阅读说明：本技术 薄膜太阳能电池的光吸收层的制备方法 (Preparation method of light absorption layer of thin-film solar cell ) 是由 王顺 高传增 李文杰 杨兵 李伟民 罗海林 冯叶 陈明 钟国华 杨春雷 于 2019-09-12 设计创作，主要内容包括：本发明公开了一种薄膜太阳能电池的光吸收层的制备方法,包括：应用磁控溅射工艺制备获得半导体预制层；在半导体预制层上制备形成硒薄膜层；将形成硒薄膜层后的半导体预制层置于退火炉中；将半导体预制层加热至第一预定温度后恒温第一预定时间；将半导体预制层从第一预定温度加热至第二预定温度后恒温第二预定时间,以使半导体预制层硒化；将半导体预制层从第二预定温度加热至第三预定温度后恒温第三预定时间,并在第三预定时间内通入硫化氢气体,以使半导体预制层硫化,制备获得硒化硫化的半导体光吸收层。本发明将半导体预制层的硒化和硫化设置在不同温度下分步进行,避免硒化的过度和不均匀性,同时也保证了硫化的质量,提高光吸收层的品质。(The invention discloses a preparation method of a light absorption layer of a thin-film solar cell, which comprises the following steps: preparing a semiconductor prefabricated layer by applying a magnetron sputtering process; preparing and forming a selenium film layer on the semiconductor prefabricated layer; placing the semiconductor prefabricated layer with the selenium film layer formed in an annealing furnace; heating the semiconductor prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time; heating the semiconductor prefabricated layer from the first preset temperature to a second preset temperature, and keeping the temperature for a second preset time to selenize the semiconductor prefabricated layer; and heating the semiconductor prefabricated layer from the second preset temperature to a third preset temperature, then keeping the temperature constant for a third preset time, and introducing hydrogen sulfide gas in the third preset time to vulcanize the semiconductor prefabricated layer to prepare the selenized and vulcanized semiconductor light absorption layer. According to the invention, selenization and vulcanization of the semiconductor prefabricated layer are carried out step by step at different temperatures, thereby avoiding excessive selenization and nonuniformity, ensuring the vulcanization quality and improving the quality of the light absorption layer.)

1. a method for preparing a light absorption layer of a thin film solar cell is characterized by comprising the following steps:

Preparing a semiconductor prefabricated layer by applying a magnetron sputtering process;

Evaporating and depositing on the semiconductor prefabricated layer to form a selenium thin film layer;

Placing the semiconductor prefabricated layer on which the selenium film layer is formed in an annealing furnace;

heating the semiconductor prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time;

Heating the semiconductor prefabricated layer from the first preset temperature to a second preset temperature, and keeping the temperature for a second preset time to selenize the semiconductor prefabricated layer;

And heating the semiconductor prefabricated layer from the second preset temperature to a third preset temperature, then keeping the temperature constant for a third preset time, and introducing hydrogen sulfide gas into the annealing furnace within the third preset time to vulcanize the semiconductor prefabricated layer to prepare the selenized and vulcanized semiconductor light absorption layer.

2. The method according to claim 1, wherein the first predetermined temperature is 80 ℃ to 200 ℃ and the first predetermined time is 3min to 5 min; the second preset temperature is 500-530 ℃, and the second preset time is 3-7 min; the third preset temperature is 550-600 ℃, and the third preset time is 4-10 min.

3. The method according to claim 1 or 2, wherein the semiconductor pre-fabricated layer is heated from room temperature to the first predetermined temperature for 0.5min to 1.5min, the semiconductor pre-fabricated layer is heated from the first predetermined temperature to the second predetermined temperature for 3min to 6min, and the semiconductor pre-fabricated layer is heated from the second predetermined temperature to the third predetermined temperature for 0.5min to 1.5 min.

4. The method of claim 1 or 2, wherein hydrogen sulfide gas is introduced into the annealing furnace for a second minute within the third predetermined time.

5. The method for producing a light-absorbing layer of a thin-film solar cell according to claim 4, wherein nitrogen gas is further introduced into the annealing furnace when hydrogen sulfide gas is introduced into the annealing furnace, and the molar ratio of the hydrogen sulfide gas to the nitrogen gas is 0.04 to 0.1.

6. The method for manufacturing a light absorption layer of a thin-film solar cell according to claim 1 or 2, wherein when the constant temperature is maintained to 300 ℃ after the third predetermined time is over, the chamber of the annealing furnace is vacuumized and then nitrogen gas is introduced until the chamber is cooled to room temperature.

7. The method as claimed in claim 1, wherein the semiconductor pre-fabricated layer is made of copper indium gallium, the molar ratio of copper to the sum of indium gallium is 0.9-0.95, and the molar ratio of gallium to the sum of indium gallium is 0.15-0.3.

8. The method of claim 7, wherein the molar ratio of the sum of selenium and indium gallium is 1.5 to 1.8 after the selenium thin film layer is formed on the semiconductor pre-fabricated layer by evaporation deposition.

9. The method of claim 1 or 8, wherein the selenium thin film layer has a thickness of 700nm to 1000 nm.

10. The method of manufacturing a light absorbing layer for a thin film solar cell according to claim 1, wherein the semiconductor preform layer on which the selenium thin film layer is deposited is placed in an annealing furnace, and then a chamber of the annealing furnace is subjected to a gas cleaning process and then a vacuum process.

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to a preparation method of a light absorption layer of a thin-film solar cell.

Background

A Copper Indium Gallium Selenide (CIGS) thin film solar cell is a high efficiency thin film solar cell having advantages of high stability, low cost and long life. The copper indium gallium selenide thin-film solar cell is essentially a direct band gap semiconductor, and the basic structure of the copper indium gallium selenide thin-film solar cell comprises a substrate, a back electrode, a light absorption layer, a buffer layer, a window layer, an antireflection layer and a metal electrode layer which are sequentially stacked, wherein the photoelectric absorption layer is a compound semiconductor thin film consisting of four elements of copper, indium, gallium and selenium. At present, methods for preparing the CIGS light absorption layer mainly comprise a co-evaporation method and a sputtering selenization method, and the sputtering selenization method is widely applied to the production process of large-size batteries because the cost of the sputtering selenization method is lower than that of the co-evaporation method.

The sputtering selenization method is that a semiconductor prefabricated layer of copper indium gallium is sputtered and deposited on a substrate, then the semiconductor prefabricated layer is placed in an atmosphere containing hydrogen selenide or selenium steam for annealing, so that four elements of copper, indium, gallium and selenium are mutually reacted and crystallized, and the copper indium gallium selenide film which accords with the stoichiometric ratio is obtained.

Generally, vulcanization is also performed in a sputtering selenization process path, the purpose of vulcanization is to enable sulfur to enter a vacancy in selenium to compensate defects, and meanwhile, the introduction of sulfur can also improve the forbidden bandwidth, so that the forbidden bandwidth of the whole light absorption layer is in a U shape (as shown in fig. 1), that is, the forbidden bandwidth of the two side surfaces of the light absorption layer is higher than the forbidden bandwidth in the light absorption layer, thereby achieving the effect of improving open-circuit voltage and further improving photoelectric conversion rate. The introduction of the sulfur source mainly comprises the introduction of hydrogen sulfide gas, the thermal evaporation of solid sulfur and gas selenium at present, wherein the hydrogen sulfide gas is adopted, so that the activity is high, and the effect is obvious.

at present, the selenization and vulcanization processes after sputtering are carried out synchronously, and specifically comprise the following steps: firstly, evaporating a selenium film layer on a copper indium gallium prefabricated layer to form a copper indium gallium selenium precursor; then putting the prepared copper indium gallium selenide precursor into an annealing furnace for preheating, wherein the preheating temperature is 80-200 ℃, and the surface of the precursor becomes flat; then, introducing hydrogen sulfide gas at the preheating temperature; and finally, heating to about 500-600 ℃ in the nitrogen protection atmosphere, and simultaneously selenizing and vulcanizing the copper indium gallium selenide precursor to form a copper indium gallium selenide sulfide (CIGSSe) light absorption layer. In the high-temperature selenization and vulcanization process, although the vulcanization can be effectively carried out and the forbidden bandwidth is increased, the selenization and vulcanization processes cannot be respectively and accurately controlled, the selenium element is diffused quickly at high temperature, random factors are large, the selenization and vulcanization degree of each film area is different, the uniformity and the repeatability of the film are poor, and the quality of the light absorption layer in industrial production is difficult to ensure. Meanwhile, by adopting the one-step selenylation and sulfurization process, although the process is simple and convenient and saves time, the activity of sulfur at high temperature is high, and a large amount of sulfur can enter the copper indium gallium selenide absorption layer by virtue of simultaneous sulfurization and selenylation, so that the forbidden bandwidth inside the copper indium gallium selenide absorption layer is increased, and therefore the forbidden bandwidth of the whole light absorption layer cannot reach the acknowledged optimal U-shaped distribution, and the photoelectric conversion rate of the thin-film battery can be reduced.

Disclosure of Invention

In view of the defects in the prior art, the invention provides a preparation method of a light absorption layer of a thin film solar cell, so as to improve the quality of the light absorption layer of the thin film solar cell and further improve the photoelectric conversion rate of the cell.

in order to achieve the purpose, the invention adopts the following technical scheme:

A preparation method of a light absorption layer of a thin film solar cell comprises the following steps:

Preparing a semiconductor prefabricated layer by applying a magnetron sputtering process;

Evaporating and depositing on the semiconductor prefabricated layer to form a selenium thin film layer;

Placing the semiconductor prefabricated layer on which the selenium film layer is formed in an annealing furnace;

Heating the semiconductor prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time;

Heating the semiconductor prefabricated layer from the first preset temperature to a second preset temperature, and keeping the temperature for a second preset time to selenize the semiconductor prefabricated layer;

And heating the semiconductor prefabricated layer from the second preset temperature to a third preset temperature, then keeping the temperature constant for a third preset time, and introducing hydrogen sulfide gas into the annealing furnace within the third preset time to vulcanize the semiconductor prefabricated layer to prepare the selenized and vulcanized semiconductor light absorption layer.

Preferably, the first preset temperature is 80-200 ℃, and the first preset time is 3-5 min; the second preset temperature is 500-530 ℃, and the second preset time is 3-7 min; the third preset temperature is 550-600 ℃, and the third preset time is 4-10 min.

Preferably, the time for heating the semiconductor prefabricated layer from room temperature to the first predetermined temperature is 0.5min to 1.5min, the time for heating the semiconductor prefabricated layer from the first predetermined temperature to the second predetermined temperature is 3min to 6min, and the time for heating the semiconductor prefabricated layer from the second predetermined temperature to the third predetermined temperature is 0.5min to 1.5 min.

preferably, hydrogen sulfide gas is introduced into the annealing furnace in a second minute within the third predetermined time.

preferably, when the hydrogen sulfide gas is introduced into the annealing furnace, nitrogen is also introduced, and the molar ratio of the hydrogen sulfide gas to the nitrogen is 0.04-0.1.

Preferably, when the constant temperature is kept to 300 ℃ after the third preset time is finished, the chamber of the annealing furnace is vacuumized and then nitrogen protection gas is introduced until the chamber is cooled to room temperature.

preferably, the semiconductor prefabricated layer is made of copper indium gallium, wherein the molar ratio of the copper to the sum of the indium gallium is 0.9-0.95, and the molar ratio of the gallium to the sum of the indium gallium is 0.15-0.3.

preferably, after the selenium thin film layer is formed on the semiconductor prefabricated layer through evaporation deposition, the molar ratio of the sum of selenium and indium gallium is 1.5-1.8.

preferably, the thickness of the selenium thin film layer is 700 nm-1000 nm.

Preferably, after the semiconductor prefabricated layer deposited to form the selenium film layer is placed in an annealing furnace, the chamber of the annealing furnace is firstly subjected to gas washing treatment and then vacuum pumping treatment.

According to the preparation method of the light absorption layer of the thin-film solar cell, the selenization and the vulcanization of the semiconductor prefabricated layer are carried out step by step at different temperatures, and the reaction competition relationship of selenium and sulfur is controlled, so that the excessive selenization and the non-uniformity are avoided, the vulcanization quality is ensured, the quality of the light absorption layer is improved, and the photoelectric conversion rate of the cell is further improved.

In a specific embodiment: firstly, selenizing at a relatively low temperature to form a good copper indium gallium selenide (CIGSe) semiconductor crystal; and then heating to a relatively high temperature to start sulfurization, wherein the activity of sulfur is greatly improved, and the sulfur can form CIGSSe crystals on the surfaces of the two sides of the light absorbing layer through a crystal boundary, so that the sulfur enters a selenium deficiency vacancy to make up for the defects of the formed CIGS crystals, and meanwhile, the forbidden bandwidth of the surfaces of the two sides of the light absorbing layer can be improved under the condition of less influence on the forbidden bandwidth inside the light absorbing layer, so that good U-shaped gradient distribution is achieved, and the high-quality light absorbing layer is obtained.

Drawings

Fig. 1 is an exemplary illustration of a light absorbing layer having a U-shaped gradient distribution of the forbidden band width;

FIG. 2 is a flowchart of a method for manufacturing a light absorbing layer of a thin film solar cell according to the present invention;

FIG. 3 is a graph of annealing temperature versus time for a selenization-sulfidation process in accordance with an embodiment of the present invention;

FIG. 4 is an I-V plot of a solar cell prepared according to an embodiment of the present invention;

Fig. 5 is an SEM image of a cross-section of a solar cell prepared according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described in accordance with the drawings are exemplary only, and the invention is not limited to these embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.

The invention provides a preparation method of a light absorption layer of a thin film solar cell, as shown in figure 2, the preparation method comprises the following steps:

And S10, preparing the semiconductor prefabricated layer by applying a magnetron sputtering process.

Specifically, the alloy elements constituting the semiconductor prefabricated layer are sputtered on a deposition substrate (for example, a back electrode of a solar cell) by a magnetron sputtering method in a vacuum environment to obtain an alloy thin film, so as to form the semiconductor prefabricated layer.

And S20, evaporating and depositing the semiconductor prefabricated layer to form a selenium thin film layer.

Specifically, solid selenium is used as a selenium source, and a selenium thin film layer is obtained by evaporation on the semiconductor prefabricated layer. Wherein the thickness of the selenium thin film layer is preferably 700nm to 1000 nm. Solid selenium is used as a selenium source, so that the use of hydrogen selenide highly toxic gas is avoided, and the safety in the production process is ensured.

In a preferred scheme, the semiconductor prefabricated layer is made of copper indium gallium, wherein the molar ratio of the sum of copper and indium gallium is 0.9-0.95, and the molar ratio of the sum of gallium and indium gallium is 0.15-0.3. The molar ratio of the selenium in the selenium film layer to the sum of the indium and gallium in the semiconductor prefabricated layer is 1.5-1.8.

And S30, placing the semiconductor prefabricated layer deposited with the selenium film layer into an annealing furnace.

after the semiconductor prefabricated layer deposited with the selenium film layer is placed in an annealing furnace, the chamber of the annealing furnace is firstly subjected to gas washing treatment and then vacuum pumping treatment. Specifically, the performing the scrubbing treatment specifically comprises: and vacuumizing the chamber of the annealing furnace, and filling nitrogen, and repeating the steps for more than 3 times.

And S40, heating the semiconductor prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time.

The step is mainly to preheat the semiconductor prefabricated layer, so that the surface of the semiconductor prefabricated layer becomes smoother. In a preferred embodiment, the first predetermined temperature may be set to be in a range of 80 ℃ to 200 ℃, and the first predetermined time may be set to be in a range of 3min to 5 min. Further, the time for heating the semiconductor prefabricated layer from the room temperature to the first predetermined temperature is preferably 0.5min to 1.5 min.

And S50, heating the semiconductor prefabricated layer from the first preset temperature to the second preset temperature, and keeping the temperature for a second preset time to selenize the semiconductor prefabricated layer.

In a preferred embodiment, the second predetermined temperature may be set to be in a range of 500 to 530 ℃, and the second predetermined time may be set to be in a range of 3 to 7 min. Further, the semiconductor prefabricated layer is heated from the first preset temperature to the second preset temperature for a time period of preferably 3min to 6 min.

Preheating the prefabricated layer plated with selenium, heating to 500-530 ℃, keeping the temperature for selenization, and growing the crystal to form a good selenized semiconductor crystal.

And S60, heating the semiconductor prefabricated layer from the second preset temperature to a third preset temperature, then keeping the temperature constant for a third preset time, and introducing hydrogen sulfide gas into the annealing furnace within the third preset time to vulcanize the semiconductor prefabricated layer to prepare the selenized and vulcanized semiconductor light absorption layer.

In a preferred embodiment, the third predetermined temperature may be set to be in a range of 550 ℃ to 600 ℃, and the third predetermined time may be set to be in a range of 4min to 10 min. Further, the semiconductor prefabricated layer is heated from the second preset temperature to the third preset temperature for a time period of 0.5-1.5 min.

The method is characterized in that gas hydrogen sulfide is used as a sulfur source, the activity is high, and the effect of using a large amount of solid elemental sulfur can be achieved only by using a small amount of solid elemental sulfur, so that nitrogen can be introduced when the hydrogen sulfide gas is introduced into the annealing furnace, and the molar ratio of the hydrogen sulfide gas to the nitrogen can be set to be 0.04-0.1.

in a preferred embodiment, hydrogen sulfide gas is introduced into the annealing furnace for the second minute within the third predetermined time.

in a preferable scheme, when the constant temperature is kept to 300 ℃ after the third preset time is finished, the chamber of the annealing furnace is vacuumized and then nitrogen protection gas is introduced until the room temperature is cooled.

The above method for producing a light-absorbing layer can be used for producing CIGSSe light-absorbing layers, and the method is also applicable to production of CZTSSe and SbSSe light-absorbing layers.

According to the preparation method of the light absorption layer, the selenization and the vulcanization of the semiconductor prefabricated layer are carried out step by step at different temperatures, and the reaction competition relationship of selenium and sulfur is controlled, so that the excessive selenization and the non-uniformity are avoided, the vulcanization quality is ensured, the quality of the light absorption layer is improved, and the photoelectric conversion rate of the battery is further improved.