TWI483409B - Solar cell and manufacturing method thereof - Google Patents

Description

Solar cell and manufacturing method thereof

The present invention relates to a method of fabricating a photovoltaic element, and more particularly to a method of fabricating a solar cell.

Due to the shortage of petrochemical energy, people's awareness of the importance of environmental protection has increased. Therefore, in recent years, people have been actively researching and developing technologies related to alternative energy and renewable energy, hoping to reduce the current dependence of human beings on petrochemical energy and the use of petrochemical energy. The impact. Among the many alternative energy and renewable energy technologies, solar cells are attracting the most attention. Mainly because solar cells can directly convert solar energy into electrical energy, and carbon dioxide or nitrides are not generated during power generation, so there is no environmental pollution problem.

The principle of a solar cell is to bond a p-type semiconductor to an n-type semiconductor to form a p-n junction. When sunlight strikes a semiconductor having this p-n structure, the energy provided by the photons excites electrons in the semiconductor to create electron hole pairs. Both electrons and holes are affected by the built-in potential, causing the holes to move in the direction of the electric field and the electrons moving in the opposite direction. If the solar cell is connected to the load by wires, a loop can be formed and current can flow through the load, which is the principle of solar cell power generation.

In a general solar cell, in order to increase the amount of sunlight entering the light, a sufficiently large distance must be maintained between the plurality of electrodes located at the front side (ie, the light incident surface) of the solar cell. However, excessive spacing often leads to current conduction. The impedance is too large, resulting in a decrease in the photoelectric conversion efficiency of the solar cell.

The present invention provides a solar cell having better photoelectric conversion efficiency.

The invention further provides a method for fabricating a solar cell, which can produce a solar cell having better photoelectric conversion efficiency.

The invention provides a solar cell comprising a substrate, an emitter, a first passivation layer, a second passivation layer, a plurality of first electrodes, a plurality of second electrodes and a first transparent conductive layer. The substrate has a front side and a back side opposite to each other. The emitter is placed on the front side. The first passivation layer is disposed on the emitter. The second passivation layer is disposed on the back surface. The first electrode is disposed on the first passivation layer, and a portion of each of the first electrodes is connected to the emitter through the first passivation layer. The second electrode is disposed on the second passivation layer and a portion of each of the second electrodes passes through the second passivation layer to reach the substrate. The first transparent conductive layer is disposed on the first passivation layer between the first electrodes.

According to the solar cell of the embodiment of the invention, the material of the first transparent conductive layer is, for example, indium tin oxide (ITO), aluminum doped zinc oxide (AZO) or fluorine-doped oxide. Fluorine doped tin oxide (FTO).

According to the solar cell of the embodiment of the invention, the first transparent conductive layer covers the first electrode, for example.

The solar cell according to the embodiment of the invention further includes an anti-reflection layer disposed between the first passivation layer and the first transparent conductive layer.

The solar cell according to the embodiment of the invention further includes An anti-reflective layer on the second passivation layer.

The solar cell according to the embodiment of the invention further includes a second transparent conductive layer disposed on the second passivation layer between the second electrodes.

According to the solar cell of the embodiment of the invention, the material of the second transparent conductive layer is, for example, indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide.

According to the solar cell of the embodiment of the invention, the second transparent conductive layer covers the second electrode, for example.

The present invention further provides a method of fabricating a solar cell by first providing a substrate having front and back surfaces opposite to each other. Then, an emitter is formed at the front side. Next, a first passivation layer is formed on the emitter, and a second passivation layer is formed on the back surface. Then, a plurality of first electrodes are formed on the first passivation layer, wherein a portion of each of the first electrodes passes through the first passivation layer to be connected to the emitter, and a plurality of second electrodes are formed on the second passivation layer, wherein A portion of each of the second electrodes passes through the second passivation layer into the substrate. Thereafter, a first transparent conductive layer is formed on the first passivation layer between the first electrodes.

According to the manufacturing method of the solar cell of the embodiment of the invention, the material of the first transparent conductive layer is, for example, indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide.

According to the method for fabricating a solar cell according to an embodiment of the invention, the method for forming the first transparent conductive layer is, for example, thermal growth, chemical vapor deposition, spraying or printing.

According to the method of fabricating a solar cell according to an embodiment of the invention, the first transparent conductive layer covers the first electrode, for example.

According to the method of fabricating a solar cell according to an embodiment of the invention, the anti-reflective layer may be formed on the first passivation layer after forming the first passivation layer and before forming the first electrode.

According to the method of fabricating a solar cell according to an embodiment of the invention, the anti-reflective layer may be formed on the second passivation layer after forming the second passivation layer and before forming the second electrode.

According to the method for fabricating a solar cell according to the embodiment of the invention, after the second electrode is formed, a second transparent conductive layer may be formed on the second passivation layer between the second electrodes.

According to the manufacturing method of the solar cell of the embodiment of the invention, the material of the second transparent conductive layer is, for example, indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide.

According to the method for fabricating a solar cell according to an embodiment of the invention, the method for forming the second transparent conductive layer is, for example, thermal growth, chemical vapor deposition, spraying or printing.

According to a method of fabricating a solar cell according to an embodiment of the invention, the second transparent conductive layer covers the second electrode, for example.

Based on the above, in the present invention, transparent conductive layers are formed between the electrodes and are connected to each other by the transparent conductive layer, so that the problem that the conduction resistance is too high due to excessive spacing between the electrodes can be avoided, and thus the improvement is improved. Photoelectric conversion efficiency of solar cells. Further, since the transparent conductive layer has high light transmittance, there is no problem that the amount of incident light is lowered.

The above described features and advantages of the present invention will be more apparent from the following description.

1A-1D are cross-sectional views showing a manufacturing process of a solar cell according to an embodiment of the invention. First, referring to FIG. 1A, a substrate 100 having a front surface 100a and a back surface 100b opposed to each other is provided. The substrate 100 may be a single crystal germanium or a polycrystalline germanium substrate. Further, the substrate 100 may be a p-type substrate or an n-type substrate. In the present embodiment, the present invention will be described with a p-type substrate, but the invention is not limited thereto. Then, an emitter 102 is formed at the front side 100a. The method of forming the emitter 102 is, for example, first providing a phosphorus-containing (or other pentavalent element) gas (for example, a mixed gas of POCl ₃ and oxygen) on the substrate 100. Then, heat treatment is performed to dope phosphorus into the substrate 100 by means of high-temperature diffusion to form an n-type emitter 102. Further, after the emitter 102 is formed, hydrofluoric acid is used to remove the phosphorus glass formed by the oxidation of the surface of the substrate 100 during the above heat treatment.

In addition, in another embodiment, before the emitter 102 is formed, the substrate 100 may be textured by an etching process to make the front surface 100a a rough surface. Since the front surface 100a is a rough surface, scattering and multiple reflections are generated when light is incident on the front surface 100a, so that the traveling path of the light in the solar cell is longer, thereby increasing the chance that the photons are absorbed.

Next, referring to FIG. 1B, a passivation layer 104 is formed on the emitter 102, and a passivation layer 106 is formed on the back surface 100b. The formation method of the passivation layer 104 and the passivation layer 106 is, for example, thermal growth, chemical vapor deposition, spraying, or printing. The material of the passivation layer 104 and the passivation layer 106 is, for example, SiO ₂ , Al ₂ O ₃ or SiN _x . In the present invention, the order of formation of the passivation layer 104 and the passivation layer 106 is not limited. That is, the passivation layer 104 may be formed first to form the passivation layer 106, or the passivation layer 106 may be formed first to form the passivation layer 104. Alternatively, when the material of the passivation layer 104 and the passivation layer 106 are the same, both may be formed in the same step.

Further, after the passivation layer 104 is formed, the anti-reflection layer 105 may also be selectively formed on the passivation layer 104. The material of the anti-reflection layer 105 is, for example, tantalum nitride. The method of forming the anti-reflection layer 105 is, for example, thermal growth, chemical vapor deposition, spraying, or printing. Similarly, after the passivation layer 106 is formed, the anti-reflection layer 107 may also be formed on the passivation layer 106. The material and formation method of the anti-reflection layer 107 are the same as those of the anti-reflection layer 105, and will not be described herein.

Then, referring to FIG. 1C, an electrode 108 is formed on the anti-reflection layer 105, wherein a portion of each of the electrodes 108 passes through the anti-reflection layer 105 and the passivation layer 104 to be connected to the emitter 102, and an electrode is formed on the anti-reflection layer 107. 110, wherein a portion of each of the electrodes 110 passes through the anti-reflective layer 107 and the passivation layer 106 to reach the substrate 100. The method for forming the electrode 108 is, for example, first forming a patterned metal paste on the anti-reflective layer 105 by screen printing (if the anti-reflective layer 105 is not formed, the patterned metal paste is formed on the passivation layer 104), Then, heat treatment is performed to remove the carrier such as resin and solvent in the patterned metal glue, and the metal powder in the patterned metal glue is sintered to a dense structure, and the metal in the patterned metal glue is penetrated and anti-reflective. Layer 105 and passivation layer 104 reach emitter 102 to form electrode 108 that is coupled to emitter 102.

In addition, the electrode 110 is formed in a similar manner to the electrode 108. The patterned metal paste is first formed on the anti-reflective layer 107 by screen printing (if the anti-reflective layer 107 is not formed, the patterned metal paste is formed. Blunt The layer 106) is further subjected to heat treatment to remove the carrier such as a resin or a solvent in the patterned metal paste, and the metal powder in the patterned metal paste is sintered into a dense structure, and the metal in the patterned metal glue is worn. The antireflection layer 107 and the passivation layer 106 are permeable and diffused into the substrate 100 to form the electrode 110. In particular, during the above heat treatment, the metal diffused from the patterned metal paste to the substrate 100 becomes a dopant in the substrate 100, which provides a back surface field (BSF).

In the present invention, the order in which the electrodes 108 and the electrodes 110 are formed is not limited. That is to say, the electrode 108 may be formed first to form the electrode 110, or the electrode 110 may be formed first to form the electrode 108.

Thereafter, referring to FIG. 1D, a transparent conductive layer 112 is formed on the anti-reflection layer 105 between the electrodes 108 (if the anti-reflection layer 105 is not formed, the transparent conductive layer 112 is formed on the passivation layer 104). The material of the transparent conductive layer 112 is, for example, indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide. The method of forming the transparent conductive layer 112 is, for example, thermal growth, chemical vapor deposition, spraying, or printing.

In the present embodiment, since the transparent conductive layer 112 is formed between the electrodes 108 to connect the electrodes 108, the problem that the conduction resistance is too high due to excessive spacing between the electrodes 108 is solved, thereby improving the solar cell. Photoelectric conversion efficiency. In addition, since the transparent conductive layer 112 has high light transmittance, it does not hinder light from entering the solar cell.

In the present embodiment, the transparent conductive layer 112 is formed between the electrodes 108 but does not cover the entire electrode 108. However, in another embodiment, a transparent conductive layer covering the entire electrode 108 may also be formed.

2 is a schematic cross-sectional view of a solar cell according to another embodiment of the invention. Referring to FIG. 2, the solar cell of the present embodiment differs from the solar cell of FIG. 1D in that the transparent conductive layer 200 covers the entire electrode 108.

Further, in another embodiment, in addition to forming the transparent conductive layer 112 between the electrodes 108, a transparent conductive layer may be formed between the electrodes 110.

3 is a schematic cross-sectional view of a solar cell according to another embodiment of the invention. Referring to FIG. 3, in the embodiment, in addition to forming the transparent conductive layer 112 between the electrodes 108, after the electrodes 110 are formed, the transparent conductive layer 300 may be formed on the anti-reflection layer 107 between the electrodes 110 ( If the anti-reflection layer 107 is not formed, the transparent conductive layer 300 is formed on the passivation layer 106). The material and formation method of the transparent conductive layer 300 are the same as those of the transparent conductive layer 112, and are not described herein. Similarly, since the transparent conductive layers 300 are formed between the electrodes 110 to connect the electrodes 110, it is possible to solve the problem that the conduction resistance is too high due to excessive spacing between the electrodes 110.

4 is a cross-sectional view of a solar cell according to still another embodiment of the present invention. Referring to FIG. 4, the solar cell of the present embodiment differs from the solar cell of FIG. 2 in that the transparent conductive layer 400 covers the entire electrode 110 except that the transparent conductive layer 200 covers the entire electrode 108. The material and formation method of the transparent conductive layer 400 are the same as those of the transparent conductive layer 200, and are not described herein.

Although the invention has been disclosed above by way of example, it is not intended to be limiting The scope of the present invention is defined by the scope of the appended claims, and the scope of the invention is defined by the scope of the appended claims. Prevail.

100‧‧‧Substrate

100a‧‧‧ positive

100b‧‧‧back

102‧‧‧ emitter

104, 106‧‧‧ Passivation layer

105, 107‧‧‧ anti-reflection layer

108, 110‧‧‧ electrodes

112, 200, 300, 400‧‧‧ transparent conductive layer

1A-1D are cross-sectional views showing a manufacturing process of a solar cell according to an embodiment of the invention.

2 is a schematic cross-sectional view of a solar cell according to another embodiment of the invention.

3 is a schematic cross-sectional view of a solar cell according to another embodiment of the invention.

4 is a cross-sectional view of a solar cell according to still another embodiment of the present invention.

100‧‧‧Substrate

102‧‧‧ emitter

104, 106‧‧‧ Passivation layer

105, 107‧‧‧ anti-reflection layer

108, 110‧‧‧ electrodes

112‧‧‧Transparent conductive layer

Claims (16)

A solar cell comprising: a substrate having a front surface and a back surface opposite to each other; an emitter disposed at the front surface; a first passivation layer disposed on the emitter; a second passivation layer disposed on the a plurality of first electrodes disposed on the first passivation layer, wherein a portion of each of the first electrodes passes through the first passivation layer and is connected to the emitter; and a plurality of second electrodes are disposed on the first electrode a second passivation layer, and a portion of each of the second electrodes passes through the second passivation layer to the substrate; a first transparent conductive layer disposed on the first passivation layer between the first electrodes; A second transparent conductive layer is disposed on the second passivation layer between the second electrodes. The solar cell of claim 1, wherein the material of the first transparent conductive layer comprises indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide. The solar cell of claim 1, wherein the first transparent conductive layer covers the first electrodes. The solar cell of claim 1, further comprising an anti-reflection layer disposed between the first passivation layer and the first transparent conductive layer. The solar cell of claim 1, further comprising an anti-reflection layer disposed on the second passivation layer. The solar cell of claim 1, wherein the material of the second transparent conductive layer comprises indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide. The solar cell of claim 1, wherein the second transparent conductive layer covers the second electrodes. A method for fabricating a solar cell, comprising: providing a substrate having a front surface and a back surface opposite to each other; forming an emitter at the front surface; forming a first passivation layer on the emitter; forming on the back surface a second passivation layer; a plurality of first electrodes are formed on the first passivation layer, wherein a portion of each of the first electrodes is connected to the emitter through the first passivation layer; and formed on the second passivation layer a plurality of second electrodes, wherein a portion of each of the second electrodes passes through the second passivation layer to reach the substrate; a first transparent conductive layer is formed on the first passivation layer between the first electrodes; Forming a second transparent conductive layer on the second passivation layer between the second electrodes. The method for fabricating a solar cell according to claim 8, wherein the material of the first transparent conductive layer comprises indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide. The method for fabricating a solar cell according to claim 8, wherein the method for forming the first transparent conductive layer comprises thermal growth and chemical conversion Learn vapor deposition, spray or print. The method for fabricating a solar cell according to claim 8, wherein the first transparent conductive layer covers the first electrodes. The method for fabricating a solar cell according to claim 8, wherein an anti-reflection layer is further formed on the first passivation layer after forming the first passivation layer and before forming the first electrodes. The method for fabricating a solar cell according to claim 8, wherein an anti-reflection layer is further formed on the second passivation layer after forming the second passivation layer and before forming the second electrodes. The method for fabricating a solar cell according to claim 8, wherein the material of the second transparent conductive layer comprises indium tin oxide, aluminum-doped zinc oxide or fluorine-doped tin oxide. The method for fabricating a solar cell according to claim 8, wherein the method for forming the second transparent conductive layer comprises thermal growth, chemical vapor deposition, spraying or printing. The method for fabricating a solar cell according to claim 8, wherein the second transparent conductive layer covers the second electrodes.