CN106653887A - Back-junction back-contact solar cell - Google Patents

Abstract

The invention provides a back-junction and back-contact solar cell, comprising: a substrate; a composite layer compounded on the front surface of the substrate; a tunnel oxide layer compounded on the back surface of the substrate; A P-type doped semiconductor layer and an N-type doped semiconductor layer on the oxide layer; a positive electrode arranged on the P-type doped semiconductor layer; a negative electrode arranged on the N-type doped semiconductor layer. The present invention proposes a back-junction and back-contact solar cell adopting a tunneling oxide layer passivation contact structure. The tunneling oxide layer passivation contact structure is adopted. This structure avoids direct contact between the metal electrode and the substrate, and effectively reduces the The recombination of carriers at the metal contact interface is reduced, and the opening voltage of the battery is increased; and because the metal contact does not bring about an increase in recombination, the metal contact can cover most of the area of the emitter and the back field, avoiding the current carrying The lateral transport of the electrons is beneficial to reduce the series resistance and further improve the battery efficiency.

Description

A back-junction back-contact solar cell

technical field

The invention belongs to the technical field of solar cells, and relates to a back-junction and back-contact solar cell, in particular to a back-junction and back-contact solar cell with a tunnel oxide layer passivation contact structure on the back.

Background technique

A solar cell, also known as a "solar chip" or a "photovoltaic cell", is a photoelectric semiconductor sheet that uses sunlight to directly generate electricity. It is a device that directly converts light energy into electrical energy through the photoelectric effect or photochemical effect. As long as the solar cell is illuminated by light that meets a certain illuminance condition, it can output voltage instantly and generate current when there is a loop. In physics, it is called solar photovoltaic (Photovoltaic, abbreviated as PV), or photovoltaic for short. The working principle of a solar cell is that when sunlight shines on the p-n junction of a semiconductor, new hole-electron pairs are formed. Under the action of the built-in electric field of the p-n junction, the photo-generated holes flow to the p-region, and the photo-generated electrons flow to the n-region, turning on the circuit Then a current is generated.

As the whole society pays more and more attention to environmental issues, solar cells, as a device that can directly convert solar energy into electrical energy, are getting more and more attention from people, and there are more and more types of solar cells. Solar cells use the photovoltaic effect of the PN junction to directly convert light energy into electrical energy. The emitter of a traditional solar cell is made on the front surface of the cell, and there are electrodes on the front and back of the cell. The incident photons excite electron-hole pairs. , the electron-hole pairs are separated by the PN junction located on the front surface of the battery, and are drawn out to the external circuit through the electrodes.

Compared with traditional solar cells, the new back-junction and back-contact cells have the potential to achieve higher conversion efficiency, and have gradually become the main research and development direction of industrialized high-efficiency cells. Back-junction back-contact battery, also known as interdigitated backcontact (IBC) solar cell (referred to as IBC battery), this kind of battery has all the emitter and back field on the back of the battery, which reduces the shading loss, and Since the electrodes are made on the back surface of the battery, there is no need to consider shading, so the electrodes can be made very wide, which greatly reduces the series resistance, and these characteristics can improve the conversion efficiency of the battery. However, a problem that most solar cells, including back-junction and back-contact solar cells, have not solved is that after the metal and the substrate form an ohmic contact, a large number of interface states will be introduced on the contact surface, which makes the carrier on the surface The recombination rate increases significantly, which can greatly reduce the performance of the battery. The usual solution is to minimize the contact area between the metal and the substrate, but this will cause the lateral transport of carriers, increase the series resistance, and reduce the performance of the battery.

Therefore, how to find a more suitable back-junction and back-contact battery, which can have better battery performance, and at the same time the technical solution is simple and easy to implement, has become an urgent problem to be solved by many front-line researchers in the field.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a back-junction and back-contact solar cell, especially a back-junction and back-contact solar cell using a tunnel oxide layer passivation contact structure. The back-junction and back-contact solar cell with passivation contact structure through the oxide layer has high cell performance, and the technical solution is simple and easy to realize.

The invention provides a back junction back contact solar cell, comprising:

Substrate;

a composite layer composited on the front surface of the substrate;

a tunnel oxide layer compounded on the back surface of the substrate;

a P-type doped semiconductor layer and an N-type doped semiconductor layer compounded on the tunnel oxide layer;

a positive electrode disposed on the P-type doped semiconductor layer;

a negative electrode disposed on the N-type doped semiconductor layer.

Preferably, the composite layer on the front surface of the substrate comprises:

a front field region compounded on the front surface of the substrate;

a front surface passivation layer compounded on the front field region;

An anti-reflection layer compounded on the front surface passivation layer.

Preferably, the P-type doped semiconductor layer and the N-type doped semiconductor layer are adjacently and alternately compounded on the tunnel oxide layer, and/or the P-type doped semiconductor layer and the N-type doped semiconductor layer Alternately composited on the tunnel oxide layer;

The ratio of the width of the P-type doped semiconductor layer to the width of the N-type doped semiconductor layer is (2˜10):1.

Preferably, when the P-type doped semiconductor layer and the N-type doped semiconductor layer are alternately compounded on the tunnel oxide layer, the width of the positive electrode is smaller than the width of the P-type doped semiconductor layer , the width of the negative electrode is smaller than the width of the N-type doped semiconductor layer, and the positive electrode is not in contact with the N-type doped semiconductor layer, and the negative electrode is not in contact with the P-type doped semiconductor layer layers are in contact.

Preferably, the composite layer on the front surface of the substrate has a suede light-trapping structure.

Preferably, the front surface of the substrate has a textured light trapping structure.

Preferably, the material of the substrate includes lightly doped silicon material, the doping concentration of the lightly doped is 10 ¹³ ~ 10 ¹⁷ cm ^-3 ; the type of doping is N type;

The silicon material includes one or more of single crystal silicon, polycrystalline silicon and silicon thin film;

The doped material includes one or more of boron, phosphorus, gallium and arsenic;

The minority carrier lifetime of the substrate is greater than or equal to 500 μs; the resistivity of the substrate is 1 to 50 Ω·cm;

The thickness of the substrate is 50-300 μm.

Preferably, the material of the tunnel oxide layer is an insulating material;

The insulating material includes one or more of silicon dioxide, titanium dioxide, aluminum oxide and silicon nitride;

The thickness of the tunnel oxide layer is 0.3-2 nm.

Preferably, the semiconductor materials of the P-type doped semiconductor layer and the N-type doped semiconductor layer each include one or more of microcrystalline silicon, polycrystalline silicon, and amorphous silicon; each of the doped materials includes boron, One or more of phosphorus, gallium and arsenic;

The doping concentrations are each 10 ¹⁸ to 10 ²¹ cm ^-3 ;

The thicknesses of the P-type doped semiconductor layer and the N-type doped semiconductor layer are each selected from 5 nm to 500 nm.

Preferably, the front field region is a highly doped region formed by diffusing phosphorus on the front surface of the substrate;

The thickness of the front field region is 0.5-2 μm;

The front surface passivation layer includes a silicon oxide layer, a silicon nitride layer, a stack of silicon oxide and silicon nitride or a silicon carbide layer;

The thickness of the front surface passivation layer is 50-100nm;

The material of the antireflection layer includes one or more of silicon nitride, ITO, silicon oxide and titanium oxide;

The thickness of the anti-reflection layer is 40-100 nm.

The invention provides a back-junction and back-contact solar cell, comprising: a substrate; a composite layer compounded on the front surface of the substrate; a tunnel oxide layer compounded on the back surface of the substrate; A P-type doped semiconductor layer and an N-type doped semiconductor layer on the oxide layer; a positive electrode arranged on the P-type doped semiconductor layer; a negative electrode arranged on the N-type doped semiconductor layer. Compared with the prior art, the present invention will introduce a large number of interface states on the contact surface after forming an ohmic contact between the metal and the substrate, which will significantly increase the carrier recombination rate on the surface and reduce the performance of the battery. A back-junction and back-contact solar cell with a passivated contact structure using a tunnel oxide layer is proposed. The present invention adopts a tunneling oxide layer passivation contact structure, which avoids the direct contact between the metal electrode and the substrate, effectively reduces the recombination of carriers at the metal contact interface, and improves the opening voltage of the battery; and because The metal contact will not increase the recombination. The metal contact can cover most of the area of the emitter and the back field, avoiding the lateral transport of carriers, which is conducive to reducing the series resistance and further improving the battery efficiency. Moreover, the preparation process adopted by the present invention has good compatibility with the existing solar cell preparation process, and is simpler and lower in production cost than the traditional back contact cell process.

Experimental results show that the back junction and back contact solar cell with tunnel oxide layer passivation contact structure on the back provided by the present invention can reach 22% cell efficiency.

Description of drawings

Fig. 1 is a schematic structural diagram of a back-junction and back-contact solar cell provided in Example 1 of the present invention;

Fig. 2 is a schematic structural diagram of a back-junction and back-contact solar cell provided in Example 2 of the present invention;

FIG. 3 is an I-V characteristic curve of a back-junction back-contact solar cell with a tunnel oxide layer passivation contact structure provided by Example 3 of the present invention.

detailed description

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent requirements of the present invention.

All raw materials in the present invention have no particular limitation on their sources, they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

The purity of all raw materials in the present invention is not particularly limited, and the present invention preferably adopts analytical purity or conventional purity requirements in the field of solar cell preparation.

All raw materials of the present invention, their grades and abbreviations belong to the conventional grades and abbreviations in this field, and each grade and abbreviation are all clear and definite in the field of its related use. Those skilled in the art can according to the grades, abbreviations and corresponding uses, It can be purchased from commercial sources or prepared by conventional methods.

The invention provides a back junction back contact solar cell, comprising:

Substrate;

a composite layer composited on the front surface of the substrate;

a tunnel oxide layer compounded on the back surface of the substrate;

a P-type doped semiconductor layer and an N-type doped semiconductor layer compounded on the tunnel oxide layer;

a positive electrode disposed on the P-type doped semiconductor layer;

a negative electrode disposed on the N-type doped semiconductor layer.

The present invention is not particularly limited to the definition and concept of the back-junction back-contact solar cell, and the definition and concept of the back-junction back-contact solar cell (IBC cell) well known to those skilled in the art can be used. Those skilled in the art can Application conditions, composite conditions and product performance are selected and adjusted.

The present invention has no special restrictions on the substrate, and the substrate or substrate of the back-junction and back-contact solar cell well known to those skilled in the art can be selected according to the actual application situation, composite situation and product performance. And adjustment, the material of the substrate in the present invention preferably includes lightly doped silicon material, and the doping type is preferably N-type.

The present invention has no special limitation on the doping concentration of the lightly doped silicon material, the doping concentration of the lightly doped silicon material well known to those skilled in the art can be used, and those skilled in the art can combine The doping concentration of the lightly doped silicon material in the present invention is preferably 10 ¹³ to 10 ¹⁷ cm ^-3 , more preferably 10 ¹³ to 10 ¹⁶ cm ^-3 , most preferably 10 ¹⁴ ~ 10 ¹⁵ cm ^-3 .

The present invention is not particularly limited to the silicon material of the lightly doped silicon material, and the silicon material of the lightly doped silicon material well-known to those skilled in the art can be used. Those skilled in the art can select according to the actual application situation, compounding situation and The product performance is selected and adjusted. The silicon material in the present invention preferably includes one or more of single crystal silicon, polycrystalline silicon and silicon thin film, more preferably single crystal silicon, polycrystalline silicon or silicon thin film.

In the present invention, the doping material of the lightly doped silicon material is not particularly limited, and the doping material well-known to those skilled in the art can be used, and those skilled in the art can select and select according to actual application conditions, compounding conditions, and product performance. Adjustment, the doped material in the present invention preferably includes one or more of boron, phosphorus, gallium and arsenic, more preferably boron, phosphorus, gallium or arsenic.

The present invention has no special limitation on the performance parameters of the substrate, and the conventional performance parameters of the substrate of the back-junction and back-contact solar cell well known to those skilled in the art can be used. performance is selected and adjusted, the minority carrier lifetime of the substrate of the present invention is preferably greater than or equal to 500 μs, more preferably greater than or equal to 800 μs, most preferably greater than or equal to 1000 μs; the resistivity of the substrate is preferably 1 to 50 Ω cm, more preferably 10 to 40Ω·cm, most preferably 20 to 30Ω·cm.

The present invention has no special limitation on the thickness of the substrate, the conventional thickness of the substrate of the back-junction and back-contact solar cell well known to those skilled in the art can be used, and those skilled in the art can make the thickness according to the actual application situation, composite situation and product performance. Selection and adjustment, the thickness of the substrate of the present invention is preferably 50-300 μm, more preferably 100-250 μm, most preferably 150-200 μm.

The present invention has no special limitation on the compounding method, and the conventional compounding method of solar cells well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to actual application conditions, compounding conditions and product performance. The present invention The recombination is preferably one or more of doping, deposition, evaporation, oxidation, coating, sol-gel and etching, more preferably growth, doping, deposition, evaporation, oxidation, coating, Sol gel or etch.

The definition of the front surface of the substrate is not particularly limited in the present invention, the definition of the front surface of the substrate well known to those skilled in the art can be used, and those skilled in the art can select and adjust according to the actual application situation, composite situation and product performance The front surface of the substrate in the present invention refers to the direction of the light-receiving surface of the substrate or the surface of the direction of the light-receiving surface of the solar cell; the back surface of the substrate refers to the direction of the backlight surface of the substrate or It is the surface in the direction of the backlight side of the solar cell.

In the present invention, the structure of the front surface of the substrate is not particularly limited, and the structure of the front surface of the substrate well-known to those skilled in the art can be used, and those skilled in the art can select and adjust according to actual application conditions, composite conditions, and product performance. , The front surface of the substrate of the present invention has a light-trapping structure, more preferably has a textured light-trapping structure.

The present invention has no particular limitation on the overall structure of the composite layer on the front surface of the substrate. The overall structure of the composite layer on the front surface of the substrate well known to those skilled in the art will suffice. Those skilled in the art can combine According to the situation and product performance, the composite layer on the front surface of the substrate in the present invention has a light-trapping structure, more preferably a suede light-trapping structure. In the present invention, the front surface of the substrate and the composite layer on the front surface of the substrate have the same light-trapping structure.

In the present invention, the light-trapping structure on the front surface is prepared by anisotropically etching the silicon surface, and its structure is many upright or inverted pyramid structures, the front field diffusion area (front field area), the front surface blunt Both the chemical layer and the anti-reflection layer are formed on this suede light-trapping structure. The present invention has no special limitation on the formation method of the light trapping structure, and the formation method of the light trapping structure well known to those skilled in the art can be selected and adjusted according to the actual application situation, composite situation and product performance. , The light trapping structure of the present invention can be formed by chemical etching or dry etching.

The composition of the composite layer on the front surface of the substrate is not particularly limited in the present invention, and the composition of the conventional composite layer on the front surface of the substrate well-known to those skilled in the art can be used. Those skilled in the art can according to actual application conditions, composite conditions and Product performance is selected and adjusted, and the composite layer on the front surface of the substrate of the present invention preferably includes:

a front field region compounded on the front surface of the substrate;

a front surface passivation layer compounded on the front field region;

An anti-reflection layer compounded on the front surface passivation layer.

The present invention has no special restrictions on the front field area, and the front field area of solar cells well known to those skilled in the art can be used. Those skilled in the art can select and adjust according to actual application conditions, composite conditions and product performance. The present invention The front field region is preferably a heavily doped region, and the doping type is preferably N-type.

In the present invention, the doping concentration of the front field region is not particularly limited, and the conventional heavy doping concentration well known to those skilled in the art can be used, and those skilled in the art can select and adjust it according to actual application conditions, compounding conditions, and product performance. In the present invention, the doping concentration of the front field region is preferably 10 ¹⁷ to 10 ¹⁹ cm ^-3 , more preferably 10 ¹⁷ to 10 ¹⁸ cm ^-3 , most preferably 10 ¹⁸ to 10 ¹⁹ cm ^-3 .

In the present invention, the doping material of the front field region is not particularly limited, and the doping material well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the actual application situation, compounding situation and product performance. In the invention, the doping material of the front field region is preferably phosphorus doped. In the present invention, the doping method of the front field region is not particularly limited, and the doping method known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the actual application situation, compounding situation and product performance. The doping method of the front field region in the invention is preferably to form such a heavily doped region by diffusing phosphorus on the front surface of the substrate.

The present invention has no special limitation on the thickness of the front field region, and the conventional thickness of the front field region of the back-junction and back-contact solar cell well known to those skilled in the art is sufficient. The performance is selected and adjusted. The thickness of the front field region in the present invention is preferably 0.5-2 μm, more preferably 0.8-1.8 μm, and most preferably 1-1.5 μm.

The present invention is not particularly limited to the front surface passivation layer, the front surface passivation layer of the solar cell well-known to those skilled in the art can be used, and those skilled in the art can select and select according to the actual application situation, composite situation and product performance. Adjustment, the front surface passivation layer of the present invention preferably includes a silicon oxide layer, a silicon nitride layer, a stack of silicon oxide and silicon nitride or a silicon carbide layer, more preferably a silicon oxide layer, a silicon nitride layer or silicon oxide and nitride stack of silicon.

The present invention has no special limitation on the performance parameters of the front surface passivation layer, and the performance parameters of the conventional front surface passivation layer well known to those skilled in the art will suffice. performance options and adjustments.

The present invention has no special limitation on the thickness of the front surface passivation layer, the conventional thickness of the front surface passivation layer of the back junction back contact solar cell well known to those skilled in the art can be used, those skilled in the art can according to the actual application situation , recombination and product performance are selected and adjusted. The thickness of the front surface passivation layer in the present invention is preferably 50-100 nm, more preferably 60-90 nm, and most preferably 70-80 nm.

In the present invention, the anti-reflection layer is not particularly limited, and the anti-reflection layer of a solar cell well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to actual application conditions, composite conditions, and product performance. The present invention The anti-reflection layer is preferably a film layer with an anti-reflection effect, and its material is more preferably one or more of silicon nitride, ITO, silicon oxide and titanium oxide, more preferably silicon nitride, ITO, silicon oxide or titanium oxide, most preferably silicon nitride or ITO.

The present invention has no special limitation on the thickness of the anti-reflection layer, and the conventional thickness of the anti-reflection layer of the back-junction back-contact solar cell well known to those skilled in the art can be used. The performance is selected and adjusted. The thickness of the anti-reflection layer in the present invention is preferably 40-100 nm, more preferably 50-90 nm, and most preferably 60-80 nm.

The front surface of the battery provided by the present invention is sequentially designed with a front field diffusion area (front field area), a front surface passivation layer and an anti-reflection layer, and furthermore, all have the same suede light trapping structure as the front surface of the substrate. Wherein the anti-reflection layer is located at the front of the battery, and may be a thin film made of silicon nitride or titanium oxide. The front surface passivation layer is between the anti-reflection layer and the substrate, and plays the role of passivating the front surface of the battery, and can be a thin film made of silicon nitride or silicon oxide. The front field region is formed by phosphorous diffusion on the front surface of the substrate to form a heavily doped N-type region on the front surface of the substrate, especially after the textured light-trapping structure is fabricated, and phosphorous is diffused on the front surface. , the doping concentration is higher than that of the substrate, between 10 ¹⁷ cm ^-3 and 10 ¹⁹ cm ^-3 . Its function is to form an electric field pointing to the inside of the substrate, reducing the concentration of minority carriers on the surface, thereby reducing the surface recombination rate.

The present invention has no particular limitation on the tunneling oxide layer (tunneling oxide layer) on the back surface of the substrate, and the tunneling oxide layer well-known to those skilled in the art will suffice. Composite conditions and product performance are selected and adjusted. The material of the tunneling oxide layer in the present invention is preferably an insulating material, that is, the tunneling oxide insulating dielectric layer. More specifically, its material preferably includes silicon dioxide, titanium dioxide, aluminum oxide and one or more of silicon nitride, more preferably silicon dioxide, titanium dioxide, aluminum oxide or silicon nitride, most preferably silicon dioxide or aluminum oxide.

In the present invention, the thickness of the tunneling oxide layer is not particularly limited, and the conventional thickness of the front field region of the back-junction and back-contact solar cell well known to those skilled in the art is sufficient. and product performance are selected and adjusted. The thickness of the tunnel oxide layer in the present invention is preferably 0.3-2 nm, more preferably 0.5-1.8 nm, more preferably 0.7-1.6 nm, and most preferably 1.0-1.5 nm.

The present invention has no special limitation on the compounding method of the tunneling oxide layer. Those skilled in the art can select and adjust according to the actual application situation, compounding situation and product performance. The compounding method of the tunneling oxide layer in the present invention is preferably It is obtained by techniques such as wet oxidation or atomic layer deposition.

Before the doped semiconductor layer is formed on the back surface of the substrate of the present invention, a very thin tunnel oxide layer is formed on the bottom of the substrate. The tunnel oxide layer mainly plays the role of chemical passivation, so the oxide layer There should be a good interface with the substrate; and since the carriers pass through the oxide layer by tunneling, in order for the carriers to easily tunnel through the oxide layer, a relatively small series resistance is obtained. The oxide layer should be reported, with a thickness between 0.5 and 2 nm. The tunnel oxide layer provided by the present invention can cover the entire back surface of the substrate, can cover a part of the back surface of the substrate, preferably completely.

The present invention has no special limitation on the P-type doped semiconductor layer compounded on the tunnel oxide layer, and the P-type doped semiconductor layer of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can make selections and adjustments according to actual application conditions, composite conditions and product performance.

The present invention is not particularly limited to the semiconductor material of the P-type doped semiconductor layer, and the semiconductor material of the P-type doped semiconductor layer of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can according to The actual application situation, composite situation and product performance are selected and adjusted, and the semiconductor material of the P-type doped semiconductor layer in the present invention preferably includes one or more of microcrystalline silicon, polycrystalline silicon and amorphous silicon, more preferably Microcrystalline silicon, polycrystalline silicon or amorphous silicon.

The present invention has no special limitation on the doping material of the P-type doped semiconductor layer, and the doping material of the P-type doped semiconductor layer of the back-junction back-contact solar cell well known to those skilled in the art can be used. A skilled person can select and adjust according to actual application conditions, composite conditions and product performance. The doped material of the P-type doped semiconductor layer in the present invention preferably includes one or more of boron, phosphorus, gallium and arsenic. , more preferably boron, phosphorus, gallium or arsenic, most preferably boron.

The present invention has no special limitation on the doping concentration of the P-type doped semiconductor layer, and the conventional doping concentration well known to those skilled in the art can be used, and those skilled in the art can choose according to the actual application situation, compounding situation and product performance. and adjustment, the doping concentration of the P-type doped semiconductor layer in the present invention is preferably 10 ¹⁸ to 10 ²¹ cm ^-3 , more preferably 10 ¹⁸ to 10 ²⁰ cm ^-3 , most preferably 10 ¹⁹ to 10 ²¹ cm ^{-3 3} .

The present invention has no special restrictions on the compounding and doping methods of the P-type doped semiconductor layer, and the compounding and doping methods known to those skilled in the art can be used. And the product performance is selected and adjusted, the P-type doped semiconductor layer of the present invention is preferably formed directly on the tunnel oxide layer by the P-type doped semiconductor layer, which can be grown by PECVD process and formed by in-situ doping , the semiconductor layer can also be grown by PECVD first, and then doped by diffusion.

In the present invention, the thickness of the P-type doped semiconductor layer is not particularly limited, and the conventional thickness of the front field region of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can combine The thickness of the P-type doped semiconductor layer in the present invention is preferably 5nm-500nm, more preferably 50nm-450nm, more preferably 100nm-400nm, and most preferably 200nm-300nm.

In the present invention, there is no special limitation on the N-type doped semiconductor layer compounded on the tunnel oxide layer, and the N-type doped semiconductor layer of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can make selections and adjustments according to actual application conditions, composite conditions and product performance.

The present invention is not particularly limited to the semiconductor material of the N-type doped semiconductor layer, and the semiconductor material of the N-type doped semiconductor layer of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can according to The actual application situation, composite situation and product performance are selected and adjusted. The semiconductor material of the N-type doped semiconductor layer of the present invention preferably includes one or more of microcrystalline silicon, polycrystalline silicon and amorphous silicon, more preferably microcrystalline silicon. crystalline silicon, polycrystalline silicon or amorphous silicon.

The present invention has no particular limitation on the doped material of the N-type doped semiconductor layer, and the doped material of the N-type doped semiconductor layer of the back-junction back-contact solar cell well known to those skilled in the art can be used. The skilled person can select and adjust the doped material of the N-type doped semiconductor layer in the present invention according to the actual application situation, composite situation and product performance, preferably each including one or more of boron, phosphorus, gallium and arsenic, More preferred is boron, phosphorous, gallium or arsenic, most preferred is phosphorous.

In the present invention, the doping concentration of the N-type doped semiconductor layer is not particularly limited, and the conventional doping concentration well known to those skilled in the art can be used, and those skilled in the art can choose according to the actual application situation, compounding situation and product performance. and adjustment, the doping concentration of the N-type doped semiconductor layer in the present invention is preferably 10 ¹⁸ to 10 ²¹ cm ^-3 , more preferably 10 ¹⁸ to 10 ²⁰ cm ^-3 , most preferably 10 ¹⁹ to 10 ²¹ cm ^{-3 3} .

The present invention has no special restrictions on the compounding and doping methods of the N-type doped semiconductor layer, and the compounding and doping methods known to those skilled in the art can be used. and product performance selection and adjustment, the N-type doped semiconductor layer in the present invention is preferably formed directly on the tunnel oxide layer, and can be grown by PECVD process and formed by in-situ doping , the semiconductor layer can also be grown by PECVD first, and then doped by diffusion.

In the present invention, the thickness of the N-type doped semiconductor layer is not particularly limited, and the conventional thickness of the front field region of the back-junction and back-contact solar cell well known to those skilled in the art can be used. Those skilled in the art can combine The thickness of the N-type doped semiconductor layer in the present invention is preferably 5nm-500nm, more preferably 50nm-450nm, more preferably 100nm-400nm, most preferably 200nm-300nm.

The present invention has no special limitation on the arrangement relationship between the P-type doped semiconductor layer and the N-type doped semiconductor layer. The setting relationship of the semiconductor layer is enough, and those skilled in the art can select and adjust according to the actual application situation, compounding situation and product performance. The P-type doped semiconductor layer and the N-type doped semiconductor layer in the present invention are preferably alternately compounded adjacent to each other. On the tunnel oxide layer, and/or the P-type doped semiconductor layer and the N-type doped semiconductor layer are alternately compounded on the tunnel oxide layer, more preferably adjacent alternately compounded on the on the tunneling oxide layer, or alternately compounded on the tunneling oxide layer.

Alternate intervals in the present invention refer to alternate distribution with a certain gap between them, that is, finger-like distribution.

The present invention has no particular limitation on the width relationship between the P-type doped semiconductor layer and the N-type doped semiconductor layer. The width relationship of the semiconductor layer is sufficient, and those skilled in the art can select and adjust according to the actual application situation, composite situation and product performance. The width of the P-type doped semiconductor layer in the present invention and the width of the N-type doped semiconductor layer The width ratio is preferably (2-10):1, more preferably (3-9):1, more preferably (4-8):1, most preferably (5-7):1.

In particular, when the P-type doped semiconductor layer and the N-type doped semiconductor layer are alternately compounded on the tunnel oxide layer, since the positive electrode cannot be in contact with the back field region, the negative electrode cannot be in contact with the emitter The width of the positive electrode is smaller than the width of the P-type doped semiconductor layer, the width of the negative electrode is smaller than the width of the N-type doped semiconductor layer, and the positive electrode is not in contact with the N-type doped semiconductor layer. The doped semiconductor layer is in contact, and the negative electrode is not in contact with the P-type doped semiconductor layer.

The present invention also includes a positive electrode arranged on the P-type doped semiconductor layer and a negative electrode arranged on the N-type doped semiconductor layer.

The present invention has no special limitation on the formation method of the positive electrode and the negative electrode, and the electrode formation method known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the actual application situation, composite situation and product performance. The electrode of the present invention is preferably formed by screen printing, sputtering or metal vaporization.

The N-type doped semiconductor layer and the P-type doped semiconductor layer on the back side of the substrate of the present invention can be connected together, or they can be separated by a trench, preferably alternately distributed in the form of interpolated fingers, and the two types of doped There is a very thin tunnel oxide layer between the hetero-semiconductor layer and the substrate. The N-type doped semiconductor layer and the P-type doped semiconductor layer distributed in the shape of fingers constitute the emitter region and the back field region of the battery.

Among them, the P-type doped semiconductor layer can be grown by PECVD method and in-situ doped, the doping impurity is preferably boron, the thickness is between 5 and 500 nm, and the doping concentration is between 10 ¹⁷ cm ^-3 and 10 ²¹ cm ^- between ³ . The N-type doped semiconductor layer is prepared by the same process as the P-type doped semiconductor layer, and the doped impurity is preferably phosphorus. The thickness and doping concentration are similar to those of the P-type doped semiconductor layer. However, the width of the N-type doped semiconductor layer is smaller than that of the P-type doped semiconductor layer, and the ratio of the width of the P-type doped semiconductor layer to the width of the N-type doped semiconductor layer should be between 2 and 10.

The positive and negative electrodes of the present invention are all formed on the back of the battery, wherein the positive electrode is drawn from the emitter region, that is, the P-type doped semiconductor layer, and the negative electrode is drawn from the back field region, that is, the N-type doped semiconductor layer.

If the emitter area and the back field area are separated, the positive and negative electrodes can completely cover the emitter area and the back field area, and if the emitter area and the back field area are connected together, then the positive and negative electrodes can cover the emitter area And most of the back field area, but the positive electrode cannot be in contact with the back field area, and the negative electrode cannot be in contact with the emitter area. Of course, the positive and negative electrodes should also be isolated.

The above steps of the present invention provide a back-junction and back-contact solar cell with a tunnel oxide layer passivation contact structure on the back, firstly as a back-junction and back-contact solar cell, the solar cell with this structure has no metal grid lines on the front surface, so there is no shading Loss, emission area and back field, the positive and negative electrodes are on the back of the battery, so the metal electrode can cover almost the entire back of the battery, which greatly reduces the series resistance of the battery, and both the positive and negative electrodes are on the back, for the battery sheet The interconnection between them is much simpler.

Moreover, the present invention adopts a tunneling oxide layer passivation contact structure, which effectively reduces the carrier recombination of the metal contact interface by adopting the tunneling oxide layer passivation contact structure, and this structure avoids direct contact between the metal electrode and the substrate , greatly reducing the recombination of carriers at the metal contact interface, without reducing the metal contact area in order to reduce interface recombination, the metal contact surface can almost cover the entire back of the battery, thereby reducing the lateral transport of carriers, which can further reduce The series resistance of the battery increases the efficiency of the battery. The invention applies the structure to the back-junction and back-contact solar cell, so that the advantages of the back-junction and back-contact solar cell are maximized. Moreover, the preparation process adopted by the present invention has good compatibility with the existing solar cell preparation process, and can even further simplify the cell preparation process and reduce production costs.

Experimental results show that the back junction and back contact solar cell with tunnel oxide layer passivation contact structure on the back provided by the present invention can reach 22% cell efficiency.

In order to further illustrate the present invention, a back-junction and back-contact solar cell provided by the present invention will be described in detail below in conjunction with examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed The embodiments and the specific operation process are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.

Example 1

Referring to FIG. 1 , FIG. 1 is a schematic structural diagram of a back-junction and back-contact solar cell provided by Embodiment 1 of the present invention. Among them, 101 is the substrate (substrate), 102 is the tunnel oxide layer, 103 is the N-type doped semiconductor layer, 104 is the P-type doped semiconductor layer, 105 is the positive electrode, 106 is the negative electrode, and 107 is the front electrode. In the field area, 108 is an anti-reflection layer, 109 is a passivation layer on the front surface, and 110 is an overall suede light-trapping structure.

It can be seen from Fig. 1 that the P-type doped semiconductor layer and the N-type doped semiconductor layer are alternately distributed in the shape of interpolated fingers, and the P-type doped semiconductor layer and the N-type doped semiconductor layer are separated by a trench. The room is insulated. Wherein the P-type doped semiconductor layer as the emitter is wider than the N-type doped semiconductor layer as the back field region.

The concrete preparation method of the solar cell of this kind structure is as follows:

A pyramid-shaped suede structure is prepared by corroding the front surface of an N-type single crystal silicon wafer with a thickness of 100 microns with a sodium hydroxide solution. The concentration of sodium hydroxide is 1%, the etching time is 5 minutes, and the temperature is 60 ℃. On the textured surface, arsenic atoms were implanted by ion implantation to form an N-type doped region on the front surface with a doping concentration of 10 ¹⁷ cm ^-3 and a doping depth of 2 microns. After forming the N-type doped region on the front surface, a layer of silicon oxide with a thickness of 20 nanometers is deposited on the front surface as a passivation layer by plasma-enhanced chemical vapor deposition, and then placed on the passivation layer by sputtering A layer of 200nm ITO was deposited as an anti-reflection layer by the way. Then, a layer of tunnel oxide layer with a thickness of 2nm is formed on the back of the silicon wafer by thermal oxygen oxidation method. N-type doped polysilicon and P-type doped polysilicon are alternately distributed on the layer, the N-type doped polysilicon has a width of 800 microns, a thickness of 100nm, and a doping concentration of 10 ¹⁹ cm ^-3 , and the P-type doped polysilicon The width is 200 microns, the thickness is 100 nm, and the doping concentration is 10 ¹⁹ cm ^-3 . There is a gap with a width of 40 microns between the N-type doped polysilicon and the P-type doped polysilicon. After forming N-type doped polysilicon and P-type doped polysilicon, the screen printing method is used to form metal contacts on the P-type doped polysilicon used as the emitter and the N-type doped polysilicon used as the back field. Covering the entire doped polysilicon layer, there is also a 40 micron gap between the positive electrode and the negative electrode, and finally a back-junction back-contact solar cell with a tunnel oxide passivation contact structure on the back is obtained.

The performance of the back-junction back-contact solar cell prepared in Example 1 of the present invention was characterized. The test uses standard test conditions (SRC) to test the I-V characteristic curve of the battery.

The test results show that the average performance parameters of the back junction and back contact solar cells prepared by the invention are as follows: the open circuit voltage is 660mV, the short circuit current density is 41.4mA, the filling factor is 78.8%, and the efficiency is 21.2%.

Example 2

Referring to FIG. 2 , FIG. 2 is a schematic structural diagram of a back-junction and back-contact solar cell provided by Embodiment 2 of the present invention. Among them, 101 is the substrate (substrate), 102 is the tunnel oxide layer, 103 is the N-type doped semiconductor layer, 104 is the P-type doped semiconductor layer, 105 is the positive electrode, 106 is the negative electrode, and 107 is the front electrode. In the field area, 108 is an anti-reflection layer, 109 is a passivation layer on the front surface, and 110 is an overall suede light-trapping structure.

As can be seen from Figure 2, the P-type doped semiconductor layer and the N-type doped semiconductor layer can also be connected together as shown in Figure 2, although they are connected together, the P-type doped semiconductor layer and the N-type doped semiconductor layer A PN junction will be formed. When the battery is working normally, the PN junction is in a reverse bias state, so it will not cause leakage.

The positive and negative electrodes of the solar cell provided by the present invention are all formed on the back of the cell, wherein the positive electrode is drawn from the P-type doped semiconductor layer, and the negative electrode is drawn from the N-type doped semiconductor layer. As shown in FIG. 1 , if the P-type doped semiconductor layer and the N-type doped semiconductor layer are separated, the electrodes can completely cover the P-type doped semiconductor layer and the N-type doped semiconductor layer. As shown in Figure 2, if the P-type doped semiconductor layer and the N-type doped semiconductor layer are connected together, then the metal electrode can only cover most of the doped semiconductor layer, and at the same time, it must be ensured that the positive electrode is not mixed with the N-type doped semiconductor layer. The doped semiconductor layer is in contact with the negative electrode, and the negative electrode is not in contact with the P-type doped semiconductor layer.

The preparation method of the solar cell of this kind structure is as follows:

A pyramid-shaped suede structure is prepared by corroding the front surface of an N-type single crystal silicon wafer with a thickness of 100 microns with a sodium hydroxide solution. The concentration of sodium hydroxide is 1%, the etching time is 5 minutes, and the temperature is 60 ℃. On the textured surface, arsenic atoms were implanted by ion implantation to form an N-type doped region on the front surface with a doping concentration of 10 ¹⁷ cm ^-3 and a doping depth of 2 microns. After forming the N-type doped region on the front surface, a layer of silicon oxide with a thickness of 20 nanometers is deposited on the front surface as a passivation layer by plasma-enhanced chemical vapor deposition, and then placed on the passivation layer by sputtering A layer of 200nm ITO was deposited as an anti-reflection layer by the way. Then, a layer of tunnel oxide layer with a thickness of 2nm is formed on the back of the silicon wafer by thermal oxygen oxidation method. N-type doped polysilicon and P-type doped polysilicon are alternately distributed on the layer, the N-type doped polysilicon has a width of 800 microns, a thickness of 100 nm, and a doping concentration of 10 ¹⁹ cm ^-3 , and the P-type doped polysilicon The width is 200 microns, the thickness is 100 nm, and the doping concentration is 10 ¹⁹ cm ^-3 . N-type doped polysilicon is in direct contact with P-type doped polysilicon, and a PN junction is formed between them. After forming N-type doped polysilicon and P-type doped polysilicon, the positive electrode is formed on the N-type doped polysilicon as the emitter, and the positive electrode is formed on the N-type doped polysilicon as the back field by screen printing. For the negative electrode, the metal partially covers the doped polysilicon layer, and there is a gap of 40 microns between the positive electrode and the negative electrode. Finally, a back-junction back-contact solar cell with a tunnel oxide layer passivation contact structure is obtained on the back.

The performance of the back-junction back-contact solar cell prepared in Example 2 of the present invention was characterized. The test uses standard test conditions (SRC) to test the I-V characteristic curve of the battery.

The test results show that the average performance parameters of the back junction and back contact solar cells prepared by the invention are as follows: the open circuit voltage is 660mV, the short circuit current density is 42mA, the filling factor is 78.0%, and the efficiency is 21.6%.

Example 3

The preparation method of the solar cell is as follows:

A pyramid-shaped suede structure is prepared by corroding the front surface of an N-type single crystal silicon wafer with a thickness of 100 microns with a sodium hydroxide solution. The concentration of sodium hydroxide is 1%, the etching time is 5 minutes, and the temperature is 60 ℃. On the textured surface, arsenic atoms were implanted by ion implantation to form an N-type doped region on the front surface with a doping concentration of 10 ¹⁷ cm ^-3 and a doping depth of 2 microns. After forming the N-type doped region on the front surface, a layer of silicon oxide with a thickness of 20 nanometers is deposited on the front surface as a passivation layer by plasma-enhanced chemical vapor deposition, and then placed on the passivation layer by sputtering A layer of 200nm ITO was deposited as an anti-reflection layer by the way. Then use thermal oxygen oxidation method to form a tunnel oxide layer with a thickness of 2nm on the back of the silicon wafer. After forming the tunnel oxide layer, use LPCVD to grow a layer of N-type doped oxide on the tunnel oxide layer. Doped polysilicon, and then protect the polysilicon in the back field region by photolithography, and then etch the unprotected polysilicon by RIE etching method, thereby forming the back field. Then use the LPCVD method to grow a layer of P-type doped polysilicon, and form the emitter region of the battery through the same photolithography and RIE etching method.

N-type doped polysilicon has a width of 800 microns, a thickness of 100 nm, and a doping concentration of 10 ¹⁹ cm ^-3 , and a P-type doped polysilicon has a width of 200 microns, a thickness of 100 nm, and a doping concentration of 10 ¹⁹ cm ^-3 . N-type doped polysilicon is in direct contact with P-type doped polysilicon, and a PN junction is formed between them. After forming N-type doped polysilicon and P-type doped polysilicon, the positive electrode is formed on the N-type doped polysilicon as the emitter, and the positive electrode is formed on the N-type doped polysilicon as the back field by screen printing. For the negative electrode, the metal partially covers the doped polysilicon layer, and there is a gap of 40 microns between the positive electrode and the negative electrode. Finally, a back-junction back-contact solar cell with a tunnel oxide layer passivation contact structure is obtained on the back.

The performance of the back-junction back-contact solar cell prepared in Example 3 of the present invention was characterized. The test uses standard test conditions (SRC) to test the I-V characteristic curve of the battery.

Referring to FIG. 3 , FIG. 3 is an I-V characteristic curve of a back-junction back-contact solar cell with a tunnel oxide layer passivation contact structure provided by Embodiment 3 of the present invention.

It can be seen from Fig. 3 that the average performance parameters of the back junction and back contact solar cells prepared by the present invention are as follows: the open circuit voltage is 662mV, the short circuit current density is 42.4mA, the fill factor is 78.5%, and the efficiency is 22.0%.

A back-junction back-contact solar cell with a tunnel oxide layer passivation contact structure on the back provided by the present invention has been introduced in detail above. In this paper, a specific example has been used to illustrate the principle and implementation of the present invention. The above implementation The description of the example is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables anyone skilled in the art to practice the present invention, including making and using any device or system, and implementing any combination Methods. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims (10)

1. A back-junction back-contact solar cell, characterized in that, comprising: Substrate; a composite layer composited on the front surface of the substrate; a tunnel oxide layer compounded on the back surface of the substrate; a P-type doped semiconductor layer and an N-type doped semiconductor layer compounded on the tunnel oxide layer; a positive electrode disposed on the P-type doped semiconductor layer; a negative electrode disposed on the N-type doped semiconductor layer. 2. The solar cell according to claim 1, wherein the composite layer on the front surface of the substrate comprises: a front field region compounded on the front surface of the substrate; a front surface passivation layer compounded on the front field region; An anti-reflection layer compounded on the front surface passivation layer. 3. The solar cell according to claim 1, characterized in that, the P-type doped semiconductor layer and the N-type doped semiconductor layer are adjacently and alternately compounded on the tunnel oxide layer, and/or the P-type doped semiconductor layers and N-type doped semiconductor layers are alternately compounded on the tunnel oxide layer; The ratio of the width of the P-type doped semiconductor layer to the width of the N-type doped semiconductor layer is (2˜10):1. 4. The solar cell according to claim 3, wherein when the P-type doped semiconductor layer and the N-type doped semiconductor layer are adjacently and alternately compounded on the tunnel oxide layer, the positive electrode The width of the negative electrode is smaller than the width of the P-type doped semiconductor layer, the width of the negative electrode is smaller than the width of the N-type doped semiconductor layer, and the positive electrode is not in contact with the N-type doped semiconductor layer, The negative electrode is not in contact with the P-type doped semiconductor layer. 5 . The solar cell according to claim 1 , wherein the composite layer on the front surface of the substrate has a suede light-trapping structure. 6. The solar cell according to claim 1, wherein the front surface of the substrate has a textured light-trapping structure. 7. The solar cell according to any one of claims 1-6, wherein the material of the substrate comprises lightly doped silicon material, and the doping concentration of the lightly doped is 10 ¹³ -10 ¹⁷ cm ^-3 ; the type of doping is N type; The silicon material includes one or more of single crystal silicon, polycrystalline silicon and silicon thin film; The doped material includes one or more of boron, phosphorus, gallium and arsenic; The minority carrier lifetime of the substrate is greater than or equal to 500 μs; the resistivity of the substrate is 1 to 50 Ω·cm; The thickness of the substrate is 50-300 μm. 8. The solar cell according to any one of claims 1-6, wherein the material of the tunnel oxide layer is an insulating material; The insulating material includes one or more of silicon dioxide, titanium dioxide, aluminum oxide and silicon nitride; The thickness of the tunnel oxide layer is 0.3-2 nm. 9. The solar cell according to any one of claims 1 to 6, wherein the semiconductor materials of the P-type doped semiconductor layer and the N-type doped semiconductor layer each include microcrystalline silicon, polycrystalline silicon and amorphous silicon One or more of them; each of the doped materials includes one or more of boron, phosphorus, gallium and arsenic; The doping concentrations are each 10 ¹⁸ to 10 ²¹ cm ^-3 ; The thicknesses of the P-type doped semiconductor layer and the N-type doped semiconductor layer are each selected from 5 nm to 500 nm. 10. The solar cell according to claim 2, wherein the front field region is a highly doped region formed by diffusing phosphorus on the front surface of the substrate; The thickness of the front field region is 0.5-2 μm; The front surface passivation layer includes a silicon oxide layer, a silicon nitride layer, a stack of silicon oxide and silicon nitride or a silicon carbide layer; The thickness of the front surface passivation layer is 50-100nm; The material of the antireflection layer includes one or more of silicon nitride, ITO, silicon oxide and titanium oxide; The thickness of the anti-reflection layer is 40-100 nm.