TW201310671A - Structure of photovoltaic cell - Google Patents

Abstract

A structure of a photovoltaic cell includes a substrate having a radiation-receiving front surface and a back surface; a surface doped region disposed on the radiation-receiving front surface; a protecting dielectric covering the surface doped region; at least a bus bar disposed on the radiation-receiving front surface; a transparent conducting film covering the protecting dielectric and the bus bar; and at least a nanoparticle penetrating the protecting dielectric and electrically connecting to the transparent conducting film and the surface doping region.

Description

Solar cell structure

The present invention relates to a solar cell structure, and more particularly to a solar cell structure having a transparent conductive film.

With the depletion of consumable energy, the development of alternative energy sources such as solar energy has long been an important development direction. Photovoltaic cells work by using the radiant energy of sunlight and semiconductor materials to generate electrical energy. The main materials of the solar cell include a semiconductor material such as a single crystal germanium, a polycrystalline germanium, an amorphous germanium substrate or a III-V compound semiconductor material, and a conductive paste used as an electrode, for example, silver paste or aluminum paste. Etc., wherein the silver paste is mainly used to form the front and back electrodes of the solar cell, and the back electrode structure usually has a plurality of aluminum pastes disposed on the semiconductor substrate.

In a conventional solar cell structure, a finger is located on a radiation-receiving front surface, the purpose of which is to receive a photocurrent from the substrate and conduct the photocurrent to a confluence with an external circuit. Bus bar. However, since the finger electrodes do not transmit light, the light-receiving front surface of the portion is inevitably shielded, so that the light-receiving area of the solar cell is lowered, which is disadvantageous for the generation of photocurrent. The front cover area of the conventional finger electrode design is about 7 to 8%. Moreover, as the price of silver plastics rises, the production of finger electrodes inevitably leads to an increase in the production cost of solar cells.

Therefore, it is necessary to provide a solar cell structure, in addition to increasing the area of light absorption, thereby increasing the photocurrent generation rate, and simultaneously reducing the amount of silver glue used to reduce the production cost of the solar cell.

It is an object of the present invention to provide a solar cell structure which can increase the area of light absorption and thereby increase the photocurrent generation rate.

In order to achieve the above object, in accordance with a preferred embodiment of the present invention, there is provided a solar cell structure comprising a substrate comprising a light-receiving front surface and a back surface; a surface doped region disposed on the light-receiving front surface of the substrate a protective dielectric layer covering the surface doped region; at least one bus electrode disposed on the light receiving front surface of the substrate; a transparent conductive film covering the protective dielectric layer and the bus electrode; and at least one nano particle And passing through the protective dielectric layer to electrically connect the transparent conductive film and the surface doped region.

According to another preferred embodiment of the present invention, a solar cell structure includes a substrate including a light-receiving front surface and a back surface, a surface doped region disposed on the light-receiving front surface of the substrate, and a protective dielectric layer. Covering the surface doped region; a first bus electrode disposed on the light receiving front surface of the substrate; a second bus electrode parallel to the first bus electrode disposed on the light receiving front surface of the substrate; and a transparent conductive film covering the front surface Protecting the dielectric layer and the bus electrode; and at least one nano particle passing through the protective dielectric layer to electrically connect the transparent conductive film and the surface doped region; wherein the front surface of the substrate is not provided with any perpendicular a bus electrode or a finger electrode perpendicular to the second bus electrode.

The invention provides a transparent conductive film which is located on the light receiving front surface of the solar cell structure, which can enhance the area of light absorption and thereby increase the photocurrent generation rate.

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

FIG. 8 is a cross-sectional view and a plan view of a solar cell structure according to a preferred embodiment of the present invention, wherein the same elements are denoted by the same reference numerals. It should be noted that the drawings are for illustrative purposes and are not mapped to the original dimensions.

Please refer to FIG. 8 , which is a cross-sectional view showing a structure of a solar cell according to a preferred embodiment of the present invention. As shown in FIG. 8, the solar cell structure 1 includes a substrate 101, and the substrate 101 includes a light-receiving front surface 101a and a back surface 101b; at least one surface-doped region 105 is disposed on the light-receiving front surface 101a; a layer 107 covering the surface doping region 105; at least one bus electrode 109 disposed on the light receiving front surface 101a of the substrate 101; a transparent conductive film 113 covering the protective dielectric layer 107 and the bus electrode 109; and at least one The nanoparticles 115 pass through the protective dielectric layer 107 to electrically connect the transparent conductive film 113 to the surface doping region 105. 9 is a top view of the solar cell structure 1 according to the present embodiment. It can be seen that at least one of the finger electrodes 117 is electrically connected to the bus electrode 109, and the transparent conductive film 113 covers the protective dielectric layer 107 and the bus electrode 109. on. In this embodiment, due to the presence of the transparent conductive film 113, the number and width of the finger electrodes 117 may be less than or finer than those of the finger electrodes used in the prior art, and one of the finger electrodes 117 may be only electrically It is connected to a bus electrode 109 without electrically connecting the two bus electrodes 109 at the same time.

Please refer to FIG. 10, which is a top view of a solar cell structure according to another embodiment of the invention. Similarly, as shown in FIGS. 8 and 9, the solar cell structure 1 includes a substrate 101, and the substrate 101 includes a light-receiving front surface 101a and a back surface 101b; at least one surface-doped region 105 is disposed on the light-receiving front surface 101a. a protective dielectric layer 107 covering the surface doping region 105; a first bus electrode 109a disposed on the light receiving front surface 101a of the substrate 101; and a second bus electrode 109b parallel to the first bus electrode 109a. The light-receiving front surface 101a of the substrate 101; a transparent conductive film 113 covering the protective dielectric layer 107 and the bus electrode 109; and at least one nano-particle 115 passing through the protective dielectric layer 107 to electrically connect the transparent conductive film 113 with The surface doped region 105; however, differs from the eighth and ninth views in that, in FIG. 10, the light-receiving front surface 101a of the substrate 101 is not provided with any perpendicular to the first bus electrode 109a or perpendicular thereto. The finger electrode of the second bus electrode 109b.

The method steps for fabricating the solar cell structure of the present invention are described in detail below with reference to the drawings. The present invention is not limited to the scope of the invention, and may be modified and retouched without departing from the spirit and scope of the invention. The details of some of the conventional process steps will not be disclosed herein, as defined by the scope of the appended claims.

Please refer to FIG. 1 to FIG. 7 . FIG. 1 to FIG. 7 are schematic diagrams showing a method for preparing a solar cell structure according to a preferred embodiment of the present invention. As shown in FIG. 1, in the initial stage of the process, a substrate 101 is provided. The substrate 101 has a first conductivity type, for example, a P-type, and the substrate 101 includes a light-receiving front surface 101a and a back surface 101b. The 101 is used to receive a source of radiation, such as sunlight or other electromagnetic bands that are available for absorption by the semiconductor layer. The substrate 101 can be a single crystal germanium wafer, a polycrystalline silicon wafer, or other conventional semiconductor substrates. Then, since the germanium wafer is formed by slicing an ingot through a wire saw, a conventional wet etching process must be performed to remove the wire saw defect on the surface of the substrate 101. Next, a conventional surface roughening process is performed on the light-receiving front surface 101a and the back surface 101b of the substrate 101. It is known that the surface roughening is aimed at reducing the reflection phenomenon of the radiation source on the light-receiving front surface 101a, thereby increasing the solar cell. Light current.

As shown in FIG. 2, a Phosphorus chloride oxide (POCl ₃ ) gas is provided by a diffusion furnace, and a surface doped region 105 is formed on the light receiving front surface 101a and the back surface 101b, and has a second conductivity type. For example, type N.

As shown in FIG. 3, a phosphosilicate glass (PSG) (not shown) on the surface of the substrate 101 is removed by hydrofluoric acid (HF) or other similarly similar wet etching method to reduce The surface of the surface doped region 105 and the resistance of the bus electrode 109 are subsequently processed.

Referring to FIG. 4, at least one nanoparticle 115 may be selectively disposed on the light receiving front surface 101a, wherein the nanoparticle 115 comprises a metal element such as gold, silver, titanium, nickel, copper, conductive oxide, graphene or Its combination. The nanoparticles 115 can be disposed on the light-receiving front side 101a in a different manner, for example, by spraying, spin coating or other conventional means of coating the nanoparticles 115. Next, a protective dielectric layer 107 having a thickness of 5 nm to 10 nm, for example, hafnium oxide, tantalum nitride or titania, may be formed over the surface doping region 105. It is known that the protective dielectric layer 107 can be formed in different ways, for example, chemical vapor deposition (CVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD). ), spray pyrolysis, spin coating, screen printing or other techniques well known in the art.

The purpose of protecting the dielectric layer 107 is to passivate the surface doped region 105 to enhance the efficiency of photocurrent generation. In addition, the protective dielectric layer 107 may also have the function of an anti-reflective coating (ARC). It should be noted here that the nanoparticles 115 will form an ohmic contact with the surface doping region 105. And since the thickness of the protective dielectric layer 107 is only between 5 nm and 10 nm, the nanoparticles 115 are sufficient to pass through the protective dielectric layer 107 to facilitate subsequent connection of the transparent conductive film 113 and the surface doping region 105.

As shown in Fig. 5, at least one bus electrode 109 and a finger electrode (not shown) are formed on the light receiving front surface 101a, and at least one contact electrode 111 is formed on the back surface 101b. In another embodiment of the present invention, the bus electrode 109 may include a first bus electrode 109a and a second bus electrode 109b parallel to the first bus electrode 109a. The above method of forming the bus electrode 109, the finger electrode and the contact electrode 111 may use screen printing or other methods such as inkjet printing, decal transfer, plating, electroless plating, But it is not limited to this. Also, the metal paste component of the bus electrode 109, the finger electrode, and the contact electrode 111 may include silver, aluminum, or other low resistance compound. In the present embodiment, due to the presence of the transparent conductive film 113, the number and width of the finger electrodes 117 may be less than or finer than those of the finger electrodes 117 used in the prior art, and a finger electrode 117 It is possible to electrically connect only to one bus electrode 109 without electrically connecting the two bus electrodes 109 at the same time.

It should be noted here that, according to another embodiment of the present invention, as shown in the top view of FIG. 6, no finger electrodes perpendicular to the bus electrodes 108a, 108b, 108c, and 108d are provided on the light-receiving front surface 101a. (not shown), therefore, the light-receiving area of the light-receiving front surface 101a can be increased, and the bus electrodes 108a, 108b can be arranged in segments with the bus electrodes 108c, 108d, respectively, that is, can be formed only on the area to be soldered to the external line. Instead of being a complete strip.

As shown in FIG. 7, after a fast firing furnace (FFF), the bus electrode 109 is in ohmic contact with the surface doped region 105, and the contact electrode 111 and the silver, aluminum and aluminum in the aluminum paste are located. The ruthenium in the glue coverage region 119 produces an eutectic alloy 112 which produces a back surface field which is known to reduce the electron-hole pair in the substrate 101. Composite probability, thus increasing the carrier collection rate. An insulating region (not shown) is formed by a laser or a dicing process, and the bus electrode 109 and the finger electrodes (not shown) are electrically insulated from the contact electrode 111.

Finally, as shown in FIG. 8, a transparent conductive film 113 is formed to cover the protective dielectric layer 107 and the bus electrode 109. The transparent conductive film 113 includes aluminum-doped zinc oxide (AZO) and indium tin oxide (AZ). ITO), antimony tin oxide (ATO), tin oxide (SnO ₂ ) or graphene. It is known that the transparent conductive film 113 has a conductive property, and thus can replace the finger electrode located on the light-receiving front surface 101a in the prior art or the film which flows as an auxiliary carrier to the finger electrode. The transparent conductive film 113 can be utilized to have a light transmitting property to reduce a light-shielding region of the light-receiving front surface 101a of the solar cell, for example, 7 to 8%.

In addition, the use of the transparent conductive film 113 can reduce the amount of use of the finger electrodes 117, thereby saving production costs. It is particularly emphasized here that since the heat resistance of the transparent conductive film 113 is poor, generally the case of high-temperature sintering, for example, 600 degrees Celsius, destroys the conductivity of the transparent conductive film 113, and therefore, according to all embodiments of the present invention, it is transparent. After the formation of the conductive film 113, the above-described high-temperature sintering process is not performed.

According to another embodiment of the present invention, the bus electrode 109 and the contact electrode 111 may be separately prepared, and the nanoparticle 115 is disposed under a process step different from the above. According to the preferred embodiment, continuing through FIG. 3, at least one contact electrode 111 is formed on the back surface 101b. Thereafter, a fast electric field (FFF) is used to generate a back surface electric field between the contact electrode 111 on the back surface 101b and the silver and aluminum in the aluminum paste and the crucible located in the aluminum paste-covered region 119. Next, at least one nano particle 115 is disposed on the light receiving front surface 101 a, wherein the nano particle 115 comprises a metal element such as gold, silver, titanium, nickel, copper or the like, a conductive oxide, graphene or a combination thereof. Next, a protective dielectric layer 107 having a thickness of 5 nm to 10 nm, for example, hafnium oxide, tantalum nitride or titania, may be formed over the surface doping region 105. And then forming a transparent conductive film 113 covering the protective dielectric layer 107 and the bus electrode 109, wherein the transparent conductive film 113 comprises aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), and antimony tin oxide ( ATO), tin oxide (SnO ₂ ) or graphene. It should be noted here that the nanoparticles 115 will form an ohmic contact with the surface doping region 105. And since the thickness of the protective dielectric layer 107 is only between 5 nm and 10 nm, the nanoparticle 115 is sufficient to pass through the protective dielectric layer 107 to facilitate electrical connection between the transparent conductive film 113 and the surface doping region 105. Thereafter, at least one bus electrode 109 on the light-receiving front surface 101a is prepared by, for example, screen printing, inkjet printing, decal transfer, plating, electroless plating, or the like, and passes through a low temperature. The rapid sintering causes the bus electrode 109 to form an ohmic contact with the surface doping region 105. It should be noted that, in this embodiment of the present invention, any finger electrode 117 perpendicular to the first bus electrode 101a or perpendicular to the second bus electrode 101b is not disposed on the light receiving front surface 101a, thereby increasing the light receiving. The light receiving area of the front side 101a.

In summary, the present invention provides a solar cell structure 1, as shown in FIG. 8, having a transparent conductive film 113 overlying the protective dielectric layer 107 and the bus electrode 109. By utilizing the transparent conductive film 113 to have light transmission and electric conduction characteristics, the finger electrode 117 located on the light receiving front surface 101a in the prior art can be reduced or replaced, thereby reducing the light shielding area of the solar cell light receiving front surface 101a. In addition, the present invention employs a transparent conductive film 113 for reducing or completely replacing the finger electrode 117, thereby saving the cost of the finger electrode 117 material.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

1. . . Solar cell structure

101. . . Substrate

101a. . . Receiving light front

101b. . . back

105. . . Surface doped region

107. . . Protective dielectric layer

108, 108a, 108b 108c, 108d, 109. . . Bus electrode

109a. . . First bus electrode

109b. . . Second bus electrode

111. . . Contact electrode

112. . . Eutectic alloy

113. . . Transparent conductive film

115. . . Nanoparticle

117. . . Finger electrode

119. . . Aluminum glue coverage area

1 to 7 are schematic views showing a manufacturing method of a solar cell structure according to an embodiment of the present invention.

Figure 8 is a cross-sectional view showing the structure of a solar cell according to another embodiment of the present invention.

FIG. 9 is a top plan view showing a solar cell structure according to another embodiment of the present invention.

Figure 10 is a plan view showing a solar cell structure in accordance with another embodiment of the present invention.

1. . . Solar cell structure

101. . . Substrate

101a. . . Receiving light front

101b. . . back

105. . . Surface doped region

107. . . Protective dielectric layer

109. . . Bus electrode

109a. . . First bus electrode

109b. . . Second bus electrode

111. . . Contact electrode

112. . . Eutectic alloy

113. . . Transparent conductive film

115. . . Nanoparticle

119. . . Aluminum glue coverage area

Claims (12)

A solar cell structure comprising: a substrate comprising a light-receiving front surface and a back surface; a surface doped region disposed on the light-receiving front surface of the substrate; and a protective dielectric layer overlying the surface doped region At least one bus bar disposed on the light receiving front surface of the substrate; a transparent conductive film covering the protective dielectric layer and the bus electrode; and at least one nano particle passing through the protective layer And an electrical layer electrically connecting the transparent conductive film and the surface doped region. The solar cell structure of claim 1, wherein the protective dielectric layer comprises cerium oxide, cerium nitride or titanium dioxide. The solar cell structure of claim 2, wherein the protective dielectric layer has a thickness of from 5 nanometers (nm) to 10 nanometers (nm). The solar cell structure according to claim 1, wherein the transparent conductive film comprises aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), antimony tin oxide (ATO), and tin oxide (SnO ₂ ). Or graphene. The solar cell structure of claim 1, wherein the nanoparticle forms an ohmic contact with the surface doped region. The solar cell structure of claim 1, wherein the nanoparticle comprises gold, silver, titanium, nickel, copper or a combination thereof. A solar cell structure comprising: a substrate comprising a light-receiving front surface and a back surface; a surface doped region disposed on the light-receiving front surface of the substrate; and a protective dielectric layer overlying the surface doped region a first bus electrode disposed on the light-receiving front surface of the substrate; a second bus electrode disposed parallel to the first bus electrode on the light-receiving front surface of the substrate; and a transparent conductive film covering the protection a dielectric layer and the bus electrode; and at least one nanoparticle passing through the protective dielectric layer to electrically connect the transparent conductive film and the surface doping region; wherein the light receiving front surface of the substrate is not provided There are any finger electrodes perpendicular to the first bus electrode or perpendicular to the second bus electrode. The solar cell structure of claim 7, wherein the protective dielectric layer comprises cerium oxide, cerium nitride or titanium dioxide. The solar cell structure of claim 8, wherein the protective dielectric layer has a thickness of from 5 nanometers (nm) to 10 nanometers (nm). The solar cell structure according to claim 7, wherein the transparent conductive film comprises aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), antimony tin oxide (ATO), and tin oxide (SnO ₂ ). Or graphene. The solar cell structure of claim 7, wherein the nanoparticle forms an ohmic contact with the surface doped region. The solar cell structure of claim 7, wherein the nanoparticle comprises gold, silver, titanium, nickel, copper or a combination thereof.