TWI532204B - A method of fabricating thin film solar cell of i-iii-vi group compounds - Google Patents

Description

I-III-VI compound thin film solar cell manufacturing method

The present invention relates to the field of thin film solar cells, and more particularly to a method for fabricating an I-III-VI compound thin film solar cell. In this way, a large amount of waste liquid recovery problem can be achieved in the process of mass production and the chemical water bath process is eliminated, and the process cost is also greatly reduced.

As the industry flourishes, the energy supply shortage highlights the importance of renewable energy. In the development of solar cells, in addition to Silicon solar cells or gallium arsenide (GaAs) solar cells, copper indium gallium selenide (CIGS) solar cells are considered to be another potential solar cell in the future. A copper indium gallium selenide compound composed of an I-III-VI 2 group element can be made of a copper indium gallium selenide solar by its high optical absorption coefficient, excellent semiconductor properties, and properties that can be made using different hard or soft substrates. The battery has the advantages of low cost and flexibility in the industry competition.

The high-efficiency CIGS solar cell process developed today mainly uses a sodium-alkali glass (SLG) as a substrate, and sequentially deposits a Mo back electrode layer, a CIGS absorber layer (Absorber), and a CdS buffer layer from bottom to top. Buffer), i-ZnO/AZO light window layer (Windows) and Ni/Al upper electrode layer (Front contact), wherein the Mo back electrode layer and the i-ZnO/AZO light window layer are mainly magnetron sputtering processes (Sputtering) Mainly, the CIGS absorption layer is completed by an evaporation process. The CdS buffer layer is prepared by Chemical Bath Deposition, and finally, the Ni/Al upper electrode layer is deposited by electron beam evaporation. When the process of large-scale development and mass production is carried out in this process, the chemical water process used in the CdS buffer layer can not be consistent with the consistency of the process, and the film quality and uniformity are also susceptible to uneven reaction. Deterioration occurs. In addition, due to the toxic effects of cadmium, the recycling of a large amount of waste liquid makes the process cost high. Therefore, various sectors are actively developing a cadmium-free buffer layer by vacuum process. In the past, Atomic Layer Deposition was used. Although high film crystallization quality can be obtained, it is not conducive to sustainable development due to expensive equipment. Evaporation lacks long-term operational stability and uniformity. Will affect the coating ability of the buffer layer on the CIGS absorber layer; the use of sputtering process (Sputtering) can improve the above-mentioned defects, but in the deposition process of high-energy sputtering atoms, the surface structure of the CIGS absorber layer is destroyed, and can not be maintained well. The pn junction. In order to improve the above disadvantages, the present invention proposes a new method for preparing a buffer layer for a solar cell, which has a large amount of waste liquid recovery in the process of mass production, and a large amount of waste liquid recovery in the chemical water bath process, which not only greatly reduces the process cost but also maintains excellent quality. Photoelectric conversion efficiency.

In view of the above problems, an object of the present invention is to provide a method for manufacturing a high-quality I-III-VI compound thin film solar cell which can achieve process consistency in a mass production stage and is advantageous for developing high quality.

In order to achieve the above object, the present invention provides a buffer layer manufacturing method for a thin film solar cell of a group I-III-VI compound, wherein the I-III-VI compound thin film solar cell has an optical absorption layer and a buffer layer, and Forming a pn junction between the optical absorbing layer and the buffer layer, wherein the pn junction is formed by depositing a reactive layer film by physical vapor deposition The buffer layer is formed on the optical absorption layer and then subjected to a rapid thermal annealing process for the reaction layer film, and the buffer layer is an n-type compound semiconductor.

The reaction layer film material is one of a stack of metal zinc, magnesium, indium, or chalcogenide or an alloy thereof; the thickness of the reaction layer film may be set to 50 nm to 900 nm. Moreover, the ambient atmosphere of the rapid thermal annealing process may be one of selenium, hydrogen selenide, sulfur, hydrogen sulfide gas or a mixture thereof. And the working temperature of the rapid thermal annealing process is 1×10 ⁻⁵ Torr to 850 Torr; the temperature of the rapid thermal annealing process is 280° C. to 480° C.; and the heating rate of the rapid thermal annealing process is 20° C./min to 180 ° C / min.

In order to achieve the above object, the present invention also provides a thin film solar cell of the I-III-VI compound formed by the above process, comprising: a glass substrate; a metal molybdenum back electrode layer formed on the glass substrate; An optical absorption layer is formed on the metal molybdenum back electrode layer, the optical absorption layer is a p-type I-III-VI compound semiconductor; a buffer layer is formed on the optical absorption layer by a buffer layer prepared according to the foregoing process method, The buffer layer is an n-type compound semiconductor; an intrinsic zinc oxide barrier layer is formed on the buffer layer; a light window layer is formed on the intrinsic zinc oxide barrier layer, and the light window layer is an n-type transparent conductive oxide semiconductor And a metal upper electrode stack formed on the light window layer, and the metal upper electrode stack comprises an upper electrode bottom layer and an upper electrode top layer.

The metal molybdenum back electrode layer has a thickness of 500 nm to 1 μm; wherein the optical absorption layer thickness can be set to 1 μm to 2 μm. Wherein, the optical absorption layer may be one of a copper indium selenide compound, a copper indium gallium selenide compound or a copper indium selenide sulfur compound; the buffer layer may be a zinc sulfide compound, a zinc selenide compound, a magnesium zinc selenide compound or selenium. One of the indium selenium compounds. In addition, the thickness of the intrinsic zinc oxide barrier layer may be set to 50 nm to 100 nm; the thickness of the light window layer is 300 nm to 500 nm; the bottom layer of the upper electrode is metallic nickel, and the thickness thereof is 50 nm to 100 nm; Metallic aluminum having a thickness of from 1 μm to 2 μm.

The invention has the effect of providing an I-III-VI compound thin film solar cell manufacturing method, which utilizes an innovative method different from the conventional method of forming a pn junction, thereby eliminating the conventional chemical water process used to affect the film quality and uniformity. The lack of it, as well as the high cost of recycling a large amount of waste liquid, can also be greatly improved.

1‧‧‧Solar battery

10‧‧‧ glass substrate

11‧‧‧Metal molybdenum back electrode layer

12‧‧‧Optical absorption layer

13‧‧‧buffer layer

131‧‧‧Metal zinc film

132‧‧‧Selenium film

133‧‧‧Reactive layer film

14‧‧‧ Essential zinc oxide barrier layer

15‧‧‧Light window layer

16‧‧‧Metal upper electrode stack

161‧‧‧Upper electrode bottom layer

162‧‧‧ top electrode top

2‧‧‧Sputter chamber

20‧‧‧Magnetron Sputtered Metallic Zinc Target

3‧‧‧Extraction chamber

30‧‧‧Selenium evaporation source

4‧‧‧Rapid heat treatment furnace

40‧‧‧Quarter heater

1 is a schematic structural view of a thin film solar cell of a group I-III-VI compound according to a preferred embodiment of the present invention; FIG. 2A is a schematic flow chart of a method for fabricating a solar cell according to a preferred embodiment of the present invention; 2B is a schematic flow chart (2) of a solar cell manufacturing method according to a preferred embodiment of the present invention; FIG. 2C is a schematic flow chart (3) of a solar cell manufacturing method according to a preferred embodiment of the present invention; The XRD diffraction analysis of the zinc selenide buffer layer film annealed at different heating rates according to a preferred embodiment of the present invention; and FIG. 4 is a zinc selenide buffer layer film annealed at different reaction temperatures according to a preferred embodiment of the present invention. XRD diffraction analysis chart; FIG. 5 is an XRD diffraction analysis chart of a zinc selenide buffer layer film annealed at different reaction pressures according to a preferred embodiment of the present invention; FIG. 6 is another preferred embodiment of the present invention. Example I-III-VI compound thin Schematic diagram of the structure of the membrane solar cell; Fig. 7 is a graph showing the I-V characteristic of the I-III-VI compound thin film solar cell according to another preferred embodiment of the present invention.

In order for your review board to have a clear understanding of the contents of the present invention, please refer to the following description.

Please refer to FIG. 1 and FIG. 2A, FIG. 2B and FIG. 2C, which are schematic diagrams of the structure of the I-III-VI compound thin film solar cell according to the preferred embodiment of the present invention; and the solar cell manufacturing method of the preferred embodiment of the present invention. Process diagram (1) (2) (3). 1 is a structure of the I-III-VI compound thin film solar cell 1 of the present invention, comprising: a glass substrate 10; a metal molybdenum back electrode layer 11 formed on the glass substrate 10, and the metal molybdenum back electrode The layer 11 has a thickness of 500 nm to 1 μm; an optical absorption layer 12 is formed on the metal molybdenum back electrode layer 11, and the optical absorption layer 12 is a p-type I-III-VI compound semiconductor having a thickness of 1 μm to 2 μm. The material is one of a copper indium selenide compound, a copper indium gallium selenide compound or a copper indium selenide sulfur compound; a buffer layer 13 is formed on the optical absorption layer 12, the buffer layer 13 is an n-type compound semiconductor, on the material It is one of a zinc sulfide compound, a zinc selenide compound, a magnesium zinc selenide compound or an indium selenide selenide compound; an intrinsic zinc oxide barrier layer 14 is formed on the buffer layer 13, and the intrinsic zinc oxide barrier layer 14 The thickness of the light window layer 15 is formed on the intrinsic zinc oxide barrier layer 14, the light window layer 15 is an n-type transparent conductive oxide semiconductor, and the thickness of the light window layer is 300 nm to 500 nm; a metal upper electrode stack 16 formed on the light window On the layer 15, the metal upper electrode stack 16 includes an upper electrode bottom layer 161 and an upper electrode top layer 162, and the upper electrode bottom layer 161 may be metallic nickel having a thickness of 50 nm to 100 nm; the upper electrode top layer 162 may be Metal aluminum with a thickness of 1μm Up to 2 μm. The main technical feature of the solar cell structure is that the pn junction formed between the optical absorption layer 12 and the buffer layer 13 is formed by the process shown in FIGS. 2A-2C, and the solar cell having a pn junction is formed through the process. In the mass production stage, the process consistency can be achieved, and the cost pressure for a large amount of waste liquid recovery can be greatly improved.

Taking FIG. 2A as an example, after the glass substrate 10, the metal molybdenum back electrode layer 11 and the optical absorption layer 12 are sequentially prepared by a conventional solar cell process, the reaction layer 133 is completed by physical vapor deposition. The metal zinc layer film 131 is sputtered onto the optical absorption layer 12 by using a magnetron sputtering metal zinc target 20 in a sputtering chamber 2. The metal zinc film 131 may also be a metal zinc. One of the stack of magnesium, indium, or chalcogenide or an alloy thereof, which is formed before the target is selected from the metal zinc in the embodiment, the first precursor film 131 is formed by using different sputtering parameters. Metallic zinc layer. Further, the metal layer film has a thickness of approximately 50 nm to 300 nm.

Referring to FIGS. 2B and 2C, after completing a metal zinc film 131 in the previous step, a selenium film 132 is deposited on the metal zinc in a vapor deposition chamber 3 by, for example, a selenium evaporation source 30. After the reaction layer film 133 is completed on the layer film 131, the buffer layer 13 is formed by performing a rapid thermal annealing process on the reaction layer film 133 in a rapid thermal processing furnace 4 by, for example, a quartz heater 40, and the buffer layer is formed. The 13th layer is an n-type compound semiconductor, and the annealing process parameters are shown in Table 1. Moreover, the ambient atmosphere of the rapid thermal annealing process may be one of selenium, hydrogen selenide, sulfur, hydrogen sulfide gas or a mixture thereof.

From the third to fifth figures, the zinc selenide buffer layer film samples prepared in the examples were analyzed by X-ray diffraction analyzer, and the zinc selenide compound film obtained by the reaction with different annealing parameters was polycrystalline. Therefore, the film structure formed by the present invention can surely obtain a better crystallization effect, and the buffer layer preparation method can be effectively applied to the solar energy of CIGS. In various fields such as batteries.

Referring again to Table 2, the IV curve measurement of the I-III-VI compound thin film solar cell of the preferred embodiment of the present invention is shown. The following is a description of the structure shown in Fig. 1 and the process shown in Figs. 2A to 2C, and the experimental environmental parameters are specifically set and the IV characteristic curve measurement of the solar cell is performed. First, in the process of forming the metal zinc layer of the metal layer film 131 by using different sputtering parameters, the background vacuum pressure of the sputtering chamber 2 is controlled at 1×10 ^-5 to 1×10 ^-6 Torr, and the magnetron is splashed. The metal zinc target 20 deposits the metal zinc layer film 131, and the metal zinc layer has a thickness ranging from 50 to 300 nm. Following the evaporation chamber 202, the selenium layer film 132 is deposited by the selenium evaporation source 203, and the selenium layer has a thickness of at least 500 nm. Finally, the reaction layer film 133 is placed in the quartz cavity 4 and rapidly heated by a quartz heater 40; the temperature setting range is from 280 ° C to 480 ° C, and the heating rate is set to 20 to 180 ° C. /min, the reaction pressure is set to 1 × 10 ^-5 to 850 Torr, and the reaction time is set to 1 to 10 min, and the buffer layer 13 of the n-type semiconductor is finally completed. As for other structures, the film stacking is performed in the manner of a conventional solar cell process. In the case of a solar cell, the conversion efficiency can be simply expressed as η = (P _max /p _in ) = ((J _sc * V _oc * FF) / P _in ) * 100%; where η is the conversion efficiency; J _sc Is the current density; V _oc is the open circuit voltage; FF is the fill factor; P _in is the input power; P _max is the maximum power. Among them, when the temperature was set to 350 ° C, the temperature increase rate was set to 60 ° C / min, the reaction pressure was set to 1 × 10 ^-2 Torr, and the reaction time was set to 3 min, there was a better efficiency performance. As shown in the second table, at this time, the measurement calculation result is V _oc = 580 mv; J _sc = 34.65 mA/cm ² ; and the conversion efficiency η = 13.68%, so that the conversion efficiency does have a better effect.

Please refer to Figure 1, Figure 2A~2C again, and Figures 6 and 7. 6 is a structure of another preferred embodiment, and the process of this embodiment is identical to the previous embodiment, except that the structure is less than the first zinc oxide barrier layer 14 in the structure, and the other They are all identical. In this embodiment, the pn junction is formed by the method shown in FIGS. 2A-2C, and the structure includes: the glass substrate 10; the metal molybdenum back electrode layer 11 is formed on the glass substrate 10; the optical absorption The layer 12 is formed on the metal molybdenum back electrode layer 11, the optical absorption layer 12 is a p-type I-III-VI compound semiconductor; the buffer layer 13 is formed on the optical absorption layer 12, and the buffer layer 13 is An n-type compound semiconductor; the light window layer 15 is formed on the buffer layer 13, the light window layer 15 is an n-type transparent conductive oxide semiconductor, such as an indium tin oxide transparent conductive layer; and the metal upper electrode layer 16 Formed on the light window layer 15, and the metal upper electrode stack 16 includes the upper electrode bottom layer 161 and the upper electrode top layer 162. Similar to the process environment of the foregoing embodiment, the IV characteristic curve measurement is also performed for the present embodiment. As shown in Figure 7. At this time, the measurement calculation result was V _oc =507.75 mv; J _sc = 37.02 mA/cm ² ; and the conversion efficiency η = 12.41%. Therefore, its conversion efficiency can also maintain better performance.

In summary, the buffer layer 13 of the present invention is formed by using a sputtering and evaporation process to form two different precursor films on the optical absorption layer 12 of the p-type semiconductor. The buffer layer 13 of the n-type semiconductor is then further formed by a rapid thermal annealing process. This approach can achieve process consistency during the mass production phase, and the cost pressure for a large amount of waste liquid recovery can be greatly improved, and the conversion efficiency issue can also maintain a better effect.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Therefore, it is to be understood that equivalents or modifications may be made without departing from the spirit and scope of the invention. Equivalent changes and modifications made below are intended to be included within the scope of the invention.

10‧‧‧ glass substrate

11‧‧‧Metal molybdenum back electrode layer

12‧‧‧Optical absorption layer

131‧‧‧Metal zinc film

132‧‧‧Selenium film

133‧‧‧Reactive layer film

3‧‧‧Extraction chamber

30‧‧‧Selenium evaporation source

Claims (6)

A method for manufacturing a buffer layer of an I-III-VI compound thin film solar cell, wherein the I-III-VI compound thin film solar cell has an optical absorption layer and a buffer layer, and forms between the optical absorption layer and the buffer layer a PN junction, wherein the PN junction is formed by physically depositing a reaction layer film on the optical absorption layer of the p-type compound semiconductor by physical vapor deposition, and continuing to perform a rapid heat on the reaction layer film. The buffer layer is formed by an annealing process, and the buffer layer is an n-type compound semiconductor, wherein the ambient atmosphere of the rapid thermal annealing process is one of selenium, hydrogen selenide, sulfur, hydrogen sulfide gas or a mixture thereof. The method for producing a buffer layer for a thin film solar cell of a group I-III-VI compound according to claim 1, wherein the reaction layer film material is a stack of metal zinc, magnesium, indium, or chalcogenide or an alloy thereof. One of them. The method for producing a buffer layer of a thin film solar cell of a group I-III-VI compound according to claim 1 or 2, wherein the thickness of the reaction layer film is from 50 nm to 900 nm. The buffer layer manufacturing method of the I-III-VI compound thin film solar cell according to claim 1, wherein the rapid thermal annealing process has a working pressure of 1 × 10 ^-5 Torr to 850 Torr. The solar cell manufacturing method according to claim 1, wherein the rapid thermal annealing process has a temperature rise reaction temperature of 280 ° C to 480 ° C. The buffer layer manufacturing method of the I-III-VI compound thin film solar cell according to claim 1, wherein the rapid thermal annealing process has a heating rate of 20 ° C / min to 180 ° C / min.