CN214588873U

CN214588873U - Heterojunction solar cell

Info

Publication number: CN214588873U
Application number: CN202121004406.9U
Authority: CN
Inventors: 薛建锋; 王金; 余义; 王永洁; 苏世杰
Original assignee: Tongwei Solar Anhui Co Ltd
Current assignee: Tongwei Solar Anhui Co Ltd; Tongwei Solar Hefei Co Ltd
Priority date: 2021-05-11
Filing date: 2021-05-11
Publication date: 2021-11-02
Anticipated expiration: 2031-05-11

Abstract

The utility model belongs to crystalline silicon solar cell field relates to a heterojunction solar cell. The method aims at the technical problems that in the prior art, B atoms are easy to diffuse into an amorphous silicon intrinsic layer due to poor thermal stability of a P-type doping layer of a heterojunction solar cell, the optical forbidden bandwidth of the P-type doping layer formed by doping pure diborane gas is low, the defect state density of boron-doped amorphous silicon and the composite current density of an emitter are increased due to doping of high-concentration diborane gas, and the like. The scheme provides a heterojunction solar cell, and the heterojunction solar cell is characterized in that a P-type doping layer is designed into a laminated structure and comprises a first P-type doping layer which is arranged to be in contact with an intrinsic amorphous silicon layer and contains trimethylboron gas deposition and an integral layered structure which is at least arranged and contains two layers of boron doping concentrations of trimethylboron and diborane gas deposition and is increased in an increasing mode.

Description

Heterojunction solar cell

Technical Field

The utility model relates to a solar cell field specifically, relates to a heterojunction solar cell.

Background

A heterojunction cell, also called HJT cell (Hetero-junction with intrinsic thin-layer), is a hybrid solar cell made of a crystalline silicon substrate and an amorphous silicon thin film, and is characterized by low temperature of the preparation process, high conversion efficiency and good high-temperature characteristics. Fig. 1 is a schematic structural diagram of an HJT solar cell. An N-type monocrystalline silicon wafer is used as a substrate, and an intrinsic amorphous silicon thin film (i-a-Si: H) and a P-type amorphous thin film (P-a-Si: H) with the thickness of 5-10 nm are sequentially deposited on the front surface of cleaned and textured N-type c-Si, so that a P-N heterojunction is formed. And sequentially depositing an i-a-Si: H thin film and an N-type amorphous silicon thin film (N-a-Si: H) with the thickness of 5-10 nm on the back surface of the silicon wafer to form a back surface field. And depositing Transparent Conductive Oxide (TCO) films on two sides of the a-Si-H doped film, and finally forming metal collectors on the top layers of the two sides by a screen printing technology. This is a typical structure of a heterojunction cell. During preparation, a monocrystalline silicon substrate layer is subjected to texturing cleaning treatment, an intrinsic amorphous silicon layer and an N-type amorphous silicon layer are deposited on the front side of the monocrystalline silicon substrate layer, an intrinsic amorphous silicon layer and a P-type amorphous silicon layer are deposited on the back side of the monocrystalline silicon substrate layer, a transparent conductive film is plated on the N/P-type amorphous silicon layer, and finally a metal electrode is manufactured on the transparent conductive film. Namely, the structure of the existing heterojunction solar cell is that an amorphous silicon intrinsic layer and a doped layer are respectively prepared on two sides of an N-type monocrystalline silicon wafer. The amorphous silicon intrinsic layer mainly passivates surface defects of crystalline silicon and reduces surface defect states, so that carrier recombination is reduced; p-type amorphous siliconThe doped layer mainly forms a PN junction with the N-type crystalline silicon, and the N-type amorphous silicon doped layer is a passivation layer forming a field effect with the N-type crystalline silicon. The P-type amorphous silicon doped layer is mainly made of diborane (B)₂H₆) Gas doping completes the amorphous silicon doped layer, typically a single layer doped layer.

For example, the Chinese patent application publication No. CN112466977A, the application date is 2018, 08 and 02, and the name is: a silicon heterojunction battery and a manufacturing method thereof; the method is disclosed for reducing the Schottky barrier between the P-type doped silicon layer and the transparent conducting layer and reducing the width of the depletion layer of the P-type doped silicon layer, thereby increasing the hole collecting capacity and improving the performance of the cell. The silicon heterojunction cell includes a silicon substrate interface inversion layer and a first transparent conductive layer. The silicon base includes a doped silicon substrate, a P-type doped silicon layer, and a first intrinsic silicon layer formed between the doped silicon substrate and the P-type doped silicon layer. An interfacial inversion layer is formed on the P-doped silicon layer. The first transparent conductive layer is formed on the interface inversion layer. The interfacial inversion layer comprises polar organic molecules. The polar organic molecules form bonds with silicon atoms in the P-type doped silicon layer. The interfacial inversion layer has a dipole moment directed from the transparent conductive layer to the P-doped silicon layer. But has the following disadvantages: (1) the P layer of the amorphous silicon doped layer formed by doping diborane gas has poor thermal stability, and B atoms are easy to diffuse into the amorphous silicon intrinsic layer, so that the passivation effect of the intrinsic layer is influenced, the open-circuit voltage of the solar cell is low, and the conversion efficiency of the solar cell is low; (2) the P layer of the amorphous silicon doped layer formed by doping diborane gas has low forbidden bandwidth, enhances the parasitic absorption of photons in short-wave and long-wave regions, increases optical loss, causes low short-circuit current of the solar cell and causes low conversion efficiency of the solar cell; (3) the increase of the doping concentration of the diborane gas in the process can cause the increase of the defect state density and the emitter recombination current density of the boron-doped amorphous silicon, and reduce the open-circuit voltage of the battery.

Disclosure of Invention

1. Technical problem to be solved by the invention

The method aims at the technical problems that in the prior art, B atoms are easy to diffuse into an amorphous silicon intrinsic layer due to poor thermal stability of a P-type doping layer of a heterojunction solar cell, the optical forbidden bandwidth of the P-type doping layer formed by doping pure diborane gas is low, the defect state density of boron-doped amorphous silicon and the composite current density of an emitter are increased due to doping of high-concentration diborane gas, and the like. The scheme provides a heterojunction solar cell, and the heterojunction solar cell is characterized in that a P-type doping layer is designed into a laminated structure and comprises a first P-type doping layer which is in contact with an intrinsic amorphous silicon layer and contains trimethylboron gas deposition and an integral layered structure which is at least provided with two layers and contains trimethylboron and diborane gas deposition and has gradually increased boron doping concentration.

2. Technical scheme

In order to achieve the purpose, the technical scheme is as follows:

the utility model discloses a heterojunction solar cell, heterojunction solar cell includes the base member piece, sets up the electrode on base member piece top surface and basal surface, and the base member piece includes:

a monocrystalline silicon substrate layer;

two groups of intrinsic amorphous silicon layers, wherein the two groups of intrinsic amorphous silicon layers comprise a first group of intrinsic amorphous silicon layers arranged on the top side of the monocrystalline silicon substrate layer and a second group of intrinsic amorphous silicon layers arranged on the bottom side of the monocrystalline silicon substrate layer;

a P-type doped layer disposed on a top side of the first set of intrinsic amorphous silicon layers;

the N-type doping layer is arranged on the bottom side of the second group of intrinsic amorphous silicon layers;

the light-transmitting conducting layers are respectively arranged on the top side of the P-type doping layer and the bottom side of the N-type doping layer, and the electrodes are arranged on the surfaces of the light-transmitting conducting layers;

the P-type doped layer is of a laminated structure pointing to the electrode direction from the top side of the first group of intrinsic amorphous silicon layers and comprises a first P-type doped layer, the first P-type doped layer is in contact with the first group of intrinsic amorphous silicon layers, the first P-type doped layer is of an integral laminated structure formed by deposition of a gas containing trimethyl boron, and at least two integral laminated structures with gradually increased boron doping concentrations formed by deposition of a gas containing trimethyl boron and diborane are arranged on the first P-type doped layer.

Further, the P-type doped layer comprises the following three layers of structures arranged in sequence from the top side of the first group of intrinsic amorphous silicon layers to the electrode direction:

the first P-type doping layer is of a boron lightly-doped integral layered structure formed by deposition of trimethyl boron-containing gas;

the second P-type doping layer is of a boron lightly doped integral layered structure formed by deposition of gas containing trimethylboron and diborane;

and the third P-type doping layer is of a boron heavily doped integral layered structure formed by depositing gas containing trimethyl boron and diborane.

Further, the thicknesses of the first P-type doping layer, the second P-type doping layer and the third P-type doping layer are respectively 2-10 nm; the thickness of the P-type doped layer is 10-20 nm.

Further, the first group of intrinsic amorphous silicon layers comprises the following three layers of structures which are sequentially arranged from the top side of the monocrystalline silicon substrate layer to the electrode direction:

a first layer of intrinsic amorphous silicon having a first conductivity type,

a second intrinsic amorphous silicon layer, both of which are an integral layered passivation structure formed by deposition of silane gas, the second intrinsic amorphous silicon layer having higher density than the first intrinsic amorphous silicon layer,

and the third intrinsic amorphous silicon layer is a laminated passivation layer deposited by gas containing silane and hydrogen.

Further, the third intrinsic amorphous silicon layer is an integral layered passivation structure comprising at least three layers, the compactness of which is sequentially increased from the top side of the second intrinsic amorphous silicon layer to the electrode direction.

Further, the second group of intrinsic amorphous silicon layers comprises the following two layers of structures which are sequentially arranged from the bottom side of the monocrystalline silicon substrate layer to the electrode direction:

a fourth layer of intrinsic amorphous silicon having a first conductivity type,

and the fourth intrinsic amorphous silicon layer and the fifth intrinsic amorphous silicon layer are both of an integral layered passivation structure formed by deposition of a silane-containing gas, and the compactness of the fifth intrinsic amorphous silicon layer is higher than that of the fourth intrinsic amorphous silicon layer.

Further, the thicknesses of the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, the third intrinsic amorphous silicon layer, the fourth intrinsic amorphous silicon layer and the fifth intrinsic amorphous silicon layer are respectively 0.5-5 nm.

Further, the thickness of the N-type doped layer is 5-10 nm; the thickness of the light-transmitting conducting layer is 90-110 nm.

Further, the monocrystalline silicon substrate layer is an N-type monocrystalline silicon substrate layer.

3. Advantageous effects

Adopt the technical scheme provided by the utility model, compare with existing well-known technique, have following beneficial effect:

(1) the utility model discloses a heterojunction solar cell, through the first P type doping layer of the low concentration that the trimethylboron doping formed, trimethylboron can produce behind the plasma bombardment can many active groups, like CH₂B^-And CHB^-These groups being capable of reacting B ions with SiH^2-/SiH^-The bonding is carried out, the thermal stability is improved, in addition, the doping concentration is low, the probability of B ions diffusing to the first group of intrinsic amorphous silicon layers is small, and the passivation performance of the first group of intrinsic amorphous silicon layers is hardly influenced by the B ions.

(2) The utility model discloses a heterojunction solar cell, compromise and need suitable B doping concentration, adopt to add a small amount of diborane in the trimethyl boron gas at second P type doping layer and dope, use trimethyl boron as leading, the built-in electric field of guaranteeing to form has sufficient width, rete forbidden bandwidth can not be too narrow and absorb too much light, sufficient doping concentration has both been kept, the forbidden bandwidth of second P type doping layer is adjusted through the active group after trimethyl boron decomposes again, it causes the narrow problem of forbidden bandwidth to use diborane doping alone not have. The third P-type doped layer has higher doping concentration, ensures the conductivity of the film, keeps good electric contact with a TCO film to be deposited subsequently, is heavily doped, and has a doping effect superior to that of trimethyl boron, so that the third layer is heavily doped by adding a small amount of trimethyl boron into diborane gas, and takes diborane as a main component. The density of defect states in the film can be obviously increased by high-concentration diborane, and after the trimethylboron is added, the Fermi level can be improved through C atoms decomposed from the trimethylboron, the free energy for forming defects is increased, and the forbidden bandwidth can be influenced, so that the forbidden bandwidth is increased by 0.1-0.3 eV.

(3) The utility model discloses a heterojunction solar cell, whole P type doped layer because trimethylboron has introduced CH^3-、CH^2-The group reduces the refractive index of the boron-doped amorphous silicon film, reduces the optical parasitic absorption loss of the film, and further reduces the recombination of the contact interface of the film. And simultaneously preparing a laminated structure containing diborane and trimethylboron with gradually increased boron doping concentration on the first P-type doping layer formed by pure trimethylboron. The technical problems that B atoms are easy to diffuse into an amorphous silicon intrinsic layer due to poor thermal stability of a P-type doping layer, the optical forbidden bandwidth of the P-type doping layer formed by doping pure diborane gas is low, the defect state density of boron-doped amorphous silicon and the composite current density of an emitter are increased due to doping of high-concentration diborane gas and the like are solved. Based on the optimization, the emitter structure with low defect state density and high optical band gap is finally realized, and the photoelectric conversion performance of the HIT solar cell is further improved by 0.05-0.2%.

Drawings

FIG. 1 is a schematic diagram of a prior art heterojunction solar cell;

fig. 2 is a schematic structural diagram of the heterojunction solar cell in example 1.

In the figure:

1. a monocrystalline silicon substrate layer; 2-1, a first intrinsic amorphous silicon layer; 2-2, a second intrinsic amorphous silicon layer; 2-3, a third intrinsic amorphous silicon layer; 2-4, a fourth intrinsic amorphous silicon layer; 2-5, a fifth intrinsic amorphous silicon layer; 3-1, a first P-type doped layer; 3-2, a second P-type doped layer; 3-3, a third P-type doped layer; 4. an N-type doped layer; 5. a light-transmitting conductive layer; 6. and an electrode.

Detailed Description

The present invention will be further described with reference to the following specific embodiments.

The technical solution in the embodiment of the present invention is described clearly and completely with reference to fig. 2, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, but not all of the embodiments; based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Example 1

A heterojunction solar cell of the present embodiment comprises a base sheet, electrodes 6 disposed on top and bottom surfaces of the base sheet, the base sheet comprising:

monocrystalline silicon substrate layer 1, monocrystalline silicon substrate layer 1 of this example is an N-type monocrystalline silicon substrate layer, with a size of 156.75mm and a thickness of 180 μm.

Two sets of intrinsic amorphous silicon layers including a first set of intrinsic amorphous silicon layers disposed on the top side of the single-crystal silicon substrate layer 1 and a second set of intrinsic amorphous silicon layers disposed on the bottom side of the single-crystal silicon substrate layer.

The first group of intrinsic amorphous silicon layers comprise the following three-layer structures which are sequentially arranged from the top side of the monocrystalline silicon substrate layer to the electrode direction:

the thickness of the first intrinsic amorphous silicon layer 2-1 is 1nm, and 1nm is the optimum value in this embodiment, and in practice, the technical effect of the present application can be achieved within the range of 0.5-5 nm.

The first intrinsic amorphous silicon layer 2-1 and the second intrinsic amorphous silicon layer 2-2 are both integral layered passivation structures formed by silane gas deposition, the compactness of the second intrinsic amorphous silicon layer 2-2 is higher than that of the first intrinsic amorphous silicon layer 2-1, the thickness is 1nm, 1nm is the optimal value in the embodiment, and in practice, the technical effect of the method can be achieved within the range of 0.5-5 nm.

And the third intrinsic amorphous silicon layer 2-3, wherein the third intrinsic amorphous silicon layer 2-3 is a laminated passivation layer deposited by gas containing silane and hydrogen and has the thickness of 6 nm.

In this embodiment, the third intrinsic amorphous silicon layer 2-3 includes the following three layers sequentially arranged from the top side of the second intrinsic amorphous silicon layer 2-2 to the electrode direction:

a first passivation layer having a hydrogen to silane gas flow ratio of 3; a second passivation layer having a hydrogen to silane gas flow ratio of 5; and the gas flow ratio of hydrogen to silane of the third passivation layer is 10, and the thickness of each passivation layer is 2 nm.

The thickness of the N-type doped layer 4 is 5 nm. The thickness of the light-transmitting conductive layer 5 is 90 nm.

The second group of intrinsic amorphous silicon layers comprise the following two-layer structures which are sequentially arranged from the bottom side of the monocrystalline silicon substrate layer to the electrode direction:

and the fourth intrinsic amorphous silicon layer 2-4 with a thickness of 5 nm.

And the fifth intrinsic amorphous silicon layer 2-5, the fourth intrinsic amorphous silicon layer 2-4 and the fifth intrinsic amorphous silicon layer 2-5 are all integral layered passivation structures formed by deposition of silane-containing gas, and the fifth intrinsic amorphous silicon layer 2-5 has higher compactness and a thickness of 5nm than the fourth intrinsic amorphous silicon layer 2-4.

A P-doped layer disposed on a top side of the first set of intrinsic amorphous silicon layers.

The P-type doped layer is of a laminated structure pointing to the electrode direction from the top side of the first group of intrinsic amorphous silicon layers and comprises a first P-type doped layer 3-1, the first P-type doped layer 3-1 is in contact with the first group of intrinsic amorphous silicon layers, the first P-type doped layer 3-1 is of an integral layered structure formed by deposition of a gas containing trimethyl boron, and at least two integral layered structures with gradually increased boron doping concentrations formed by deposition of a gas containing trimethyl boron and diborane are arranged on the first P-type doped layer 3-1. In this embodiment, the first P-type doped layer 3-1 is a boron lightly doped integral layer structure deposited by a gas containing trimethylboron. Further comprising: a second P-type doped layer 3-2, wherein the second P-type doped layer 3-2 is a boron lightly doped integral layered structure formed by deposition of gas containing trimethylboron and diborane; and the third P-type doping layer 3-3 is a boron heavily doped integral layer structure formed by depositing gases containing trimethyl boron and diborane. The thicknesses of the first P-type doped layer 3-1, the second P-type doped layer 3-2 and the third P-type doped layer 3-3 are all 5 nm; the thickness of the P-type doped layer is 15 nm.

The N-type doped layer 4 is arranged on the bottom side of the second group of intrinsic amorphous silicon layers; the thickness of the N-type doped layer 4 is 10 nm.

The light-transmitting conducting layer 5 is respectively arranged on the top side of the P-type doped layer and the bottom side of the N-type doped layer 4, and the electrode 6 is arranged on the surface of the light-transmitting conducting layer 5; the thickness of the light-transmitting conductive layer 5 is 100 nm.

The heterojunction solar cell of the embodiment has the emitter structure with low defect state density and high optical band gap, and improves the photoelectric conversion performance of the heterojunction solar cell.

Example 2

The difference between the high-efficiency silicon heterojunction solar cell of this embodiment and embodiment 1 is that:

the gas flow ratio of hydrogen to silane of the first passivation layer is 3, and the thickness of the first passivation layer is 1 nm; the gas flow ratio of hydrogen to silane of the second passivation layer is 5, and the thicknesses of the second passivation layer and the second passivation layer are both 2 nm; and the gas flow ratio of hydrogen to silane of the third passivation layer is 10, and the thickness of the third passivation layer is 3 nm.

Example 3

the first intrinsic amorphous silicon layer 2-1 has a thickness of 3 nm.

And the second intrinsic amorphous silicon layer 2-2, the first intrinsic amorphous silicon layer 2-1 and the second intrinsic amorphous silicon layer 2-2 are both integral layered passivation structures formed by silane gas deposition, and the second intrinsic amorphous silicon layer 2-2 has higher compactness and 3nm thickness than the first intrinsic amorphous silicon layer 2-1.

And the third intrinsic amorphous silicon layer 2-3, wherein the third intrinsic amorphous silicon layer 2-3 is a laminated passivation layer deposited by gas containing silane and hydrogen and has the thickness of 9 nm.

a first passivation layer having a hydrogen to silane gas flow ratio of 3; a second passivation layer having a hydrogen to silane gas flow ratio of 5; and the gas flow ratio of hydrogen to silane of the third passivation layer is 10, and the thickness of each passivation layer is 3 nm.

The thickness of the N-type doped layer 4 is 8 nm. The thickness of the light-transmitting conductive layer 5 is 100 nm.

and the fourth intrinsic amorphous silicon layer 2-4 with a thickness of 3 nm.

And the fifth intrinsic amorphous silicon layer 2-5, the fourth intrinsic amorphous silicon layer 2-4 and the fifth intrinsic amorphous silicon layer 2-5 are all integral layered passivation structures formed by deposition of silane-containing gas, and the fifth intrinsic amorphous silicon layer 2-5 has higher compactness and 3nm thickness than the fourth intrinsic amorphous silicon layer 2-4.

The light-transmitting conducting layer 5 is respectively arranged on the top side of the P-type doped layer and the bottom side of the N-type doped layer 5, and the electrode 6 is arranged on the surface of the light-transmitting conducting layer 5; the thickness of the light-transmitting conductive layer 5 is 100 nm.

Example 4

This embodiment is a method for manufacturing a heterojunction solar cell according to embodiment 1, and the method includes the following steps:

(1) texturing and cleaning treatment are carried out on a monocrystalline silicon substrate layer with the size of 156.75mm and the thickness of 180 mu m, wherein the monocrystalline silicon substrate layer is an N-type monocrystalline silicon wafer.

(2) And depositing a first group of intrinsic amorphous silicon layers on the top side (P side) of the monocrystalline silicon substrate layer by PECVD equipment, wherein the first group of intrinsic amorphous silicon layers comprise a first intrinsic amorphous silicon layer 2-1, a second intrinsic amorphous silicon layer 2-2 and a third intrinsic amorphous silicon layer 2-3.

The first intrinsic amorphous silicon layer 2-1 is prepared by adopting pure SiH silane on the top surface (P surface) of the monocrystalline silicon substrate layer 1₄Depositing a passivation layer with a thickness of 0.5-5 nm at a high speed (the deposition speed is 0.6-1.2 nm/s);

the second intrinsic amorphous silicon layer 2-2 is prepared by applying pure silane SiH on the top side of the first intrinsic amorphous silicon layer 2-1₄A passivation layer deposited at a low speed (the deposition speed is 0.2-0.6 nm/s) and the thickness is 0.5-5 nm.

The third intrinsic amorphous silicon layer 2-3 is formed by SiH silane on the top side 2-2 of the second intrinsic amorphous silicon layer₄And a hydrogen gas low-speed deposited stacked passivation layer comprising three layers with different [ H ]₂]/[SiH₄]The passivation layer is formed by deposition according to the gas flow ratio, the gas flow ratio of the first passivation layer is 1-5, the thickness is 0.5-5 nm, the gas flow ratio of the second passivation layer is 5-10, the thickness is 0.5-5 nm, the gas flow ratio of the third passivation layer is 10-15, and the thickness is 0.5-5 nm.

The third intrinsic amorphous silicon layer 2-3 adopts a laminated structure, the functions of the laminated structure comprise passivating the surface of a silicon wafer and preventing doping diffusion from entering an inner layer structure, and three layers of films of the laminated structure respectively adopt different gas flow ratios [ SiH ═ SiH₄]/[H₂]The first passivation layer gas flow rate ratio is [ H ]₂]/[SiH₄]1-5, the gas flow ratio of the second passivation layer is [ H [ ]₂]/[SiH₄]The gas flow ratio of the third passivation layer is [ H ] 5-10₂]/[SiH₄]10-15, introducing SiH with the same gas flow into the chamber₄In the same chamber H₂The larger the relative ratio of gas flow rates of (A) is, the lower the deposition rate of the film layer is, and the deposition of the film layer isThe lower the volume rate, the denser the deposited amorphous silicon film, so that the density of the stacked structure increases from the inside to the outside in order to prevent the diffusion of B ions well, and the stacked structure is not limited to three layers, but may be a plurality of layers as long as the density gradually increases, but also provide partial passivation performance.

(3) A second set of intrinsic amorphous silicon layers, comprising a fourth intrinsic amorphous silicon layer 2-4 and a fifth intrinsic amorphous silicon layer 2-5, is deposited on the bottom side (N-face) of the monocrystalline substrate layer 1 of the cell by means of a PECVD apparatus. Wherein the fourth intrinsic amorphous silicon layer 2-4 is prepared by adopting pure silane SiH on the N surface of the monocrystalline silicon substrate layer 1₄Depositing a passivation layer with a thickness of 0.5-5 nm at a high speed (the deposition speed is 0.6-1.2 nm/s); the fifth intrinsic amorphous silicon layer 2-5 is formed by using SiH silane on the bottom surface of the fourth intrinsic amorphous silicon layer 2-4₄And a passivation layer deposited by hydrogen at a low speed, wherein the gas flow ratio is 5-10, and the thickness is 0.5-5 nm.

(4) And depositing and preparing an N-type amorphous silicon layer, namely an N-type doping layer 4, on the bottom side of the second group of intrinsic amorphous silicon layers by using plasma enhanced chemical vapor, wherein the thickness of the N-type doping layer is 5-10 nm.

(5) And depositing and preparing a P-type amorphous silicon layer, namely a P-type doping layer, on the top side of the first group of intrinsic amorphous silicon layers by using plasma chemical vapor, wherein the total thickness is 10-20 nm.

The importance of the thickness of the P-type doped layer is set to be smaller than the flow ratio (the P-type amorphous silicon layer is prepared by plasma chemical vapor deposition, the total thickness is 10-20 nm; SiH is assumed₄With a gas flow rate of 1, a first P-type doped layer 3-1 is deposited on the top side of the first set of intrinsic amorphous silicon layers, which is lightly doped with trimethylboron gas with a gas flow rate ratio TMB]/[SiH₄]1 to 5, and 2 to 10nm thick; depositing a second P-type doped layer 3-2 on top of the first P-type doped layer 3-1 using a gas flow ratio TMB]/[B₂H₆]Doping for 1-5 to form a doped layer with a thickness of 2-10 nm; depositing a third P-doped layer 3-3 on top of the second P-doped layer 3-2 using [ TMB]/[B₂H₆]The volume ratio is 0.2-1, and a heavily doped layer is formed by doping, wherein the thickness is 2-10 nm.

First P-type doped layer 3-1The product condition is as follows: gas flow SiH₄200 to 400sccm of silane gas, 600 to 2000sccm of TMB (trimethylboron gas), H₂200-1000 sccm, the air pressure range is 0.5-2 mbar, the radio frequency power range is 1000-3000W, the thickness is 2-10 nm, and the temperature is 190-200 ℃;

the deposition conditions of the second P-type doped layer 3-1 are as follows: gas flow rate B₂H₆200 to 400sccm, TMB 200 to 2000sccm, SiH₄200 to 500sccm, H₂200-1000 sccm, the air pressure range is 0.5-2 mbar, the radio frequency power range is 1000-2000W, the thickness is 2-10 nm, and the temperature is 190-200 ℃;

the deposition conditions of the third P-type doped layer 3-1 are as follows: the gas flow rate TMB is 200-400 sccm, B₂H₆(diborane) is 200 to 2000sccm, SiH₄200 to 500sccm, H₂200 to 1000sccm, a gas pressure range of 0.5 to 2mbar, a radio frequency power range of 1000 to 2000W, a thickness of 2 to 10nm, and a temperature of 190 to 200 ℃.

In this embodiment, the flow ratios of the two gases in the first P-type doped layer 3-1, the second P-type doped layer 3-2 and the third P-type doped layer 3-3 are respectively 1, 1 and 0.5, which are optimal values. The thicknesses of the first P-type doped layer 3-1, the second P-type doped layer 3-2 and the third P-type doped layer 3-3 are respectively 2nm, 3nm and 5nm, which are optimal values. The principle of gradual increase is followed for the thickness, the thinnest of the innermost layer and the thickest of the outermost layer.

(6) And respectively depositing a light-transmitting conductive layer 5(TCO conductive film) with the thickness of 90-110 nm on the N/P surface of the cell by PVD equipment.

(7) Front and back Ag electrodes were formed by screen printing.

(8) And forming good ohmic contact between the silver grid line and the TCO conductive film through solidification.

(9) A test of the electrical performance of the cells was conducted.

The heterojunction solar cell prepared in this example is shown in fig. 2.

Comparative example 1

The structure of a prior art heterojunction cell is shown in fig. 1:

1. firstly, texturing and cleaning treatment is carried out on an N-type monocrystalline silicon wafer.

2. Depositing intrinsic amorphous silicon and an N-type amorphous silicon film on the front surface of the silicon wafer, wherein the intrinsic amorphous silicon layer on the front surface comprises two layers:

a first layer: pure SiH₄Gas deposition with a rate of 0.7nm/s and a thickness of 3 nm;

a second layer: SiH₄And H₂Two gases with a flow ratio of SiH₄:H₂The deposition rate was 1.2nm/s with a thickness of 5nm, 1: 10. The value of SiH for N-type amorphous silicon film₄、H₂、PH₃The three gases were mixed, the deposition rate was 1.4nm/s and the thickness was 8 nm.

3. Depositing intrinsic amorphous silicon and a P-type amorphous silicon film on the back surface of a silicon wafer, wherein the intrinsic amorphous silicon layer on the front surface comprises two layers: a first layer: pure SiH₄The gas deposition rate is 0.75nm/s, and the thickness is 4 nm; a second layer: SiH₄And H₂Two gases with a flow ratio of SiH₄:H₂The deposition rate was 1.2nm/s with a thickness of 6nm, 1: 10. The value of SiH in the P-type amorphous silicon film₄、H₂、B₂H₆The three gases were mixed, the deposition rate was 2nm/s and the thickness was 10 nm.

4. And plating a transparent conductive film on the amorphous silicon, wherein the thickness of the transparent conductive film is 90 nm.

5. And finally, manufacturing a metal electrode on the transparent conductive film.

6. Cell efficiency and electrical parameters were tested.

Table 1 comparison of the performance of the heterojunction solar cells prepared in the comparative example and the example

As can be seen from table 1:

1. from the aspect of current Isc, the experimental group and the comparative group are increased by about 10mA, which shows that the arrangement of the P-type doping layer can improve the conductivity of the film layer and reduce the current loss in the current transmission process; the band gap width is increased by 0.1-0.3 eV, which acts on the current to increase it.

2. The open-circuit voltage Voc is improved by 0.2-0.5 mV, which shows that the arrangement of the intrinsic amorphous silicon layers 2-1, 2-2 and 2-3 can play a role in improving passivation performance, namely the influence of B atom diffusion is reduced to a certain extent.

3. From the aspect of the filling factor Fff, the efficiency is improved mainly due to the FF improvement, compared with the FF improvement of 0.14-0.33%, the FF improvement is mainly that the passivation effect is improved, and in addition, the contact resistance between the film layers is reduced. The structural design of the utility model can reduce the B atom recombination influence and promote the passivation performance and the setting of P type doped layer three-layer stromatolite reduces the contact resistance between the rete, reduces resistive loss certainly.

Claims

1. A heterojunction solar cell comprising a substrate sheet, electrodes disposed on a top surface and a bottom surface of the substrate sheet, wherein: the base sheet includes:

a monocrystalline silicon substrate layer;

2. The heterojunction solar cell of claim 1, wherein: the P-type doped layer comprises the following three layers of structures which are sequentially arranged from the top side of the first group of intrinsic amorphous silicon layers to the electrode direction:

3. The heterojunction solar cell of claim 2, wherein: the thicknesses of the first P-type doping layer, the second P-type doping layer and the third P-type doping layer are respectively 2-10 nm; the thickness of the P-type doped layer is 10-20 nm.

4. The heterojunction solar cell of claim 1, wherein: the first group of intrinsic amorphous silicon layers comprise the following three-layer structures which are sequentially arranged from the top side of the monocrystalline silicon substrate layer to the electrode direction:

a first layer of intrinsic amorphous silicon having a first conductivity type,

5. The heterojunction solar cell of claim 4, wherein: the third intrinsic amorphous silicon layer is an integral layered passivation structure comprising at least three layers, the compactness of which is sequentially increased from the top side of the second intrinsic amorphous silicon layer to the electrode direction.

6. The heterojunction solar cell of claim 4, wherein: the second group of intrinsic amorphous silicon layers comprise the following two-layer structures which are sequentially arranged from the bottom side of the monocrystalline silicon substrate layer to the electrode direction:

a fourth layer of intrinsic amorphous silicon having a first conductivity type,

7. The heterojunction solar cell of claim 6, wherein: the thicknesses of the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, the third intrinsic amorphous silicon layer, the fourth intrinsic amorphous silicon layer and the fifth intrinsic amorphous silicon layer are 0.5-5 nm respectively.

8. A heterojunction solar cell according to any of claims 1 to 7, wherein: the thickness of the N-type doped layer is 5-10 nm; the thickness of the light-transmitting conducting layer is 90-110 nm.

9. The heterojunction solar cell of claim 8, wherein: the monocrystalline silicon substrate layer is an N-type monocrystalline silicon substrate layer.