TWI491054B - Manufacturing method of solar cell - Google Patents

Description

Solar cell manufacturing method

A method of manufacturing a solar cell, and more particularly to a method of manufacturing a solar cell capable of forming a uniform back electric field.

In recent years, as global petrochemical fuels have gradually dried up, people have begun to actively seek and develop alternative energy sources, such as solar energy, wind power or hydropower, among which solar energy utilization is the most important technological development direction. However, the conversion efficiency of solar energy into electrical energy is easily limited by the structural design and manufacturing methods of solar cells.

The basic solar cell includes a twinned substrate having a P-N interface, an antireflective layer, a front metal electrode, and a rear metal electrode.

The conventional solar cell manufacturing method first provides a twinned substrate formed with a PN interface, then deposits a passivation layer on the front and back sides of the substrate, and forms an opening in the passivation layer by physical or chemical means, and then The aluminum paste is formed on the passivation layer by screen printing and contacts the substrate through the opening, and then forms a partial back electric field and completes the front and back metallization through a high temperature sintering process.

However, in the prior art, a partial back electric field and a metal electrode are simultaneously formed by a high temperature sintering process. Therefore, at the same time of sintering, the aluminum molecules and the ruthenium molecules will reach a temperature of Eutectic composition, and the two substances will flow under mutual melting factors, that is, the ruthenium molecules of the twin crystal substrate will flow to the aluminum glue. At the same time, the aluminum molecules in the aluminum gel will flow to the twinned substrate.

Furthermore, due to the fluidity of the substance itself, the phase balance factor needs to be considered, and when the eutectic temperature is lower than the eutectic temperature, the two substances will return to the original configuration, resulting in a slow flow of the ruthenium molecule in the aluminum paste. It is impossible to flow back to the original area during the cooling process, resulting in a plurality of voids at the junction of the twinned substrate and the metal electrode after curing, resulting in a decrease in the photoelectric conversion efficiency of the entire solar cell.

In addition, when a partial back electric field is formed through a sintering process, since the aluminum paste formed by screen printing is not easily filled in the opening on the passivation layer to be in contact with the substrate, and there is a problem of a difference in solid solubility between the aluminum-bismuth alloys, The non-uniform back electric field is easily formed between the substrate and the conductive material, which causes the passivation effect and the conductivity to deteriorate, and also reduces the conversion efficiency of the solar cell.

In view of this, the inventors have made many researches and improvements on how to improve the photoelectric conversion efficiency of solar cells based on years of experience in manufacturing and designing solar cells, and finally obtained a practical invention.

The main object of the present invention is to provide a method for manufacturing a solar cell capable of forming a uniform back electric field and avoiding formation of voids between the substrate and the metal electrode, thereby improving the photoelectric conversion efficiency of the solar cell.

In an embodiment of the present invention, the method for manufacturing a solar cell includes the following steps: First, providing a substrate structure including a front surface, a rear surface, and a plurality of the front surface and the rear surface a substrate on the side surface, a roughened structure formed on the front surface, and a plurality of insulating layers formed on the side surfaces; then, a plurality of back electric fields are formed Within the substrate, and extending inwardly from the back surface of the substrate.

Subsequently, a front passivation layer is formed on the roughened structure, and a post passivation layer is formed on the back surface of the substrate; and then, the passivation layer forms a plurality of openings with respect to the back electric fields; Finally, a positive electrode is formed on the front passivation layer and electrically connected to the substrate structure, and a back electrode is formed on the back passivation layer and electrically connected to the back electric fields through the openings.

Preferably, the substrate is a semiconductor substrate of a first conductivity type, and the roughened structure is doped with a dopant of a second conductivity type.

Preferably, the back electric fields have a height which is between 5 μm and 35 μm.

Preferably, the back electric fields have a width which is between 30 μm and 300 μm.

In summary, the solar cell manufacturing method of the present invention first forms a back electric field and then forms a back electrode, thereby forming a uniform back electric field and accurately controlling the height and width of the back electric field, so that the fabricated solar cell has Good back passivation and excellent electrical conductivity.

Furthermore, the method for manufacturing the solar cell can effectively avoid the formation of voids between the substrate and the metal electrode, thereby improving the conductivity of the electrode and further improving the photoelectric conversion efficiency of the solar cell.

1 and 2, FIG. 1 is a schematic flow chart of a method for manufacturing a solar cell of the present invention, and FIG. 2 is a schematic cross-sectional view of a solar cell fabricated by applying the method for manufacturing a solar cell of the present invention.

The manufacturing method of the solar cell includes the following steps: step S10 a substrate structure 10 is provided; in step S12, a plurality of back electric fields 20 are formed in the substrate structure 10; in step S14, a passivation layer 30 is formed on the substrate structure 10; in step S16, a plurality of layers are formed on the passivation layer 30. The openings 321 of the back electric field 20; and step S18, a conductive layer 40 is formed on the passivation layer 30, and is electrically connected to the substrate structure 10 and the back electric fields 20 through the openings 321 . The details of each step will be detailed below.

Referring to Figures 2A through 2D, a cross-sectional view corresponding to step S10 is shown. In the embodiment, the step of providing a substrate structure 10 further includes the following steps: First, a substrate 11 is provided, which is a semiconductor substrate of a first conductivity type and has a front surface 111, a rear surface 112, and a plurality of a side surface 113 between the front surface 111 and the rear surface 112; then, a roughening process is performed to form the roughened structure 12 on the front surface 111 and the rear surface 112 of the substrate 11; subsequently, the second conductive type is doped The foreign matter is doped on the roughened structure 12 of the front surface 111 to form an emitter; then, the roughened structure 12 of the surface 112 after the substrate 11 is removed; and finally, an insulating layer 13 is formed on the substrate The side surface 113 of the 11 is formed to form the substrate structure 10.

Specifically, the substrate 11 may be a single crystal germanium substrate doped with a dopant of a first conductivity type, a polycrystalline germanium substrate, a microcrystalline germanium substrate, an amorphous germanium substrate, a gallium arsenide substrate, or the like, and before the substrate 11 Surface 111 may be an incident light surface, while substrate 11 rear surface 112 may be a backlight surface.

The roughening process may wash or etch the front surface 111 and the rear surface 112 of the substrate 11 with an acid or an alkali solution to form a roughened structure 12 on the front surface 111 and the rear surface 112 of the substrate 11, for example, a pyramid structure having an uneven size. To reduce the incident light back to the first reflection Probability, in other words, reduces the reflectivity of sunlight.

The dopant of the second conductivity type may be doped on the roughened structure 12 of the front surface 111 of the substrate 11 by furnace tube diffusion, screen printing, spin coating or spray method, so that the first conductivity type is formed on the substrate structure 10. The region and the second conductive type region, for example, the P-type conductive region and the N-type conductive region, wherein electrons of the N-type conductive region will infiltrate into the P-type conductive region and fill the holes therein. It should be noted that the doping concentration of the P-type conductive region and the N-type conductive region may be adjusted according to actual needs; in addition, in order to make the technical features of the present invention more specific, the second conductivity type will be included below. The roughened structure of the dopant is designated 12a.

Further, a vicinity of the PN interface in the substrate structure 10 may form a carrier depletion region due to recombination of electron-holes, and the P-type conductive region and the N-type conductive region may have negative and positive charges, respectively. Form a built-in electric field. Accordingly, when sunlight is irradiated to the PN structure, the P-type conductive region and the N-type conductive region absorb sunlight to generate an electron-hole pair, and the built-in electric field provided by the carrier depletion region allows electrons to flow in the battery. .

The roughening structure 12 can be removed via a back polishing process; and the insulating layer 13 can be formed on the substrate 11 by chemical vapor deposition (CVD) or physical vapor deposition (PVD) with a high dielectric material. The side surface is used to insulate the side surface of the substrate 11 and to protect the solar cell (such as scratch protection, moisture resistance, etc.).

Referring to FIGS. 2E to 2G, a schematic cross-sectional view corresponding to step S12 is shown. The step of forming the plurality of back electric fields 20 in the substrate 11 further comprises the steps of: firstly forming an aluminum paste 21 on the back surface 112 of the substrate 11; then, subsequently performing a high temperature sintering process, the aluminum glue 21 metal The conductive structure 22 and the back electric field 20 relative to the conductive structure 22 are formed; and finally, the conductive structure 22 is removed.

Specifically, the aluminum glue 21 can be formed on the back surface 112 of the substrate 11 by means of partial screen printing. The high-temperature sintering process can be baked and sintered at a temperature ranging from 570 ° C to 840 ° C to metallize the aluminum rubber 21 to form a conductive structure 22; when the sintering reaches a predetermined temperature (for example, 577 ° C), eutectic is generated. In the phenomenon, the substrate 11 and the conductive structure 22 are fused and connected to each other, thereby forming a back electric field 20 at the opposite side of the conductive structure 22. It is worth mentioning that at this time, a passivation layer (not shown) is not disposed between the substrate 11 and the conductive structure 22, so that a back electric field 20 with better uniformity can be formed, and the height and width of the back electric field 20 can be accurately controlled. The resulting solar cell has good back passivation effect and excellent electrical conductivity.

It is further worth mentioning that the back electric field 20 formed by the above steps has a height h and a width d, wherein the height h is preferably between 5 μm and 35 μm, and the width d is preferably between 30 μm and 300 μm. Thereby, the performance of the back electric field 20 can be improved, thereby reducing the phenomenon that electrons flow out from the back surface of the solar cell. Thereafter, the conductive structure 22 can be removed by mechanical polishing using CMP or the like to facilitate the subsequent step of depositing a passivation layer on the substrate structure 10.

Referring to FIG. 2H, a cross-sectional view corresponding to step S14 is shown. The step of forming a passivation layer 30 on the substrate structure 10 may form a front passivation layer 31 on the front surface 111 of the substrate 11 by chemical vapor deposition (CVD) or physical vapor deposition (PVD). A rear passivation layer 32 is formed on the rear surface 112 of the substrate 11 at the same time. It should be mentioned that in addition to reducing the recombination speed of the surface carriers of the solar cell, the passivation layer 30 can also improve the photocurrent and protect the solar cell (such as scratch protection). , anti-moisture and other effects.

Referring to FIG. 2I, a cross-sectional view corresponding to step S16 is shown. The step of forming the openings 321 in the passivation layer 30 may be performed by using a laser or an etching method to form the openings 321 with respect to the back electric field 20 on the back passivation layer 32, wherein the etching is performed. The etching solution used in the procedure may be selected from phosphoric acid, hydrofluoric acid or nitric acid. Specifically, the openings 321 may be disposed at equal intervals or at non-equal intervals according to actual needs; further, the openings 321 may be circular or line-shaped, and the state of the opening 321 It is not limited.

Referring to Figures 2 and 2J, a cross-sectional view corresponding to step S18 is shown. The step of forming a conductive layer 40 on the passivation layer 30 further comprises the steps of: first, forming a conductive paste 41 on the front passivation layer 31 and the back passivation layer 32; and then performing a high temperature sintering process. The conductive paste 41 is metallized to form a positive electrode 42 and a back electrode 43. The positive electrode 42 is electrically connected to the roughened structure 12 through the front passivation layer 31, and the back electrode 43 is electrically connected through the openings 321 Corresponding to these back electric fields 20.

Specifically, the conductive paste 41 may be formed on the front passivation layer 31 and the back passivation layer 32 by partial screen printing or coating, and filled in the opening 321 of the back passivation layer 32. Furthermore, the conductive paste 41 may have a metal material such as aluminum, indium tin oxide, nickel, copper, titanium or tin. The high-temperature sintering process can be baked and sintered at a temperature ranging from 570 ° C to 840 ° C to remove the volatile solvent in the conductive paste 41 to metallize the conductive paste 41.

In more detail, during the high-temperature sintering process, the conductive paste 41 on the front passivation layer 31 passes through the front passivation layer 31 and is electrically connected to the roughened structure 12 due to a change in molecular structure, that is, electrically connected to the solar cell. Shot At the same time, the conductive paste 41 on the back passivation layer 32 is electrically connected to the back electric field 20 through the opening 321 . It is further worth mentioning that by forming the back electric field 20 after forming the back electric field 20, it is possible to effectively avoid the formation of voids between the substrate structure 11 and the conductive paste 41.

Thereafter, a cooling or cooling process is performed to cure the substrate structure 10 and the conductive paste 41, and form the positive electrode 42 and the back electrode 43. According to this, the solar cell can transmit the electrons that have undergone photo-electrical conversion reaction to the outside through the connection of the positive electrode 42 and the back electrode 43 to the external carrier.

In summary, the manufacturing method of the solar cell of the present invention has the following advantages compared to the conventional manufacturing method:

1. The solar cell manufacturing method of the present invention first forms a back electric field and then forms a back electrode, so that in the process of forming a back electric field, the conductive paste formed by partial screen printing can directly contact the substrate without passing through a passivation layer. Through hole. Thereby, a uniform back electric field can be formed, and the height and width of the back electric field can be precisely controlled, so that the fabricated solar cell has good back passivation effect and excellent electrical conductivity.

2. Furthermore, the formed back electric field has a better height and width, which can improve the performance of the back electric field, thereby reducing the phenomenon that electrons flow out from the back surface of the solar cell.

3. In addition, the manufacturing method can effectively avoid the formation of voids between the substrate and the metal electrode by forming a back electric field and then forming a back electrode, thereby improving the conductivity of the electrode and further improving the photoelectric conversion efficiency of the solar cell. .

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Therefore, the shapes, structures, features, and spirits described in the claims of the present invention are equally varied and modified. The decoration should be included in the scope of the patent application of the present invention.

10‧‧‧Substrate structure

11‧‧‧Substrate

111‧‧‧ front surface

112‧‧‧Back surface

113‧‧‧ side surface

12, 12a‧‧‧ roughened structure

13‧‧‧Insulation

20‧‧‧ Back electric field

21‧‧‧Aluminum adhesive

22‧‧‧Electrical structure

30‧‧‧ Passivation layer

31‧‧‧ front passivation layer

32‧‧‧After passivation layer

321‧‧‧Opening

40‧‧‧ Conductive layer

41‧‧‧Conductive adhesive

42‧‧‧ positive electrode

43‧‧‧ Back electrode

1 is a schematic flow chart of a method for manufacturing a solar cell of the present invention; FIG. 2 is a schematic cross-sectional view of a solar cell of the present invention; and FIG. 2A is a schematic structural view of a substrate for providing a method for fabricating the solar cell of the present invention; FIG. 2C is a schematic structural view showing a step of forming a roughened structure corresponding to the steps of the method for fabricating the solar cell of the present invention; FIG. 2C is a schematic structural view of a dopant doped with a second conductivity type corresponding to the steps of the method for fabricating the solar cell of the present invention; FIG. 2E is a schematic view showing the structure of the method for manufacturing the solar cell according to the present invention, and FIG. 2E is a schematic view showing the structure of the method for manufacturing the solar cell according to the present invention; FIG. 2F is a schematic view showing the structure of the aluminum paste; FIG. 2G is a schematic structural view showing a step of forming a back electric field corresponding to the steps of the manufacturing method of the solar cell of the present invention; FIG. 2H is a schematic diagram of a method for manufacturing a solar cell according to the present invention; Step form a schematic diagram of the structure of the passivation layer; Figure 2I corresponds to The steps of a method for manufacturing a solar cell of the invention forming a schematic structural diagram of openings; and Figure 2J schematic view of the conductive paste is formed as the corresponding steps of a method for manufacturing a solar cell of the present invention.

10‧‧‧Substrate structure

11‧‧‧Substrate

111‧‧‧ front surface

112‧‧‧Back surface

113‧‧‧ side surface

12a‧‧‧Roughened structure

13‧‧‧Insulation

20‧‧‧ Back electric field

30‧‧‧ Passivation layer

31‧‧‧ front passivation layer

32‧‧‧After passivation layer

321‧‧‧Opening

40‧‧‧ Conductive layer

42‧‧‧ positive electrode

43‧‧‧ Back electrode

Claims (10)

A method of manufacturing a solar cell, comprising the steps of: providing a substrate structure comprising: a substrate having a front surface, a rear surface, and a plurality of side surfaces between the front surface and the rear surface, a roughened structure of the front surface and a plurality of insulating layers formed on the side surfaces; a plurality of back electric fields are formed in the substrate and extend inwardly from a back surface of the substrate; a front passivation layer is formed on the substrate Roughening the structure, and forming a post-passivation layer on the back surface of the substrate; forming a plurality of openings opposite to the back electric field; and forming a positive electrode on the front passivation layer and electrically Connected to the substrate structure, and a back electrode is formed on the back passivation layer and electrically connected to the back electric fields through the openings. The method of manufacturing a solar cell according to claim 1, wherein the step of providing a substrate structure comprises the steps of: providing the substrate, which is a semiconductor substrate of a first conductivity type and having the front surface, and thereafter a surface and the side surface between the front surface and the rear surface; performing a roughening process to form a roughened structure on the front surface and the back surface of the substrate; doping the second conductivity type dopant a roughened structure of the front surface to form an emitter; a roughened structure of the surface after removing the substrate; and an insulating layer formed on a side surface of the substrate to form the substrate structure. The method for manufacturing a solar cell according to claim 2, wherein the roughening process forms a roughened structure on the front surface and the rear surface of the substrate by acid solution cleaning, alkali solution cleaning or etching. The method for manufacturing a solar cell according to claim 1, wherein the step of forming a plurality of back electric fields in the substrate comprises the steps of: forming an aluminum paste on a back surface of the substrate; performing a high temperature In a sintering process, the aluminum paste is metallized to form a conductive structure and form a back electric field relative to the conductive structure, wherein the back electric field has a height and a width; and the conductive layer is removed. The method for manufacturing a solar cell according to claim 4, wherein the aluminum gel is formed on the back surface of the substrate by partial screen printing, and the temperature of the high temperature sintering process ranges from 570 ° C to 840 ° C. The conductive structure is removed by mechanical polishing. The method of manufacturing a solar cell according to claim 4, wherein the height is between 5 μm and 35 μm. The method of manufacturing a solar cell according to claim 4, wherein the width is between 30 μm and 300 μm. The method of manufacturing a solar cell according to claim 1, wherein the step of forming a positive electrode on the front passivation layer comprises the steps of: forming a conductive paste on the front passivation layer and thereafter On the passivation layer; and performing a high temperature sintering process to metallize the conductive paste to form the a positive electrode and the back electrode, wherein the positive electrode is electrically connected to the roughened structure through the front passivation layer, and the back electrode is electrically connected to the back electric fields through the openings. The method for manufacturing a solar cell according to claim 8, wherein the conductive paste is formed on the front passivation layer and the back passivation layer by a partial screen printing and fills the openings. The sintering process has a temperature range of 570 ° C to 840 ° C. The method of manufacturing a solar cell according to claim 1, wherein the openings are formed on the back passivation layer by laser or etching.