CN113206164A - Cast tandem multi-junction photovoltaic cell - Google Patents

Cast tandem multi-junction photovoltaic cell Download PDF

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Publication number
CN113206164A
CN113206164A CN202110455918.5A CN202110455918A CN113206164A CN 113206164 A CN113206164 A CN 113206164A CN 202110455918 A CN202110455918 A CN 202110455918A CN 113206164 A CN113206164 A CN 113206164A
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junction
crystalline silicon
type
silicon
substrate
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高文秀
佐佐木实
赵百通
高向曈
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YIXING YUYUAN ENERGY EQUIPMENT TECHNOLOGY DEVELOPMENT CO LTD
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YIXING YUYUAN ENERGY EQUIPMENT TECHNOLOGY DEVELOPMENT CO LTD
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0725—Multiple junction or tandem solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H01L31/022433—Particular geometry of the grid contacts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses a cast tandem multijunction photovoltaic cell, which comprises: the battery comprises a battery substrate and a battery cover, wherein the battery substrate is provided with a plurality of through holes; a crystalline silicon pn junction; a second pn junction with the forbidden band width of 1.5-2.5 eV, wherein the crystalline silicon pn junction is positioned between the battery substrate and the second pn junction; a back surface electrode electrically connected to the silicon pn junction via a conductor filled in the through-hole of the battery substrate; and a surface electrode electrically connected to the second pn junction. The preparation process of the photovoltaic cell comprises the following steps: filling the through-hole of the battery substrate with a conductor; a step of forming a crystalline silicon pn junction on a cell substrate; a step of forming a second pn junction on the crystalline silicon pn junction; and forming a back electrode and a surface electrode. Compared with the existing tandem photovoltaic cell, the photovoltaic cell provided by the invention has the advantages of simple and easily-controlled production operation, low cost and high photoelectric conversion efficiency.

Description

Cast tandem multi-junction photovoltaic cell
Technical Field
The invention belongs to the field of photovoltaic cells, and particularly relates to a cast tandem multi-junction photovoltaic cell.
Background
One important weakness of silicon-based photovoltaic cells is the indirect transition photoelectric effect generation. Under the influence of the forbidden band width of silicon, the wavelengths capable of participating in power generation are limited, and the wavelengths with energy larger than 1.12eV do not participate in the photovoltaic power generation process, so that the conversion efficiency of the photovoltaic cell is not improved, and the reference of fig. 1 is provided. The traditional tandem photovoltaic cell structure can obviously increase the cell thickness, semiconductor crystals with different forbidden band widths have different lattice constants, and generally, crystals with large lattice constants have relatively smaller forbidden band widths. Especially when crystals with different lattice constants are combined, lattice mismatch is formed on two sides of a heterojunction interface, and stress and other factors which have negative influence on power generation, such as the factors become recombination centers of minority carriers, at the heterojunction interface are generated.
Conventional tandem cells already have many physical models, such as the three-tandem model: the InGaP/GaAs/Ge and InGaP/GaAs/InGaAs structures can meet the forbidden bandwidth requirements of tandem cells, but the crystal growth technology is difficult, the cost is high, and the InGaP/GaAs/InGaAs structure has almost no market commercial value except the application with no cost for aerospace military and the like.
Disclosure of Invention
The invention aims to overcome the defects of the traditional tandem cell and provide a cast tandem multijunction photovoltaic cell which is simple and easy to control in production operation and low in cost.
In order to achieve the purpose, the invention adopts the following technical scheme;
a cast tandem multijunction photovoltaic cell, the photovoltaic cell comprising:
the battery comprises a battery substrate and a battery cover, wherein the battery substrate is provided with a plurality of through holes;
a crystalline silicon pn junction;
a second pn junction with the forbidden band width of 1.5-2.5 eV, wherein the crystalline silicon pn junction is positioned between the battery substrate and the second pn junction;
a back surface electrode electrically connected to the silicon pn junction via a conductor filled in the through-hole of the battery substrate;
and a surface electrode electrically connected to the second pn junction.
Preferably, the crystalline silicon pn junction is a monocrystalline silicon pn junction or a polycrystalline silicon pn junction.
More preferably, the thickness of the crystalline silicon pn junction is 40-60 microns.
Preferably, the second pn junction is CdTe and Ca1.7Fe0.3Te、Ca2Si、ZnTe、Os2Si3、Zn0.75Sn0.25Te、Cd0.5Zn0.5Te or an amorphous silicon pn junction.
More preferably, the thickness of the second pn junction is 0.4-2 microns.
More preferably, the second pn junction is Ca2Si or Os2Si3A pn junction with a transition layer forming a silicon concentration gradient between the second pn junction and the silicon pn junction.
Preferably, the thickness of the transition layer is no greater than 0.1 microns.
More preferably, the thickness of the transition layer is 0.01-0.05 microns.
Preferably, the battery substrate is a ceramic substrate, and the conductor filled in the through hole of the battery substrate is conductive glass.
Preferably, the photovoltaic cell has one of the following layered structures:
battery substrate/n-type crystalline silicon/p-type crystalline silicon/n-type Ca2Si/p type Ca2Si；
Battery substrate/p-type crystalline silicon/n-type crystalline silicon/p-type Ca2Si/n type Ca2Si；
Cell substrate/n-type crystalline silicon/p-type crystalline silicon/transition layer with silicon concentration gradient/n-type Ca2Si/p type Ca2Si；
Or cell substrate/p-type crystalline silicon/n-type crystalline silicon/transition layer with silicon concentration gradient/p-type Ca2Si/n type Ca2Si。
The invention discloses a preparation method of a cast tandem multi-junction photovoltaic cell, which comprises the following steps:
filling the through-hole of the battery substrate with a conductor;
a step of forming a crystalline silicon pn junction on a cell substrate;
a step of forming a second pn junction on the crystalline silicon pn junction;
and forming a back electrode and a surface electrode.
Specifically, the method comprises the following steps:
filling the through-hole of the battery substrate with a conductor;
a step of forming n-type crystalline silicon on a cell substrate;
performing boron diffusion on the n-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the n-type second semiconductor to form a second pn junction;
a step of forming a back electrode and a surface electrode;
alternatively, the first and second electrodes may be,
filling the through-hole of the battery substrate with a conductor;
a step of forming p-type crystalline silicon on a cell substrate;
performing phosphorus diffusion on the p-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the p-type second semiconductor to form a second pn junction;
and forming a back electrode and a surface electrode.
Preferably, the specific operation of filling the through-hole of the battery substrate with the conductor includes: the molten conductor is drawn into the through-hole of the battery substrate in a vacuum and an argon atmosphere.
Preferably, n-type or p-type crystalline silicon is formed on the battery substrate by a casting method, and the specific operation is that liquid silicon is dripped on the battery substrate at the temperature of 1250-1400 ℃, the battery substrate is rotated, after the liquid silicon is thrown off on the battery substrate to form a layer of film, a cold source is added on the upper surface of the film, and the film is solidified.
Preferably, the surface of the n-type crystalline silicon or the p-type crystalline silicon is subjected to texturing treatment before boron diffusion is performed on the n-type crystalline silicon or phosphorus diffusion is performed on the p-type crystalline silicon.
Preferably, a transition layer having a silicon concentration gradient is formed on the crystalline silicon pn-junction prior to forming the second pn-junction.
Preferably, the silicon concentration gradient is such that the molar ratio of silicon to the second semiconductor gradually transitions from 1:0 to 0: 1.
Preferably, the step of forming the back electrode comprises evaporating a thin metal layer on the back of the cell substrate.
The thin power generation layer is extremely thin, a carrier generation mechanism and a photovoltaic power generation structure can be redesigned, and the potential possibility of breaking through the theoretical photovoltaic power generation efficiency limit is realized. Furthermore, the silicon-based cell can be used as a substrate, and a Wide bandgap (WG: 1.5-2.5 eV) photovoltaic material is grown on the silicon-based cell to manufacture a multilayer series cell, wherein the initial efficiency can exceed 40% (the theoretical value exceeds 50%). The battery is designed to be fully reinforced in the mechanical structure, and therefore, the battery can be safely used for electric vehicles, road power generation and other purposes.
Drawings
Fig. 1 is a schematic diagram of the contribution of solar wavelengths to photovoltaic power generation.
Fig. 2 is a schematic diagram of a cast tandem multijunction photovoltaic cell of the present invention.
Fig. 3 is a schematic flow diagram of a process for manufacturing a cast tandem multi-junction photovoltaic cell of the present invention.
FIG. 4 shows the sputtering of Ca of the present invention2Schematic representation of Si.
Fig. 5 is a schematic diagram of a fresnel lens with unequal thickness.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.
Fig. 2 is a schematic diagram of the structure of a cast tandem multijunction photovoltaic cell of the present invention, comprising:
a battery substrate 10 having a plurality of through holes;
crystalline silicon pn junctions (21, 22);
second pn junctions (31, 32) with a forbidden band width of 1.5-2.5 eV, wherein the crystalline silicon pn junctions are positioned between the cell substrate and the second pn junctions;
a back electrode electrically connected to the crystalline silicon pn junction through a conductor 11 filled in the through-hole of the battery substrate;
and a surface electrode 40 electrically connected to the second pn junction.
In the present invention, the pn junction is defined by "second" and is not intended to be expressed or implied in terms of order, position, number, and the like, merely to distinguish the pn junction from a crystalline silicon pn junction.
The second pn junction of the present invention is also a second semiconductor pn junction comprising a p-type second semiconductor and an n-type semiconductor, and the second semiconductor has an energy gap of 1.5 to 2.5 eV.
The cast tandem multijunction photovoltaic cell of the present invention has one of the following layered structures:
the solar cell comprises a cell substrate, n-type crystalline silicon, p-type crystalline silicon, an n-type second semiconductor and a p-type second semiconductor;
the cell substrate/p-type crystalline silicon/n-type crystalline silicon/p-type second semiconductor/n-type second semiconductor.
The cell substrate is a composite ceramic composed of silicon carbide and silicon dioxide, needle-shaped through holes are densely distributed on the cell substrate, the through holes are basically parallel to the normal line of the substrate, the thickness of the substrate is about 5-15 mm, the densely distributed through holes can relieve or remove the stress of the substrate on one hand, and on the other hand, conductive substances which are not easy to diffuse with crystalline silicon can be absorbed by the through holes, so that the substrate can play a double-insurance role as the other pole of a photovoltaic cell.
The through holes on the battery substrate can be integrally formed during ceramic die casting, and can also be drilled by using high-power laser. Conductive glass may be selected as the conductive substance filling the through-holes.
The crystalline silicon pn junction of the cast tandem multi-junction photovoltaic cell can be a monocrystalline silicon pn junction or a polycrystalline silicon pn junction.
The crystalline silicon pn junction of the invention can be formed by boron (B) element diffusion on n-type crystalline silicon and can also be formed by phosphorus (P) element diffusion on P-type crystalline silicon.
The thickness of the crystalline silicon pn junction can be controlled to be 40-60 micrometers, the light absorption with the spectral energy of 1.5eV in the range is optimal, and the light absorption can reach 95% when the thickness is about 48 micrometers. Thicknesses below 40 microns significantly reduce the absorption of light at a spectral energy of 1.5eV, and above 60 microns, the absorption of light at a spectral energy of 1.5eV is very limited in increase.
The cast tandem multi-junction photovoltaic cell selects a semiconductor material with the forbidden band width of 1.5-2.5 eV as a second pn junction, mainly absorbs near ultraviolet rays, is complementary with a crystalline silicon pn junction, and can cover the main wavelength of the solar spectrum on the earth surface. The second pn junction may be selected from the following semiconductor materials: CdTe (Eg ═ 1.44eV) and Ca1.7Fe0.3Te(Eg＝1.75eV)、Ca2Si(Eg＝1.9eV)、ZnTe(Eg＝2.26eV)、Os2Si3(Eg＝2.3eV)、Zn0.75Sn0.25Te(Eg＝1.85eV)、Cd0.5Zn0.5Te (Eg ═ 1.74eV) or amorphous silicon (α -Si, Eg ═ 1.7 eV). An oxide or sulfide semiconductor having a band gap of 1.5 to 2.5eV can be selected.
The thickness of the second pn junction can be controlled to be 0.4-2 microns, and if the thickness is larger than the second pn junction, the transparency is reduced, the light absorption of the lower layer crystalline silicon pn junction can be obviously reduced, and if the thickness is smaller than the second pn junction, the absorption of near ultraviolet rays can be obviously reduced.
Preferred Ca in the present invention2Si or Os2Si3The semiconductor is used as a material of the second pn junction. Such a semiconductor is suitable for growing a transition layer having a silicon concentration gradient between the second pn junction of the upper layer and the crystalline silicon pn junction of the lower layer (the transition layer is omitted from fig. 2). The transition layer can greatly reduce the problem of mismatching of lattice interfaces between the upper layer and the lower layer, ensure the quasi-continuity of lattices, prevent carriers from scattering and compounding, maintain the current density between the layers to be equivalent, obviously reduce the interface resistance (which is not properly solved so far), effectively control the thickness of the pn junction of the upper layer, and adjust the photovoltaic power generation efficiency within a large range. During the growth process, Si and Ca can be adjusted through gradient2Si or Os2Si3To obtain a transition layer forming a silicon concentration gradient.
The thickness of the transition layer can be controlled to be not more than 0.1 micron, and is preferably controlled to be 0.01 to 0.05 micron.
The back electrode is a metal layer of tin (Sn), silver (Ag), aluminum (Al), copper (Cu), or the like, and is led out through a back electrode lead wire 12.
The surface electrode 40 is made of metal such as silver (Ag), aluminum (Al), or copper (Cu), and an ITO film 50 having a thickness of about 2 to 5 μm is deposited thereon and then led out through a surface electrode lead wire 41.
The cast tandem multijunction photovoltaic cell of the present invention has one of the following layered structures:
battery substrate/n-type crystalline silicon/p-type crystalline silicon/n-type Ca2Si/p type Ca2Si；
Battery substrate/p-type crystalline silicon/n-type crystalline silicon/p-type Ca2Si/n type Ca2Si；
Cell substrate/n-type crystalline silicon/p-type crystalline silicon/transition layer with silicon concentration gradient/n-type Ca2Si/p type Ca2Si；
Or cell substrate/p-type crystalline silicon/n-type crystalline silicon/transition layer with silicon concentration gradient/p-type Ca2Si/n type Ca2Si。
The manufacturing process for casting the tandem multi-junction photovoltaic cell comprises the following steps:
filling the through-hole of the battery substrate with a conductor;
a step of forming a crystalline silicon pn junction on a cell substrate;
a step of forming a second pn junction on the crystalline silicon pn junction;
and forming a back electrode and a surface electrode.
When the cast tandem multi-junction photovoltaic cell forms a crystalline silicon pn junction, an n-type crystalline silicon layer can be formed on a cell substrate, or a p-type crystalline silicon layer can be formed.
The method specifically comprises the following steps:
filling the through-hole of the battery substrate with a conductor;
a step of forming n-type crystalline silicon on a cell substrate;
performing boron diffusion on the n-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the n-type second semiconductor to form a second pn junction;
a step of forming a back electrode and a surface electrode;
alternatively, the first and second electrodes may be,
filling the through-hole of the battery substrate with a conductor;
a step of forming p-type crystalline silicon on a cell substrate;
performing phosphorus diffusion on the p-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the p-type second semiconductor to form a second pn junction;
and forming a back electrode and a surface electrode.
The specific operation of filling the through-hole of the battery substrate with the conductor includes: the molten conductor is drawn into the through-hole of the battery substrate in a vacuum and an argon atmosphere.
The method comprises the steps of forming an n-type or p-type crystalline silicon layer on a battery substrate by adopting a casting method (throwing sheet), dripping liquid silicon on the battery substrate with the temperature of 1250-1400 ℃, rotating the battery substrate to enable the liquid silicon to be thrown away on the battery substrate to form a layer of thin film, and adding a cold source on the upper surface of the thin film to enable the thin film to be solidified downwards from the surface, wherein the cold source is solid or inert gas with the temperature lower than 1000 ℃.
The temperature of the battery substrate is controlled to be 1250-1400 ℃, and the liquid silicon is prevented from being partially solidified on the substrate instantaneously.
And (3) after the wafer is thrown on the battery substrate to obtain n-type or p-type crystalline silicon, boron diffusion or phosphorus diffusion is carried out to obtain the crystalline silicon pn junction.
The method adopts the traditional process to carry out boron diffusion or phosphorus diffusion, and the diffusion depth is 3-7 microns.
Before boron diffusion or phosphorus diffusion, texturing treatment can be carried out on the crystalline silicon, so that textured rugged suede is obtained on the surface, and the purposes of increasing the sunlight absorption of the silicon and improving the short circuit current (Isc) are achieved.
In the texturing, the surface of crystalline silicon is etched by alkali, and an uneven textured surface is formed on the surface of the crystalline silicon by utilizing different etching speeds (namely anisotropy) of different crystal planes.
The back electrode is obtained by evaporating a metal (such as tin, silver, aluminum or copper) thin layer on the back of the battery substrate, and the metal thin layer can play a role in conducting electricity, improving the thermal conductivity of the battery and improving the warping degree of the battery.
The manufacturing process of the surface electrode comprises the following steps: and laying metal wires (such as silver, aluminum or copper) on the second pn junction according to a preset pattern layout, and then evaporating a layer of conductive glass. The conductive glass layer may also be etched in a pattern corresponding to the metal wire.
The manufacturing process for casting the tandem multi-junction photovoltaic cell further comprises the following steps:
and forming a transition layer with a silicon concentration gradient on the crystalline silicon pn junction.
When the transition layer is grown, the molar ratio of silicon to the second semiconductor is gradually transited from 1:0 to 0:1, so that the transition layer with the gradient change of the silicon concentration is formed.
The step of forming the transition layer and the second pn junction is performed in a vacuum and argon atmosphere environment, the argon pressure is 40-80 kPa, and the temperature of the battery substrate is 420-480 ℃.
The method comprises the steps of firstly carrying out heat treatment on a battery substrate in a vacuum and argon atmosphere environment, wherein the argon pressure is 30-60 kPa, the temperature is 450-550 ℃, so that the purpose of degassing conductive glass in a through hole of the battery substrate is achieved, and then carrying out the step of forming a transition layer and a second pn junction.
To form more suitable Ca for the transition layer of silicon concentration gradient2Si is an example, and generally, the depletion layer thickness of a semiconductor pn junction is determined simply by the concentrations of a p-type semiconductor and an n-type semiconductor, and in the present invention, p-type Ca2Si (or n-type Ca)2Si) and n-type crystalline silicon (or p-type crystalline silicon) to assist in determining the concentration gradient, and the vapor deposition film junction has a means of controlling the thickness of the depletion layer. The slowness of the concentration gradient can be controlledThe depletion layer is thickened, and the depletion layer is properly thickened to be beneficial to the photovoltaic cell from the application point of view, but the thickening of the depletion layer generally needs to reduce the doping concentration, and the content resistance of the photovoltaic cell can be increased. To solve the above mentioned contradiction in the conventional concept, the concentration gradient transition layer of the present invention can find an optimum amount between the doping amount and the depletion layer thickness to make p-type Ca2Si and n-type Ca2The concentration area (namely, the controllable depletion area) with the Si ratio of 1:1 close can be precisely controlled and realized, and the thickness of the controllable depletion area is larger, so that the sunlight absorptivity can be obviously improved. But considering Ca2The absorption coefficient of Si sunlight realizes that the thickness of a precise controllable depletion layer area can be finely coordinated according to specific conditions.
Example 1
The solar cell substrate is sintered by adopting a mixture of silicon carbide and silicon dioxide powder (the mass ratio is 5:1) (the sintering temperature is 1600 ℃), the thickness is 6 mm, and holes are formed on the substrate by using high-power laser to obtain densely distributed pinholes.
And sucking the conductive glass into the pin holes of the battery substrate under the negative pressure high temperature and Ar atmosphere.
Transferring the cell substrate to 1250-1400 deg.C in argon atmosphere (40-80 kPa), dropping liquid silicon (doping element is phosphorus) onto the cell substrate (such as 50 μm thick, 210 × 210mm side length) when the cell substrate is heated to the temperature2The silicon chip that needs the weight of silicon material about 5.2g), get rid of a piece mechanism and drive the base plate and rotate and get rid of the piece (rotational speed scope: 300-5000 rpm) and the speed is increased from slow to fast, the set rotating speed is reached within 1-10 seconds, liquid silicon is thrown away on a battery substrate to form a layer of thin film, then a solid cold source with the temperature lower than 1000 ℃ is added on the upper surface of the thin film, the thin film is solidified downwards from the surface, and therefore an n-type monocrystalline silicon layer is formed on the battery substrate.
Polishing the back of the battery substrate, cleaning, corroding the surface of the silicon wafer with an alkali alcohol solution to form a suede, cleaning, drying, and performing boron atom diffusion treatment according to the traditional process to obtain a p-type monocrystalline silicon layer with the diffusion depth of less than 5 microns, thereby forming a monocrystalline silicon pn junction on the battery substrate.
As shown in fig. 4(a-c), the cell substrate on which the single-crystal silicon pn junction is formed is first subjected to heat treatment in a chamber at an argon pressure of 50kPa and a temperature of 500 c, and the surface of the conductive glass in the substrate is degassed. Then, the manufacture of a transition layer and a second pn junction is carried out in a cavity with the argon pressure of 60kPa and the substrate temperature of 450 ℃: starting the silicon gun source and n-Ca2Si gun source, silicon and Ca2The mol ratio of Si is gradually transited from 1:0 to 0:1, a transition layer with 0.05 mu m is obtained by sputtering, and the sputtering of Ca is continued2Si forms 0.6 μm n-Ca2A Si thin film. Then p-Ca is turned on2Si gun source, sputtering to form 0.3 μm p-Ca2A Si thin film.
Manufacturing a surface electrode: and (3) arranging annular metal wires (corresponding to the Fresnel lens) on the upper surface of the cell according to a preset pattern in a cavity with the temperature environment of 300 ℃ by adopting a physical vacuum method, evaporating ITO with the thickness of 2 micrometers, and then electrically connecting surface electrode lead wires.
Manufacturing a back electrode: and plating a layer of tin on the back surface of the battery substrate, and then electrically connecting the back electrode lead wires.
The average photoelectric conversion efficiency of the cell is 42% under the packaging condition of a non-uniform thickness Fresnel lens (as shown in FIG. 5, h1 ≠ h2 … … ≠ hn, n ═ 1,2,3,4 … …) (the distance between the cell and the Fresnel lens is 1/5-2/3 of the distance between the Fresnel lens and the focal point).
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A cast tandem multijunction photovoltaic cell, characterized by: the photovoltaic cell includes:
the battery comprises a battery substrate and a battery cover, wherein the battery substrate is provided with a plurality of through holes;
a crystalline silicon pn junction;
a second pn junction with the forbidden band width of 1.5-2.5 eV, wherein the crystalline silicon pn junction is positioned between the battery substrate and the second pn junction;
a back surface electrode electrically connected to the silicon pn junction via a conductor filled in the through-hole of the battery substrate;
and a surface electrode electrically connected to the second pn junction.
2. The cast tandem multijunction photovoltaic cell of claim 1, wherein: the crystalline silicon pn junction is a monocrystalline silicon pn junction or a polycrystalline silicon pn junction;
preferably, the thickness of the crystalline silicon pn junction is 40-60 microns.
3. The cast tandem multijunction photovoltaic cell of claim 1, wherein: the second pn junction is CdTe and Ca1.7Fe0.3Te、Ca2Si、ZnTe、Os2Si3、Zn0.75Sn0.25Te、Cd0.5Zn0.5Te or an amorphous silicon pn junction;
preferably, the thickness of the second pn junction is 0.4-2 microns;
preferably, the second pn junction is Ca2Si or Os2Si3A pn junction with a transition layer forming a silicon concentration gradient between the second pn junction and the silicon pn junction;
more preferably, the transition layer has a thickness of no greater than 0.1 microns;
more preferably, the thickness of the transition layer is 0.01-0.05 microns.
4. The cast tandem multijunction photovoltaic cell of claim 1, wherein: the battery substrate is a ceramic substrate, and the conductor filled in the through hole of the battery substrate is conductive glass.
5. The cast tandem multijunction photovoltaic cell of claim 1, wherein: the photovoltaic cell has one of the following layered structures:
battery substrate/n-type crystalline silicon/p-type crystalline silicon/n-type Ca2Si/p type Ca2Si；
Battery substrate/p-type crystalline silicon/n-type crystalline silicon/p-type Ca2Si/n type Ca2Si；
Cell substrate/n-type crystalline silicon/p-type crystalline silicon/transition layer with silicon concentration gradient/n-type Ca2Si/p type Ca2Si；
Or cell substrate/p-type crystalline silicon/n-type crystalline silicon/transition layer with silicon concentration gradient/p-type Ca2Si/n type Ca2Si。
6. The method of making a cast tandem multijunction photovoltaic cell of claim 1, comprising:
filling the through-hole of the battery substrate with a conductor;
a step of forming a crystalline silicon pn junction on a cell substrate;
a step of forming a second pn junction on the crystalline silicon pn junction;
and forming a back electrode and a surface electrode.
7. The method of claim 6, wherein:
filling the through-hole of the battery substrate with a conductor;
a step of forming n-type crystalline silicon on a cell substrate;
performing boron diffusion on the n-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the n-type second semiconductor to form a second pn junction;
a step of forming a back electrode and a surface electrode;
alternatively, the first and second electrodes may be,
filling the through-hole of the battery substrate with a conductor;
a step of forming p-type crystalline silicon on a cell substrate;
performing phosphorus diffusion on the p-type crystalline silicon to form a crystalline silicon pn junction;
a step of sputtering a p-type second semiconductor on the crystalline silicon pn junction;
a step of sputtering an n-type second semiconductor on the p-type second semiconductor to form a second pn junction;
and forming a back electrode and a surface electrode.
8. The production method according to claim 6 or 7, characterized in that: the specific operation of filling the through-hole of the battery substrate with the conductor includes: sucking the molten conductor into the through-hole of the battery substrate in a vacuum and argon atmosphere;
preferably, forming n-type or p-type crystalline silicon on the battery substrate by adopting a casting method, and specifically, dropping liquid silicon on the battery substrate at 1250-1400 ℃, rotating the battery substrate, and adding a cold source on the upper surface of the film after the liquid silicon is thrown away on the battery substrate to form a layer of film so as to solidify the film;
preferably, the surface of the n-type crystalline silicon or the p-type crystalline silicon is subjected to texturing treatment before boron diffusion is performed on the n-type crystalline silicon or phosphorus diffusion is performed on the p-type crystalline silicon.
9. The method of claim 6, wherein: before forming the second pn junction, forming a transition layer with silicon concentration gradient on the crystalline silicon pn junction;
preferably, the silicon concentration gradient is such that the molar ratio of silicon to the second semiconductor gradually transitions from 1:0 to 0: 1.
10. The method of claim 6, wherein: the step of forming the back electrode includes depositing a thin metal layer on the back side of the cell substrate.
CN202110455918.5A 2021-04-26 2021-04-26 Cast tandem multi-junction photovoltaic cell Pending CN113206164A (en)

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