WO2015027946A1

WO2015027946A1 - Dielectric passive film and solar cell and preparation method thereof

Info

Publication number: WO2015027946A1
Application number: PCT/CN2014/085612
Authority: WO
Inventors: 叶继春; 王洪喆; 高平奇; 潘淼; 韩灿
Original assignee: 中国科学院宁波材料技术与工程研究所
Priority date: 2013-08-30
Filing date: 2014-08-29
Publication date: 2015-03-05
Also published as: CN104425633B; CN104425633A

Abstract

Disclosed is a surface dielectric passive film suitable for silicon based materials. The dielectric passive film is a silicon nitride dielectric passive film located on the surface of the silicon based material, and the passive film contains doping elements selected from the group consisting of: doping elements imparting electronegativity to the silicon nitride dielectric passive film, doping elements imparting electropositivity to the silicon nitride dielectric passive film, or combinations thereof. The surface dielectric passive film is not only controllable in quantity of electricity and electric property and excellent in field passivation effect, but can also enhance the passivation effect by way of illumination so that a saturated passivation value can be reached under illumination within a short period of time. In addition, further disclosed is a film-coated silicon substrate and solar cell containing the surface dielectric passive film and a preparation method thereof.

Description

Medium passivation film and solar cell and preparation method thereof

Technical field

The present invention relates to the field of solar cell materials, and in particular to a silicon nitride dielectric passivation film containing a doping element for a surface of a silicon-based material, and a silicon-based solar cell including a dielectric passivation film and a method of fabricating the same. Background technique

Semiconductor materials are the core materials for the preparation of photovoltaic solar cells. However, the surface of these semiconductor materials (for example, silicon) will have a certain number of surface recombination centers such as dangling bonds. These recombination centers will cause carriers to recombine on the semiconductor surface, reducing The lifetime of the carrier ultimately limits the efficiency of the solar cell. For this reason, people have reduced the number of surface dangling bonds by growing a passivation film on the surface of the silicon material, and reduced the surface sub-composite, thereby achieving surface passivation. This passivation method by reducing the dangling bonds on the surface of the semiconductor material is commonly referred to as chemical passivation. The passivation film usually contains a large amount of fixed charges, which form an electrostatic field at the interface between the film and the silicon, reducing or increasing the surface minority concentration, depending on the electrical properties of the charge and the conductivity type of the substrate, such as the minority of p-type silicon. For electrons, when the passivation film has a negatively charged fixed charge, the recombination of the minority at the interface is inhibited. The way in which the passivation effect is enhanced by establishing an electric field at the surface of the semiconductor is called field effect passivation. A good passivation film generally has both chemical passivation and field effect passivation.

With the development of high-efficiency battery structures such as PERL and HIT, which are constantly creating battery efficiency records, double-sided passivation has received more and more attention. The backside of existing crystalline silicon (polycrystalline and single crystal) cells are all A1 electrodes. A1 forms a high doping on the back surface, thereby forming high and low sections, and has a certain electric field passivation effect. However, the backside structure of the structure is substantially free of any chemical passivation effect, and the overall passivation effect is low. Many dielectric films can passivate the unsaturated dangling bonds of the silicon wafer well, so that the battery effect is greatly improved, such as A1 ₂ 0 ₃ , Si _x N _y , a-Si, Si0 ₂ , Ti0 ₂ and the like. Among them, silicon nitride film has been widely used in passivation of crystalline silicon solar cells due to its good optical matching and passivation properties. However, when SiNx grown by PECVD is used for back-passivation of a p-type battery, an inversion layer is formed on the back side of the battery, causing parasitic shunting, resulting in deterioration of battery type performance. To this end, the industry generally uses the ALD method to grow a very thin layer of A1 ₂ 0 ₃ between SiNx and silicon wafers. The A1 ₂ 0 ₃ brings good chemical passivation effect. However, the ALD equipment suitable for industrial production is very expensive, nearly 30 million yuan/set, which greatly hinders the application and popularization of the technology in solar cells.

In addition, crystalline silicon solar cells generally produce photo-induced attenuation under illumination, while crystalline silicon cells with A1 ₂ 0 ₃ as a passivation layer produce photo-enhancement under illumination, but effective minority lifetimes from annealing The value of the increase to the saturation value takes a long time and is placed in the dark, and this passivation enhancement effect is restored to the state before the illumination. 24 hours a day, according to the 12 hours of light in a day, the A1 ₂ 0 ₃ applied to the silicon solar cell can't be upgraded to one-tenth of the saturated passivation value to decay to the state before the light. It does not play its practical role in the application of conventional solar devices, and its production cost is high. If the film's electrical properties and power are controllable without increasing or increasing the lower cost, it has good field effect passivation; it has excellent anti-reflection and passivation properties, and can be under illumination. It can enhance the passivation effect and can be upgraded to saturation passivation value under short-time illumination. This will effectively increase the actual power generation of solar cells, which will surely become a major technological breakthrough in the field of crystalline silicon solar energy. Further promotion of the battery. The passivation film of the present invention was developed based on such a consideration. Summary of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon nitride dielectric passivation film having element doping on a silicon-based material, and a silicon-based solar cell containing the dielectric passivation film and a method of fabricating the same.

A first aspect of the present invention provides a surface dielectric passivation film suitable for a silicon-based material, the surface dielectric passivation film comprising a silicon nitride dielectric passivation film on a surface of a silicon-based material, and the nitriding The passivation film of the silicon medium contains a doping element selected from the group consisting of: a passivation film of a silicon nitride dielectric film exhibiting a negatively charged doping element, and a passivation film of the silicon nitride dielectric being positively charged. Sex doping element, or a combination thereof;

The doping element that renders the silicon nitride dielectric passivation film negatively elective is selected from the group consisting of: phosphorus, arsenic, antimony or a combination thereof; and the passivation film of the silicon nitride dielectric exhibits a positively doping The element is selected from the group consisting of: boron, aluminum, gallium, indium, antimony, zinc, or a combination thereof. In another preferred embodiment, the doping element is present in a passivating effective amount.

In another preferred embodiment, a non-silicon nitride dielectric passivation film or an additional silicon nitride dielectric passivation film is further disposed over the silicon nitride dielectric passivation film (the side away from the silicon substrate). In another preferred embodiment, the silicon nitride dielectric passivation film (on the side close to the silicon substrate) further has a non-silicon nitride dielectric passivation film or an additional silicon nitride dielectric passivation film. And the non-silicon nitride dielectric passivation film does not change the field passivation effect of the silicon nitride dielectric passivation film on the silicon-based material. In another preferred embodiment, the non-silicon nitride dielectric passivation film is a dielectric passivation film containing a component selected from the group consisting of: Si0 ₂ , Ti0 ₂ , A1 ₂ 0 ₃ , a-Si, ITO, c-Si Or a combination thereof.

In another preferred embodiment, the non-silicon nitride dielectric film further comprises:

The doping element that renders the silicon nitride dielectric passivation film negatively charged; and/or

The passivation film of the silicon nitride dielectric is rendered positively doped.

In another preferred embodiment, the doping element causes the silicon nitride dielectric passivation film to exhibit a negative charge, and the total content of the doping element is

0.01-50%, preferably 1-30%, more preferably 2-20%, based on the total atomic number of the film layer in which the doping element is located in the passivation film of the silicon nitride dielectric.

In another preferred embodiment, the doping element causes the silicon nitride dielectric passivation film to exhibit positive polarity, and the total content of the doping element is 0.01-50%, more preferably 1-30%, more preferably The ground is 2-20%, based on the total atomic number of the film layer in which the doping element is located in the passivation film of the silicon nitride medium.

In another preferred embodiment, the total electrical property of the silicon nitride dielectric passivation film is positively charged, and the silicon-based material is n-type or P-type, preferably n-type; or

The total electrical property of the silicon nitride dielectric passivation film is negatively charged, and the silicon-based material is P-type or n-type, preferably P-type. In another preferred embodiment, the silicon nitride dielectric passivation film is formed by chemical vapor deposition or physical vapor deposition. In another preferred embodiment, the non-silicon nitride dielectric passivation film is formed by another method of chemical vapor deposition or physical vapor deposition, and the chemical vapor deposition method comprises: PECVD, APCVD, LPCVD , ALD, etc.

In another preferred embodiment, the physical vapor deposition method includes: sputtering, evaporation, and the like.

In another preferred embodiment, the silicon nitride dielectric passivation film is formed by plasma enhanced chemical vapor deposition. In another preferred embodiment, the silicon nitride in the passivation film of the silicon nitride dielectric is mainly prepared by a plasma enhanced chemical vapor deposition (PECVD) growth apparatus compatible with existing conventional silicon-based solar cell devices.

In another preferred embodiment, the surface of the silicon-based material has a single layer film or a multilayer composite film, and at least one film is the passivation film of the silicon nitride dielectric, and the single layer or layers The total electrical properties of the composite membrane are either negative or positive.

In another preferred embodiment, the total electrical properties of the single or multi-layer composite film are positively charged above the surface of the n-type silicon-based material. In another preferred embodiment, the total electrical properties of the layer or multilayer composite film are negatively charged above the surface of the p-type silicon-based material.

In another preferred embodiment, the multilayer composite film comprises:

(a) one or more passivation layers of silicon nitride dielectric; and/or

(b) one or more non-silicon nitride dielectric passivation film layers selected from the group consisting of SiO ₂ , Ti _{2 2} , A _{1 2} 0 ₃ , a-Si, ITO, c-Si, or a combination thereof.

Wherein each film layer in (b) optionally contains:

In another preferred embodiment, the doping element which renders the silicon nitride dielectric passivation film negatively elective is selected from the group consisting of phosphorus, arsenic, antimony or a combination thereof;

In another preferred embodiment, the doping element that renders the silicon nitride dielectric passivation film positively electrified is selected from the group consisting of boron, aluminum, gallium, indium, antimony, zinc, or a combination thereof.

In another preferred embodiment, the constitution of each of the film layers in (a) is the same or different.

In another preferred embodiment, the constitution of each of the film layers in (b) is the same or different.

In another preferred embodiment, each of the film layers in (b) is on the silicon nitride dielectric passivation film (away from the side of the silicon-based material) or below (on the side close to the silicon-based material).

In another preferred embodiment, there is also one or more features selected from the group consisting of:

The total thickness of the surface dielectric passivation film described in (a) is from 1 to 300 nm; (preferably from 10 to 100 nm)

(b) after the annealing treatment of the silicon nitride dielectric passivation film, the passivation performance is enhanced under illumination;

5-2; Preferably, the amount is 0. 3-2, preferably 0. 5-2;

(d) the silicon-based material has a thickness of from 1 to 1000 μm, preferably from 20 to 280 μm;

(e) the silicon-based material comprises polycrystalline silicon or single crystal silicon;

(f) the reflectivity of the silicon-based material having the surface dielectric passivation film is reduced by 0.1% to 10% compared to the control material, the control material It is a silicon-based control material using a conventional single-layer silicon nitride film (undoped) as a passivation layer.

In another preferred embodiment, the silicon nitride dielectric passivation film has the following illumination enhancement passivation effect:

(1) τ ι / τ ₀ > 1.05, preferably > 3, more preferably >7;

Where τ i is the minority carrier lifetime of the silicon-based material having the passivation film of the silicon nitride dielectric under steady state under illumination; and τ. For the control material, the minority life of the steady state is reached under illumination;

(2) η ι- η ₀ >0.05%, preferably >0.3%, more preferably >0.5%;

Wherein n i is the photoelectric conversion efficiency of the silicon-based material having the passivation film of the silicon nitride medium under steady state under illumination; and 3⁄4 is the photoelectric conversion efficiency of the control material under steady state under illumination;

Wherein, the control material is a silicon-based control material using a conventional single-layer silicon nitride dielectric film (undoped) as a passivation layer. A second aspect of the invention provides a coated silicon substrate, the coated silicon substrate comprising:

(a) a silicon-based material;

(b) a surface dielectric passivation film according to the first aspect of the surface of the silicon-based material.

In another preferred embodiment, the silicon-based material is a silicon-based material having a surface without a film layer or a silicon-based material having a dielectric passivation film on the surface, and the dielectric passivation film may be a non-silicon nitride dielectric passivation film. A silicon nitride dielectric passivation film containing a doping element, or a composite film thereof.

In another preferred embodiment, the silicon-based material comprises a silicon substrate, a silicon substrate. A third aspect of the invention provides a method for preparing a silicon-based material surface dielectric passivation film, the method comprising:

(a) providing a silicon-based material;

(b) performing a chemical vapor deposition reaction in the presence of the first gas, the second gas, and the third gas to form a passivation film of a silicon nitride dielectric over the surface of the silicon-based material, thereby producing the first aspect Surface dielectric passivation film or coated silicon substrate having the surface dielectric passivation film;

Wherein the first gas is a silicon germanium or a silicon germanium gas;

The second gas is ammonia or nitrogen;

The third gas is a gas containing a doping element, and the third gas is selected from the group consisting of: phosphine, arsine, hydrogen halide, hydrogen halide, phosphorus trifluoride, phosphorus pentafluoride, boron lanthanum , boron trifluoride, trimethyl aluminum (TMA), trimethyl gallium (TMG), trimethyl indium (TMI), diethyl zinc (DeZn), etc. or a combination thereof.

In another preferred embodiment, the non-silicon nitride dielectric passivation film in the surface dielectric passivation film is prepared by a chemical or physical vapor deposition method.

In another preferred embodiment, the method further comprises the steps of: depositing one or more silicon nitride dielectric passivation film layers and/or non-silicon nitride dielectric blunt on the surface of the silicon-based material prepared in the previous step. Film layer.

In another preferred embodiment, the flow volume ratio of the first gas to the third gas is 100: 0.01 to 200, preferably 100: 1-90. In another preferred embodiment, the first gas and the second gas have a flow volume ratio of 1: 1 to 12, preferably 1: 2 to 7. In another preferred embodiment, in the PECVD reaction, the deposition temperature is 150 to 500 °C.

In another preferred embodiment, the method further comprises the step of: annealing the sample (coated silicon substrate) after forming the passivation film of the silicon nitride dielectric.

In another preferred embodiment, the apparatus used for the annealing treatment is a conventional annealing furnace or a rapid thermal annealing furnace.

In another preferred embodiment, the step of annealing is carried out in an atmosphere containing air or a protective gas.

In another preferred embodiment, the annealing treatment is carried out at 150 to 1000 °C.

In another preferred embodiment, the annealing treatment is carried out for 0.5 to 120 minutes. A fourth aspect of the invention provides a solar cell comprising the surface dielectric passivation film of the first aspect or the coated silicon substrate of the second aspect. It is to be understood that within the scope of the invention, the various technical features of the invention described above and the technical features specifically described hereinafter (as in the embodiments) may be combined with each other to form a new or preferred embodiment. Due to space limitations, we will not repeat them here. DRAWINGS

1 is a schematic view showing the field passivation effect of a passivation film of a silicon nitride dielectric with a fixed positive charge on a surface of an n-type silicon substrate;

2 is a schematic view showing the field passivation effect of a passivation film of a silicon nitride dielectric with a fixed negative charge on a p-type silicon substrate;

Figure 3 is a graph showing the change of the minority carrier lifetime in the process of the first embodiment;

4 is a comparison diagram of CV test results before and after illumination of the MIS device in Embodiment 1;

5 is a comparison diagram of CV test results before and after illumination of the MIS device in Embodiment 2;

Figure 6 is a graph showing changes in the lifetime of minority carriers in the process of Example 2;

Figure 7 is a graph showing the change in lifetime of the minority carrier in the process of Example 3 over time. detailed description

The inventors have invented a silicon nitride dielectric passivation film for the surface of a silicon-based material after extensive and intensive research. The silicon nitride dielectric passivation film is doped with one or more doping elements such that the silicon nitride dielectric passivation film has a negative (or positive) electrical property. For example, after the phosphorus element is doped into the passivation film of the silicon nitride dielectric, the dielectric passivation film is negatively charged, and the dielectric passivation film is positively charged after the boron element is doped into the passivation film of the silicon nitride dielectric. The negatively charged silicon nitride dielectric passivation film is used on the P-type silicon-based material, or the positively-charged silicon nitride dielectric passivation film is used on the n-type silicon-based material to not only maintain the original solar cell. Excellent anti-reflection and passivation, and can make the passivation effect of the silicon nitride dielectric passivation film on p-type and n-type silicon substrates enhance under illumination and reach under short-time illumination. Saturated passivation value. The present invention has been completed on this basis.

As used herein, "chemical passivation" means that during the deposition process, the reaction gas can release atomic hydrogen, or other chemical bonds, which saturate the dangling bonds in the silicon wafer, deactivate the defects, and achieve surface passivation and bulk passivation. purpose.

As used herein, "electrically passivated" refers to a dielectric passivation film having a negative (or positive) electrical property on the surface of a silicon wafer. These charges accumulate on the contact surface of the silicon wafer and the dielectric passivation film, creating a barrier on the surface of the silicon wafer, so that minority carriers (hereinafter referred to as "small children" are not easily transported to the surface for recombination, also known as field blunt Chemical.

As used herein, "silicon substrate", "wafer" are used interchangeably and refer to the substrate material used to prepare the solar cell of the present invention.

As used herein, the silicon-based material "refers to a silicon-based material that is in direct contact with a dielectric film (rather than a solar cell host substrate). As used herein, "silicon nitride dielectric passivation film" refers to silicon nitride. A dielectric passivation film that is the main component.

As used herein, "non-silicon nitride dielectric passivation film" means a dielectric passivation film containing a component selected from the group consisting of, but not limited to, Si0 ₂ , Ti0 ₂ , A1 ₂ 0 ₃ , a-Si, ITO, c-Si.

As used herein, "passivation film", "dielectric passivation film" are used interchangeably and refer to a film used to passivate a silicon substrate. Passivation film

The silicon nitride dielectric passivation film of the present invention is mainly a dielectric passivation film made of negative (or positive) electric silicon nitride doped with one or more elements, wherein the silicon nitride medium is blunt The negatively charged elements of the film include, but are not limited to, phosphorus, arsenic, antimony, or a combination thereof, preferably phosphorus. The positively charged elements of the passivation film of the silicon nitride dielectric include, but are not limited to, boron, aluminum, gallium, indium, antimony, zinc, or a combination thereof. Preferred is: boron.

The coated silicon substrate of the present invention has a single layer film or a multilayer composite film, and the number of film layers of the multilayer composite film is preferably 1-5 layers.

When it is a single layer film, the passivation film is a silicon nitride dielectric passivation film; when the passivation film is a multilayer composite film, the composite film includes at least one layer of the element doped silicon nitride medium according to the present invention. A passivation film, such as one or more layers of a silicon nitride dielectric passivation film, which may also include one or more layers of non-silicon nitride dielectric passivation films of other compositions, such as Si0 ₂ , Ti0 ₂ , A1 ₂ 0 ₃ , a-Si, ITO, c-Si and other film layers.

The composition of each of the silicon nitride dielectric passivation film layer or the non-silicon nitride dielectric passivation film layer may be the same or different, that is, the content of doping elements in each passivation film layer of the silicon nitride dielectric may be the same or different, silicon nitride The dielectric passivation film layer may be doped with an element which makes the silicon nitride dielectric passivation film be negatively charged or an element which makes the silicon nitride dielectric passivation film be positively charged, or may be doped by mixing two elements. miscellaneous. 5-2。 More preferably, the x/y value is preferably 0.3-3, more preferably 0. 5-2. The Si/N value of the silicon nitride dielectric passivation film may be the same or different. The content of the components in each of the non-silicon nitride dielectric passivation film layers may be the same or different.

It should be understood that each non-silicon nitride dielectric passivation film layer may also include a doping element that renders the silicon nitride dielectric passivation film negatively charged and/or renders the silicon nitride dielectric passivation film positively charged. Doping element.

The order between the layers can be randomly combined, but it must be ensured that the net charge in all layers is not equal to zero, that is, while the total layer is negative (or positive), the negative (or positive) Sexually has an electrical passivation effect on the surface of the silicon wafer. Optionally having a non-silicon nitride dielectric passivation film between the surface of the silicon substrate and the passivation film of the silicon nitride dielectric, and a passivation film of the non-silicon nitride dielectric on the surface of the passivation film of the silicon nitride dielectric Or a silicon nitride dielectric passivation film.

The superimposed combination structure of each film layer includes, but is not limited to, the following examples:

(1) One or more layers of silicon nitride dielectric passivation film are directly attached to the surface of the silicon substrate, and then adhered to the surface of the passivation film of the silicon nitride dielectric. One or more layers of other non-silicon nitride dielectric passivation film.

(2) A non-silicon nitride dielectric passivation film with one or more layers of other components directly attached to the surface of the silicon substrate, and one or more layers of silicon nitride adhered to the surface of the non-silicon nitride dielectric passivation film of other components. Dielectric passivation film.

(3) A silicon nitride dielectric passivation film is directly adhered to the surface of the silicon substrate, and a non-silicon nitride dielectric passivation film of other composition is adhered on the surface of the passivation film of the silicon nitride dielectric, and then A passivation film of a silicon nitride dielectric is adhered to the surface of the non-silicon nitride dielectric passivation film, and thus alternately stacked.

If the multilayer composite film is a silicon nitride dielectric passivation film directly in contact with the silicon substrate, the multilayer composite film also has a good chemical passivation effect; if the multilayer composite film is passivated by a non-silicon nitride medium The film is directly in contact with the silicon substrate, and the chemical passivation effect is directly related to the chemical properties of the non-silicon nitride dielectric passivation film layer. A non-silicon nitride dielectric passivation film layer having excellent chemical passivation effect includes: Si0 ₂ , A1 ₂ 0 ₃ , a-Si, and the like.

The thickness of each film layer may be the same or different, and the total film thickness is between 1 and 300 nm, preferably 10 to 100 nm. When the total thickness of the passivation film is less than 1 nm, high passivation effect may not be exhibited. When the total thickness of the passivation film is above 300 nm, the preparation cost may be too high.

The usual passivation of silicon nitride film is mainly determined by chemical passivation, and since it is positively charged, it has a certain electrical effect. However, since the silicon nitride film has a large fixed positive charge, it is generally considered to be unsuitable as a passivation film corresponding to the p-type silicon substrate, and the p-region in the n-type or p-type silicon substrate.

In the present invention, a conventional silicon nitride passivation film is reinforced by doping a certain amount of doping elements in a conventional silicon nitride passivation film to make the silicon nitride passivation film negative (or positive). Electrical passivation so that a silicon nitride film, which is usually mainly chemically passivated, can be used as a passivation film for a p-type silicon substrate, and a p-region in an n-type or p-type silicon substrate, and also has Light enhances the passivation effect. For example, a negatively-charged silicon nitride passivation film on the surface of a p-type silicon substrate (incorporating a certain amount of phosphorus), or a positively-charged silicon nitride passivation film on the surface of the n-type silicon substrate ( The incorporation of a certain amount of boron element can make the silicon nitride as a passivation layer also enhance the passivation of p-type and n-type silicon.

Controlling the p-type of the p-type silicon substrate, and the p-region in the n-type or p-type silicon substrate, and the electronegativity of the surface of the n-type silicon substrate by controlling the content of the doping element in the passivation film (eg, increasing the p-type) The negative charge of the surface of the silicon substrate or the positive charge of the surface of the n-type silicon substrate), thereby repelling minority carriers to the surface to aggregate, reducing surface recombination, thereby further enhancing surface passivation. The total content of the doping element is generally from 0.01 to 50%, more preferably from 1 to 30%, and most preferably from 2 to 20%, based on the total atomic number of the film layer in which the doping element is present in the passivation film of the silicon nitride dielectric.

It should be understood that when the doping element is a positively charged element, the silicon nitride dielectric passivation film of the present invention can be applied to an n-type or p-type silicon substrate by controlling the amount of the doping element; When it is a negatively charged element, the silicon nitride dielectric passivation film of the present invention can be applied to a p-type or n-type silicon substrate by controlling the amount of the doping element. Preferably, when the doping element is a positively charged element, the silicon substrate is n-type; when the doping element is a negatively charged element, and the silicon substrate is p-type.

The passivation film of the silicon nitride medium with element doping has the effect of light enhancement passivation under illumination, the surface recombination is related to the surface minority concentration, the lower the surface minority concentration, the smaller the surface recombination degree, and the better the passivation effect.

For n-type silicon semiconductors, minority carriers are holes (positively charged). As shown in Figure 1, there is boron doping on the surface. Element of the silicon nitride dielectric passivation film of the n-type silicon substrate, before the illumination, due to band bending, in the contact area between the silicon substrate and the passivation film layer with a fixed positive charge, the formation of holes by silicon The potential barrier of the substrate moving toward the interface hinders its movement toward the surface. After illumination, the amount of fixed positive charge in the passivation film layer is increased, and the hindrance effect is more obvious. The concentration of the minority particles accumulated on the surface of the silicon substrate is lower, and the surface recombination degree is smaller, thereby making the photo-enhanced surface blunt. The role of the role.

For p-type silicon, the minority carriers are electrons (negatively charged). As shown in FIG. 2, for a p-type silicon substrate having a silicon nitride dielectric passivation film doped with phosphorus on the surface, before the illumination, the band is bent, and the passive substrate is fixed on the silicon substrate and the negative charge. The contact area of the layer forms a barrier to the movement of electrons from the silicon substrate to the interface, preventing it from moving toward the surface. After illumination, the amount of negatively charged negative charge in the passivation film layer is increased, and the hindrance effect is more obvious. The concentration of the minority particles accumulated on the surface of the silicon substrate is lower, and the surface recombination degree is smaller, thereby making the photo-enhanced surface blunt. The role of the role. It can be seen from the figure that the passivation of the silicon nitride passivation layer also enhances the passivation of the n-type and p-type silicon substrates.

The silicon nitride dielectric passivation film of the invention has the following light enhancement passivation effect:

(1) τ ι / τ ₀ > 1.05, preferably > 3, more preferably >7;

(2) η ι- η ₀ >0.05%, preferably >0.3%, more preferably >0.5%;

Wherein, the control material is a silicon-based control material using a conventional single-layer silicon nitride dielectric film (undoped) as a passivation layer. The coated silicon substrate of the present invention has the following anti-reflection effect: a reduction of 0.1% to 10% compared to a conventional silicon-based control material in which a single-layer silicon nitride film (undoped) is used as a passivation layer. After the n-type and p-type silicon-based materials coated with the surface dielectric passivation film of the present invention are placed in the dark, the passivation effect is restored to the state before the light irradiation. The effective minority carrier lifetime of silicon wafers passivated by silicon nitride film takes less than one hour from the value after annealing to the saturation value (ie, the passivation saturation value), and does not currently contain any doping elements. Compared with the silicon nitride passivation film, the passivation effect is enhanced. Compared with the A1 ₂ 0 ₃ passivation film, the time to reach the saturation passivation value is significantly shortened, and the practical performance is stronger. Coated silicon substrate and method for manufacturing solar cell

The coated silicon substrate and solar cell of the present invention can be formed by conventional chemical vapor deposition (including PECVD, APCVP, LPCVD, ALD, etc.) or physical vapor deposition (including sputtering, evaporation, etc.). The deposition of silicon nitride in the surface dielectric passivation film can be carried out using a chemical vapor deposition growth apparatus compatible with conventional conventional silicon-based solar cell devices.

The invention is preferably prepared by plasma enhanced chemical vapor deposition (PECVD). A preferred method of preparation is: forming a dielectric passivation film on the surface of a silicon-based material by performing a PECVD reaction on a mixed gas containing a first gas, a second gas, and a third gas, wherein the first gas is silicon germanium (Si3⁄4) Or a silicon germanium (3⁄4⁄4) gas, the second gas is ammonia (NH ₃ ), the third gas is a gas containing a doping element, and the third gas includes but is not limited to: phosphine, arsine, helium Hydrogen, hydrogen, Phosphorus trifluoride, phosphorus pentafluoride, boron lanthanum, boron trifluoride, trimethyl aluminum (TMA), trimethyl gallium (TMG), trimethyl indium (TMI), diethyl zinc (DeZn), Or a combination of the above gases. Preferred are phosphine and boron lanthanum.

The thickness of the silicon substrate is preferably from 1 to 1000 μm, more preferably from 20 to 280 μm. Silicon substrates include, but are not limited to, polycrystalline silicon, monocrystalline.

The silicon nitride dielectric passivation film of the present invention may be attached to the front side and/or the back side of the solar cell silicon material of the present invention, and the silicon nitride dielectric passivation film is applicable to p-type and n-type solar cells. Herein, the surface of the silicon substrate on which the sunlight is incident on the solar light of the solar cell is referred to as a light receiving surface (ie, the front surface), and the surface opposite to the light receiving surface, that is, the surface of the silicon substrate on the non-sunlight incident side is referred to as a reverse side or a back surface. .

In a preferred method of preparation, when the silicon-based material in direct contact with the dielectric film is a p-type silicon substrate, the third gas includes, but is not limited to: phosphine, arsine, hydrogen halide, germanium Hydrogen, phosphorus trifluoride, phosphorus pentafluoride, etc.; preferably phosphine. When the silicon-based material is an n-type silicon substrate, the third gas includes but is not limited to: boron lanthanum, boron trifluoride, trimethyl aluminum (TMA), trimethyl gallium (TMG), trimethyl indium (TMI), diethylzinc (DeZn), preferably boron bismuth.

The flow volume ratio of silicon germanium or silicon germanium gas to ammonia gas is 1 : 1-12, preferably 1 : 2-7. 100: 0.01-200, preferably 100: 1-90, of a silicon germanium gas and a third gas such as phosphonium or boron germanium. By controlling the flow ratio of silicon germanium or silicon germanium gas and ammonia gas, and the flow volume ratio of silicon germanium or silicon germanium gas and third gas (such as phosphine or boron germanium), thereby controlling the content of doping elements, thereby achieving Control of the passivation effect.

In the present invention, it is preferred to subject the silicon substrate to an annealing treatment after forming the dielectric passivation film. The equipment used for the annealing treatment is a conventional annealing furnace or a rapid thermal annealing furnace. The annealing treatment in the present invention means heat treatment of a silicon substrate. This annealing treatment is preferably carried out in an atmosphere containing air or a protective gas. The annealing treatment preferably heats the silicon substrate at 150 to 1000 ° C, more preferably at 350 to 750 ° C. This is because when the annealing treatment is performed at a temperature of less than 150 ° C, the annealing effect may not be obtained; when the annealing treatment temperature exceeds 1000 ° C, the passivation film of the surface is destroyed (hydrogen detachment in the film), possibly Causes its characteristics to decline. In addition, the annealing treatment is preferably carried out for 0.5 to 120 minutes because the time is too short, and the annealing effect may not be obtained; if the time is too long, the passivation film of the surface is destroyed (hydrogen detachment in the film), which may cause a decrease in characteristics thereof. .

In addition, in the gas atmosphere at the time of performing the above-mentioned annealing treatment, the atmosphere of the protective gas is preferably used, and specific examples thereof include at least one selected from the group consisting of nitrogen gas and argon gas. The characteristics of the formed solar cell can be further improved by the above annealing treatment. Compared to the prior art, the present invention includes the following main advantages:

(1) The surface dielectric passivation film of the present invention has excellent passivation properties for solar cells;

(2) The coated silicon substrate and the solar cell of the present invention have a light-enhanced passivation effect;

(3) The coated silicon substrate and the solar cell of the present invention can reach the saturation passivation value in less than one hour under illumination, thereby improving the practicability of the passivation film of the silicon nitride medium;

(4) The coated silicon substrate and solar cell of the present invention have excellent antireflection properties;

(5) The solar cell efficiency of the present invention is improved. The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are merely illustrative of the invention and are not intended to limit the scope of the invention. The experimental methods in the following examples which do not specify the specific conditions are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described may be employed in the methods of the present invention. The preferred embodiments and materials described herein are for illustrative purposes only. The p-type and n-type polished single crystal silicon wafers used in the examples of the present invention were purchased from Hefei Kejing Material Technology Co., Ltd. The steps of cleaning, drying, etc. before use of the silicon wafer are carried out by a conventional method.

The coated silicon substrate and the preparation of the solar cell were all prepared by a known PECVD method. The equipment uses PECVD growth equipment compatible with existing conventional silicon-based solar cell equipment.

The annealing treatment is carried out using a conventional annealing furnace or a rapid thermal annealing furnace.

The minority life test method, namely the microwave photoconductive attenuation method, is tested in accordance with ASTM International Standard -1535.

The reflectance of the samples was measured using a HELIOS LAB-RE reflectance tester from AudioDev GmbH.

The CV (capacitor voltage) test of the sample was performed using Keithley's Keithley Model 4200-SCS Semiconductor Parameter Analyzer.

The battery conversion efficiency test was measured using the SoliA solar cell volt-ampere characteristic test system of Newport Oriel, USA. Example 1

(1) Preparing p-type polished single crystal silicon wafer samples A and B having an area of 125 X 125 mm ² and a thickness of about 200 μm, respectively, for cleaning and drying;

(2) A phosphorus-doped silicon nitride film with a thickness of about 70 nm is deposited on the surface of sample A by using a PECVD apparatus. The percentage of phosphorus atoms in the silicon nitride film is about 3%, and the deposition temperature is 250 ° C. The volumetric flow ratio to 33⁄4 is 5:100, the flow ratio of SiH^N3⁄4 is 1 : 2, and the reaction chamber pressure is 30Pa;

A non-phosphorus-doped silicon nitride film having a thickness of about 70 nm is deposited on the surface of the sample B at a deposition temperature of 250 ° C, a flow ratio of Si to N 3⁄4 of 1: 2, and a reaction chamber pressure of 30 Pa;

(3) Annealing the sample A at 420 ° C for 10 min in a nitrogen atmosphere to measure the life of the minority carrier;

(4) At room temperature, use a xenon lamp (0.5 suns) to irradiate the A sample with light, and perform the minority carrier life test every few minutes. After the sample has a small sub-life of saturation (refer to ASTM International Standard - 1535), the sample is taken again. Place it in the darkroom for a period of time and measure the life of the minority. The method is the same as above.

The sample was made into a MIS (Metal-Insulator-Semiconductor) device, and the samples before and after the illumination were subjected to CV test. The test results are shown in Fig. 4.

(5) The above two films are used for passivation of the front surface of the n-type solar cell. The relative change value of minority carrier lifetime during the whole process is shown in Figure 3. The values of each parameter are shown in Table 1.

Table 1

It can be seen from Fig. 3 and Table 1 that the annealed sample can rapidly rise to a saturation value after a short time (less than 60 min) illumination, unlike the photoinduced attenuation when an undoped silicon nitride passivation film is used ( LID) phenomenon. Compared with the A1 ₂ 0 ₃ passivated silicon wafer, the lifetime of the silicon wafer needs to be increased from the value after annealing to the saturation value of about 80 hours. The passivation film of the present invention shows better practical value. And the sample A has a significantly lower reflectance than the sample B (note: these are polished silicon wafers), while the battery efficiency after saturation is increased by 0.63%, thus indicating a phosphorus-doped silicon nitride medium. The passivation film has anti-reflection effect, which can effectively achieve lower surface reflection, so that more sunlight can enter the solar cell for photoelectric conversion.

After the first illumination, it rises to the saturated passivation value for a short time. After the dark room is left for a period of time, the second illumination is performed. After the dark room is left for a period of time, the third illumination is performed, and the sample A can be raised to a saturated blunt in a short time. The value shows that Sample A has better stability.

The CV test results in Figure 4 show that the flat-band voltage (the voltage applied to the device when the semiconductor surface band is flat) is positive, indicating that the prepared dielectric film is negatively charged; after illumination, the flat-band voltage value is positive. Shift, indicating that the fixed negative charge of the film increases after illumination, indicating that the increase in the lifetime of the sample is mainly due to the enhancement of surface field effect passivation. Example 2:

(1) Prepare n-type polished single crystal silicon wafer samples C and D with an area of 125 X 125 mm ² and a thickness of about 200 μm, respectively, for cleaning and drying;

(2) A boron-doped silicon nitride film with a thickness of about 90 nm is deposited on the surface of the sample C by a PECVD apparatus. The percentage of boron atoms in the silicon nitride film is about 10%, and the deposition temperature is 320 ° C, 8 ₂ The volumetric flow ratio to 513⁄4 is 20:100, the ratio of flow to 51 is 1:3, and the pressure in the reaction chamber is 50 Pa. A layer of boron-doped silicon nitride film with a thickness of about 90 nm is deposited on the surface of sample D. The temperature is 320 ° C, the flow ratio of 51 to 1: 3, the reaction chamber pressure is 50 Pa;

(3) Annealing the C sample at 350 ° C for 25 min in a nitrogen atmosphere to measure the life of the minority carrier;

(4) At room temperature, the C sample is irradiated with a xenon lamp (0.5 suns), and the minority carrier life test is performed every 1 to 10 minutes. After the sample has a small sub-lifetime to reach a saturation value, the sample is placed in the dark room for a period of time, and the measurement is performed. The life of the youngest. The sample was made into a MIS (Metal-Insulator-Semiconductor) device, and the samples before and after the illumination were subjected to CV test, and the test results are shown in Fig. 5.

(5) The above two films are used for passivation of the front surface of a p-type solar cell. The relative change in minority lifetime over the course of the process is shown in Figure 6. The values of each parameter are shown in Table 2.

Table 2

It can be seen from Fig. 6 and Table 2 that the annealed sample C can rapidly rise to a saturation value after a short time (less than 60 min) illumination, unlike the photoinduced attenuation when an undoped silicon nitride passivation film is used ( LID) phenomenon. Compared with the A1 ₂ 0 ₃ passivated silicon wafer, the lifetime of the silicon wafer needs to be increased from the value after annealing to the saturation value of about 80 hours. The passivation film of the present invention shows better practical value. And the sample C has a significantly lower reflectance than the sample D, and the battery efficiency after saturation is increased by 0.29%, thus indicating that the boron-doped silicon nitride dielectric passivation film has an anti-reflection effect. Effectively achieve lower surface reflections, allowing more sunlight to enter the solar cell for photoelectric conversion.

After the first illumination, it rises to the saturated passivation value for a short time. After the dark room is left for a period of time, the second illumination is performed. After the dark room is left for a period of time, the third illumination is performed, and the sample C can be raised to a saturated blunt in a short time. The value of the sample shows that the sample C has better stability.

The CV test results in Figure 5 show that the flat-band voltage is negative, indicating that the prepared dielectric film is positively charged; after illumination, the flat-band voltage value is negatively shifted, indicating that the fixed negative charge of the film increases after illumination, indicating the sample The increase in lifetime of the minority is mainly due to the enhancement of surface field effect passivation. Example 3:

(1) Preparing n-type polished single crystal silicon wafer samples E and F with an area of 125 X 125 mm ² and a thickness of about 200 μm, respectively, for cleaning and drying;

(2) is deposited by a PECVD apparatus in a thickness of about lOnm E SiO ₂ layer surface of the sample, and then grown to a thickness of 65nm boron-doped silicon nitride film, a silicon nitride film in a percentage of about 12% boron atom The deposition temperature is 300 ° C, the volume flow ratio of B3⁄4 to SiH ₄ is 15 : 100, the flow ratio of 33⁄4 to ₃ is 2: 3, the pressure in the reaction chamber is 40 Pa; and the thickness of the surface of sample F is about 10 nm. SiOJl, a 65nm thick boron-doped silicon nitride film is deposited at a deposition temperature of 300 ° C, a volume flow ratio of B ₂ ft to Si 3⁄4 is 15 : 100, and a reaction chamber pressure of 40 Pa;

(3) Annealing the E sample at 320 ° C for 20 min in a nitrogen atmosphere to measure the lifetime of the sample; (4) At room temperature, the E sample is irradiated with a xenon lamp (0.5 suns), and the minority carrier life is taken every 1 to 10 minutes. After the sample has reached the saturation value, the sample is placed in the dark room for a period of time to measure the minority carrier lifetime. .

(4) The above two films are used for passivation of the front surface of a p-type solar cell.

The relative change in minority lifetime over the course of the process is shown in Figure 7. The values of each parameter are shown in Table 3.

table 3

It can be seen from Fig. 7 and Table 3 that the annealed sample can rapidly rise to a saturation value after a short time (less than 60 min) illumination, unlike the photoinduced attenuation when an undoped silicon nitride passivation film is used ( LID) phenomenon. Compared with the A1 ₂ 0 ₃ passivated silicon wafer, the lifetime of the silicon wafer needs to be increased from the value after annealing to the saturation value of about 80 hours. The passivation film of the present invention shows better practical value. And the sample E has a significantly lower reflectance than the sample F, and the battery efficiency after saturation under illumination is increased by 0.41%, thus indicating multilayer passivation of a boron-doped silicon nitride dielectric passivation film. The film has anti-reflection effect, which can effectively achieve lower surface reflection, enabling more sunlight to enter the solar cell for photoelectric conversion.

After the first illumination, it rises to the saturated passivation value for a short time. After the dark room is left for a period of time, the second illumination is performed. After the dark chamber is left for a period of time, the third illumination is performed. The sample E can be raised to a saturated blunt in a short time. The value of the sample E shows that the sample E has better stability. Example 4

(1) Preparing p-type polished single crystal silicon wafer samples G and H having an area of 125 X 125 mm ² and a thickness of about 200 μm, respectively, for cleaning and drying;

(2) A phosphorus-doped silicon nitride film with a thickness of about 50 nm is deposited on the surface of the sample G by a PECVD apparatus. The percentage of phosphorus atoms in the silicon nitride film is about 5%, and the deposition temperature is 300 ° C. The volumetric flow ratio to 51 is 10:100, the flow ratio of Si to N3⁄4 is 2:3, and the pressure in the reaction chamber is 30Pa;

An aluminum oxide film having a thickness of about 35 nm is deposited on the surface of the sample H by an ALD apparatus;

(3) The sample G is annealed at 300 ° C for 10 min in a nitrogen atmosphere to measure the life of the minority carrier;

(4) At room temperature, the G and H samples were irradiated with a xenon lamp (0.5 suns), and the minority carrier lifetime test was performed every few minutes. After the sample lifetime of the sample reached a saturation value (refer to ASTM International Standard-1535), The sample was placed in a dark room for a period of time, and the life of the minority was measured. The method is the same as above, and the test results are shown in Table 4.

(5) Both films were used for passivation of the back surface of a p-type solar cell. Table 4

It can be seen from Table 4 that the annealed sample G can quickly rise to a saturation value after a short time (less than 60 min) illumination, and the sample H takes a longer time to reach saturation (greater than 60 min). Moreover, the efficiency of the sample G and the sample H is higher than that of the non-passivation film on the back side, and the degree of improvement is basically the same, indicating that the phosphorus-doped silicon nitride can passivate the p-type silicon surface well, which is almost identical to that of the aluminum oxide. effect. All of the documents mentioned in the present application are hereby incorporated by reference in their entirety as if they are individually incorporated by reference. In addition, it is to be understood that various modifications and changes may be made by those skilled in the art in the form of the appended claims.

Claims

Claim

A surface dielectric passivation film suitable for a silicon-based material, characterized in that the surface dielectric passivation film comprises a silicon nitride dielectric passivation film on a surface of a silicon-based material, and the silicon nitride The dielectric passivation film contains a doping element selected from the group consisting of: a silicon nitride dielectric passivation film exhibiting a negatively charged doping element, and a silicon nitride dielectric passivation film exhibiting positive electrical properties. Doping element, or a combination thereof;

The doping element that renders the silicon nitride dielectric passivation film negatively elective is selected from the group consisting of: phosphorus, arsenic, antimony or a combination thereof; and the passivation film of the silicon nitride dielectric exhibits a positively doping The element is selected from the group consisting of: boron, aluminum, gallium, indium, antimony, zinc or a combination thereof.

2. The surface dielectric passivation film according to claim 1, wherein the doping element causes the silicon nitride dielectric passivation film to exhibit a negative charge, and the total content of the doping element is 0.01-50%. Preferably, it is 1-30%, more preferably 2-20%, based on the total atomic number of the film layer in which the doping element is present in the passivation film of the silicon nitride medium; or

The doping element causes the silicon nitride dielectric passivation film to exhibit positive polarity, and the total content of the doping element is 0.01-50%, more preferably 1-30%, more preferably 2-20%, The total atomic number of the film layer in which the doping element is located in the passivation film of the silicon nitride dielectric.

3. The surface dielectric passivation film according to claim 1, wherein the total electrical property of the silicon nitride dielectric passivation film is positive, and the silicon-based material is n-type or p-type. , preferably n type; or

The total electrical property of the silicon nitride dielectric passivation film is negatively charged, and the silicon-based material is P-type or n-type, preferably P-type.

The surface dielectric passivation film according to claim 1, wherein the silicon nitride dielectric passivation film is formed by a chemical vapor deposition method or a physical vapor deposition method.

The surface dielectric passivation film according to claim 1, wherein the silicon nitride dielectric passivation film is formed by plasma enhanced chemical vapor deposition.

6. The surface dielectric passivation film according to claim 5, wherein the silicon nitride dielectric passivation film is prepared by using a plasma enhanced chemical vapor deposition growth apparatus.

7. The surface dielectric passivation film according to claim 1, wherein the surface of the silicon-based material has a single layer film or a multilayer composite film, and at least one film is the silicon nitride. The dielectric passivation film, while the total electrical property of the single or multi-layer composite film is negative or positive.

8. The surface dielectric passivation film according to claim 7, wherein the multilayer composite film comprises:

(a) one or more passivation layers of silicon nitride dielectric; and/or

(b) one or more non-silicon nitride dielectric passivation film layers selected from the group consisting of SiO ₂ , Ti _{2 2} , Al ₂ O ₃ , a-Si, ITO, c-Si, or combinations thereof,

Wherein each film layer in (b) optionally contains:

9. The surface dielectric passivation film of claim 1 further comprising one or more features selected from the group consisting of:

The total thickness of the surface dielectric passivation film of (a) is 1 to 300 nm;

(3) The silicon nitride dielectric passivation film in the SLNJ mo layer x / y is 0. 3-3;

(d) the silicon-based material has a thickness of 1-1000 microns;

(f) The reflectivity of the silicon-based material having the surface dielectric passivation film is reduced by 0.1% to 10% compared to the control material, and the comparative material is a conventional single-layer silicon nitride film (undoped) as a passivation layer Silicon based control material.

10. A coated silicon substrate, characterized in that the coated silicon substrate comprises:

(a) a silicon-based material;

(b) A surface dielectric passivation film according to any one of claims 1 to 9 located on the surface of the silicon-based material.

11. A method of preparing a silicon-based material surface dielectric passivation film, the method comprising:

(a) providing a silicon-based material;

(b) performing a chemical vapor deposition reaction in the presence of the first gas, the second gas, and the third gas, forming a silicon nitride dielectric passivation film over the surface of the silicon-based material, thereby producing the method of claim 1. Surface dielectric passivation film or coated silicon substrate having the surface dielectric passivation film;

Wherein the first gas is a silicon germanium or a silicon germanium gas;

The second gas is ammonia or nitrogen;

The third gas is a gas containing a doping element, and the third gas is selected from the group consisting of: phosphine, arsine, hydrogen halide, hydrogen halide, phosphorus trifluoride, phosphorus pentafluoride, boron lanthanum , boron trifluoride, trimethyl aluminum (TMA), trimethyl gallium (TMG), trimethyl indium (TMI), diethyl zinc (DeZn) or a combination thereof.

A solar cell characterized by comprising the surface dielectric passivation film according to any one of claims 1 to 9 or the coated silicon substrate according to claim 10.