanium based solar cell 4 is completed. In particular, the back electrode 48 is filled with a plurality of microstructures 442. The bismuth-based solar cell 4 shown in Fig. 18 has a PERC structure.

In a specific embodiment, the front electrode 46 can be formed by partially coating silver paste on the anti-reflective layer 47. The back electrode 48 can be formed by coating aluminum paste on the back passivation layer 44 and co-firing. The process is formed together. During the sintering process, aluminum partially diffuses into the back surface 404, forming a back surface electric field 482, as shown in FIG.

Referring to Table 3, the average battery characteristics of the test pieces obtained by the test piece according to the third preferred embodiment of the present invention, including the photoelectric conversion efficiency (Efficiency, Eff), Open circuit voltage (V _oc ), short circuit current (I _sc ), and fill factor (Fill Factor, FF). Table 3 also lists the results of a typical PERC-based photovoltaic component as a reference group 3 for comparison.

From the test data of Table 3, it can be clearly seen that the bismuth-based photovoltaic element 4 manufactured by the method according to the third preferred embodiment of the present invention has better battery characteristics than the typical PERC-based photovoltaic element (reference group). 3) Various batteries.

In summary, it is clear that the germanium-based photovoltaic elements fabricated according to the method of the present invention not only have a PERC structure, but also have higher photoelectric conversion efficiency than typical PERC-based photovoltaic elements.

The features and spirit of the present invention are intended to be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents that are within the scope of the invention as claimed. Therefore, the scope of the patent application of the present invention should be construed broadly in the light of the above description, so that it covers all possible changes and arrangements.

Claims (13)

 A method of fabricating a germanium-based photovoltaic component, comprising the steps of: preparing a p-type germanium wafer, wherein the p-type germanium wafer has a front surface and a back surface; performing a roughening process on the front surface; Performing a phosphorus diffusion process on the roughened front surface to form a pn junction in the p-type germanium wafer near one of the roughened front surfaces and forming a phosphorous glass on the roughened front surface a layer; removing the phosphor glass layer on the roughened front surface; forming a back passivation layer to cover the back surface; performing a heat treatment process to form a hafnium oxide layer on the roughened front surface, and Simultaneously annealing the back passivation layer; forming an anti-reflective layer to cover the yttria layer; partially removing the back passivation layer to form a plurality of microstructures on the back passivation layer, wherein each of the microstructures The back surface is exposed; a front electrode is formed on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface; and a back electrode is formed on the back passivation layer, wherein Filling the plurality of back electrode microstructures.   The method of claim 1, wherein the composition of the back passivation layer is selected from the group consisting of Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _{x ,} and SiO _x N _y /SiN _x , And the composition of the anti-reflection layer is selected from the group consisting of SiN _x , SiO ₂ /SiN _x and SiN _x /SiO _x N _y .  The method of claim 1, wherein the p-type germanium wafer is a p-type single crystal germanium wafer or a p-type poly germanium wafer.    The method of claim 1, wherein a temperature range of the heat treatment process ranges from 300 ° C to 900 ° C, and one of the heat treatment processes has a process time ranging from 1 minute to 120 minutes, and one of the heat treatment processes includes One of a group of free air, nitrogen, and oxygen.    A method of fabricating a germanium-based photovoltaic component, comprising the steps of: preparing a p-type germanium wafer, wherein the p-type germanium wafer has a front surface and a back surface; performing a roughening process on the front surface; Performing a phosphorus diffusion process on the roughened front surface to form a pn junction in the p-type germanium wafer near one of the roughened front surfaces and forming a phosphorous glass on the roughened front surface a layer; removing the phosphor glass layer on the roughened front surface; performing a heat treatment process to form a front yttrium oxide layer on the roughened front surface, and simultaneously forming a back surface oxidation on the back surface a back passivation layer is formed to cover the back ruthenium oxide layer; an anti-reflection layer is formed to cover the front ruthenium oxide layer; the back passivation layer and the back ruthenium oxide layer are partially removed and formed on the back passivation layer a plurality of microstructures, wherein the back surface is exposed in each of the microstructures; a front electrode is formed on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface; Forming a back electrode on the back passivation layer, wherein the plurality of back electrode fills the microstructures.   The method of claim 5, wherein the composition of the back passivation layer is selected from the group consisting of Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _{x ,} and SiO _x N _y /SiN _x , And the composition of the anti-reflection layer is selected from the group consisting of SiN _x , SiO ₂ /SiN _x and SiN _x /SiO _x N _y .  The method of claim 5, wherein the p-type germanium wafer is a p-type single crystal germanium wafer or a p-type poly germanium wafer.    The method of claim 5, wherein one of the heat treatment processes has a temperature range of from 300 ° C to 900 ° C, and one of the heat treatment processes has a process time ranging from 1 minute to 120 minutes, and one of the heat treatment processes includes One of a group of free air, nitrogen, and oxygen.    A method of fabricating a germanium-based photovoltaic component, comprising the steps of: preparing a p-type germanium wafer, wherein the p-type germanium wafer has a front surface and a back surface; performing a roughening process on the front surface; Performing a phosphorus diffusion process on the roughened front surface to form a pn junction in the p-type germanium wafer near one of the roughened front surfaces and forming a phosphorous glass on the roughened front surface a layer; removing the phosphor glass layer on the roughened front surface; forming an anti-reflective layer to coat the roughened front surface; forming a back passivation layer to cover the back surface; performing a heat treatment process and simultaneously Performing an annealing treatment on the back passivation layer and the anti-reflective layer; partially removing the back passivation layer to form a plurality of microstructures on the back passivation layer, wherein the back surface is exposed in each microstructure; Forming a front electrode on the anti-reflective layer, wherein the front electrode forms an ohmic contact with the roughened front surface; and forming a back surface electrode on the back passivation layer, wherein the back surface electrode fills the Microstructure.   The method of claim 9, wherein the composition of the back passivation layer is selected from the group consisting of Al ₂ O ₃ /SiN _x , SiO ₂ /SiN _{x ,} and SiO _x N _y /SiN _x , The composition of the anti-reflection layer is selected from the group consisting of SiN _x , SiO ₂ /SiN _x and SiN _x /SiO _x N _y , and the p-type germanium wafer is a p-type single crystal twin Round or a p-type polysilicon wafer.  The method of claim 9, wherein the temperature of one of the heat treatment processes ranges from 300 ° C to 900 ° C, and one of the heat treatment processes ranges from 1 minute to 120 minutes, and one of the heat treatment processes includes Free air, nitrogen, and one of a group of oxygen, hydrogen, and argon.    A germanium-based photovoltaic device comprising: a p-type germanium wafer, wherein the p-type germanium wafer has a roughened front surface and a back surface, and includes a pn junction adjacent to the roughened front surface; a back passivation layer is formed to cover the back surface, wherein a plurality of microstructures are formed on the back passivation layer, and the back surface is exposed in each microstructure; a ruthenium oxide layer is formed in the On the roughened front surface, in the process of forming the ruthenium oxide layer, the back passivation layer is simultaneously subjected to an annealing treatment; an anti-reflection layer is formed to cover the ruthenium oxide layer; and a front electrode is formed on the surface An anti-reflective layer and an ohmic contact with the roughened front surface; and a back electrode formed on the back passivation layer, wherein the back electrode fills the plurality of microstructures.    A germanium-based photovoltaic device comprising: a p-type germanium wafer, wherein the p-type germanium wafer has a roughened front surface and a back surface, and includes a pn junction adjacent to the roughened front surface; a front ruthenium oxide layer formed on the roughened front surface; a back ruthenium oxide layer formed on the back surface, wherein the front ruthenium oxide layer is formed simultaneously with the back ruthenium oxide layer; a passivation layer is formed to coat the back ruthenium oxide layer, wherein a plurality of microstructures are formed on the back passivation layer, and the back surface is exposed in each microstructure; an anti-reflection layer is formed to cover the a front yttrium oxide layer; a front electrode formed on the anti-reflective layer and forming an ohmic contact with the roughened front surface; and a back electrode formed on the back passivation layer, wherein the back electrode is filled Multiple microstructures.