CN103343318A - Preparation method of light absorption layer of solar battery - Google Patents

Abstract

The invention relates to a method for preparing a light-absorbing layer of a solar cell, comprising preparing a metal film precursor, the metal film precursor being a copper-zinc-tin-sulfur precursor film or a copper-zinc-tin-selenium precursor film; preparing a film laminated on the metal film precursor The tin covering layer on the upper layer is obtained to be stacked with a copper zinc tin sulfur film precursor of a tin covering layer or a copper zinc tin selenium film precursor being laminated with a tin covering layer; and under an oxygen-free condition and in a hydrogen sulfide atmosphere, the stacked The copper-zinc-tin-sulfur film precursor of the tin coating layer is subjected to high-temperature annealing; or under oxygen-free conditions and in a selenium atmosphere, the copper-zinc-tin-selenium thin film precursor laminated with the tin coating layer is subjected to high-temperature annealing to obtain the light absorption of the solar cell. layer steps. The tin capping layer can prevent the volatilization of SnS ₂ or SnSe ₂ in the metal film precursor during high temperature annealing. After annealing, the Sn in the tin capping layer forms SnS ₂ or SnSe ₂ and breaks away from the crystal, effectively inhibiting the loss of Sn.

Description

Preparation method of light absorbing layer of solar cell

technical field

The invention relates to the technical field of photovoltaic device preparation, in particular to a method for preparing a light absorbing layer of a solar cell.

Background technique

The band gap of CZTS (copper zinc tin sulfur, Cu ₂ ZnSnS ₄ ) and CZTSe (copper zinc tin selenium, Cu ₂ ZnSnSe ₄ ) with kesterite structure is very close to the optimal band gap of 1.5eV for semiconductor solar cells , its absorption coefficient can reach 10 ⁴ cm ^-1 . The elements copper, zinc, tin, sulfur, and selenium in copper, zinc, tin, sulfur, and selenium are very abundant on the earth, cheap, and all are environmentally friendly elements without toxic components. They have become a hot research field in the field of photovoltaics today. It is possible to become the mainstream product of photovoltaic cells in the future.

The main preparation process route of CZTS thin-film solar cells and CZTSe thin-film solar cells is to prepare metal precursor thin films by magnetron sputtering, co-evaporation, electrodeposition, solution method and other methods under low temperature conditions, and then anneal at high temperature to form the metal thin films. The precursor is placed in a high-temperature state, so that the atoms in the metal film precursor undergo a chemical reaction, and the reaction product crystallizes to obtain a polycrystalline CZTS film or CZTSe film, which is the light-absorbing layer of the solar cell. After annealing, the CZTS film or CZTSe film is deposited by water bath method to deposit cadmium sulfide (CdS), aluminum-doped zinc oxide (AZO) film growth, and electron beam evaporation to make Ni-Al electrode, which is a thin film solar cell device.

The so-called high-temperature annealing process is a process in which the metal film precursor is rapidly heated up in vacuum and maintained at the temperature for a period of time, and then naturally cooled.

Taking the CZTS metal thin film precursor as an example, the following reactions gradually occur during the high-temperature annealing process of the CZTS metal thin film precursor:

In the first stage, a binary phase is generated:

Cu+S→ _Cu2S ;

In the second stage, the binary phase reacts to form the ternary phase:

_Cu2S + _{SnS2 → Cu2SnS3} ;

In the third stage, the quaternary phase is generated:

Cu ₂ SnS ₃ +ZnS→Cu ₂ ZnSnS ₄ .

Recent studies on binary phases have found that Sn and S two elements begin to form SnS ₂ at 300°C, and begin to volatilize in large quantities at 400°C, and the binary phase no longer exists in solid state at 460°C, which is much lower than Crystallization temperature required for CZTS. The EDS energy spectrum analysis of the composition changes of the film precursor and crystalline film before and after the annealing of the quaternary phase CZTS film precursor shows that the loss of Sn after the annealing of the CZTS film precursor can be as high as 24%, and the loss of Sn element The phenomenon exists not only on the surface of the film, but also inside the entire film layer. Therefore, before the CZTS film reaches the reaction temperature, the Sn element will lose a large amount with the volatilization of _SnS2 . The consequence is that the amount of Sn component in the CZTS thin film component is not easy to control, which affects the quality of the CZTS thin film layer.

The properties of CZTSe and CZTS are similar. Se and S belong to the same group of elements, and the properties of the binary phases SnSe ₂ and SnS ₂ are also similar. It can be compared with the above principle. During the high-temperature annealing process of the CZTSe metal film precursor, due to _the The volatilization causes a large loss of Sn, which causes the deviation of the composition of the CZTSe film, thus affecting the quality of the CZTSe film layer.

Contents of the invention

Based on this, it is necessary to provide a method for preparing a light absorbing layer of a solar cell capable of suppressing Sn loss.

A method for preparing a light absorbing layer of a solar cell, comprising the steps of:

preparing a metal thin film precursor, the metal thin film precursor being a copper zinc tin sulfur thin film precursor or a copper zinc tin selenium thin film precursor;

Prepare the tin covering layer laminated on the metal thin film precursor to obtain the metal thin film precursor laminated with the tin covering layer, the metal thin film precursor laminated with the tin covering layer is copper zinc tin sulfur laminated with the tin covering layer A thin film precursor or a CuZnTnSe thin film precursor laminated with a tin capping layer; and

Under oxygen-free conditions and in a hydrogen sulfide atmosphere, the copper-zinc-tin-sulfur film precursor laminated with a tin coating layer is subjected to high-temperature annealing; or under an oxygen-free condition and in a selenium atmosphere, the stacked tin coating layer is The copper-zinc-tin-selenium film precursor is annealed at high temperature to obtain the light absorption layer of the solar cell.

In one of the embodiments, the step of preparing the metal thin film precursor is to prepare the metal thin film precursor by co-sputtering or co-evaporation.

In one of the embodiments, the step of preparing the metal thin film precursor is to sputter copper, zinc sulfide and tin disulfide onto the substrate by a co-sputtering method to form a copper-zinc-tin layer stacked on the substrate. Sulfur thin film precursor; or co-sputtering copper, zinc selenide and tin diselenide onto the substrate to form a copper zinc tin selenide thin film precursor stacked on the substrate.

In one of the embodiments, the step of preparing the metal thin film precursor is to vapor-deposit copper, zinc sulfide, tin and sulfur onto the substrate by co-evaporation to form a copper-zinc-tin-sulfur layer stacked on the substrate. A thin film precursor; or co-evaporating copper, zinc selenide, tin and selenium onto a substrate to form a copper zinc tin selenium thin film precursor stacked on the substrate.

In one of the embodiments, the step of pre-sputtering is also included before the preparation of the metal film precursor by the co-sputtering method.

In one of the embodiments, the step of preparing the tin covering layer laminated on the metal film precursor is to deposit elemental tin on the metal film precursor by using magnetron sputtering or thermal evaporation to obtain a layered Precursors for thin metal films with tin overlays.

In one embodiment, the thickness of the tin capping layer is 150 nanometers.

In one embodiment, the temperature of the high temperature annealing is 550° C., and the time is 15 minutes.

In one embodiment, the pressure of the hydrogen sulfide is 2×10 ³ Pa.

In one of the embodiments, the step of performing high-temperature annealing on the copper-zinc-tin-sulfur thin film precursor laminated with a tin coating layer under oxygen-free conditions and in a hydrogen sulfide atmosphere is specifically: The copper-zinc-tin-sulfur film precursor of the covering layer is placed in an annealing furnace, and hydrogen sulfide is introduced to a pressure of 2×10 ³ Pa, and then nitrogen is introduced to a pressure of 4×10 ⁴ Pa. layered copper zinc tin sulfur thin film precursor to 550 ℃, naturally cooled after 15 minutes of heat preservation; described under anaerobic conditions and in a selenium atmosphere, the copper zinc tin selenium thin film precursor stacked with a tin coating layer is subjected to high temperature The annealing step is specifically as follows: placing the copper-zinc-tin-selenide thin film precursor laminated with a tin coating layer in an annealing furnace, feeding selenium sulfide to a pressure of 2×10 ³ Pa, and then feeding nitrogen gas to a pressure of 4× 10 ⁴ Pa, and then heat the copper-zinc-tin-selenide thin film precursor laminated with a tin covering layer to 550° C., keep it warm for 15 minutes, and then cool it down naturally.

The preparation method of the light-absorbing layer of the above-mentioned solar cell forms a tin covering layer on the surface of the metal thin film precursor, and utilizes the tin covering layer to stop in the high-temperature annealing process, the volatilization of SnS in the copper-zinc-tin- _sulfur film precursor or the copper-zinc-tin-selenide The volatilization of SnSe ₂ in the thin film precursor can achieve the purpose of inhibiting the loss of Sn element in the metal thin film precursor. The Sn in the capping layer gradually forms _SnS2 and detaches from the CZTS crystal surface under the hydrogen sulfide atmosphere, or forms _SnSe2 and detaches from the CZTSe crystal surface under the selenium sulfide atmosphere, this process will not affect the composition of the CZTS crystal or the CZTSe crystal, The loss of Sn caused by the volatilization of _SnS2 or _SnSe2 is avoided, so that a higher-quality CZTS light-absorbing layer or CZTSe light-absorbing layer is prepared.

Description of drawings

Fig. 1 is the flowchart of the preparation method of the light absorbing layer of the solar cell of one embodiment;

FIG. 2 is a schematic diagram of step S110 of the method for preparing the light absorbing layer of the solar cell shown in FIG. 1 .

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, specific implementations of the present invention will be described in detail below in conjunction with the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described here, and those skilled in the art can make similar improvements without departing from the connotation of the present invention, so the present invention is not limited by the specific implementations disclosed below.

Please refer to FIG. 1 , a method for preparing a light absorbing layer of a solar cell according to an embodiment includes the following steps S110 to S130 .

Step S110: preparing a metal thin film precursor.

The metal thin film precursor is a copper zinc tin sulfur (CZTS) thin film precursor or a copper zinc tin selenium (CZTSe) thin film precursor.

Please also refer to Figure 2, first provide the substrate. The substrate is a glass substrate. After the substrate is cleaned and dried, molybdenum is deposited on the clean and dry substrate to form a molybdenum back electrode layer laminated on the substrate to obtain a substrate 101 laminated with a molybdenum back electrode layer. Preferably, the thickness of the molybdenum back electrode layer is 800 nm or 150 nm.

Taking the copper zinc tin sulfur (CZTS) film precursor as _the metal film precursor as an example, copper (Cu), zinc sulfide (ZnS) and tin Zinc and tin disulfide were sputtered onto the molybdenum back electrode layer. The preparation process is as follows:

The substrate 101 laminated with the molybdenum back electrode layer was placed on the sample holder of the sputtering chamber of the sputtering equipment. The molybdenum back electrode layer of the substrate 101 laminated with the molybdenum back electrode layer faces the substrate stopper 102 .

To evacuate the sputtering chamber, first use a mechanical pump to evacuate until the reading of the resistance gauge is 5×10 ¹ Pa, then turn on the molecular pump to evacuate until the reading of the ionization gauge is 2×10 ^-3 Pa. Turn on the gas flow meter, feed 99.999% high-purity argon gas into the sputtering chamber at a flow rate of 12 sccm, and control the vacuum system to maintain the reading of the ionization gauge at 1.1×10 ^-1 Pa. Rotate the sample holder, turn on the RF sputtering power supply of each target (Cu target, ZnS target, SnS ₂ target and Sn target), adjust the output power and reflection power of the power supply, and make the target glow. After 10 minutes of pre-sputtering, each target shutter (Cu target shutter 103 , ZnS target shutter 104 and SnS ₂ target shutter 105 ), substrate shutter 102 and film thickness gauge shutter (not shown) were turned on. The sputtering rate was detected by a film thickness meter. After sputtering for 1 hour, the Cu target baffle 103, the ZnS target baffle 104 and the SnS ₂ target baffle 105 were closed to form a copper zinc tin sulfur thin film precursor stacked on the molybdenum back electrode layer of the substrate.

Preferably, the thickness of the copper-zinc-tin-sulfur thin film precursor is 1.3 microns to 1.7 microns.

Preferably, the power of the Cu target is 60W, the power of the ZnS target is 75W, and the power of the _SnS2 target is 70W.

Pre-sputtering refers to turning on the RF sputtering power supply of each target (Cu target, ZnS target, SnS ₂ target and Sn target), adjusting the power output power and reflected power to make the target glow, but not turning on the Cu target at this time The baffle plate 103, the ZnS target baffle plate 104, the SnS ₂ target baffle plate 105, the Sn target baffle plate 106 and the substrate baffle plate 102 are used to remove impurities on the surface of each target material. Preferably, the pre-sputtering time is 10 minutes to ensure that the impurities on each target are fully removed before opening the Cu target shutter 103, ZnS target shutter 104, _SnS2 target shutter 105 and substrate shutter 102 Prepare the precursor, sputter copper, zinc sulfide and tin disulfide onto the molybdenum back electrode layer, and sputter copper, zinc sulfide and tin disulfide onto the molybdenum back electrode layer to form an impurity-free copper-zinc-tin-sulfur precursor body film.

When the metal thin film precursor is a copper zinc tin selenium thin film precursor, the method for preparing the copper zinc tin selenium thin film precursor by co-sputtering is roughly the same as the above method for preparing the copper zinc tin sulfur thin film precursor, the difference is that the target Replace with Cu target, ZnSe target, SnSe ₂ target. After 10 minutes of pre-sputtering, each target shutter (Cu target shutter, ZnSe target shutter, _SnSe2 target shutter), substrate shutter and film thickness meter shutter were opened. The sputtering rate was detected by a film thickness meter. After sputtering for 1 hour, close the Cu target shutter, the ZnSe target shutter and the SnSe ₂ target shutter to form a copper zinc tin selenium thin film precursor stacked on the back electrode layer of the substrate. Preferably, the power of the Cu target is 60W, the power of the ZnSe target is 75W, and the power of the _SnSe2 target is 70W.

Preferably, the thickness of the copper zinc tin selenium thin film precursor is 1.3 microns to 1.7 microns.

In other embodiments, co-evaporation can also be used to prepare the metal thin film precursor. Co-evaporative deposition of copper, zinc sulfide and tin disulfide onto the molybdenum back electrode layer of the substrate to form a copper zinc tin sulfur film precursor laminated on the molybdenum back electrode layer; or copper, zinc selenide, tin and selenium Co-evaporating and depositing on the molybdenum back electrode layer of the substrate to form a copper zinc tin selenium thin film precursor laminated on the molybdenum back electrode layer.

Co-evaporation is used to prepare metal thin film precursors in a molecular beam epitaxy system (MBE system). Put the substrate 101 laminated with the molybdenum back electrode layer on the sample stage of the MBE chamber, heat the Cu source furnace, the ZnS source furnace, the Sn source furnace, the S source furnace and the sample stage respectively to the preset temperature, and open the Cu source furnace baffle plate, ZnS source furnace baffle plate, Sn source furnace baffle plate, S source furnace baffle plate and sample platform baffle plate are evaporated to obtain copper zinc tin sulfur thin film precursor.

When the copper-zinc-tin-sulfur film precursor is prepared by the co-evaporation method, preferably, the preset temperatures of the Cu source furnace, the ZnS source furnace, the Sn source furnace, the S source furnace and the sample stage are 1210°C, 765°C, 1140°C, 200°C, respectively. ℃ and 200℃.

When the copper-zinc-tin-selenium film precursor is prepared by the co-evaporation method, preferably, the preset temperatures of the Cu source furnace, the ZnSe source furnace, the Sn source furnace, the Se source furnace and the sample stage are 1210°C, 765°C, 1140°C, 210°C, respectively. ℃ and 200℃.

Step S120: preparing a tin capping layer stacked on the metal thin film precursor to obtain a metal thin film precursor stacked with a tin capping layer.

The precursor of the metal film laminated with a tin covering layer is a precursor of a copper zinc tin sulfur film laminated with a tin covering layer or a precursor of a copper zinc tin selenium film laminated with a tin covering layer.

After the copper-zinc-tin-sulfur film precursor is formed on the molybdenum back electrode layer of the substrate, open the Sn target baffle 106, and after sputtering for 10 minutes, close the Sn target baffle 106, and turn off the power supply of each target, film thickness meter, and sample rotation and a gas flowmeter, after cooling for 30 minutes, a tin covering layer is formed on the copper-zinc-tin-sulfur thin film precursor to obtain a copper-zinc-tin-sulfur thin film precursor laminated with a tin covering layer.

Or, after the copper zinc tin selenium thin film precursor is formed on the molybdenum back electrode layer of the substrate, open the Sn target baffle, after sputtering for 10 minutes, close the Sn target baffle, turn off the power supply of each target, the film thickness meter, and the sample rotation and a gas flowmeter, after cooling for 30 minutes, a tin covering layer is formed on the copper zinc tin selenium thin film precursor to obtain a copper zinc tin selenium thin film precursor laminated with a tin covering layer.

Preferably, the power of the Sn target is 50W.

The vapor pressure of Sn is very small, only 10 ^-4 Pa at 1100 °C, and it can be considered as stable and non-volatile. Therefore, the tin coating is very stable and can prevent the SnS ₂ in the copper-zinc-tin-sulfur precursor film from volatilizing or Prevent the volatilization of _SnSe2 in the copper zinc tin selenium precursor thin film.

The thickness of the tin covering layer is 100 nm to 200 nm, preferably 150 nm. The thickness of the tin coating should be thick enough to suppress the volatilization of SnS ₂ or SnSe ₂ inside the metal thin film precursor on the one hand, but not too thick so that it can be completely removed in subsequent steps. When the thickness of the tin covering layer is 150 nanometers, the above two requirements can be better satisfied.

In other embodiments, tin can also be deposited on the metal thin film precursor by thermal evaporation to prepare a tin capping layer stacked on the metal thin film precursor. When thermal evaporation is used to form the tin coating layer, the preset temperature of the Sn source furnace is preferably 1150°C.

Step S130: Under an oxygen-free condition and a hydrogen sulfide atmosphere, perform high-temperature annealing on the copper-zinc-tin-sulfur thin film precursor laminated with a tin coating layer; or under an oxygen-free condition and in a selenium atmosphere, anneal the The copper-zinc-tin-selenide film precursor is annealed at high temperature to obtain the light absorption layer of the solar cell.

For CuZnSnS thin film precursors:

Put the copper-zinc-tin-sulfur thin film precursor laminated with a tin coating layer into an annealing furnace, and use a mechanical pump to evacuate from 1×10 ⁵ Pa until the reading of the thin film vacuum gauge is 0 Pa. Continue pumping for 5 minutes with a timer to ensure that the annealing furnace is clean.

Close the angle valve of the mechanical pump, first pass 99.999% hydrogen sulfide gas to 2×10 ³ Pa into the annealing furnace, and then pass 99.999% high-purity nitrogen gas to 4×10 ⁴ Pa. Turn on the heating power switch, raise the temperature from room temperature to 530-600 °C at a rate of 7.6 °C per minute, keep at 530-600 °C for 15-20 minutes, and then cool naturally to room temperature. The substrate temperature was monitored by armored K-type thermocouples during the heating process.

Preferably, the high-temperature annealing temperature is 550° C., and the annealing time is 15 minutes. 550°C reaches the crystallization temperature of the copper-zinc-tin-sulfur (CZTS) precursor film, and annealing at 550°C for 15 minutes can form a dense CZTS light-absorbing layer and obtain a high-quality solar cell light-absorbing layer.

During the high-temperature annealing process, the Sn in the tin cap layer continuously reacts with H ₂ S gas to generate SnS ₂ , and the SnS ₂ is continuously volatilized, and the tin cap layer is finally removed without affecting the final light absorption layer of the solar cell.

After the substrate temperature is cooled to room temperature, turn on the angle valve of the mechanical pump, pump the annealing furnace to 0 Pa, close the angle valve of the mechanical pump, pass 99.999% high-purity nitrogen to 5×10 ⁴ Pa, and then turn on the angle valve of the mechanical pump to evacuate to 0Pa, clean the gas in the annealing furnace to prevent hydrogen sulfide gas from remaining in the annealing furnace. Close the mechanical pump angle valve, pass 99.999% high-purity nitrogen gas to 1×10 ⁵ Pa, open the annealing furnace chamber, and take out the finished product.

For copper zinc tin selenium thin film precursor:

Put an evaporating boat into the annealing furnace, place selenium particles in the evaporating boat, heat the evaporating boat to 200°C, and feed 99.999% high-purity nitrogen gas to 4×10 ⁴ Pa. Turn on the heating power switch, raise the temperature from room temperature to 530-600 °C at a rate of 7.6 °C per minute, keep at 530-600 °C for 15-20 minutes, and then cool naturally to room temperature. The substrate temperature was monitored by armored K-type thermocouples during the heating process.

Preferably, the high temperature annealing temperature is 550° C., and the annealing time is 15 minutes. 550°C reaches the crystallization temperature of the copper-zinc-tin-selenium (CZTSe) precursor thin film, and annealing at 550°C for 15 minutes can form a dense CZTSe light-absorbing layer and obtain a high-quality light-absorbing layer for solar cells.

During the high-temperature annealing process, the Sn in the tin cap layer continuously reacts with the selenium vapor to form SnSe ₂ , and the SnSe ₂ is continuously volatilized, and the tin cap layer is finally removed without affecting the final light absorbing layer of the solar cell.

When the nitrogen partial pressure is 4×10 ⁴ Pa and the temperature of the evaporation boat is 200° C., the partial pressure of the selenium vapor is 2×10 ³ Pa. When the partial pressure of the selenium vapor needs to be adjusted, the partial pressure of the selenium vapor can be changed by adjusting the temperature of the evaporation boat.

The light-absorbing layer after annealing is observed to be gray on the surface of the finished product, uniform and non-reflective, and does not fall off after being washed with water. The diagonal resistance measured by a multimeter is about 500-700 kilohms, and the Sn of the tin covering layer has been completely volatilized and volatilized.

During the high-temperature annealing process, high-purity nitrogen gas is also introduced to prevent the metal film precursor laminated with the tin capping layer from being oxidized. It can be understood that during annealing in the MBE cavity, since the interior of the MBE cavity is always kept at a high vacuum (<10 ^-5 Pa), there will be no oxidizing gases such as oxygen in the environment, and the precursor of the metal film will not be oxidized. Therefore, It can be annealed directly in high vacuum MBE without introducing protective inert gas.

When the metal film precursor is prepared by co-evaporation, the high-temperature annealing step is also directly carried out in the MBE cavity, without taking out the sample and putting it into the annealing furnace, which is convenient to operate.

The annealing process continues directly inside the MBE chamber. The temperature of the Se source furnace was maintained at 210°C, the baffle of the Se source furnace was opened, and the temperature of the sample stage was raised from 200°C to 550°C at a constant rate of 15°C per minute, which took 23.3 minutes, and kept for 10 minutes after reaching 550°C, and the sample was closed Stand heating power supply to cool the sample naturally. When the temperature of the sample is lower than 250°C, close the Se source furnace baffle. After the annealing is completed, take out the sample to obtain the CZTSe light absorption layer of the solar cell.

When the tin covering layer on the surface of the finished product is not volatilized completely, the sample is whitish, and the diagonal resistance is only a few hundred ohms. thousand ohms. In the above two situations, for the preparation of the CZTS light-absorbing layer, it is necessary to adjust the thickness of the tin covering layer, or adjust the H ₂ S concentration, or adjust the annealing time of the precursor under the H ₂ S atmosphere, so as to ensure that the Sn in the tin covering layer completely volatile. For the preparation of the CZTSe light absorbing layer, it is necessary to adjust the temperature of the Se evaporation boat or the source furnace in the annealing furnace, and at the same time adjust the amount of Se particles in the Se evaporation boat.

The preparation method of the light-absorbing layer of the above-mentioned solar cell forms a tin covering layer on the surface of the metal thin film precursor, and utilizes the tin covering layer to stop in the high-temperature annealing process, the volatilization of SnS in the copper-zinc-tin- _sulfur film precursor or the copper-zinc-tin-selenide The volatilization of SnSe ₂ in the thin film precursor can achieve the purpose of suppressing the loss of Sn element in the metal thin film precursor. The Sn in the layer gradually forms _SnS2 and detaches from the CZTS crystal surface under the hydrogen sulfide atmosphere, or forms _SnSe2 and detaches from the CZTSe crystal surface under the selenium atmosphere. This process will not affect the composition of the CZTS crystal or CZTSe crystal, avoiding the The volatilization of SnS ₂ or SnSe ₂ leads to the loss of Sn, thereby preparing a higher-quality CZTS light-absorbing layer or CZTSe light-absorbing layer.

The preparation method of the light-absorbing layer of the solar cell is green and pollution-free, has low equipment requirements, is simple and easy to operate, and is suitable for wide use in laboratory research and industrial production.

The method for preparing the light absorbing layer of the above solar cell will be further described below through specific examples.

Example 1

Fabrication of light absorbing layers for solar cells

1. Preparation of copper zinc tin selenium thin film precursor by co-evaporation method

Place the glass substrate coated with a molybdenum back electrode layer with a thickness of 150nm on the MBE sample stage, turn on the rotary switch of the sample stage, and set the temperature of the Cu source furnace, the ZnSe source furnace, the Sn source furnace, the Se source furnace and the sample stage respectively. At 1210°C, 765°C, 1140°C, 210°C and 200°C, open the Cu source furnace baffle, ZnSe source furnace baffle, Sn source furnace baffle, Se source furnace baffle and sample stage baffle at the same time, vapor deposition 720 Second, obtain copper zinc tin selenium thin film precursor, the mol ratio of the element of this copper zinc tin selenium thin film precursor is Cu:Zn:Sn:Se=1.8:1.1:1.3:3.9;

2. Preparation of tin coating by evaporation method

Keep the temperature of the Sn source furnace of MBE at 1140°C for 10 minutes. After the Sn beam current is stable, turn on the sample rotation power supply, the sample stage baffle and the Sn source furnace baffle in sequence. After 3 minutes of evaporation, turn off the Sn source furnace baffle, the sample stage baffle and the sample rotation power supply in sequence. Evaporation is finished, after cooling for 30 minutes, a tin coating layer laminated on the metal film precursor is formed to obtain a copper-zinc-tin-selenium film precursor laminated with a tin coating layer, wherein the thickness of the tin coating layer is 150 nanometers;

3. High temperature annealing

The annealing process continues directly inside the MBE chamber. The temperature of the Se source furnace is maintained at 210°C. Open the baffle of the Se source furnace. The temperature of the sample stage is raised from 200°C to 550°C at a constant speed. It takes 15 minutes. After reaching 550°C, keep it for 10 minutes. Turn off the heating power of the sample stage and let the sample cool naturally. , when the temperature of the sample is lower than 250°C, close the Se source furnace baffle, the annealing is finished, and the sample is taken out to obtain the CZTSe light absorbing layer of the solar cell.

Example 2

Fabrication of light absorbing layers for solar cells

1. Co-sputtering method to prepare copper-zinc-tin-sulfur thin film precursor

Place the glass substrate coated with a molybdenum back electrode layer with a thickness of 150nm on the magnetron sputtering sample stage, turn on the rotary switch of the sample stage, and set the power of Cu target, ZnS target and _SnS2 target to 60w, 75w and 70w respectively , after pre-sputtering for 10 minutes, open the Cu target shutter, ZnS target shutter, _SnS2 target shutter and substrate shutter at the same time, and sputter for 1 hour to obtain the copper-zinc-tin-sulfur thin film precursor, copper-zinc-tin-sulfur The molar ratio of the components of the film precursor is Cu:Zn:Sn:Se=1.8:1.1:1.3:3.9;

2. Preparation of tin coating by sputtering

The power of the Sn target is set to 50w. After 10 minutes of pre-sputtering, the Sn target baffle is opened, and the Sn target baffle is closed after 10 minutes of sputtering. After the sputtering is over, the tin laminated on the metal film precursor is formed after cooling for 30 minutes. Covering layer, obtain the copper zinc tin sulfur thin film precursor that is laminated with tin covering layer, wherein, the thickness of tin covering layer is 150 nanometers;

3. Take out the copper-zinc-tin-sulfur precursor film laminated with the tin coating layer, put it into the annealing furnace, and use a mechanical pump to evacuate until the reading of the film vacuum gauge is 0Pa. Continue pumping for 5 minutes with a timer to ensure that the annealing furnace is clean. Then, H ₂ S (purity 99.999%) gas is passed to the annealing furnace to 2×10 ³ Pa, and then 99.999% high-purity nitrogen gas is passed to 4×10 ⁴ Pa. Raise from room temperature to 550°C at a rate of 7.6°C per minute, keep at 550°C for 15 minutes, and then cool naturally to room temperature. The substrate temperature was monitored by armored K-type thermocouples during the heating process. After the substrate temperature is cooled to room temperature, the remaining H ₂ S atmosphere in the annealing furnace is cleaned, and the sample is taken out to obtain the CZTS light absorption layer of the solar cell.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. A preparation method for a light absorbing layer of a solar cell, comprising the steps of: preparing a metal thin film precursor, the metal thin film precursor being a copper zinc tin sulfur thin film precursor or a copper zinc tin selenium thin film precursor; Prepare the tin covering layer laminated on the metal thin film precursor to obtain the metal thin film precursor laminated with the tin covering layer, the metal thin film precursor laminated with the tin covering layer is copper zinc tin sulfur laminated with the tin covering layer A thin film precursor or a CuZnTnSe thin film precursor laminated with a tin capping layer; and Under oxygen-free conditions and in a hydrogen sulfide atmosphere, the copper-zinc-tin-sulfur film precursor laminated with a tin coating layer is subjected to high-temperature annealing; or under an oxygen-free condition and in a selenium atmosphere, the stacked tin coating layer is The copper-zinc-tin-selenium film precursor is annealed at high temperature to obtain the light absorption layer of the solar cell. 2. The method for preparing the light absorbing layer of a solar cell according to claim 1, wherein the step of preparing the metal thin film precursor is to prepare the metal thin film precursor by a co-sputtering method or a co-evaporation method. 3. the preparation method of the light-absorbing layer of solar cell according to claim 2 is characterized in that, the step of described preparation metal thin film precursor is to adopt co-sputtering method to sputter copper, zinc sulfide and tin disulfide to On the substrate, form a copper zinc tin sulfur thin film precursor laminated on the substrate; or use co-sputtering method to sputter copper, zinc selenide and tin diselenide onto the substrate to form the CuZnSnSe thin film precursors on substrates. 4. The preparation method of the light-absorbing layer of a solar cell according to claim 2, characterized in that, the step of preparing the metal film precursor is to use co-evaporation to evaporate and deposit copper, zinc sulfide, tin and sulfur onto the substrate On the bottom, form a copper zinc tin sulfur thin film precursor laminated on the substrate; or use co-evaporation method to vaporize and deposit copper, zinc selenide, tin and selenium on the substrate to form a layer laminated on the substrate CuZnSnSe thin film precursor. 5 . The method for preparing the light-absorbing layer of a solar cell according to claim 2 , characterized in that, the step of pre-sputtering is also included before the metal thin film precursor is prepared by the co-sputtering method. 6 . 6. the preparation method of the light-absorbing layer of solar cell according to claim 1 is characterized in that, the step of described preparation layering on the tin capping layer on described metal thin film precursor is to adopt magnetron sputtering or thermal evaporation Deposit tin on the metal thin film precursor to obtain the metal thin film precursor laminated with a tin covering layer. 7. The method for preparing the light absorbing layer of a solar cell according to claim 1, wherein the thickness of the tin covering layer is 150 nanometers. 8 . The method for preparing the light-absorbing layer of a solar cell according to claim 1 , wherein the high-temperature annealing is performed at a temperature of 550° C. for 15 minutes. 9 . The method for preparing a light absorbing layer of a solar cell according to claim 1 , wherein the gas pressure of the hydrogen sulfide is 2×10 ³ Pa. 10. The preparation method of the light-absorbing layer of solar cell according to claim 1, is characterized in that, described under anaerobic condition and hydrogen sulfide atmosphere, the copper zinc tin sulfur thin film that is laminated with tin covering layer The step of performing high-temperature annealing on the precursor is as follows: placing the copper-zinc-tin-sulfur thin film precursor laminated with a tin coating layer in an annealing furnace, feeding hydrogen sulfide to a pressure of 2×10 ³ Pa, and then feeding nitrogen gas to The air pressure is 4×10 ⁴ Pa, and then the copper-zinc-tin-sulfur thin film precursor with the tin covering layer is heated to 550° C., kept for 15 minutes and then cooled naturally; The step of performing high-temperature annealing on the copper-zinc-tin-selenium film precursor with a tin covering layer is specifically: placing the copper-zinc-tin-selenium thin film precursor with a tin covering layer and the selenium particles in an annealing furnace, and passing nitrogen gas until the air pressure is 4×10 ⁴ Pa, then heat the copper-zinc-tin-selenide thin film precursor with the tin covering layer to 550° C., keep it warm for 15 minutes, and then cool naturally.

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