CN1314134C - Method for preparing silicon thin film heterojunction solar cell - Google Patents

Abstract

A method for preparing a silicon thin-film heterojunction solar cell used in the field of semiconductor technology. Substrate cleaning: the surface of the substrate is initially cleaned by using a semiconductor cleaning process, and then the substrate is placed in deionized water and cleaned by ultrasonic waves. Rinse several times with ionized water and dry with nitrogen gas; prepare intrinsic amorphous silicon layer: prepare intrinsic amorphous silicon layer by hot wire chemical vapor deposition technology, measure the temperature of tungsten wire with optical pyrometer, and the temperature of heater and sample are respectively Measured by two thermocouples, the temperature is controlled by an electronic temperature controller, and a thin film is grown on the surface of the substrate; an emission layer is deposited on the intrinsic amorphous silicon thin film; the formation of the front and back electrodes: by sputtering The process forms electrodes on the front and back of the battery; finally, a vacuum thermal annealing process is performed. The thin film of the present invention has light stability. Under the standard light intensity of AM1.5 and 100mW/ ^cm2 , the photoconductive gain of the obtained silicon thin film can reach 10 ⁶ , and amorphous silicon and crystalline silicon heterojunction solar cells based on this thin film The efficiency reaches 12.5%.

Description

Preparation method of silicon thin film heterojunction solar cell

technical field

The invention relates to a method for preparing a solar cell, in particular to a method for preparing a silicon thin film heterojunction solar cell, which is used in the technical field of semiconductors.

Background technique

In the past few years, breakthroughs have been made in heterojunction solar cells based on amorphous silicon and crystalline silicon. This type of cell has the advantages of high efficiency and low cost, and it is very likely to become a replacement product for crystalline silicon solar cells. To achieve market promotion, an important process required for the formation of pn junctions in the production of bulk crystalline silicon solar cells: high temperature diffusion, will be omitted in the production of heterojunction solar cells. The heterojunction solar cell composed of new amorphous silicon and crystalline silicon has a simple structure and less process. It combines the advantages of high carrier mobility of crystalline silicon with the process advantages of low-temperature chemical vapor deposition of amorphous silicon. From the perspective of economy, technology and science, heterojunction solar cells composed of amorphous and crystalline silicon are more advanced.

In 2002, Japan's Sanyang Electric Co., Ltd. successfully prepared a solar cell based on this structure, and its efficiency reached 21% (High-efficiency a-Si/c-Si heterojunction solar cell "high-efficiency a-Si/c-Si Heterojunction solar cells" T.Sawada, N.Terada, et al, Proc.of the IEEE Elst World Conference PVSEC (Proceedings of the First International IEEE Photovoltaic Science and Engineering Conference) p.1219, Hawaii 1994), preparation of amorphous The technology used in the silicon emission layer is plasma-enhanced chemical vapor deposition (PECVD). It has been found that this technology has some inevitable shortcomings of the process itself. First, the bombardment of the plasma on the surface of the amorphous silicon film increases The carrier recombination defect density; second, the instability of plasma; third, under radio frequency irradiation, silane has high molecular polymerization (that is, forms powder); fourth, the deposition speed is slow; fifth, the silane Low utilization. Therefore, people expect a simpler process to replace PECVD and overcome the shortcomings of PECVD. In recent years, it has been reported in the literature that device-level amorphous silicon films can be deposited by using hot wire chemical vapor deposition (HW-CVD). We use this method to deposit an amorphous silicon film with high photoconductive gain, and use this film to prepare an amorphous silicon film and a crystalline silicon heterojunction solar cell with excellent performance.

Contents of the invention

The object of the present invention is to aim at the above-mentioned deficiencies and defects existing in the prior art, provide a kind of preparation method of silicon thin film heterojunction solar cell, make it adopt hot filament chemical vapor deposition (HW-CVD) to prepare high-quality non- crystalline silicon thin film, and use this thin film material as the emitter layer and crystalline silicon to form a-Si/c-Si heterojunction solar cells. The hot wire chemical vapor deposition process overcomes the shortcomings of the plasma process on the surface of the amorphous silicon film, and reduces the carrier recombination defect density in the film; and because there is no high-frequency discharge during the deposition process, the probability of silane molecule polymerization (Powder formation) is greatly reduced, so that high-quality amorphous silicon films can be formed. On the basis of the formation of the amorphous silicon thin film, the amorphous emission layer and the crystalline silicon heterojunction solar cell are prepared. A solar cell of this structure with a stable efficiency of 12% was obtained. By controlling the temperature of the heating wire and the substrate, the ratio of the reaction gas, the film thickness of the amorphous emission layer and the doping process, the influence on the performance of the heterojunction solar cell composed of the amorphous emission layer and crystalline silicon is realized.

The present invention is realized through the following technical solutions, and concrete steps are as follows:

(1) Substrate cleaning: Use p-type or n-type Czochralski monocrystalline silicon wafers with a resistivity of 2-4 Ωcm as the substrate, the silicon wafers are (100) oriented, mirror polished, and the thickness is 250 μm. Use the conventional semiconductor cleaning process to clean the surface of the substrate, use 3% hydrofluoric acid to remove the silicon dioxide layer on the surface of the silicon wafer, then put the substrate in deionized water and use ultrasonic cleaning, rinse with deionized water for several times Second, blow dry with nitrogen.

(2) Preparation of intrinsic amorphous silicon layer: The intrinsic amorphous silicon layer ia-Si is prepared by the hot wire chemical vapor deposition process, which plays a role in improving the output performance of the amorphous emission layer and crystalline silicon heterojunction solar cells , to provide high temperature heating wire with a diameter of 0.7mm tungsten wire. The temperature of the tungsten wire is measured with an optical pyrometer. The distance between the sample and the tungsten wire is about 7cm. The temperature of the heater and the sample is measured by two thermocouples, and the temperature is controlled by an electronic temperature controller. In order to prevent possible contamination and ensure the uniformity of the film, a baffle is used to separate the substrate from the tungsten wire before and after deposition. The background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane and hydrogen. The reaction gas is decomposed by the high-temperature tungsten wire to form a large number of active silicon-hydrogen units, which then diffuse to the surface of the substrate and react to grow on the surface of the substrate to form a thin film. Through the influence of process parameters such as tungsten wire temperature, substrate temperature, deposition pressure and the ratio of each reaction gas on the a-Si:H structure and photoelectric characteristics, the process parameters are optimized to prepare high-quality amorphous silicon thin films. The variation range of the deposition conditions is as follows: the temperature of the tungsten wire is 1600-2100°C; the temperature of the substrate is 150-400°C, and the deposition pressure is 0.1-10Pa. The flow ratio of silane in the total gas is adjustable in the range of 100% to 10%.

(3) Using the hot wire chemical vapor deposition process, an emission layer with a thickness of about 10-30 nm is deposited on the intrinsic amorphous silicon film. The conductivity of the emission layer is opposite to that of the substrate, that is, the p Solar cell prototypes with ⁺ a-Si/ia-Si/nc-Si and n ⁺ -a-Si/ia-Si/pc-Si structures. The specific process conditions are: the distance between the sample and the tungsten wire is 7cm. The background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane, borane or phosphine and hydrogen, the flow ratio of silane in the total gas is adjustable from 100% to 10%, and the doping concentration can be adjusted by the flow ratio of borane or phosphine to silane Adjust the flow ratio to be within the range of B ₂ H ₆ (or PH ₃ )/SiH ₄ =1%-5%. The reactive gas is decomposed by the high-temperature tungsten wire to form active reactive groups, and then diffuses to the vicinity of the substrate surface, and reacts and grows on the substrate surface to form a thin film. The variation range of the deposition conditions is as follows: the temperature of the tungsten wire is 1600-2100°C; the temperature of the substrate is 150-400°C; the deposition pressure is 0.1-10Pa. Changing the deposition time and the gas ratio of B ₂ H ₆ /SiH ₄ or PH ₃ /SiH ₄ can effectively control the thickness of the emission layer and the doping concentration of the emission layer, thereby improving the performance of the battery.

(4) For the formation of front and back electrodes, a layer of ITO transparent conductive film (Sn-doped In ₂ O ₃ ) with a thickness of about 80nm is deposited on the front of the battery by radio frequency sputtering process. role, but also plays the role of optical anti-reflection. The sample is heated to 200°C, the sputtering gas is argon and oxygen, the partial pressure ratio of argon and oxygen is 10:1, the total pressure is 0.5Pa, the sputtering power density is 40mW/cm2, and the sputtering deposition time is 40 minutes . Then use a mask and vacuum thermal evaporation to deposit silver metal grid lines on the ITO film. The back of the battery also uses vacuum thermal evaporation to deposit aluminum metal back electrodes.

(5) Vacuum thermal annealing process. In order to form a good ohmic contact between the silver grid line and the ITO layer, the aluminum back layer and c-Si, after the electrode is completed, a vacuum thermal annealing process is also performed. The annealing temperature is 250 ° C, and the time is It is 30 minutes.

The temperature of the tungsten wire is another most basic parameter. The temperature of the tungsten wire is controlled within the range of 1600-2100°C. The thin film has an amorphous structure, but in this range, there is also an optimal process condition for obtaining high photoconductive gain.

The third hot wire CVD process condition that affects the properties of the film is the substrate temperature. The selected substrate temperature varies in the range of 150-400°C. When the substrate temperature is greater than 300°C, there is a tendency to microcrystallization, the dark conductance increases, and the photoelectric The lead gain is reduced. A higher substrate temperature will increase the mobility of reactive species on the surface and reduce the H content in the sample. When the substrate temperature is higher than 300°C, microcrystallization occurs, which causes an increase in the density of defect states, reduces the photoconductive gain, and deteriorates the photoelectric performance. Usually, it is more appropriate to choose the substrate temperature at about 250°C.

The fourth hot wire CVD process condition that affects the properties of the film is the ratio of the reaction gas. The reaction gas is a mixed gas of silane and hydrogen. The flow rate of each reaction gas is measured and controlled by a mass flow meter. The flow ratio of silane in the total gas is It can be adjusted within the range of 100% to 10%. At high silane flow rate, the obtained film is dominated by amorphous structure, and high-quality amorphous silicon film with high photoconductive gain can be obtained. Under the condition of 80% silane flow rate, the obtained The silicon thin film has begun to crystallize, the dark conductance increases, and the photoelectric performance deteriorates.

The tungsten wire temperature is 1950°C, the substrate temperature is 210°C, and the deposition pressure is 1Pa. The flow ratio of silane in the total gas is 50%, the photoconductivity of the a-Si:H sample prepared by the hot wire CVD method only decreases by about 10% after 7 hours of light irradiation, while the photoconductivity of the sample prepared by the PECVD method under the same conditions The decrease is nearly an order of magnitude, indicating that the low-pressure HW-CVD method is an effective technique to improve the stability of a-Si.

The composition and structural properties of the film of the present invention can be described by Auger electron spectrum, Raman scattering spectrum and X-ray diffraction spectrum. The photoelectric properties of a-Si samples are known by measuring the photoconductivity and dark conductance. Coplanar electrodes are used in conductometric measurements. According to Auger electron spectrum analysis, it can be seen that the thin film does not contain unfavorable impurities, and the content of the film layer is uniform.

Analysis with X-ray and Raman electron energy spectrum shows that the deposition pressure is the main parameter to control the microstructure of the thin film. When the deposition pressure is below _Pg =1Pa, no diffraction peak can be observed in the energy spectrum of the sample. When _Pg is increased to Above 1Pa, diffraction peaks begin to appear, indicating that the film begins to crystallize, and the crystallization peak is located at 2θ equal to 28°, representing the preferred crystallization in the (111) direction. The peak diffraction intensity increases with the increase of _Pg . When P _g reaches 10Pa, (220) and (311) diffraction peaks appear at 2θ equal to 47.2° and 56°, and the degree of film crystallization increases with the increase of deposition pressure. Corresponding to the crystallization of the film, the conductivity also changes with _Pg . Under a standard light intensity, the ratio of the photoconductivity to the dark conductivity of the film (photoconductivity gain) is also greatly affected by the deposition pressure. When P When _g is 1Pa and greater than 1Pa, the dark conductivity increases. The above analysis shows that the microcrystallization of the film occurs, and the photoconductive gain begins to become poor. Only when P _g is less than 1Pa, a-Si presents a better high photoconductive gain. characteristics. According to the above results, in order to obtain the amorphous silicon thin film with high photoconductive gain, the deposition pressure should be lowered to below 1Pa in the experiment.

The present invention has substantive characteristics and significant progress. First, from the perspective of material preparation, compared with the plasma CVD technology usually used to prepare a-Si, this technology has the following characteristics and significant technological progress: (1) It can avoid the damage of ions to the growth surface in the glow discharge method; (2) the active units or energy particles generated can remove weak Si-Si bonds, weak Si-H bonds and reduce micro-voids, so as to obtain more ideal silicon disordered network; (3) higher substrate temperature can reduce the hydrogen content in the film; (4) high temperature filament can fully decompose silane. (5) High-speed film deposition is conducive to industrialization. Therefore, using low-pressure HW-CVD to prepare a-Si thin films and apply them to devices will be one of the ways to improve the stability of amorphous silicon thin film devices. Secondly, from the perspective of solar cell devices, amorphous silicon thin film and crystalline silicon heterojunction solar cells omit the diffusion process in the process of crystalline silicon solar cells, reducing energy consumption in the cost. Compared with amorphous silicon thin film solar cells, amorphous silicon thin film and crystalline silicon heterojunction solar cells overcome the degradation of photovoltaic performance under light, which is called the S-W effect, and the stability problem of amorphous silicon thin film (a-Si) (ie S-W effect) hinders the further application of amorphous silicon thin film solar cells.

And the hot wire vapor deposition process of the present invention is the technology of the HW-CVD growth photovoltaic amorphous silicon thin film with deposition pressure at 0.1～10Pa, and adopts this thin film and crystalline silicon to form the heterojunction solar cell, both in these two respects Achieved technological progress.

Detailed ways

Embodiment 1 and Embodiment 2 are solar cells with p ⁺ -a-Si/ia-Si/nc-Si structure, and Embodiment 3 and Embodiment 4 are solar cells with n ⁺ -a-Si/ia-Si/pc-Si structure solar cell:

Embodiment one

The chemical pretreatment is carried out by the above-mentioned step one.

The second step is adopted to prepare the intrinsic amorphous silicon layer. First, a thin intrinsic amorphous silicon layer ia-Si is deposited on nc-Si crystalline silicon, and the thickness of the ia-Si layer is 20nm. The specific process conditions are: the distance between the sample and the tungsten wire is 8cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane and hydrogen, the flow ratio of silane in the total gas is 100%, the temperature of the tungsten wire is 2100°C, the temperature of the substrate is 300°C, the deposition pressure is 0.1Pa, and the deposition time is 2 minutes.

Step 3 is adopted to prepare the doped emitting layer, and the flow ratio of borane to silane is controlled at B ₂ H ₆ /SiH ₄ =1%. On the amorphous silicon layer, a p ⁺ -a-Si emission layer with a thickness of 30nm is deposited. The conductivity of the emission layer is opposite to that of the substrate, that is, p ⁺ -a-Si/ia-Si/nc -Prototype of solar cell with Si structure. The specific process conditions are that the distance between the sample and the tungsten wire is 8cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The tungsten wire temperature is 2100°C; the substrate temperature is 150°C; the deposition pressure is 0.1Pa; the deposition time is 3 minutes.

Use step 4 to prepare the upper and lower electrodes, deposit a layer of ITO transparent conductive film (Sn-doped In ₂ O ₃ ) with a thickness of about 80nm on the front of the battery by radio frequency sputtering process, and then use mask method on the ITO film, vacuum thermal evaporation Silver metal gridlines are deposited. The back of the battery also uses vacuum thermal evaporation to deposit aluminum metal back electrodes.

The vacuum thermal annealing process is carried out in step 5, so that the silver grid line and the ITO layer, the aluminum back layer and the c-Si form an ohmic contact.

Implementation effect: Finally, the performance test of the battery is carried out. Under the irradiation of AM1.5, 100mW/cm ² standard light intensity, the photoconductivity gain of the deposited intrinsic silicon film in this example 1 reaches 10 ⁶ , and the prepared heterojunction solar cell The efficiency reaches 12%, and the fill factor reaches 70%.

Embodiment two

Use the above-mentioned step 1 to carry out the front chemical pretreatment;

Step 2 is adopted to prepare the intrinsic amorphous silicon layer. First, a thin intrinsic amorphous silicon layer ia-Si, ia-Si layer is deposited on the nc-Si crystalline silicon with a thickness of 10nm. The specific process conditions are: sample and tungsten The distance between the wires is 8 cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane and hydrogen, the flow ratio of silane in the total gas is 80%, the temperature of the tungsten wire is 1900°C, the temperature of the substrate is 250°C, the deposition pressure is 2Pa, and the deposition time is 1 minute.

Use step 3 to prepare the doped emission layer, control the flow ratio of borane to silane at B ₂ H ₆ /SiH ₄ =3%, and deposit a p ⁺ -a-Si emission layer with a thickness of 30nm on the amorphous silicon layer , the conductivity of the emissive layer is opposite to that of the substrate, that is, the prototype of a solar cell with a p ⁺ -a-Si/ia-Si/nc-Si structure. The specific process conditions are that the distance between the sample and the tungsten wire is 8cm, the background vacuum of the deposition system is 5×10 ^-4 Pa, the temperature of the tungsten wire is 1900°C, the substrate temperature is 200°C, the deposition pressure is 10Pa, and the deposition time is 3 minutes.

Use step 4 to prepare the upper and lower electrodes, deposit a layer of ITO transparent conductive film (Sn-doped In ₂ O ₃ ) with a thickness of about 80nm on the front of the battery by radio frequency sputtering process, and then use mask method on the ITO film, vacuum thermal evaporation Silver metal gridlines are deposited. The back of the battery also uses vacuum thermal evaporation to deposit aluminum metal back electrodes.

The vacuum thermal annealing process is carried out in step 5, so that the silver grid line and the ITO layer, the aluminum back layer and the c-Si form an ohmic contact.

Implementation effect: Finally, the performance test of the battery is carried out. Under the irradiation of AM1.5, 100mW/cm ² standard light intensity, the photoconductivity gain of the intrinsic silicon thin film deposited in Example 2 reaches 10 ⁵ , and the prepared heterojunction solar cell The efficiency reaches 11.5%, and the fill factor reaches 65%.

Embodiment three

Use the above-mentioned step 1 to carry out the front chemical pretreatment;

Adopt step 2 to prepare intrinsic amorphous silicon layer, at first on pc-Si crystalline silicon deposit a thin intrinsic amorphous silicon layer ia-Si, ia-Si layer, thick 20nm, specific process condition is: sample and tungsten The distance between the wires is 8 cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane and hydrogen, the flow ratio of silane in the total gas is 50%, the temperature of the tungsten wire is 1800°C, the temperature of the substrate is 200°C, the deposition pressure is 6Pa, and the deposition time is 2 minutes.

Step 3 is used to prepare the doped emission layer, the flow ratio of phosphine and silane is controlled at PH ₅ /SiH ₄ =4%, and a 30nm thick n ⁺ -a-Si emission layer is deposited on the amorphous silicon layer, the The conductivity of the emission layer is opposite to that of the substrate, which constitutes the prototype of the solar cell with the n ⁺ -a-Si/ia-Si/pc-Si structure. The specific process conditions are that the distance between the sample and the tungsten wire is 6 cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The tungsten filament temperature is 1800°C; the substrate temperature is 200°C; the deposition pressure is 4Pa; the deposition time is 3 minutes.

Use step 4 to prepare the upper and lower electrodes, deposit a layer of ITO transparent conductive film (Sn-doped In ₂ O ₃ ) with a thickness of about 80nm on the front of the battery by radio frequency sputtering process, and then use mask method on the ITO film, vacuum thermal evaporation Silver metal gridlines are deposited. The back of the battery also uses vacuum thermal evaporation to deposit aluminum metal back electrodes,

The vacuum thermal annealing process is carried out in step 5, so that the silver grid line and the ITO layer, the aluminum back layer and the c-Si form an ohmic contact.

Implementation effect: Finally, the performance test of the battery was carried out. Under the irradiation of AM1.5, 100mW/cm ² standard light intensity, the photoconductive gain of the intrinsic silicon thin film deposited in Example 3 reached 5×10 ⁴ , and the prepared heterojunction The solar cell has an efficiency of 10% and a fill factor of 68%.

Embodiment Four

Use the above-mentioned step 1 to carry out the front chemical pretreatment;

Adopt step 2 to prepare intrinsic amorphous silicon layer, at first on pc-Si crystalline silicon deposit a thin intrinsic amorphous silicon layer ia-Si, ia-Si layer, thick 20nm, specific process condition is: sample and tungsten The distance between the wires is 8 cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The reaction gas is a mixed gas of silane and hydrogen, the flow ratio of silane in the total gas is 10%, the temperature of the tungsten wire is 1600°C, the temperature of the substrate is 150°C, the deposition pressure is 10Pa, and the deposition time is 3 minutes.

Step 3 is adopted to prepare the doped emission layer, the flow ratio of phosphine and silane is controlled at PH ₅ /SiH ₄ =5%, and an n ⁺ a-Si emission layer with a thickness of 30 nm is deposited on the amorphous silicon layer, the emission The conductivity of the layer is opposite to that of the substrate, which constitutes the prototype of the solar cell with the n ⁺ -a-Si/ia-Si/pc-Si structure. The specific process conditions are that the distance between the sample and the tungsten wire is 8cm, and the background vacuum of the deposition system is 5×10 ^-4 Pa. The tungsten wire temperature is 1600°C; the substrate temperature is 300°C; the deposition pressure is 1Pa; the deposition time is 4 minutes.

Use step 4 to prepare the upper and lower electrodes, deposit a layer of ITO transparent conductive film (Sn-doped In ₂ O ₃ ) with a thickness of about 80nm on the front of the battery by radio frequency sputtering process, and then use mask method on the ITO film, vacuum thermal evaporation Silver metal gridlines are deposited. The back of the battery also uses vacuum thermal evaporation to deposit aluminum metal back electrodes.

The vacuum thermal annealing process is carried out in step 5, so that the silver grid line and the ITO layer, the aluminum back layer and the c-Si form an ohmic contact.

Implementation effect: Finally, the performance test of the battery was carried out. Under the irradiation of AM1.5, 100mW/cm ² standard light intensity, the photoconductive gain of the intrinsic silicon thin film deposited in Example 4 reached 10 ⁶ , and the prepared heterojunction solar The cell has an efficiency of 12.5% and a fill factor of 70%.

Claims (6)

1, a kind of preparation method of silicon thin film heterojunction solar cell is characterized in that, concrete steps are as follows:

(1) substrate cleans: the surface of adopting the semiconductor cleaning to carry out substrate is just cleaned, and removes the silicon dioxide layer of silicon chip surface with 3% hydrofluoric acid, substrate is placed on uses ultrasonic waves for cleaning in the deionized water again, and with the deionized water rinsing several, nitrogen dries up;

(2) preparation intrinsic amorphous silicon layer: adopt hot wire chemical vapor deposition prepared intrinsic amorphous silicon layer i-a-Si, it is the tungsten filament of 0.7mm that the heated filament employing diameter of high temperature is provided, the tungsten filament temperature is measured with leucoscope, the temperature of heater and sample is respectively by two thermocouple measurements, control temperature with electronic temperature controller, perhaps before and after deposition, substrate and tungsten filament are separated with a baffle plate, reacting gas is decomposed to form a large amount of activated silica hydrogen primitives by the high temperature tungsten filament, silicon hydrogen primitive is diffused into substrate surface again, forms film in the substrate surface reactions growth;

(3) adopt hot wire chemical vapor deposition technology, deposit the emission layer of a bed thickness 10～30nm again on the intrinsic amorphous silicon film, the conductivity of this emission layer is opposite with the conductivity of substrate, promptly constitutes

p ⁺A-Si/i-a-Si/n-c-Si and n ⁺The solar cell original shape of-a-Si/i-a-Si/p-c-Si structure;

(4) formation of positive backplate, deposit the ITO transparent conductive film of a bed thickness 80nm in the front of battery with sputtering technology, use mask, vacuum thermal evaporation depositing silver metal grid lines again on ito thin film, vacuum thermal evaporation deposition of aluminum metal back electrode is also adopted at the back side of battery;

(5) vacuum annealing technology after electrode is finished, is carried out vacuum annealing.

2, the preparation method of silicon thin film heterojunction solar cell according to claim 1 is characterized in that, in the step (1), select p-type or n-type for use, resistivity is substrate at the pulling of crystals silicon chip of 2～4 Ω cm, and silicon chip is (100) orientation, mirror finish, thickness are 250 μ m.

3, the preparation method of silicon thin film heterojunction solar cell according to claim 1, it is characterized in that, in step (2) and the step (3), the sedimentary condition excursion is as follows: 1600～2100 ℃ of tungsten filament temperature, 150～400 ℃ of underlayer temperatures, deposition pressure 0.1～10Pa, the flow-rate ratio of silane in total gas is in 100% to 10% scope.

4, the preparation method of silicon thin film heterojunction solar cell according to claim 1 is characterized in that, in the step (3), concrete process conditions are: the distance of sample and tungsten filament is 7cm, and the background vacuum pressure of depositing system is 5 * 10 ^-4Pa, reacting gas are silane, borine or phosphine and hydrogen mixed gas, and doping content is by regulating the flow-rate ratio of borine or phosphine and silane, and flow-ratio control is at B ₂H ₆Or PH ₃/ SiH ₄In=1%～5% scope, reacting gas is decomposed to form active reactive group by the high temperature tungsten filament, is diffused into the substrate surface annex then, forms film in the substrate surface reactions growth.

5, the preparation method of silicon thin film heterojunction solar cell according to claim 1, it is characterized in that, in the step (4), the ITO transparent conductive film of sputtering sedimentation one bed thickness 80nm on doped amorphous silicon film emission layer, during deposition, sample is heated to 200 ℃, sputter gas is argon gas and oxygen, the voltage ratio of argon gas and oxygen is 10: 1, and total pressure is 0.5Pa, and sputtering power density is 40mW/cm ², the sputtering sedimentation time is 40 minutes.

6, the preparation method of silicon thin film heterojunction solar cell according to claim 1 is characterized in that, in the step (5), annealing temperature is 250 ℃, and the time is 30 minutes.