TWI463685B - Multi-layer stacked film, method for manufacturing the same, and solar cell utilizing the same - Google Patents

Description

Multilayer stacked light absorbing film, manufacturing method thereof and solar cell

The present invention relates to a solar cell, and more particularly to a multilayered light absorbing film of the photoelectric conversion layer thereof, a method of manufacturing the same, and a solar cell.

The CIGS solar cell is a solar cell having a chalcopyrite type compound layer as a photoelectric conversion layer and a zinc oxide (ZnO) as a transparent window layer. Chalcopyrite type compounds suitable for CIGS solar cells are based on Cu (copper), In (indium), Ga (gallium), and Se (selenium), and may be added to control the band gap. (sulfur). At present, it is still necessary to change the structure of the photoelectric conversion layer to further improve the photoelectric conversion efficiency of the CIGS solar cell without significantly changing the basic composition (CIGS).

An embodiment of the present invention provides a multi-layer stacked light absorbing film, comprising: a first layer on a substrate, and a first layer of CuIn _1-x Ga _x Se ₂ , wherein 0<x 1; the second layer is on the first layer, and the second layer is CuInSe ₂ ; the third layer is on the second layer, and the third layer is Cu _z Se, where 0<z 2; the fourth layer is on the third layer, and the fourth layer is CuInSe ₂ ; and the fifth layer is on the fourth layer, and the fifth layer is CuIn _1-x' Ga _x' (Se _1-y S _y ) ₂ , where 0<x' 1, and 0 y<1.

An embodiment of the invention provides a solar cell comprising the above-described multilayer stacked light absorbing film.

An embodiment of the present invention provides a method for fabricating a multilayer stacked light absorbing film, comprising: forming a first layer on a substrate, and the first layer is In _1-x Ga _x Se ₂ , wherein 0<x 1; forming a second layer on the first layer, and the second layer is InSe ₂ ; forming a third layer on the second layer, and the third layer is Cu _z Se, wherein 0<z 2; forming a fourth layer on the third layer, and the fourth layer is InSe ₂ ; and forming a fifth layer on the fourth layer, and the fifth layer is In _1-x' Ga _{x '} (Se _1-y S _y ) ₂ , where 0<x' 1, and 0 y<1, wherein Cu in the third layer will diffuse into the first layer, the second layer, the third layer, the fourth layer, and the fifth layer.

An embodiment of the present invention provides a method of fabricating a multilayer stacked light absorbing film 100, as shown in FIG. First, a first layer 11 is formed on the substrate 1, and the first layer 11 is CuIn _1-x Ga _x Se ₂ , where 0<x 1. In an embodiment of the invention, 0.23 x 0.33, that is, the Ga/In ratio in the first layer 11 is between 0.3 and 0.5. In another embodiment of the present invention, the first layer 11 is formed into a gradation structure, and the x value of the portion of the first layer 11 near the substrate 10 is greater than the x of the portion of the first layer 11 near the second layer 12. value. In other words, the bottom and surface portions of the multilayered light absorbing film 100 have a higher proportion of Ga. The energy gap size of the first layer 11 can be adjusted by selecting the value of x (Ga content). The method of forming the first layer 11 may be simultaneous deposition of Cu, In, Ga, and Se, and the deposition method may be a sputtering method, an evaporation method, a physical vapor deposition method, or other suitable deposition methods. In an embodiment of the invention, the substrate 1 may be soda glass (SLG), stainless steel (Steel Stainless), gallium arsenide (GaAs), a polymer such as poly-liminamide (PI), or other common Substrate material.

A second layer 12 is then formed on the first layer 11, and the second layer 12 is CuInSe ₂ . The method of forming the second layer 12 may be simultaneous deposition of Cu, In, and Se, and the deposition method may be sputtering, evaporation, physical vapor deposition, or other suitable deposition methods. Since the second layer 12 does not contain Ga, its energy gap is smaller than that of the first layer 11, thereby absorbing long-wavelength sunlight to increase the short-circuit current density (Jsc) of the solar cell.

The third layer 13 is then formed on the second layer 12 and third layer 13 based Cu _z Se, where 0 <z 2. The method of forming the third layer 13 may be simultaneous deposition of Cu and Se, and the deposition method may be sputtering, evaporation, physical vapor deposition, or other suitable deposition methods. In an embodiment of the present invention, a tempering process may be performed in a Se atmosphere after forming the third layer 13 to improve the defect density of the materials in the first layer 11, the second layer 12, and the third layer 13, and tempered The process temperature is between 400 ° C and 600 ° C. The form of Cu _z Se in the liquid phase at a high temperature contributes to the growth of the film grain.

A fourth layer 14 is then formed on the third layer 13, and the fourth layer 14 is CuInSe ₂ . The method of forming the fourth layer 14 may be simultaneous deposition of Cu, In, and Se, and the deposition method may be a sputtering method, an evaporation method, a physical vapor deposition method, or other suitable deposition methods. Since the fourth layer 14 does not contain Ga, its energy gap is smaller than that of the fifth layer 15 formed later, thereby absorbing long-wavelength sunlight to increase the short-circuit current density (Jsc) of the solar cell.

Finally, a fifth layer 15 is formed on the fourth layer 14, and the fifth layer 15 is CuIn _1-x' Ga _x' (Se _1-y S _y ) ₂ , where 0<x' 1, and 0 y<1. In an embodiment of the invention, 0.219 x' 0.324, that is, the Ga/In ratio in the fifth layer 15 is between 0.28 and 0.48. In another embodiment of the present invention, the fifth layer 15 is formed into a gradual structure, and the x' value of the fifth layer 15 near the portion of the fourth layer 14 is smaller than the portion of the fifth layer 15 away from the fourth layer 14. The x' value. Further, the y value of the portion of the fifth layer 15 adjacent to the fourth layer 14 is smaller than the y value of the portion of the fifth layer 15 away from the fourth layer 14. In other words, the surface portion of the multilayered light absorbing film 100 has a higher proportion of Ga and S. When the surface of the fifth layer 15 has an S element substituted part of the Se element, the surface energy gap of the fifth layer 15 can be increased. The method of forming the fifth layer 15 may be simultaneous deposition of Cu, In, Ga, and Se (and S), and the deposition method may be a sputtering method, an evaporation method, a physical vapor deposition method, or other suitable deposition methods. The light absorbing film 100 of the multilayer stack has been substantially completed so far, and its energy gap is V-shaped as shown in Fig. 2.

In an embodiment of the invention, the ratio (T':T) of the total thickness T' of the fourth layer 14 and the fifth layer 15 to the total thickness T of the first layer 11 and the second layer 12 is 1:5. Between 1:7. If the ratio of T'/T is too high, the film flatness and the parallel resistance are not good. If the ratio of T'/T is too low, the Cu _z Se conductive phase is likely to be generated in the surface and grain boundaries. In an embodiment of the invention, the ratio (T1/T2) of the thickness T1 of the first layer 11 to the thickness T2 of the second layer 12 is between 2:3 and 3:2. If the ratio of T1/T2 is too high, the short-circuit current is not good. If the ratio of T1/T2 is too low, the parallel resistance and open circuit voltage are not good. In an embodiment of the invention, the multi-layer stacked light absorbing film 100 has a thickness of between 2 μm and 3 μm. If the multilayered light absorbing film 100 is too thick, the series resistance is increased to cause a decrease in the short circuit current. If the multi-layer stacked light absorbing film 100 is too thin, the film absorption spectrum capability is lowered to reduce the magnitude of the short-circuit current.

In another embodiment of the present invention, the sixth layer 16 may be further formed on the fifth layer 15, and the sixth layer is CuGaS. The method of forming the sixth layer 16 may be to simultaneously deposit Cu, Ga, and S, and the deposition method may be a sputtering method, an evaporation method, a physical vapor deposition method, or other suitable deposition methods. Since the sixth layer 16 does not contain indium and selenium and contains only gallium and sulfur, the energy gap of the upper surface of the multilayered light absorbing film 100 can be further increased.

In another embodiment of the present invention, the first layer 11, the second layer 12, the third layer 13, the fourth layer 14, and the fifth layer 15 are sequentially formed on the substrate 1, but only the third layer 13 is included. Copper (Cu _z Se, where 0<z 2), the remaining layers are free of copper. For example, the first layer 11 and the fifth layer 15 are In _1-x Ga _x Se ₂ , and the second layer 12 and the fourth layer 14 are InSe ₂ . However, the high temperature tempering process performed during/after deposition allows the copper of the third layer 13 to diffuse into the first layer 11, the second layer 12, the third layer 13, the fourth layer 14, and the fifth layer 15, also A light absorbing film structure in which CuIn _1-x Ga _x Se ₂ /CuInSe ₂ /Cu _z Se/CuInSe ₂ /CuIn _1-x Ga _x Se ₂ stacked is formed.

The above-described multilayer stacked light absorbing film structure 100 can be used as a photoelectric conversion layer of a solar cell, as shown in FIG. Before forming the multilayered light absorbing film 100 on the substrate 1, the electrode layer 10 is first formed on the substrate 1. The electrode layer 10 may be a metal, an alloy, other conductive materials, or a multilayer structure as described above. In an embodiment of the invention, the electrode layer 10 is a molybdenum layer. Then, a plurality of stacked light absorbing films 100 are formed on the electrode layer 10, and then a transparent conductive oxide such as a buffer layer 17 such as CdS, a transparent window layer 18 such as ZnO, a transparent conductive layer 19 such as ITO, AZO, GZO, or FTO is formed. And another electrode layer 20 (such as a metal, an alloy, other conductive materials, or a multilayer structure as described above) On it. In an embodiment of the invention, the electrode layer 20 may be a two-layer structure of nickel/aluminum.

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

[Examples] Solar cell preparation

Sodium glass (CG glass) was placed on the In-line sputter machine. First, a 1 μm molybdenum electrode layer is deposited on the substrate by DC sputtering, and a multilayer stacked light absorbing film is deposited on the molybdenum electrode by evaporation or sputtering. Then, a 60 nm cadmium sulfide was deposited on the multi-layered light absorbing film as a buffer layer by sputtering in a water bath, and a 50 nm i-ZnO layer was deposited on the cadmium sulfide layer as a transparent window layer, followed by sputtering of a transparent conductive layer AZO. A metal electrode of Ni/Al is deposited by sputtering on the AZO layer to complete the solar cell.

Example 1

For the substrate, the molybdenum electrode, the cadmium sulfide, the i-ZnO layer, and the metal electrode of Ni/Al, see "Solar Cell Preparation". As for the multilayered light absorbing film, the deposition is as follows. First, a simultaneous deposition of In (deposition rate of 2 Å / s), Ga (deposition rate of 1.5 Å / s), and Se (deposition rate of 55 Å / s) to form a first layer (InGaSe), this deposition step It took 26 minutes and the substrate temperature was 400 °C. Next, a deposit of In (deposition rate of 2 Å/s) and Se (deposition rate of 55 Å/s) was simultaneously sputter deposited to form a second layer (InSe), this deposition step lasted 15 minutes, and the substrate temperature was 400 °C. Simultaneous sputtering deposition Cu (deposition rate of 3 Å/s) and Se (deposition rate of 55 Å/s) to form a third layer (CuSe), this deposition step lasted 13.5 minutes, and the substrate temperature was 600 °C. Next, a deposit of In (deposition rate of 1.3 Å/s) and Se (deposition rate of 55 Å/s) were simultaneously sputter deposited to form a fourth layer (InSe), which was carried out for 5 minutes and the substrate temperature was 600 °C. Finally, a simultaneous deposition of In (deposition rate of 1.3 Å / s), Ga (deposition rate of 2.9 Å / s), and Se (deposition rate of 55 Å / s) to form a fifth layer (InGaSe), this deposition step It took 2 minutes and the substrate temperature was 600 °C. The above deposition parameters are as shown in Table 1, and the physical properties of the solar cell having the multilayered light absorbing film are as shown in Table 4.

Comparative example 1

For the substrate, the molybdenum electrode, the cadmium sulfide, the i-ZnO layer, and the metal electrode of Ni/Al, see "Solar Cell Preparation". As for the three-layer stacked light absorbing film, the deposition manner is as follows. First, simultaneously depositing In (deposition rate 2Å/s), Ga (deposition rate 1Å/s), and Se (deposition rate 55 Å/s) to form the first layer (InGaSe), the deposition step lasts. 41 minutes and the substrate temperature was 400 °C. Next, Cu was deposited by sputtering (deposition rate of 3 Å/s) and Se (deposition rate of 55 Å/s) to form a second layer (CuSe). This deposition step lasted 15.5 minutes and the substrate temperature was 600 °C. Final simultaneous sputtering deposition In (deposition rate of 1.3 Å/s), Ga (deposition rate of 0.5 Å/s), and Se (deposition rate of 55 Å/s) to form a third layer (InGaSe), this deposition step lasts 11 minutes, and The substrate temperature was 600 °C. The above deposition parameters are shown in Table 2, and the physical properties of the solar cell having the three-layer stacked light absorbing film are shown in Table 4.

Example 2

For the substrate, the molybdenum electrode, the cadmium sulfide, the i-ZnO layer, and the metal electrode of Ni/Al, see "Solar Cell Preparation". As for the multilayered light absorbing film, the deposition is as follows. First, simultaneously depositing In (deposition rate 2Å/s), Ga (deposition rate 1Å/s), and Se (deposition rate 55 Å/s) to form the first layer (InGaSe), the deposition step lasts. 41 minutes and the substrate temperature was 400 °C. Next, Cu was deposited by sputtering (deposition rate of 3 Å/s) and Se (deposition rate of 55 Å/s) to form a second layer (CuSe). This deposition step lasted 15.5 minutes and the substrate temperature was 600 °C. Thereafter, tempering was carried out in an atmosphere of Se (deposition rate of 55 Å/s) for 30 minutes, and the substrate temperature was 600 °C. Finally, simultaneously depositing In (deposition rate of 1.3 Å / s), Ga (deposition rate of 0.5 Å / s), and Se (deposition rate of 55 Å / s) to form a third layer (InGaSe), this deposition step It took 11 minutes and the substrate temperature was 600 °C. The above deposition parameters are shown in Table 3, and the physical properties of the solar cells having the multilayered light absorbing film are as shown in Table 4.

It can be seen from the comparison between Example 1 and Comparative Example 1 that the InSe layer is interposed between the InGaSe layer and the CuSe layer, thereby effectively improving the performance of the solar cell. From the comparison between Comparative Example 1 and Example 2, it can be seen that the tempering process is performed in a Se atmosphere after forming the CuSe layer, and the efficiency of the solar cell can be effectively improved.

Example 3

For the substrate, the molybdenum electrode, the cadmium sulfide, the i-ZnO layer, and the metal electrode of Ni/Al, see "Solar Cell Preparation". As for the multilayered light absorbing film, the deposition is as follows. First, a simultaneous deposition of In (deposition rate of 2 Å / s), Ga (deposition rate of 2.8 Å / s), and Se (deposition rate of 55 Å / s) to form a first layer (InGaSe), this deposition step It took 10 minutes and the substrate temperature was 400 °C. Next, a deposit of In (deposition rate of 2 Å/s) and Se (deposition rate of 55 Å/s) were simultaneously sputter deposited to form a second layer (InSe), which was carried out for 31 minutes and the substrate temperature was 600 °C. Thereafter, Cu was deposited by sputtering (deposition rate of 2.8 Å/s) and Se (deposition rate of 55 Å/s) to form a third layer (CuSe), which was carried out for 22 minutes and the substrate temperature was 600 °C. Next, a deposit of In (deposition rate of 1 Å/s) and Se (deposition rate of 55 Å/s) was simultaneously sputter deposited to form a fourth layer (InSe), which was performed for 3.5 minutes and the substrate temperature was 600 °C. Finally, the deposition of In (deposition rate is 1Å/s), Ga (deposition rate of 2.8Å/s), and Se (deposition rate of 55 Å/s) are simultaneously deposited to form the fifth layer (InGaSe). This deposition step lasts. 4.5 minutes and the substrate temperature was 600 °C. The above deposition parameters are as shown in Table 5, and the physical properties of the solar cell having the multilayered light absorbing film are as shown in Table 7. The elemental depth analysis of the above-mentioned multilayer stacked light absorbing film is as shown in Fig. 4. Although only the deposition process of the third layer has copper, the copper will rapidly diffuse to the first layer, the second layer, the third layer, and the fourth layer. And the fifth floor.

Example 4

For the substrate, the molybdenum electrode, the cadmium sulfide, the i-ZnO layer, and the metal electrode of Ni/Al, see "Solar Cell Preparation". As for the multilayered light absorbing film, the deposition is as follows. First, simultaneous deposition of Cu (deposition rate of 0.9 Å / s), In (deposition rate of 2 Å / s), Ga (deposition rate of 2.8 Å / s), and Se (deposition rate of 55 Å / s) A first layer (CuInGaSe) was formed, this deposition step lasted 10 minutes, and the substrate temperature was 400 °C. Then, simultaneously depositing Cu (deposition rate of 0.9 Å/s), In (deposition rate of 2 Å/s) and Se (deposition rate of 55 Å/s) to form a second layer (CuInSe), the deposition step lasts. 31 minutes and the substrate temperature was 600 °C. Thereafter, Cu was deposited by sputtering (deposition rate of 0.9 Å/s) and Se (deposition rate of 55 Å/s) to form a third layer (CuSe), which was carried out for 22 minutes and the substrate temperature was 600 °C. Then, simultaneously depositing Cu (deposition rate of 0.9 Å/s), In (deposition rate of 1 Å/s) and Se (deposition rate of 55 Å/s) to form a fourth layer (CuInSe), this deposition step lasts 3.5. Minutes and the substrate temperature was 600 °C. Finally, simultaneous deposition of Cu (deposition rate of 0.9 Å / s), In (deposition rate of 1 Å / s), Ga (deposition rate of 2.8 Å / s), and Se (deposition rate of 55 Å / s) to form The fifth layer (CuInGaSe), this deposition step lasted 4.5 minutes, and the substrate temperature was 600 °C. The above deposition parameters are as shown in Table 6, and the physical properties of the solar cell having the multilayered light absorbing film are as shown in Table 7.

It can be seen from the seventh table that the deposition steps of the first to fifth layers all contain Cu, and the deposition process of only the third layer contains copper to complete a similar multilayer stacked light absorbing film. Even though the deposition steps of the first, second, fourth and fifth layers of Table 5 are copper free, copper can reach the surface and bottom of the CIGS by a high diffusion rate. Therefore, the layering steps of the first layer to the fifth layer all contain Cu, or only a certain The process steps of the layer (such as the third layer) containing Cu are all feasible processes, and it is only necessary to keep the total content of Cu the same, and the solar cells made in Example 3 or 4 have similar conversion efficiencies (%).

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

T, T', T1, T2‧‧‧ thickness

1‧‧‧Substrate

10, 20‧‧‧ electrode layer

11‧‧‧ first floor

12‧‧‧ second floor

13‧‧‧ third floor

14‧‧‧ fourth floor

15‧‧‧5th floor

16‧‧‧6th floor

17‧‧‧ Buffer layer

18‧‧‧ Transparent window layer

19‧‧‧Transparent conductive layer

100‧‧‧Multilayer stacked light absorbing film

1 is a schematic structural view of a multi-layer stacked light absorbing film according to an embodiment of the present invention; FIG. 2 is an energy level diagram of a multi-layer stacked light absorbing film according to an embodiment of the present invention; and FIG. 3 is a first embodiment of the present invention. In the embodiment, a schematic diagram of a solar cell; and FIG. 4 is an embodiment of the present invention in which a multi-layer stacked light absorbing film is analyzed in elemental depth.

T, T', T1, T2‧‧‧ thickness

1‧‧‧Substrate

10, 20‧‧‧ electrode layer

11‧‧‧ first floor

12‧‧‧ second floor

13‧‧‧ third floor

14‧‧‧ fourth floor

15‧‧‧5th floor

16‧‧‧6th floor

100‧‧‧Multilayer stacked light absorbing film

Claims (13)

A multi-layer stacked light absorbing film comprising: a first layer on a substrate, and the first layer is CuIn _1-x Ga _x Se ₂ , wherein 0<x 1; a second layer is located on the first layer, and the second layer is CuInSe ₂ ; a third layer is located on the second layer, and the third layer is Cu _z Se, wherein 0<z 2; a fourth layer is on the third layer, and the fourth layer is CuInSe ₂ ; and a fifth layer is on the fourth layer, and the fifth layer is CuIn _1-x' Ga _{x '} (Se _1-y S _y ) ₂ , where 0<x' 1, and 0 y<1. The multi-layer stacked light absorbing film of claim 1, wherein a ratio of a total thickness of the fourth layer and the fifth layer to a total thickness of the first layer and the second layer is 1: 5 to 1:7. The multi-layer stacked light absorbing film of claim 1, wherein the first layer and the second layer have a thickness ratio of between 2:3 and 3:2. The multi-layer stacked light absorbing film according to claim 1, wherein 0.23 x 0.33. The multi-layer stacked light absorbing film according to claim 1, wherein 0.219 x' 0.324. The multi-layer stacked light absorbing film of claim 1, wherein the first layer is a gradual structure, and the portion of the first layer adjacent to the substrate has an x value greater than the second layer. The x value of the part. Multilayer stacked light absorbing thin as described in claim 1 a film, wherein the fifth layer is a gradual structure, the x' value of the portion of the fifth layer adjacent to the fourth layer is smaller than the x' value of the portion away from the fourth layer, and the fifth layer The y value near the portion of the fourth layer is smaller than the y value away from the portion of the fourth layer. The multi-layer stacked light absorbing film according to claim 1, further comprising a sixth layer on the fifth layer, and the sixth layer is CuGaS. A solar cell comprising the multilayered light absorbing film of claim 1 of the patent application. The solar cell of claim 9, further comprising: a first electrode layer interposed between the substrate and the multi-layer stacked light absorbing film; a buffer layer on the multi-layer stacked light absorbing film a transparent window layer on the buffer layer; a transparent conductive layer on the transparent window layer; and a second electrode layer on the transparent conductive layer. A method for manufacturing a multilayer stacked light absorbing film, comprising: forming a first layer on a substrate, and the first layer is In _1-x Ga _x Se ₂ , wherein 0<x 1; forming a second layer on the first layer, and the second layer is InSe ₂ ; forming a third layer on the second layer, and the third layer is Cu _z Se, wherein 0 < z 2; forming a fourth layer on the third layer, and the fourth layer is InSe ₂ ; and forming a fifth layer on the fourth layer, and the fifth layer is In _1-x' Ga _{x '} (Se _1-y S _y ) ₂ , where 0<x' 1, and 0 y<1, wherein the Cu of the third layer is diffused in the first layer, the second layer, the third layer, the fourth layer, and the fifth layer. The method for manufacturing a multi-layer stacked light absorbing film according to claim 11, further comprising: performing a tempering process in a selenium atmosphere after forming the third layer and before forming the fourth layer, and The temperature of the tempering process is between 400 ° C and 600 ° C. The method for manufacturing a multi-layer stacked light absorbing film according to claim 11, further comprising: forming a sixth layer on the fifth layer, wherein the sixth layer is CuGaS.