WO2022134992A1 - Solar cell, production method therefor and photovoltaic module - Google Patents

Abstract

Provided are a solar cell, a production method therefor and a photovoltaic module, relating to the technical field of solar photovoltaics. The solar cell comprises: a silicon substrate, a titanium nitride layer, a low-work-function metal layer and a metal electrode layer. The titanium nitride layer is arranged on one side of the silicon substrate, the low-work-function metal layer is arranged on the side of the titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the side of the low-work-function metal layer away from the titanium nitride layer, wherein the activity of low-work-function metal contained in the low-work-function metal layer is higher than the that of metal titanium. In the present disclosure, if the titanium nitride layer, which acts as a carrier selection transport layer, is oxidized to generate a titanium oxide layer, then the low-work-function metal layer can reduce the titanium oxide layer, thereby improving the conductivity of the titanium nitride layer, such that the electron transport efficiency is improved, the barrier height between the metal electrode and the titanium nitride layer is reduced, so that the contact resistance of the solar cell can be reduced and the efficiency of the solar cell can be improved.

Description

Solar cell and production method, photovoltaic module

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is required to be submitted to the China Patent Office on December 23, 2020, with the application number of 202011548705.9, titled "Solar Cells and Production Methods, and Photovoltaic Modules"; and submitted to the China Patent Office on December 24, 2020, with the application number of 202011556800.3 , the priority of the Chinese patent application entitled "Solar Cell and Production Method, Photovoltaic Module", the entire content of which is incorporated herein by reference.

technical field

The present disclosure relates to the technical field of solar photovoltaics, and in particular, to a solar cell, a production method, and a photovoltaic assembly.

Background technique

With the continuous consumption of traditional energy and its negative impact on the environment, the development and utilization of solar energy, as a pollution-free and renewable energy source, has developed rapidly.

A distinguishing feature of solar cells is their ability to direct light-generated electrons and holes into asymmetrically conductive paths, that is, to separate charge carriers and then collect them through the positive and negative electrodes, thereby outputting electrical energy. Conventional crystalline silicon solar cells are doped near the surface of the silicon substrate to obtain electron selective contact and hole selective contact to achieve carrier separation. However, due to the doping technology, heavy doping is bound to occur. It affects the performance of the cell. At the same time, the high temperature process of the doping technology will introduce more impurities and affect the lifetime of minority carriers, resulting in lower efficiency of the solar cell. Therefore, the electron selectivity can be arranged on one side of the silicon substrate Or a hole-selective titanium nitride layer acts as a carrier-selective layer to collect electrons or holes in the silicon substrate, thereby separating the carriers in the silicon substrate, without doping the silicon substrate. Hole-selective contact and electron-selective contact for separation of charge carriers.

However, in the current solution, the titanium nitride layer, which is the carrier selection layer, is oxidized to form a titanium oxide layer. Due to the poor conductivity of the titanium oxide layer, the electron transport efficiency is poor, and the metal electrode and the titanium oxide layer have poor electron transport efficiency. The height of the potential barrier between them is high, thereby increasing the contact resistance of the solar cell and reducing the efficiency of the solar cell.

In addition to this, a remarkable feature of solar cells is their ability to direct light-generated electrons and holes into asymmetrically conductive paths, that is, to separate charge carriers and then collect them through the positive and negative electrodes, thereby outputting electrical energy. Conventional crystalline silicon solar cells are doped near the surface of the silicon substrate to obtain electron selective contact and hole selective contact to achieve carrier separation. However, due to the doping technology, heavy doping is bound to occur. affect battery performance. Since titanium nitride is a metalloid material, its high electrical conductivity and low contact resistivity make it a material that facilitates carrier transport and collection. In addition, titanium nitride itself can passivate the silicon substrate surface to The surface recombination of carriers is inhibited, and the deposition rate of titanium nitride is relatively fast. Therefore, a titanium nitride layer with electron selectivity or hole selectivity can be arranged on one side of the silicon substrate as a carrier selection layer. The electrons or holes in the silicon substrate are collected, thereby separating charge carriers in the silicon substrate without doping the silicon substrate.

However, in the current scheme, the work function of titanium nitride prepared by conventional methods is large, and the electron transport efficiency is poor, which is not suitable for extracting and collecting electron carriers, resulting in low efficiency of solar cells. .

Overview

The present disclosure provides a solar cell, a production method, and a photovoltaic module, aiming at solving the problem that a titanium nitride layer serving as a carrier selection layer in a solar cell is oxidized to generate a titanium oxide layer, resulting in high contact resistance of the solar cell, and solar cells The problem of low battery efficiency.

In a first aspect, embodiments of the present disclosure provide a solar cell, the solar cell comprising:

Silicon substrate, titanium nitride layer, low work function metal layer and metal electrode layer;

The titanium nitride layer is arranged on one side of the silicon substrate, the low work function metal layer is arranged on the side of the titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the low work function a side of the metal layer away from the titanium nitride layer;

Wherein, the low work function metal contained in the low work function metal layer has higher activity than metal titanium.

Optionally, the low work function metal includes: any one of calcium, magnesium, aluminum, barium, cesium, strontium, ytterbium, cerium, samarium, europium, neodymium, thorium, gadolinium, hafnium, lutetium and lanthanum.

Optionally, the solar cell further comprises: a titanium oxide layer and a silicon oxide layer;

The silicon oxide layer is arranged between the silicon substrate and the titanium nitride layer, and the titanium oxide layer is arranged between the titanium nitride layer and the low work function metal layer;

Wherein, the titanium oxide layer and the silicon oxide layer are formed in the process of oxidizing the titanium nitride layer.

Optionally, the solar cell further comprises: a silicide layer;

the silicide layer is disposed between the silicon substrate and the titanium nitride layer;

The silicide layer includes any one of cobalt disilicide, platinum silicide and titanium disilicide.

Optionally, the silicon substrate is an n-type silicon substrate.

Optionally, the metal electrode layer comprises: any one of aluminum, aluminum/silver, nickel/copper, nickel/copper/tin, chromium/palladium/silver and nickel/copper/silver.

Optionally, the thickness of the titanium nitride layer is less than 20 nanometers.

In a second aspect, embodiments of the present disclosure provide a method for producing a solar cell, the method comprising:

A titanium nitride layer is prepared on one side of the silicon substrate;

preparing a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate;

preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer;

Wherein, the low work function metal contained in the low work function metal layer has higher activity than metal titanium.

Optionally, after the step of preparing the titanium nitride layer on one side of the silicon substrate, the method further includes:

The titanium nitride layer is oxidized to form a silicon oxide layer between the titanium nitride layer and the silicon substrate, and a titanium oxide layer is formed on the side of the titanium nitride layer away from the silicon substrate.

Optionally, before the step of preparing the titanium nitride layer on one side of the silicon substrate, the method further includes:

preparing a metal layer on one side of the silicon substrate;

annealing the metal layer, and the metal layer reacts with the silicon substrate to form a silicide layer;

Wherein, the metal layer includes any one of cobalt, platinum and titanium.

Optionally, the oxidation treatment includes any one of dry oxidation, wet oxidation and plasma oxidation.

Optionally, when the oxidation treatment is dry oxidation, the heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidation atmosphere of the oxidation treatment includes nitrogen and oxygen;

When the oxidation treatment is wet oxidation, the heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidation atmosphere of the oxidation treatment includes nitrogen and water;

When the oxidation treatment is plasma oxidation, the heat treatment temperature of the oxidation treatment is 25-300 degrees Celsius.

In a third aspect, an embodiment of the present disclosure provides a photovoltaic assembly, wherein the photovoltaic assembly includes any one of the aforementioned solar cells.

Based on the above solar cell, production method, and photovoltaic assembly, the present disclosure has the following beneficial effects: the solar cell in the present disclosure includes: a silicon substrate, a titanium nitride layer, a low work function metal layer and a metal electrode layer; the titanium nitride layer is disposed on the silicon On one side of the substrate, the low work function metal layer is arranged on the side of the titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the side of the low work function metal layer away from the titanium nitride layer; The work function metal is more active than the titanium metal. In the present disclosure, since a low work function metal layer is provided on the side of the titanium nitride layer away from the silicon substrate, and the low work function metal contained in the low work function metal layer is more active than the metal titanium, if it is used as a carrier The titanium nitride layer of the selective transport layer is oxidized to form a titanium oxide layer, and the low work function metal layer can reduce the titanium oxide layer, thereby improving the conductivity of the titanium nitride layer, improving the electron transfer efficiency, and reducing the metal electrode and the metal electrode. The potential barrier height between the titanium nitride layers can reduce the contact resistance of the solar cell and improve the efficiency of the solar cell.

The present disclosure also provides a solar cell, a production method, and a photovoltaic module, aiming to solve the problem of low efficiency of the solar cell due to the large work function of the titanium nitride when titanium nitride is used as the carrier selection layer. .

In a fourth aspect, embodiments of the present disclosure provide a solar cell, the solar cell comprising:

Silicon substrate, doped titanium nitride layer, low work function metal layer and metal electrode layer;

The doped titanium nitride layer is arranged on one side of the silicon substrate, the low work function metal layer is arranged on the side of the doped titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the side of the silicon substrate. a side of the low work function metal layer away from the doped titanium nitride layer;

The low work function metal contained in the low work function metal layer is more active than the metal titanium;

Wherein, the low work function metal is contained in the doped titanium nitride layer, and the low work function metal contained in the doped titanium nitride layer is in the process of annealing the low work function metal layer , formed by diffusion into the low work function metal layer.

Optionally, between the silicon substrate and the doped titanium nitride layer further comprises: a first oxide layer and a second oxide layer;

The first oxide layer is arranged on one side of the silicon substrate, and the second oxide layer is arranged on the side of the first oxide layer away from the silicon substrate;

wherein the low work function metal is more active than the metal contained in the first oxide layer;

The second oxide layer is a metal oxide layer generated by the low work function metal in the low work function metal layer passing through the doped titanium nitride layer and reacting with the first oxide layer.

Optionally, the first oxide layer includes: any one of magnesium oxide, aluminum oxide, hafnium oxide, titanium oxide, niobium oxide, tantalum oxide, gallium oxide, zinc oxide and cesium oxide.

Optionally, the concentration of the low work function metal in the doped titanium nitride layer gradually decreases from the side close to the low work function metal layer to the side close to the silicon substrate.

Optionally, the solar cell further comprises: a first titanium nitride layer;

The first titanium nitride layer is disposed between the low work function metal layer and the metal electrode layer.

Optionally, the thickness of the doped titanium nitride layer is 1-10 nanometers, and the thickness of the first titanium nitride layer is 5-500 nanometers.

Optionally, the low work function metal includes: any one of calcium, magnesium, aluminum, barium, cesium, strontium, ytterbium, cerium, samarium, europium, neodymium, thorium, gadolinium, hafnium, lutetium and lanthanum.

Optionally, the metal electrode layer includes any one of aluminum, silver, aluminum/silver, nickel/copper/tin, chromium/palladium/silver, and nickel/copper/silver.

Optionally, the thickness of the low work function metal layer is 0.1-10 nanometers.

In a fifth aspect, embodiments of the present disclosure provide a method for producing a solar cell, the method comprising:

A titanium nitride layer is prepared on one side of the silicon substrate;

preparing a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate;

preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer;

The low work function metal layer is annealed, and the low work function metal in the low work function metal layer diffuses into the titanium nitride layer to form a doped titanium nitride layer.

Optionally, the step of preparing the titanium nitride layer on one side of the silicon substrate specifically includes:

preparing a first oxide layer on one side of the silicon substrate;

preparing the titanium nitride layer on the side of the first oxide layer away from the silicon substrate;

The step of performing annealing treatment on the low work function metal layer and diffusing the low work function metal in the low work function metal layer into the titanium nitride layer to form a doped titanium nitride layer specifically includes:

The low work function metal layer is annealed, the low work function metal in the low work function metal layer diffuses into the titanium nitride layer to form the doped titanium nitride layer, and the low work function metal layer is diffused into the titanium nitride layer. The low work function metal in the functional metal layer passes through the doped titanium nitride layer and reacts with the first oxide layer to form a second oxide layer.

Optionally, the step of the annealing treatment includes:

The annealing is carried out in a mixed gas of nitrogen and hydrogen in a temperature range of 350-450 degrees Celsius, and the ratio of nitrogen and hydrogen in the mixed gas is 10:1.

Optionally, after the step of annealing in a mixed gas of nitrogen and hydrogen within a temperature range of 350-450 degrees Celsius, the method further includes:

The secondary annealing is carried out in a nitrogen annealing atmosphere in the temperature range of 400-700 degrees Celsius.

Optionally, the step of preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer specifically includes:

preparing a first titanium nitride layer on the side of the low work function metal layer away from the titanium nitride layer;

The metal electrode layer is prepared on the side of the first titanium nitride layer away from the low work function metal layer.

Optionally, the first oxide layer includes: any one of magnesium oxide, aluminum oxide, hafnium oxide, titanium oxide, niobium oxide, tantalum oxide, gallium oxide, zinc oxide and cesium oxide.

In a sixth aspect, an embodiment of the present disclosure provides a photovoltaic assembly, wherein the photovoltaic assembly includes any one of the aforementioned solar cells.

Based on the above solar cell, production method, and photovoltaic assembly, the present disclosure has the following beneficial effects: the solar cell in the present disclosure includes: a silicon substrate, a doped titanium nitride layer, a low work function metal layer and a metal electrode layer; The layer is arranged on one side of the silicon substrate, the low work function metal layer is arranged on the side of the doped titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the side of the low work function metal layer away from the doped titanium nitride layer; The low work function metal contained in the metal layer is higher than the activity of metal titanium; wherein, the low work function metal is contained in the doped titanium nitride layer, and the low work function metal contained in the doped titanium nitride layer is in the low work function. During the annealing process of the metal layer, it is formed by diffusion from the low work function metal layer. In the present disclosure, since the low work function metal layer can be diffused during the annealing process, a doped titanium nitride layer doped with the low work function metal in the low work function metal layer is generated, so that the doped titanium nitride layer is The work function is reduced, which promotes electron transport, thereby improving the efficiency of solar cells.

Brief Description of Drawings

In order to illustrate the technical solutions of the embodiments of the present disclosure more clearly, the following briefly introduces the drawings that are used in the description of the embodiments of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure. , for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative labor.

FIG. 1 shows a schematic structural diagram of a first solar cell in an embodiment of the present disclosure;

FIG. 2 shows a schematic structural diagram of a second type of solar cell in an embodiment of the present disclosure;

FIG. 3 shows a schematic structural diagram of a third solar cell in an embodiment of the present disclosure;

FIG. 4 shows a flow chart of steps of a method for producing a solar cell in an embodiment of the present disclosure;

Description of drawing numbers:

10-silicon substrate, 20-titanium nitride layer, 30-low work function metal layer, 40-metal electrode layer, 50-silicon oxide layer, 60-titanium oxide layer, 70-silicide layer;

FIG. 5 shows a schematic structural diagram of a first solar cell in an embodiment of the present disclosure;

FIG. 6 shows a schematic structural diagram of a second type of solar cell in an embodiment of the present disclosure;

FIG. 7 shows a schematic structural diagram of a third solar cell in an embodiment of the present disclosure;

FIG. 8 shows a flow chart of steps of a method for producing a solar cell in an embodiment of the present disclosure;

Description of drawing numbers:

110-silicon substrate, 120-doped titanium nitride layer, 130-low work function metal layer, 140-metal electrode layer, 150-first oxide layer, 160-second oxide layer, 170-first titanium nitride layer .

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, but not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

A solar cell, a production method, and a photovoltaic photovoltaic assembly provided by the present disclosure will be described in detail below by listing several specific embodiments.

FIG. 1 shows a schematic structural diagram of a first solar cell provided by an embodiment of the present disclosure. Referring to FIG. 1 , the solar cell may include: a silicon substrate 10 , a titanium nitride layer 20 , a low work function metal layer 30 and a metal electrode layer 40 .

The titanium nitride layer 20 is disposed on one side of the silicon substrate 10 , the low work function metal layer 30 is disposed on the side of the titanium nitride layer 20 away from the silicon substrate 10 , and the metal electrode layer 40 is disposed on the low work function metal layer 30 away from the nitride One side of the titanium layer 20, and the low work function metal contained in the low work function metal layer 30 is more active than the metal titanium.

In the embodiment of the present disclosure, the silicon substrate may be an n-type silicon substrate, that is, the doping type of the silicon substrate is n-type doping, and the corresponding dopants may include phosphorus (P), arsenic ( Any one or more of As), bismuth element (Bi) and antimony element (Sb), the doping concentration is 5×10 ¹⁴ -1×10 ¹⁶ cm ^-3 , and the n-type silicon substrate has higher contamination The resistance of the contaminants on the lifetime can be reduced, resulting in a higher lifetime, and since the n-type silicon substrate has no boron-oxygen defects, performance degradation can be avoided. The lightly doped silicon substrate can reduce the Auger recombination and band gap narrowing effects caused by doping, improve the lifetime and carrier diffusion length of minority carriers, and improve the current density of solar cells, so that higher conversion efficiency. The silicon substrate may also be a p-type silicon substrate, that is, the doping type of the silicon substrate is p-type doping, and the corresponding dopants may include boron (B), aluminum (Al), gallium in group III elements. Any one or more of element (Ga) and indium element (In).

In the embodiments of the present disclosure, the above-mentioned titanium nitride layer may be disposed on the backlight surface of the silicon substrate, or may be disposed on the light-facing surface of the silicon substrate. The titanium nitride layer may have hole selectivity or electron selectivity, and thus can be used as a A hole-selective transport layer or an electron-selective transport layer to collect holes or electrons in a silicon substrate to separate carriers in a silicon substrate, which can be formed without heavily doping the silicon substrate for carrier separation hole-selective contact or electron-selective contact. At the same time, by oxidizing the titanium nitride layer, a silicon oxide layer with tunneling passivation can be formed at the interface between the titanium nitride layer and the silicon substrate, and titanium oxide can be formed on the side of the titanium nitride layer away from the silicon substrate. Floor. The silicon oxide layer can passivate the surface defects, so that there is no need to grow the silicon oxide layer separately to improve the defects of the insufficient passivation ability of the titanium nitride layer. The titanium oxide layer can enhance the surface passivation effect, and the titanium nitride layer also has excellent passivation. In conclusion, in the embodiments of the present disclosure, the passivation effect of the surface can be greatly enhanced by one oxidation treatment, which has the advantage of a simple process. In addition, since the process conditions corresponding to different types of titanium nitride layers are different, titanium nitride layers with different work functions and different types can be prepared by adjusting the process conditions.

In the embodiment of the present disclosure, the above-mentioned low work function metal layer is disposed on the side of the titanium nitride layer away from the silicon substrate. If a titanium oxide layer is formed on the surface of the titanium nitride layer, the titanium oxide layer is located between the low work function metal layer and the nitrided surface. Between the titanium layers, since the low work function metal layer contains low work function metal, and the low work function metal is more active than the metal titanium, therefore, the low work function metal layer containing the low work function metal can reduce the titanium oxide layer, avoiding Due to the poor conductivity of the titanium oxide generated by oxidation on the surface of the titanium nitride, the contact resistance increases, thereby improving the conductivity of the titanium nitride layer, improving the electron transfer efficiency and reducing the metal electrode and the nitride. The height of the potential barrier between the titanium layers can reduce the contact resistance of the solar cell and improve the efficiency of the solar cell.

It should be noted that, if the silicon substrate is an n-type silicon substrate, the work function of the low work function metal in the low work function metal layer may be lower than that of aluminum (4.28 eV).

In the embodiment of the present disclosure, the above-mentioned metal electrode layer is used for collecting and exporting carriers. When exposed to light, the silicon substrate acts as a light absorbing layer to generate electron-hole pairs. Due to the selective transport of minority carriers by the titanium nitride layer and the low work function metal layer, the minority carriers are transported to the low work function. The functional metal layer is then extracted by the metal electrode layer connected to it, so as to realize the separation of carriers, so that a potential difference is generated between the metal electrode layer and the silicon substrate, that is, a voltage is generated, thereby converting light energy into electrical energy.

In an embodiment of the present disclosure, a solar cell includes: a silicon substrate, a titanium nitride layer, a low work function metal layer and a metal electrode layer; the titanium nitride layer is disposed on one side of the silicon substrate, and the low work function metal layer is disposed on one side of the silicon substrate. The titanium nitride layer is on the side away from the silicon substrate, and the metal electrode layer is arranged on the side of the low work function metal layer away from the titanium nitride layer; wherein, the low work function metal contained in the low work function metal layer is more active than the metal titanium. In the present disclosure, since a low work function metal layer is provided on the side of the titanium nitride layer away from the silicon substrate, and the low work function metal contained in the low work function metal layer is more active than the metal titanium, if it is used as a carrier The titanium nitride layer of the selective transport layer is oxidized to form a titanium oxide layer, and the low work function metal layer can reduce the titanium oxide layer, thereby improving the conductivity of the titanium nitride layer, improving the electron transfer efficiency, and reducing the metal electrode and the metal electrode. The potential barrier height between the titanium nitride layers can reduce the contact resistance of the solar cell and improve the efficiency of the solar cell.

Optionally, the above-mentioned low work function metals include: any one of calcium, magnesium, aluminum, barium, cesium, strontium, ytterbium, cerium, samarium, europium, neodymium, thorium, gadolinium, hafnium, lutetium and lanthanum, that is, low work function metals. The metal activity order of the work function metal is before the metal titanium, and the low work function metal is higher than the metal titanium activity. At the same time, the stronger the activity of the low work function metal, the greater the reduction degree of titanium oxide. Increasing its conductivity to improve electron transport through this layer, improving band alignment with the surface of the silicon substrate, lowering the barrier height of the metal/titania layer, overcoming the limitations of typical n-type silicon substrate-metal contact, enabling Undoped ohmic contacts on lightly doped n-type silicon substrates.

Optionally, FIG. 2 shows a schematic structural diagram of a second type of solar cell provided by an embodiment of the present disclosure. Referring to FIG. 2 , the solar cell may further include: a titanium oxide layer 60 and a silicon oxide layer 50 , and the silicon oxide layer 50 is disposed on the Between the silicon substrate 10 and the titanium nitride layer 20, the titanium oxide layer 60 is disposed between the titanium nitride layer 20 and the low work function metal layer 30, wherein the titanium oxide layer 60 and the silicon oxide layer 50 are opposite to the titanium nitride layer 30. The layer 20 is formed during the oxidation treatment.

Specifically, after the titanium nitride layer is prepared on one side of the silicon substrate, a silicon oxide layer with tunneling passivation can be formed at the interface between the titanium nitride layer and the silicon substrate by performing an oxidation treatment on the titanium nitride layer. , and a titanium oxide layer is formed on the side of the titanium nitride layer away from the silicon substrate. Since the silicon oxide layer can passivate the surface defects, there is no need to grow the silicon oxide layer separately to improve the defects of the insufficient passivation ability of the titanium nitride layer, the titanium oxide layer can enhance the surface passivation effect, and the titanium nitride layer also has excellent In summary, the passivation performance of the surface can be greatly enhanced by one oxidation treatment, which has the advantage of a simple process.

Optionally, FIG. 3 shows a schematic structural diagram of a third solar cell provided by an embodiment of the present disclosure. Referring to FIG. 3 , the solar cell may further include: a silicide layer 70 , and the silicide layer 70 is disposed on the silicon substrate 10 Between the titanium nitride layer 20 and the titanium nitride layer 20, the contact resistance can be further reduced and the efficiency of the solar cell can be improved.

The silicide layer may include any one of cobalt disilicide, platinum silicide and titanium disilicide.

Optionally, the above-mentioned silicon substrate may be an n-type silicon substrate. Since the n-type silicon substrate has a higher resistance to contaminants, the influence of contaminants on the lifespan can be reduced, thereby having a higher lifespan. The silicon substrate has no boron-oxygen defects, thus avoiding performance degradation.

Optionally, the above-mentioned metal electrode layer may include any one of aluminum, aluminum/silver, nickel/copper, nickel/copper/tin, chromium/palladium/silver, and nickel/copper/silver.

Optionally, the thickness of the titanium nitride layer may be less than 20 nanometers, preferably less than 15 nanometers, such as 8 nanometers, and the thickness of the titanium oxide layer formed on the surface of the titanium nitride layer may be less than the thickness of the titanium nitride layer.

The present disclosure also provides a method for producing a solar cell. Referring to FIG. 4 , it shows a flow chart of the steps of the method for producing a solar cell provided by an embodiment of the present disclosure. The method may include the following steps:

In step 101, a titanium nitride layer is prepared on one side of the silicon substrate.

In this step, a silicon substrate can be obtained first, and then a titanium nitride layer is prepared on one side of the silicon substrate.

In the embodiment of the present disclosure, the silicon substrate may be an n-type silicon substrate, and the silicon substrate may be a silicon wafer after surface de-damage, polishing, or texturing and diffusion.

Specifically, the titanium nitride layer can be deposited by means of thermal atomic deposition or plasma-assisted or enhanced atomic deposition, and the titanium nitride layer can be an electron selective transport layer or a hole selective transport layer.

Optionally, before depositing the titanium nitride layer, a metal layer may be deposited on the surface of the silicon substrate, and the metal layer may be annealed, so that the metal layer reacts with the silicon substrate to form a silicide layer, thereby forming a silicide layer between the silicon substrate and the titanium nitride layer. A silicide layer is prepared between the layers.

Wherein, the metal layer may include any one of cobalt, platinum and titanium, and correspondingly, the silicide layer may include any one of cobalt disilicide, platinum silicide and titanium disilicide.

Optionally, after the titanium nitride layer is prepared, the titanium nitride layer can be oxidized, so as to form an ultra-thin silicon oxide layer between the titanium nitride layer and the silicon substrate, on the side of the titanium oxide layer away from the silicon substrate A titanium oxide layer is formed.

It should be noted that, if a silicide layer needs to be formed between the titanium nitride layer and the silicon substrate, after the metal layer is deposited on the surface of the silicon substrate, the titanium nitride layer can be deposited on the side of the metal layer away from the silicon substrate, and the In one oxidation treatment, the metal in the metal layer reacts with the silicon substrate to form a silicide layer, and at the same time, an ultra-thin silicon oxide layer and a titanium oxide layer are formed.

Optionally, the above oxidation treatment may include any one of dry oxidation, wet oxidation and plasma oxidation.

Optionally, in the case that the above-mentioned oxidation treatment is dry oxidation, the heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidizing atmosphere of the oxidation treatment includes nitrogen and oxygen; in the case that the above-mentioned oxidation treatment is wet oxidation, the oxidation treatment The heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidation environment of the oxidation treatment includes nitrogen and water; in the case that the above oxidation treatment is plasma oxidation, the heat treatment temperature of the oxidation treatment is 25-300 degrees Celsius, and the plasma oxidation can use an inductor Coupled plasma (Inductively Coupled Plasma, ICP) reactor or microwave plasma oxidizer to complete.

Step 102 , preparing a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate.

In this step, after the titanium nitride layer is prepared on one side of the silicon substrate, a low work function metal layer can be further prepared on the side of the titanium nitride layer away from the silicon substrate.

The activity of the low work function metal contained in the low work function metal layer is higher than that of titanium metal.

Step 103 , preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer.

In this step, after the low work function metal layer is prepared, a metal electrode layer may be further prepared on the side of the low work function metal layer away from the titanium nitride layer.

In the embodiments of the present disclosure, the metal electrodes may be fabricated by various known methods, and may not require a high-temperature sintering process to reduce thermal budget and adverse effects on battery performance, for example, by screen printing, printing, laser The metal electrode layer is formed by transfer of low temperature paste or electron beam evaporation, thermal evaporation and electroplating.

A solar cell, a production method, and a photovoltaic photovoltaic assembly provided by the present disclosure will be described in detail below by listing several specific embodiments.

FIG. 5 shows a schematic structural diagram of a first solar cell provided by an embodiment of the present disclosure. Referring to FIG. 5 , the solar cell may include: a silicon substrate 110 , a doped titanium nitride layer 120 , a low work function metal layer 130 and a metal electrode Layer 140.

The doped titanium nitride layer 120 is disposed on one side of the silicon substrate 110, the low work function metal layer 30 is disposed on the side of the doped titanium nitride layer 120 away from the silicon substrate 110, and the metal electrode layer 40 is disposed on the low work function metal layer 130 is away from the side of the doped titanium nitride layer 120, and the low work function metal layer 30 contains a low work function metal which is more active than metal titanium.

Specifically, the doped titanium nitride layer 120 contains a low work function metal, and the low work function metal contained in the doped titanium nitride layer 120 is annealed from the low work function metal layer 130 during the annealing process. The work function metal layer 130 is diffused into the formed.

In the embodiment of the present disclosure, the doping type of the silicon substrate may be n-type doping or p-type doping. When the doping type of the silicon substrate is n-type doping, the corresponding dopant may include V Any one or more of phosphorus (P), arsenic (As), bismuth (Bi) and antimony (Sb) among the group elements; when the doping type of the silicon substrate is P-type doping, The corresponding dopant may include any one or more of boron element (B), aluminum element (Al), gallium element (Ga), and indium element (In) among the group III elements.

Wherein, the doped titanium nitride layer disposed on the silicon substrate may be disposed on the backlight surface of the silicon substrate, or may be disposed on the light-directing surface of the silicon substrate. Since titanium nitride is a metalloid material, its high electrical conductivity and low contact resistivity make it a material that facilitates carrier transport and collection. In addition, titanium nitride itself can passivate the silicon substrate surface to The surface recombination of carriers is inhibited, and the deposition rate of titanium nitride is relatively fast. Therefore, a titanium nitride layer with electron selectivity or hole selectivity can be arranged on one side of the silicon substrate as a carrier selection layer. The electrons or holes in the silicon substrate are collected, thereby separating charge carriers in the silicon substrate without doping the silicon substrate. However, the work function of titanium nitride prepared by conventional methods is large, which makes the electron transport efficiency of titanium nitride poor, and is not suitable for extracting and collecting electron carriers, resulting in low efficiency of solar cells.

Therefore, in the embodiments of the present disclosure, the titanium nitride layer disposed on the surface of the silicon substrate can be prepared as a doped titanium nitride layer, that is, the titanium nitride layer is disposed on the surface of the titanium nitride layer far from the silicon substrate. The work function metal layer, and the low work function metal layer contained in the low work function metal layer is more active than the metal titanium, so that in the process of annealing the low work function metal layer, the low work function metal layer in the low work function metal layer has a low work function metal layer. Diffusion into the titanium nitride layer to form a doped titanium nitride layer, so that the work function of the doped titanium nitride layer is reduced, electron transport is promoted, and the efficiency of the solar cell is improved.

Specifically, the doping level of the low work function metal in the doped titanium nitride layer depends on the work function and diffusivity of the low work function metal in the low work function metal layer, as well as the thickness and annealing conditions of the titanium nitride layer, nitrogen The thicker the thickness of the titanium oxide layer, the more hindered the diffusion of the low work function metal, and the worse the doping effect. Therefore, it is possible to select the low work function metal with high diffusion ability, that is, the active low work function metal, and reduce the titanium nitride. The thickness of the layer, the adjustment of annealing conditions, etc., can improve the doping level of the low work function metal in the doped titanium nitride layer.

It should be noted that the work function of the low work function metal in the low work function metal layer may be lower than that of aluminum (4.28 eV) to improve the selective transport of electron carriers.

In the embodiment of the present disclosure, the above-mentioned metal electrode layer is used for collecting and exporting carriers. When exposed to light, the silicon substrate acts as a light absorbing layer to generate electron-hole pairs. Since the doped titanium nitride layer and the low work function metal layer have good carrier selection and transport, the carriers are transported to The low work function metal layer is then extracted by the metal electrode layer connected to it, so as to realize the separation of carriers, so that a potential difference is generated between the metal electrode layer and the silicon substrate, that is, a voltage is generated, thereby converting light energy into electrical energy.

In an embodiment of the present disclosure, a solar cell includes: a silicon substrate, a doped titanium nitride layer, a low work function metal layer and a metal electrode layer; the doped titanium nitride layer is disposed on one side of the silicon substrate, and the low work function The metal layer is arranged on the side of the doped titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the side of the low work function metal layer away from the doped titanium nitride layer; the low work function metal layer contains a lower work function metal than the metal layer. The activity of titanium; wherein, the doped titanium nitride layer contains low work function metal, and the low work function metal contained in the doped titanium nitride layer is in the process of annealing the low work function metal layer. Formed by diffusion into the work function metal layer. In the present disclosure, since the low work function metal layer can be diffused during the annealing process, a doped titanium nitride layer doped with the low work function metal in the low work function metal layer is generated, so that the doped titanium nitride layer is The work function is reduced, which promotes electron transport, thereby improving the efficiency of solar cells.

Optionally, FIG. 6 shows a schematic structural diagram of a second type of solar cell provided by an embodiment of the present disclosure. Referring to FIG. 6 , between the silicon substrate 110 and the doped titanium nitride layer 120 may further include: a first oxide layer 150 and the second oxide layer 160 , the first oxide layer 150 is disposed on one side of the silicon substrate 110 , and the second oxide layer 160 is disposed on the side of the first oxide layer 150 away from the silicon substrate 110 .

The activity of the low work function metal in the low work function metal layer 130 is higher than that of the metal contained in the first oxide layer 150 , and the second oxide layer 160 is doped by the low work function metal in the low work function metal layer 130 through doping. The titanium hetero nitride layer 120 is a metal oxide layer formed by reacting with the first oxide layer 150, that is, since the low work function metal in the low work function metal layer 130 is more active than the metal contained in the first oxide layer 150, then The low work function metal in the low work function metal layer 130 can diffuse through the doped titanium nitride layer 120, react with the first oxide layer 150 to form a second oxide layer 160, and the generated second oxide layer 160 can enhance the solar cell The surface passivation effect can be improved, and at the same time, the diffusion of the low work function metal in the low work function metal layer 130 in the doped titanium nitride layer 120 can be promoted.

Optionally, the first oxide layer may include: magnesium oxide (MgO _x ), aluminum oxide (Al ₂ O ₃ ), hafnium dioxide (HfO ₂ ), titanium oxide (TiO _x ), niobium oxide (NbO _x ) , any one of tantalum oxide (TaO _x ), gallium oxide (GaO _x ), zinc oxide (ZnO _x ) and cesium oxide (CsO _x ). Sure. The first oxide layer can act as an electron-selective contact to facilitate the selection and transport of electron carriers in the silicon substrate, wherein titanium dioxide (TiO ₂ ), zinc monoxide (ZnO), and tantalum oxide (TaO _x ) have smaller The conduction band difference and the large valence band difference provide obstacles for holes, and MgO _x and CsO _x can generate a dipole moment, which can reduce the work function of the electrode through the de-pinning of the Fermi level, thereby making the electron transport more efficient. The barrier height becomes smaller.

In addition, the first oxide layer may also include silicon dioxide (SiO ₂ ), and SiO ₂ may also react with the low work function metal passing through the doped titanium nitride layer to form the second oxide layer.

Optionally, the concentration of the low work function metal in the doped titanium nitride layer gradually decreases from the side close to the low work function metal layer to the side close to the silicon substrate.

Specifically, since the low work function metal in the doped titanium nitride layer is generated by the diffusion of the low work function metal in the low work function metal layer on the side of the doped titanium nitride layer away from the silicon substrate, the doping nitrogen The concentration of the low work function metal in the titanium oxide layer is distributed in a gradient from the direction away from the silicon substrate to the direction close to the silicon substrate, and the concentration of the low work function metal decreases gradually due to the increase of the diffusion distance of the low work function metal.

Optionally, FIG. 7 shows a schematic structural diagram of a third solar cell provided by an embodiment of the present disclosure. Referring to FIG. 7 , the solar cell may further include a first titanium nitride layer 170 , wherein the first titanium nitride layer is provided between the low work function metal layer 130 and the metal electrode layer 140 .

Since the titanium nitride layer is disposed on the side of the low work function metal layer 130 close to the silicon substrate 110, it is used to form the doped titanium nitride layer 120 between the silicon substrate 110 and the low work function metal layer 130, and the first titanium nitride layer is The layer 170 is disposed on the side of the low work function metal layer 130 away from the silicon substrate 110. Since the titanium nitride has metalloid conductivity, the first titanium nitride layer 170 can be directly used as the electrode layer of the solar cell to collect and export the For carriers, the metal electrode layer 140 is disposed on the side of the first titanium nitride layer 170 away from the low work function metal layer 130 , so as to prevent the first titanium nitride layer 170 from being oxidized in the air and avoid the degradation of the battery performance.

Optionally, the thickness of the doped titanium nitride layer can be 1-10 nanometers, that is, the thickness of the titanium nitride layer used to form the doped titanium nitride layer is also 1-10 nanometers, and the thickness of the titanium nitride layer is about 1-10 nanometers. The diffusion of low work function metal has an important influence. The thicker the thickness of the titanium nitride layer, the greater the hindrance to the diffusion of low work function metal elements, and the worse the doping effect. The doped nitride obtained after titanium nitride doping The decrease in the work function of titanium is not obvious, therefore, the improvement of electron transport cannot be promoted. The thickness of the first titanium nitride layer may be 5-500 nanometers, so that the thickness of the first titanium nitride layer is larger than that of the titanium nitride layer, which can be used as an electrode layer of a solar cell, and at the same time, a low work function is obtained The low work function metal in the metal layer is diffused and doped to the titanium nitride layer in the direction of the silicon substrate to form a doped titanium nitride layer without affecting the work function of the first titanium nitride layer. Therefore, the first titanium nitride layer The work function of is greater than that of the doped titanium nitride layer.

Optionally, the low work function metal includes: any one of calcium, magnesium, aluminum, barium, cesium, strontium, ytterbium, cerium, samarium, europium, neodymium, thorium, gadolinium, hafnium, lutetium and lanthanum. The activity of the functional metal is greater than that of the metal titanium, that is, the activity of the metal precedes the metal titanium, so that it can diffuse in the titanium nitride layer to form the doped titanium nitride layer. At the same time, if the low work function metal is required to react with the first oxide layer to form a second oxide layer, the activity sequence of the low work function metal is located before the metal element in the first oxide layer, and the activity of the low work function metal is stronger, and The greater the reaction degree of the first oxide layer is, the more significant the doping effect on the titanium nitride layer is.

Optionally, the metal electrode layer may include any one of aluminum, silver, aluminum/silver, nickel/copper/tin, chromium/palladium/silver, and nickel/copper/silver, and the arrangement of the metal electrode layer can be avoided on the one hand. The oxidation of the first titanium nitride in the air can avoid the deterioration of the battery performance. On the other hand, it can improve the energy band alignment on the surface of the crystalline silicon and reduce the resistance, thereby promoting the transmission and collection of electrons and improving the battery performance.

The present disclosure also provides a method for producing a solar cell, referring to FIG. 8 , which shows a flow chart of the steps of the method for producing a solar cell provided by an embodiment of the present disclosure, and the method may include the following steps:

In step 1101, a titanium nitride layer is prepared on one side of the silicon substrate.

In this step, a silicon substrate can be obtained first, and then a titanium nitride layer, that is, an undoped titanium nitride layer, is prepared on one side of the silicon substrate.

Specifically, a titanium nitride layer can be prepared on one side of the silicon substrate, so as to further prepare a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate, so that under the condition of annealing, the low work function metal layer in the low work function metal layer can be prepared. The low work function metal diffuses into the titanium nitride layer, thereby preparing a doped titanium nitride layer.

Optionally, before preparing the titanium nitride layer, a first oxide layer may be first prepared on one side of the silicon substrate, and a titanium nitride layer may be further prepared on the side of the first oxide layer away from the silicon substrate, so as to further prepare the titanium nitride layer on the side of the first oxide layer. A low work function metal layer is prepared on the side away from the silicon substrate, so that under the condition of annealing, the low work function metal in the low work function metal layer is diffused into the titanium nitride layer, thereby preparing a doped titanium nitride layer, and , after the low work function metal in the low work function metal layer passes through the doped titanium nitride layer, it can react with the first oxide layer to form a second oxide layer.

Step 1102 , preparing a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate.

In this step, after the titanium nitride layer is prepared on one side of the silicon substrate, a low work function metal layer may be further prepared on the side of the titanium nitride layer away from the silicon substrate.

Step 1103 , preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer.

In this step, after the low work function metal layer is prepared on the side of the titanium nitride layer away from the silicon substrate, a metal electrode layer may be prepared on the side away from the titanium nitride layer of the low work function metal layer.

Optionally, in the case where the solar cell further includes the first titanium nitride layer, after the low work function metal layer is prepared on the side of the titanium nitride layer far away from the silicon substrate, the low work function metal layer may be separated from the titanium nitride layer on the side of the low work function metal layer away from the titanium nitride layer. A first titanium nitride layer is first prepared on one side, and a metal electrode layer is further prepared on the side of the first titanium nitride layer away from the low work function metal layer, so that the first titanium nitride layer can be directly used as the electrode layer of the solar cell to collect And the carriers are derived, and the metal electrode layer is arranged on the side of the first titanium nitride layer away from the low work function metal layer, so that the oxidation of the first titanium nitride layer in the air can be prevented and the performance of the battery can be prevented from being degraded.

Step 1104 , annealing the low work function metal layer, and the low work function metal in the low work function metal layer diffuses into the titanium nitride layer to form a doped titanium nitride layer.

In this step, after the low work function metal layer or the metal electrode layer is prepared, the low work function metal layer may be annealed, so that the low work function metal in the low work function metal layer diffuses into the titanium nitride layer , thereby forming a doped titanium nitride layer.

In the embodiment of the present disclosure, if the first oxide layer is disposed between the silicon substrate and the titanium nitride to be doped, the annealing treatment of the low work function metal layer can also make the low work function metal layer in the low work function metal layer. After the metal passes through the doped titanium nitride layer, it reacts with the first oxide layer to form a second oxide layer.

Optionally, the above-mentioned annealing treatment for the low work function metal layer may include: in a temperature range of 350-450 degrees Celsius, annealing is performed in a mixed gas of nitrogen and hydrogen, and the ratio of nitrogen and hydrogen in the mixed gas is 10: 1.

Optionally, after the above-mentioned annealing treatment is performed on the low work function metal layer, secondary annealing may be further performed in a nitrogen annealing atmosphere within a temperature range of 400-700 degrees Celsius. The higher the annealing temperature, the greater the reduction in the work function of the titanium nitride layer, and the smaller the work function of the resulting doped titanium nitride layer. However, there is a critical value of the annealing temperature. If the annealing temperature is lower than the critical value, the work function of the doped titanium nitride layer will decrease with the increase of the annealing temperature. If the temperature is higher than the critical value, the work function of the titanium nitride layer will decrease. Not only will the function not decrease, but it will also increase to some extent. At the same time, if a first oxide layer is arranged between the silicon substrate and the titanium nitride to be doped, the thickness of the first oxide layer decreases with the increase of the annealing temperature. The metal oxide layer (ie, the second oxide layer), resulting in oxygen scavenging.

It should be noted that, the corresponding parts of the above-mentioned solar cell and the production method of the solar cell can be referred to, and have the same or similar beneficial effects.

In addition, an embodiment of the present disclosure also provides a photovoltaic assembly, including any one of the aforementioned solar cells, and both sides of the solar cell may be provided with an encapsulation film, a cover plate, a back plate, and the like. Has the same or similar beneficial effects as the aforementioned solar cells.

The embodiments of the present disclosure have been described above in conjunction with the accompanying drawings, but the present disclosure is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present disclosure, many forms can be made without departing from the scope of the present disclosure and the protection scope of the claims, which all fall within the protection of the present disclosure.

Claims (26)

1. A solar cell, characterized in that the solar cell comprises:

   Silicon substrate, titanium nitride layer, low work function metal layer and metal electrode layer;

   The titanium nitride layer is arranged on one side of the silicon substrate, the low work function metal layer is arranged on the side of the titanium nitride layer away from the silicon substrate, and the metal electrode layer is arranged on the low work function a side of the metal layer away from the titanium nitride layer;

   Wherein, the low work function metal contained in the low work function metal layer has higher activity than metal titanium.
2. The solar cell according to claim 1, wherein the solar cell further comprises: a titanium oxide layer and a silicon oxide layer;

   the silicon oxide layer is arranged between the silicon substrate and the titanium nitride layer, and the titanium oxide layer is arranged between the titanium nitride layer and the low work function metal layer;

   Wherein, the titanium oxide layer and the silicon oxide layer are formed in the process of oxidizing the titanium nitride layer.
3. The solar cell according to claim 1, wherein the solar cell further comprises: a silicide layer;

   the silicide layer is disposed between the silicon substrate and the titanium nitride layer;

   The silicide layer includes any one of cobalt disilicide, platinum silicide and titanium disilicide.
4. The solar cell according to claim 1, wherein the silicon substrate is an n-type silicon substrate.
5. The solar cell of claim 1, wherein the thickness of the titanium nitride layer is less than 20 nanometers.
6. The solar cell according to claim 1, wherein the titanium nitride layer is a doped titanium nitride layer, the doped titanium nitride layer comprises the low work function metal, and the doped titanium nitride layer comprises the low work function metal. The low work function metal contained in the titanium nitride layer is formed by diffusing into the low work function metal layer during the annealing process of the low work function metal layer.
7. The solar cell according to claim 6, wherein the silicon substrate and the doped titanium nitride layer further comprise: a first oxide layer and a second oxide layer;

   The first oxide layer is arranged on one side of the silicon substrate, and the second oxide layer is arranged on the side of the first oxide layer away from the silicon substrate;

   wherein the low work function metal is more active than the metal contained in the first oxide layer;

   The second oxide layer is a metal oxide layer formed by the low work function metal in the low work function metal layer passing through the doped titanium nitride layer and reacting with the first oxide layer.
8. The solar cell according to claim 7, wherein the first oxide layer comprises: magnesium oxide, aluminum oxide, hafnium oxide, titanium oxide, niobium oxide, tantalum oxide, gallium oxide, zinc oxide and oxide Any of cesium.
9. The solar cell according to claim 6, wherein the concentration of the low work function metal in the doped titanium nitride layer gradually increases from the side close to the low work function metal layer to the side close to the silicon substrate decrease.
10. The solar cell according to claim 6, wherein the solar cell further comprises: a first titanium nitride layer;

    The first titanium nitride layer is disposed between the low work function metal layer and the metal electrode layer.
11. The solar cell according to claim 10, wherein the thickness of the doped titanium nitride layer is 1-10 nanometers, and the thickness of the first titanium nitride layer is 5-500 nanometers.
12. The solar cell according to any one of claims 1-11, characterized in that,

    The low work function metal includes any one of calcium, magnesium, aluminum, barium, cesium, strontium, ytterbium, cerium, samarium, europium, neodymium, thorium, gadolinium, hafnium, lutetium and lanthanum.
13. The solar cell according to any one of claims 1-11, wherein the metal electrode layer comprises: aluminum, aluminum/silver, nickel/copper, nickel/copper/tin, chromium/palladium/silver, and nickel /copper/silver any of them.
14. The solar cell according to any one of claims 6-11, wherein the thickness of the low work function metal layer is 0.1-10 nanometers.
15. A production method of a solar cell, characterized in that the method comprises:

    A titanium nitride layer is prepared on one side of the silicon substrate;

    preparing a low work function metal layer on the side of the titanium nitride layer away from the silicon substrate;

    preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer;

    Wherein, the low work function metal contained in the low work function metal layer has higher activity than metal titanium.
16. The method according to claim 15, wherein after the step of preparing the titanium nitride layer on one side of the silicon substrate, the method further comprises:

    The titanium nitride layer is oxidized to form a silicon oxide layer between the titanium nitride layer and the silicon substrate, and a titanium oxide layer is formed on the side of the titanium nitride layer away from the silicon substrate.
17. The method according to claim 16, wherein the oxidation treatment comprises any one of dry oxidation, wet oxidation and plasma oxidation.
18. The method of claim 16, wherein:

    When the oxidation treatment is dry oxidation, the heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidation atmosphere of the oxidation treatment includes nitrogen and oxygen;

    When the oxidation treatment is wet oxidation, the heat treatment temperature of the oxidation treatment is 300-600 degrees Celsius, and the oxidation atmosphere of the oxidation treatment includes nitrogen and water;

    When the oxidation treatment is plasma oxidation, the heat treatment temperature of the oxidation treatment is 25-300 degrees Celsius.
19. The method according to claim 15, wherein before the step of preparing the titanium nitride layer on one side of the silicon substrate, the method further comprises:

    preparing a metal layer on one side of the silicon substrate;

    annealing the metal layer, and the metal layer reacts with the silicon substrate to form a silicide layer;

    Wherein, the metal layer includes any one of cobalt, platinum and titanium.
20. The method of claim 15, wherein the method comprises: annealing the low work function metal layer, and the low work function metal in the low work function metal layer diffuses into the titanium nitride layer, a doped titanium nitride layer is formed.
21. The method according to claim 20, wherein the step of preparing the titanium nitride layer on one side of the silicon substrate specifically comprises:

    preparing a first oxide layer on one side of the silicon substrate;

    preparing the titanium nitride layer on the side of the first oxide layer away from the silicon substrate;

    The step of performing annealing treatment on the low work function metal layer and diffusing the low work function metal in the low work function metal layer into the titanium nitride layer to form a doped titanium nitride layer specifically includes:

    The low work function metal layer is annealed, the low work function metal in the low work function metal layer diffuses into the titanium nitride layer to form the doped titanium nitride layer, and the low work function metal layer is diffused into the titanium nitride layer. The low work function metal in the functional metal layer passes through the doped titanium nitride layer and reacts with the first oxide layer to form a second oxide layer.
22. The method according to claim 20 or 21, wherein the step of annealing comprises:

    The annealing is carried out in a mixed gas of nitrogen and hydrogen in a temperature range of 350-450 degrees Celsius, and the ratio of nitrogen and hydrogen in the mixed gas is 10:1.
23. The method according to claim 22, characterized in that, after the step of annealing in a mixed gas of nitrogen and hydrogen in a temperature range of 350-450 degrees Celsius, the method further comprises:

    The secondary annealing is carried out in a nitrogen annealing atmosphere in the temperature range of 400-700 degrees Celsius.
24. The method according to claim 20 or 21, wherein the step of preparing a metal electrode layer on the side of the low work function metal layer away from the titanium nitride layer specifically includes:

    preparing a first titanium nitride layer on the side of the low work function metal layer away from the titanium nitride layer;

    The metal electrode layer is prepared on the side of the first titanium nitride layer away from the low work function metal layer.
25. The method of claim 21, wherein the first oxide layer comprises: magnesium oxide, aluminum oxide, hafnium oxide, titanium oxide, niobium oxide, tantalum oxide, gallium oxide, zinc oxide, and cesium oxide any of the .
26. A photovoltaic module is characterized by comprising the solar cell of any one of claims 1-14.

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