CN108470778A - Solar cell inactivating film and passivating back solar cell and preparation method thereof - Google Patents

Abstract

The invention provides a solar cell passivation film, a rear passivation solar cell and a preparation method thereof, and relates to the technical field of solar cells. The solar cell passivation film includes a high work function semiconductor material layer and a silicon nitride layer arranged in sequence, The high work function semiconductor material layer is used to be in contact with the battery base. The use of the solar cell passivation film can alleviate the technical problems of difficult and costly preparation of the Al ₂ O ₃ passivation film in the local contact solar cell in the prior art, and achieve the purpose of reducing the process difficulty and cost.

Description

Solar cell passivation film, rear passivated solar cell and preparation method thereof

technical field

The invention relates to the technical field of solar cells, in particular to a solar cell passivation film, a rear passivated solar cell and a preparation method thereof.

Background technique

Partial contact solar cells are also called PERC solar cells. Currently, cells with this structure use a laminated dielectric passivation film composed of Al ₂ O ₃ /SiNx to passivate the back of the cell. The passivation principle of Al ₂ O ₃ /SiNx passivation film is different according to different preparation methods and film thickness. For the thinner Al ₂ O ₃ /SiNx stack, the passivation mechanism is carried by the Al ₂ O ₃ layer itself The field passivation provided by the fixed negative charge and the H chemical passivation provided by the SiNx layer are superimposed on each other; and for the thicker Al ₂ O ₃ layer (generally exceeding 10nm), the preparation method is deposited by PECVD, then the passivation is It is the field passivation formed by the fixed negative charge provided by Al ₂ O ₃ itself, and its chemical passivation comes from the superposition of H in Al ₂ O ₃ film and H in SiNx. Since _Al2O3 is negatively charged, the chemical passivation and field _- effect passivation of dangling bonds can be realized simultaneously on the backside. Although this method is currently a commercialized high-efficiency solar cell manufacturing technology, which can achieve a conversion efficiency greater than 21%, it has the following disadvantages:

1) Although Al ₂ O ₃ deposition technology is mature, the equipment is expensive. The domestic equipment is about 5 million to 10 million, and the imported equipment is generally more than 10 million;

2) The additional process steps are not only the additional Al ₂ O ₃ and SiNx deposition processes, but also the laser mold opening process, which will increase the production cost of the enterprise;

3) Due to the use of a smaller contact area in local contact, the fill factor will be reduced.

In addition, there are technical disclosures that use ultra-thin Al ₂ O ₃ as an insertion passivation layer and require it to have tunneling properties, and then use thermal evaporation to deposit a layer of high work function transition metal oxide on the outside of the Al ₂ O ₃ film. The selective transport of carriers is achieved by using material materials. This structure is apparently a brand new structure, but it is difficult to prepare and it is not suitable to achieve high efficiency. The main reasons are as follows:

1) The ultra-thin Al ₂ O ₃ tunneling layer is extremely sensitive to the thickness requirement, usually 1-2nm, so the thickness control itself is a technical difficulty;

2) In order to achieve better field effect passivation of Al ₂ O ₃ , the thickness of Al ₂ O ₃ needs to be greater than 2nm, so tunneling and good passivation cannot be achieved at the same time;

3) Al ₂ O ₃ requires annealing to exert its perfect passivation performance. The back electrode is still prepared by screen printing and sintering at high temperature. less efficient or even inefficient;

4) Al ₂ O ₃ equipment is expensive, which increases the manufacturing cost of the battery.

In view of this, the present invention is proposed.

Contents of the invention

The first purpose of the present invention is to provide a solar cell passivation film to alleviate the technical problems of difficult and costly preparation of Al ₂ O ₃ passivation films in partial contact solar cells in the prior art.

The second object of the present invention is to provide a backside passivation solar cell, in which a composite film of a high work function semiconductor material layer and a silicon nitride layer is used as a passivation layer, so as to ensure the conversion efficiency of the cell while reducing the cost of the cell. cost.

The third object of the present invention is to provide a method for preparing a rear passivated solar cell, which can reduce the manufacturing cost of the passivation film of the cell.

In order to realize the above-mentioned purpose of the present invention, special adopt following technical scheme:

A solar battery passivation film, comprising a high work function semiconductor material layer and a silicon nitride layer arranged in sequence, and the high work function semiconductor material layer is used for contacting with the battery substrate.

Further, the work function of the semiconductor material in the high work function semiconductor material layer is greater than that of p-type silicon.

Further, the work function of the semiconductor material in the high work function semiconductor material layer is greater than 5eV.

Further, the high work function semiconductor material is a transition metal oxide.

Further, the transition metal oxide includes one or a combination of at least two of tungsten oxide, vanadium oxide, zirconium oxide or molybdenum oxide.

Further, the thickness of the high work function semiconductor material layer is 5-100 nm.

Further, the thickness of the silicon nitride layer is 10-150 nm.

A backside passivated solar cell, comprising a battery substrate, a back electrode and the above-mentioned passivation film, the passivation film is located between the battery substrate and the back electrode, and the passivation film is provided with an open area, The back electrode contacts the battery base through the opening area.

Further, the battery substrate is a P-type silicon wafer.

Further, a silicon nitride anti-reflection film is provided on the front of the battery base.

A method for preparing the above-mentioned back passivated solar cell, comprising sequentially preparing a passivation film and a back electrode on the back of a cell substrate to obtain the back passivated solar cell.

Further, a high work function semiconductor material layer of a passivation film is prepared on the back of the battery substrate by thermal evaporation, atomic layer deposition or magnetron sputtering;

Preferably, the evaporation rate during the evaporation process is 0.1-10A/s;

Preferably, a silicon nitride layer of a passivation film is prepared on the surface of the high work function semiconductor material layer by using a deposition process.

Compared with the prior art, the present invention has the following beneficial effects:

The solar cell passivation film provided by the invention is made up of high work function semiconductor material layer and silicon nitride layer, and its passivation mechanism is as follows: 1) high work function semiconductor material belongs to high work function material (greater than the work function of battery substrate Si ), when the high work function semiconductor material and silicon are in metallurgical contact, due to the difference in work function (ie Fermi level), electrons will move from the battery substrate Si material to the high work function semiconductor material layer, Thus, a hole-rich layer, i.e. p+ layer, is produced on the Si surface, which indirectly reduces the minority carrier concentration on the Si surface, thereby reducing recombination; 2) The high work function semiconductor material layer reacts with the Si matrix to form a layer of 0.1- 2nm SiO ₂ , providing chemical passivation.

The backside passivation solar cell provided by the present invention uses a high work function semiconductor material layer and a silicon nitride layer as a passivation film, and the high work function semiconductor material layer can induce a layer of hole enrichment layer on the surface of the Si substrate, and SiNx can Provide good H passivation; the high work function semiconductor material layer is continuously and evenly distributed on the surface of the silicon wafer of the battery substrate, and the SiNx layer covers the surface of the high work function semiconductor material layer, thereby realizing effective passivation of p-type Si, thereby improving the The conversion efficiency of the battery.

The advantages of the back passivated solar cell provided by the present invention:

1) In the surface passivation solar cell provided by the present invention, the requirement for the thickness uniformity of the passivation film is low, which reduces the preparation technical threshold;

2) The high work function semiconductor material in the passivation film itself is a semiconductor. For the metallization process of one-time sintering, it can alleviate the phenomenon of insufficient contact performance caused by sintering problems, and help reduce the defective rate of products;

3) The high work function semiconductor material itself is a semiconductor material and has carrier transport properties. Therefore, the passivation film composed of the high work function semiconductor material layer and the silicon nitride layer can reduce the contact resistance of the solar cell, thereby increasing its fill factor;

4) It can be combined with a conductive film to realize the preparation of p-type double-sided batteries.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

FIG. 1 is a schematic structural view of a rear passivated solar cell provided in Example 1 of the present invention.

Icons: 10-P-type silicon wafer; 20-n+ diffusion layer; 30-silicon nitride antireflection film; 40-negative electrode; 50-high work function semiconductor material layer; 60-silicon nitride layer; 70-back electrode.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, or in a specific orientation. construction and operation, therefore, should not be construed as limiting the invention.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

One aspect of the present invention provides a passivation film for a solar cell, comprising a high work function semiconductor material layer and a silicon nitride layer arranged in sequence, and the high work function semiconductor material layer is used to contact the battery base.

The solar cell passivation film provided by the invention is made up of high work function semiconductor material layer and silicon nitride layer, and its passivation mechanism is as follows: 1) high work function semiconductor material belongs to high work function material (greater than the work function of battery substrate Si ), when the high work function semiconductor material and silicon are in metallurgical contact, due to the difference in work function (ie Fermi level), electrons will move from the battery substrate Si material to the high work function semiconductor material layer, Thus, a hole-rich layer, i.e. p+ layer, is produced on the Si surface, which indirectly reduces the minority carrier concentration on the Si surface, thereby reducing recombination; 2) The high work function semiconductor material layer reacts with the Si matrix to form a layer of 0.1- 2nm SiO ₂ , providing chemical passivation.

It should be noted that the number of layers of the specific high work function semiconductor material layer is not specifically limited in the present invention, wherein the high work function semiconductor material layer may be one layer or several layers. The opening area in the present invention is a through hole, and in the opening area, the substrate and the back electrode are in direct contact.

In some embodiments of the present invention, the work function of the semiconductor material in the high work function semiconductor material layer is greater than that of p-type silicon; optionally, the work function of the semiconductor material in the high work function semiconductor material layer is greater than 5eV. High work function semiconductor materials are transition metal oxides.

It can be understood that, in the above embodiments, there is no specific limitation on the specific type of transition metal oxide, as long as the work function requirement is met.

In some embodiments of the present invention, the transition metal oxide includes one or a combination of at least two of tungsten oxide, vanadium oxide, zirconium oxide or molybdenum oxide.

The combination of at least two can be, for example, a combination of a layer of tungsten oxide and a layer of vanadium oxide, or a combination of a layer of tungsten oxide and a layer of molybdenum oxide, or a combination of a layer of vanadium oxide and a layer of molybdenum oxide, or a layer of oxide A combination of tungsten, a layer of vanadium oxide and a layer of molybdenum oxide.

In some embodiments of the present invention, the thickness of the high work function semiconductor material layer is 5-100 nm. For example, the thickness of the high work function semiconductor material layer may be 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

In some embodiments of the present invention, the thickness of the silicon nitride layer is 10-150 nm. For example, the silicon nitride layer may have a thickness of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm or 150 nm.

The second aspect of the present invention provides a backside passivated solar cell, comprising a battery base, a back electrode and the above-mentioned passivation film, the passivation film is located between the battery base and the back electrode, and the The passivation film is provided with an open area, and the back electrode passes through the open area and contacts the battery base.

The backside passivation solar cell provided by the present invention uses a high work function semiconductor material layer and a silicon nitride layer as a passivation film, and the high work function semiconductor material layer can induce a layer of hole enrichment layer on the surface of the Si substrate, and SiNx can Provide good H passivation; the high work function semiconductor material layer is continuously and evenly distributed on the surface of the silicon wafer of the battery substrate, and the SiNx layer covers the surface of the high work function semiconductor material layer, thereby realizing effective passivation of p-type Si, thereby improving the The conversion efficiency of the battery.

The advantages of the back passivated solar cell provided by the present invention:

1) In the surface passivation solar cell provided by the present invention, the requirement for the thickness uniformity of the passivation film is low, which reduces the preparation technical threshold;

2) The high work function semiconductor material in the passivation film itself is a semiconductor. For the metallization process of one-time sintering, it can alleviate the phenomenon of insufficient contact performance caused by sintering problems, and help reduce the defective rate of products;

3) The high work function semiconductor material itself is a semiconductor material and has carrier transport properties. Therefore, the passivation film composed of the high work function semiconductor material layer and the silicon nitride layer can reduce the contact resistance of the solar cell, thereby increasing its fill factor;

4) It can be combined with a conductive film to realize the preparation of p-type double-sided batteries.

In some embodiments of the present invention, the battery substrate is a P-type silicon wafer.

The p-type silicon chip, with a resistivity of 1-3Ω·cm, acts as an absorbing layer, and its main function is to convert photons that meet the conditions into electrons.

Doping on the front of the p-type silicon wafer forms an n+ diffusion layer, also known as the emitter, whose main function is to form a p-n junction with the p-type silicon wafer to selectively transport electrons, with a depth of about 0.5 μm.

In some embodiments of the present invention, a silicon nitride anti-reflection film is provided on the front of the battery substrate. The silicon nitride anti-reflection film has a thickness of about 75nm. Its main functions are: 1) Provide H atoms for dangling bond saturation; 2) Play the role of anti-reflection and increase the transmittance of light; 3) Use its own positive charge to provide field effect passivation.

The third aspect of the present invention provides a method for preparing the above-mentioned back passivated solar cell, wherein a passivation film and a back electrode are sequentially prepared on the back of the cell substrate to obtain the back passivated solar cell.

In some embodiments of the present invention, the high work function semiconductor material layer of the passivation film is prepared on the back of the battery substrate by thermal evaporation, atomic layer deposition or magnetron sputtering; optionally, according to the high work function semiconductor material The thickness of the layer, the evaporation rate during the evaporation process is 0.1-10A/s.

It can be understood that there are various methods for preparing the high work function semiconductor material layer, such as vapor deposition, magnetron sputtering, or atomic layer deposition.

The evaporation method is used to prepare the high work function semiconductor material layer. During the preparation process, the temperature of the battery substrate is at room temperature, which realizes the low temperature process and reduces the influence of high temperature on crystal defects.

In some embodiments of the present invention, a silicon nitride layer of a passivation film is prepared on the surface of the high work function semiconductor material layer by using a deposition process.

It can be understood that the back electrode in the present invention plays a role of transporting holes to an external circuit. The back electrode can be a metal electrode, or a transparent conductive film TCO, which can be prepared by evaporation or magnetron sputtering.

In some embodiments of the present invention, the preparation method of the above-mentioned rear passivated solar cell includes the following steps: the silicon wafer is sequentially cleaned and textured, _POCl3 is diffused, the back junction is removed, the silicon nitride anti-reflection film is coated, and the reverse surface is sequentially prepared. A work function semiconductor material layer and a silicon nitride layer, screen printing and sintering on the front and back surfaces to obtain the rear passivated solar cell.

The present invention will be further described in detail below in conjunction with examples.

Example 1

As shown in Figure 1, this embodiment is a backside passivated solar cell, including the following parts:

1) P-type silicon wafer 10: resistivity 2Ω·cm, used as an absorbing layer to convert qualified photons into electrons, and the size of the P-type silicon wafer is 2×2cm ² ;

2) n+ diffusion layer 20: also known as the emitter, the main function is to form a pn junction with p-Si to selectively transport electrons, with a depth of about 0.5 μm, using POCl ₃ as a phosphorus source, and diffused in a tube furnace. ;

3) Silicon nitride anti-reflection film 30: deposited by PECVD, with a thickness of about 75nm;

4) Negative electrode 40: obtained by screen printing and high-temperature sintering;

5) High work function semiconductor material layer 50: obtained by thermal evaporation, its function is: through the difference in work function, a p+ layer is introduced into the Si material to indirectly provide field passivation; at the same time, it reacts with the Si matrix to form a layer of 1nm SiO ₂ , providing chemical passivation;

The high work function semiconductor material layer in this embodiment is a vanadium oxide layer with a thickness of 9nm, abbreviated as 9nm-V ₂ O ₅ ;

6) Silicon nitride layer 60: prepared by PECVD deposition, with a thickness of 100nm, its main function is to provide H atoms, enhance the chemical passivation of the passivation film, and also reflect long-wavelength photons and play a protective role;

7) Back electrode 70: it is a metal electrode, which is obtained by magnetron sputtering, thermal evaporation or screen printing, and plays the role of transporting holes to the external circuit.

Example 2

This embodiment is a back passivated solar cell. Compared with Embodiment 1, the difference lies in that the high work function semiconductor material layer is different. The high work function semiconductor material layer in this embodiment is 9nm-V ₂ O ₅ /3nm-WO ₃ , and other parts are the same as in Embodiment 1.

Example 3

This embodiment is a back passivated solar cell. Compared with Embodiment 1, the difference lies in that the high work function semiconductor material layer is different. The high work function semiconductor material layer in this embodiment is 9nm-V ₂ O ₅ /6nm-WO ₃ , and other parts are the same as in Embodiment 1.

Example 4

This embodiment is a back passivated solar cell. Compared with Embodiment 1, the difference lies in that the high work function semiconductor material layer is different. The high work function semiconductor material layer in this embodiment is 9nm-V ₂ O ₅ /9nm-WO ₃ , and other parts are the same as in Embodiment 1.

Example 5

This embodiment is a back passivated solar cell. Compared with Embodiment 1, the difference lies in that the high work function semiconductor material layer is different. The high work function semiconductor material layer in this embodiment is 9nm-V ₂ O ₅ /12nm-WO ₃ , and other parts are the same as in Embodiment 1.

Example 6

This embodiment is a back passivated solar cell. Compared with Embodiment 1, the difference lies in that the high work function semiconductor material layer is different. The high work function semiconductor material layer in this embodiment is 9nm-V ₂ O ₅ /12nm-MoO ₃ , and other parts are the same as in Embodiment 1.

Comparative example 1

This comparative example is a rear passivated solar cell, compared with Example 1, the difference lies in that the passivation layer is different. The passivation layer in this comparative example is an aluminum back field. Others are the same as in Example 1.

Comparative example 2

This comparative example is a rear passivated solar cell, compared with Example 1, the difference lies in that the passivation layer is different. The passivation layer in this comparative example is composed of a layer of aluminum oxide and a layer of silicon nitride, and the others are the same as in the first embodiment.

The performances of the solar cells provided in Examples 1-6 and Comparative Examples 1 and 2 were tested respectively, and the results are listed in Table 1.

Table 1 Test results

As can be seen from the test results in Table 1, the passivation film provided by the present invention can have excellent passivation performance, and the opening pressure of the solar cell with the result of the passivation film is compared with the passivation film of the current aluminum oxide-silicon nitride, The difference is almost the same, but the filling factor is higher, indicating that the passivation film provided by the present invention has reached the passivation level of the aluminum oxide-silicon nitride passivation film.

In addition, the solar cell provided by the present invention has higher open voltage and short-circuit current than the current solar cell with an ordinary aluminum back field, and the conversion efficiency of the solar cell can be increased by 1%-2%.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. a kind of solar cell inactivating film, which is characterized in that including the high work function semiconductor material layer set gradually and nitrogen SiClx layer, the high work function semiconductor material layer with cell matrix for contacting.

2. solar cell inactivating film according to claim 1, which is characterized in that in high work function semiconductor material layer The work function of semi-conducting material is more than the work function of p-type silicon；

Preferably, the work function of the semi-conducting material in high work function semiconductor material layer is more than 5eV；

Preferably, high work function semi-conducting material is transition metal oxide.

3. solar cell inactivating film according to claim 2, which is characterized in that the transition metal oxide includes oxygen Change tungsten, vanadium oxide, zirconium oxide or one kind in molybdenum oxide or at least two combination.

4. according to claim 1-3 any one of them solar cell inactivating films, which is characterized in that the high work function is partly led The thickness of body material layer is 5-100nm.

5. according to claim 1-3 any one of them solar cell inactivating films, which is characterized in that the thickness of the silicon nitride layer Degree is 10-150nm.

6. a kind of passivating back solar cell, which is characterized in that any including cell matrix, back electrode and claim 1-5 Passivating film described in, the passivating film is between the cell matrix and the back electrode, and the passivating film is equipped with and opens Bore region, the back electrode penetrate through the opening area and are contacted with the cell matrix.

7. passivating back solar cell according to claim 6, which is characterized in that the cell matrix is P-type wafer.

8. passivating back solar cell according to claim 6, which is characterized in that the cell matrix front is equipped with nitrogen SiClx antireflective film.

9. a kind of preparation method of claim 6-8 any one of them passivating back solar cell, which is characterized in that in electricity The pond matrix back side is sequentially prepared passivating film and back electrode, obtains the passivating back solar cell.

10. preparation method according to claim 9, which is characterized in that use hot evaporation, atomic layer deposition or magnetron sputtering The high work function semiconductor material layer of passivating film is prepared at the cell matrix back side in technique；

Preferably, the evaporation rate during being deposited is 0.1-10A/s；

Preferably, the silicon nitride of passivating film is prepared in the high work function semi-conducting material layer surface using depositing operation Layer.