TW201914044A - Solar cell and method of manufacturing same - Google Patents

Abstract

The disclosure provides a solar cell and a method for manufacturing the same. A solar cell includes: a metal electrode; a photoelectric conversion layer disposed on the metal electrode; a titanium oxide layer disposed on the photoelectric conversion layer; and a transparent conductive oxide layer disposed on the titanium oxide layer. The photoelectric conversion layer includes an absorption layer and a surface modification layer of the absorption layer, and the surface modification layer of the absorption layer includes a bivalent or / and trivalent metal ion modified absorption layer.

Description

Solar cell and manufacturing method thereof

This disclosure relates to a solar cell and a method for manufacturing the same.

Copper indium gallium selenium (CIGS) solar cells are a type of thin-film solar cells. They consume less energy than traditional silicon-based solar cells during production and attract attention because of their advantages such as high photoelectric conversion efficiency and low cost.

Copper indium gallium selenium (CIGS) is a chalcopyrite structure compound whose crystal structure is a square structure. It has the advantages of high optical absorption coefficient, wide absorption band range, high chemical stability, and direct energy gap. Suitable as a material for solar cells. A general CIGS solar cell has an electrode layer, a CIGS layer, a CdS layer, an i-ZnO layer, an AZO layer, and a finger electrode formed on the substrate in this order. Although the i-ZnO layer on the CdS layer can alleviate the problem of incomplete coverage of the CdS layer and reduce the damage of the CdS layer by ion bombardment when the AZO layer is sputtered, the thickness of the CdS layer and the i-ZnO layer can reach 100 nm to 150 nm, so it will also absorb part of the incident light and reduce the efficiency of the solar cell. On the other hand, the large resistance of the CdS layer and the i-ZnO layer is also disadvantageous for current collection.

In summary, a new CIGS solar cell structure is currently needed to overcome the problems caused by the conventional CdS layer and i-ZnO layer.

According to an embodiment of the present disclosure, a solar cell is provided, including: a metal electrode; a photoelectric conversion layer provided on the metal electrode; a titanium oxide layer provided on the photoelectric conversion layer; and a transparent conductive oxide layer provided on On the titanium oxide layer. The photoelectric conversion layer includes an absorption layer and a surface modification layer of the absorption layer, and the surface modification layer of the absorption layer includes a bivalent or / and trivalent metal ion modified absorption layer.

According to another embodiment of the present disclosure, a method for manufacturing a solar cell is provided, which includes: providing a substrate; forming a metal electrode on the substrate; forming an absorption layer on the metal electrode; and including bivalent or / and trivalent Metal ion liquid performs ion exchange treatment on the surface of the absorption layer to form a surface modification layer of the absorption layer on the absorption layer, wherein the operating temperature of the ion exchange treatment is between 25 ° C and 100 ° C; forming titanium oxide Layer on the surface modification layer; and forming a transparent conductive oxide layer on the titanium oxide layer.

In order to have a better understanding of the above and other aspects of the present invention, a number of embodiments are given below for detailed description as follows:

The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed herein. It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to match the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not intended to limit the implementation of the present invention. The limited conditions are not technically significant. Any modification of the structure, change of the proportional relationship, or adjustment of the size shall still fall within the scope of this invention without affecting the effects and goals that the invention can produce. The technical content disclosed by the invention can be covered.

In the embodiment of the present disclosure, the solar cell includes an absorption layer, a surface modification layer of the absorption layer, and a titanium oxide layer. Because the thickness of the surface modification layer of the absorption layer and the titanium oxide layer are both thin, it is possible to The light before the sunlight enters the absorption layer of the solar cell is reduced by the two layers, thereby increasing the cell efficiency of the solar cell.

The following are detailed examples of the disclosure. The detailed composition proposed in the embodiment is for illustrative purposes, and is not intended to limit the scope of the disclosure content to be protected. Those with ordinary knowledge should modify or change these components according to the needs of actual implementation.

FIG. 1 is a schematic diagram of a solar cell according to an embodiment of the disclosure. The solar cell 10 includes a metal electrode 100, a photoelectric conversion layer 200, a titanium oxide layer 300, a transparent conductive layer 400, and an upper metal electrode 500, which are sequentially stacked. The photoelectric conversion layer 200 includes an absorption layer 210 and a surface modification layer 220 of the absorption layer. The surface modification layer 220 of the absorption layer includes an absorption layer modified by a divalent or / and trivalent metal ion, wherein an element of the divalent or trivalent metal ion is different from an element of the absorption layer. In one embodiment, the divalent metal includes Zn, Cd, Mg, or Sn. In one embodiment, the trivalent metal includes In, Al, Ga, or Sn.

In one embodiment, the absorption layer 210 is disposed between the metal electrode 100 and the surface modification layer 220 of the absorption layer.

In the solar cell 10 of FIG. 1, because the titanium oxide layer 300 has smaller resistance and better light transmittance, it can provide a higher photocurrent, thereby improving cell efficiency.

In FIG. 1, the thickness of the surface modification layer 220 and the titanium oxide layer 300 of the absorption layer are both thin. For example, the thickness of the surface modification layer 220 of the absorption layer is greater than 0 nm and less than 100 nm. The thickness of the titanium oxide layer is greater than 0 nm and less than 100 nm. In this way, it is possible to reduce the light absorbed by the two layers before the sunlight enters the absorption layer 210 of the solar cell, thereby increasing the cell efficiency of the solar cell.

In one embodiment, the absorption layer 210 of the solar cell includes copper indium gallium selenium, copper indium gallium selenium sulfide, copper gallium selenium, copper gallium selenosulfide, or copper indium selenium. Because the selenium or sulfur element in the absorption layer may gradually diffuse into the titanium oxide layer 300 during the manufacturing process, the titanium oxide layer 300 further includes sulfur or selenium element, and the titanium oxide layer 300 is amorphous. phase.

In an embodiment, the material of the metal electrode 100 includes chromium, molybdenum, copper, silver, gold, platinum, or an alloy thereof, but is not limited thereto.

In one embodiment, the material of the transparent conductive oxide layer 400 includes indium tin oxide, indium zinc oxide, aluminum zinc oxide, gallium zinc oxide, aluminum gallium zinc oxide, cadmium tin oxide, and zinc oxide. , Or zirconium dioxide, but is not limited thereto.

In more detail, in the embodiment of the present disclosure, as shown in the solar cell 20 in FIG. 2, a method for manufacturing a solar cell includes a substrate 600 such as plastic, stainless steel, glass, quartz, or other common substrate materials. Next, a metal electrode 100 is formed on the substrate 600, and a formation method thereof may be sputtering, physical vapor deposition, or spraying. In one embodiment, the metal electrode 100 may be chromium, molybdenum, copper, silver, gold, platinum, other metals, or an alloy thereof. Next, an absorption layer 210 is formed on the metal electrode 100. In one embodiment, the absorption layer 210 may be copper indium gallium selenium (CIGS), copper indium gallium selenium sulfide (CIGSS), copper gallium selenium sulfide (CGS), copper gallium selenosulfide (CGSS), or copper indium selenium (CIS) . The formation method of the absorption layer 210 may be a method such as a vapor deposition method, a sputtering method, a plating method, or a nanoparticle coating method.

Next, the absorption layer on the metal electrode 100 is subjected to ion exchange treatment in an acidic or alkaline solution with a divalent (M ₁ ⁺² ) or / and trivalent (M ₂ ⁺³ ) metal ionic liquid. The operating temperature is about 25 ℃ -100 ℃. Ion exchange monovalent metal (eg, Cu ⁺¹ ) on the absorption layer with divalent (M ₁ ⁺² ) or / and trivalent (M ₂ ⁺³ ) metal ions on the ion exchange layer at this operating temperature, For example, part of the copper ions (Cu ⁺¹ ) on the absorption layer is exchanged with divalent or / and trivalent metal ions to form a surface modified layer of the absorption layer. In one embodiment, the divalent metal includes Zn, Cd, Mg, or Sn. In one embodiment, the trivalent metal includes In, Al, Ga, or Sn. Because only the modified layer of the absorption layer formed by the ion exchange method is applied on the absorption layer, the thickness of the layer is relatively thin. For example, the thickness of the surface modification layer 220 of the absorption layer is greater than 0 nm and less than 100 nm. This value-changing layer can provide n-type characteristics, so it can form a homo-junction with the p-type CIGS absorption layer. However, if the thickness of the surface modification layer 220 of the absorption layer is too thick, it will directly affect the width of the empty region, thereby reducing Battery efficiency. If the thickness of the surface modification layer 220 of the absorption layer is too thin, a good homo-junction cannot be formed, which will directly affect the battery efficiency.

Next, ALD is used to form a titanium oxide layer 300 on the modified layer 220 of the absorption layer. The temperature of the atomic layer deposition is between 100 ° C and 180 ° C, and the precursor of the atomic layer deposition may be tetraisopropyl. Titanium oxide. If the temperature of the atomic layer deposition is too high, the modified layer 220 and the absorption layer 210 of the absorption layer may be damaged. If the temperature of the atomic layer deposition is too low, in addition to the significant decrease in the coating speed, the carbon in the precursor cannot be removed, so the quality of the film is greatly reduced. In an embodiment, because the selenium or sulfur element therein may gradually diffuse into the titanium oxide layer 300 during the manufacturing process of the absorption layer, the titanium oxide layer 300 may further include sulfur or selenium element. The titanium oxide layer 300 is an amorphous phase. It is worth noting that the precursors used for atomic layer deposition must not contain halogens such as TiCl ₄ , TiBr ₄ , or the like to avoid halogens generated during the deposition process from corroding the modified layer 220 (or even the absorption layer) of the underlying absorber layer. 210). In one embodiment, the thickness of the titanium oxide layer 300 is greater than 0 and less than or equal to 100 nm. In one embodiment, the thickness of the titanium oxide layer 300 is greater than 0 and less than or equal to 30 nm. If the thickness of the titanium oxide layer 300 is too thick, the amount of penetrating light will be reduced, thereby reducing the battery efficiency. If the titanium oxide layer 300 does not exist, the leakage current of the battery cannot be effectively suppressed, and damage to the modified layer 220 of the absorption layer by ion bombardment during sputtering of the transparent conductive oxide layer 400 cannot be avoided.

A transparent conductive oxide layer 400 is then formed on the titanium oxide layer 300. In an embodiment, the material of the transparent conductive oxide layer 400 may be indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), aluminum gallium Zinc oxide (AGZO), cadmium tin oxide, zinc oxide, zirconium dioxide, or other transparent conductive materials. The method for forming the transparent conductive oxide layer 400 may be a sputtering method, a vapor deposition method, an atomic layer deposition method, a thermal cracking method, a nanoparticle coating method, and other related processes.

In one embodiment, an upper metal electrode 500 is formed on the transparent conductive oxide layer 400 according to circumstances. The upper metal electrode 500 is, for example, a finger electrode, and the material of the upper metal electrode 500 may be a nickel-aluminum alloy, and a forming method thereof may be sputtering, lithography, etching, and / or other suitable processes.

Compared with the conventional i-ZnO layer having a buffer layer CdS and a transparent conductive oxide layer in the conventional solar cell, the above-mentioned titanium oxide layer 300 has a smaller resistance and a higher light incident amount, and the above-mentioned modified layer can provide n Type characteristics, can form a homo-junction with CIGS absorption layer of p-type, which can make solar cells have better photoelectric conversion efficiency.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with the accompanying drawings as follows:

Examples

Example 1

First, 1000 nm of Cr and Mo were plated on a stainless steel substrate as metal electrodes through a sputtering process. Then, a CuInGa nanoparticle oxidation precursor is coated on the Mo film by a coating method, and then a reduction and selenization vulcanization process is performed to prepare a CIGSeS absorption layer (about 3000 nm). Then the CIGSeS absorption layer was cleaned with a 5 wt% KCN aqueous solution to remove the copper selenium compound, and then the CdSO ₄ aqueous solution (10 ^-3 M) was mixed with ammonia water (1 M) to form a Cd ion solution for ion exchange on the surface of the absorption layer, where The ion exchange operation temperature is controlled at about 65 ° C, and a thin surface modification layer of the absorption layer can be formed on the absorption layer. Subsequent to ALD plating of titanium oxide layer, the coating temperature is controlled at 120 ° C, the thickness of the coating is 10 nm, and then the AZO layer (Al doped-ZnO) of 300 nm is plated on the surface of the absorber layer in a sputtering process. The layer is used as a transparent conductive oxide layer, and finally a Ni-Al finger electrode is plated on the transparent conductive oxide layer to complete the solar cell of Example 1.

Example 2

The preparation method is similar to that in Example 1, except that In ₂ (SO ₄ ) ₃ and tartaric acid (0.1 M) are used to prepare In-containing ionic liquid (0.2M) for ion exchange on the surface of the absorption layer, wherein the operating temperature of the ion exchange is Controlled at about 75 ° C.

Comparative example

Comparative Example 1-2

First, 1000 nm Cr and Mo alloys were plated on a stainless steel substrate through a sputtering process as metal electrodes. Then, a CuInGa nanoparticle oxidation precursor is coated on the Mo film by a coating method, and then a reduction and selenization vulcanization process is performed to prepare a CIGSeS absorption layer (about 3000 nm). Then, the CIGSeS absorption layer was cleaned with a 5 wt% KCN aqueous solution to remove the copper-selenium compound, thereby forming an absorption layer. Then, a 50 nm thick CdS film was plated on the absorption layer as a buffer layer by a chemical bath method, in which the temperature of the chemical bath method was controlled at 65 ° C. Next, a 50 nm thick i-ZnO layer is prepared on the buffer layer by a sputtering process, and then a 300 nm AZO layer (Al doped -ZnO) is deposited on the i-ZnO layer as a transparent conductive oxide layer by a sputtering process. Finally, Ni-Al finger electrodes were plated on the transparent conductive oxide layer to complete the solar cell of Comparative Example 1-2.

In terms of experimental design, the examples and comparative examples are semi-finished solar cell structures of the same process when forming the metal electrode to the absorbing layer, and then the semi-finished product of the same solar cell is divided into two groups of semi-finished products of the same area (eg, Example 1 And Comparative Example 1, Example 2 and Comparative Example 2, each of which is the same piece of semi-finished product), and then a modified layer / titanium oxide layer / AZO / Ni-Al finger electrode with an absorption layer (such as Example 1-2) and forming a CdS / i-ZnO / AZO / Ni-Al finger electrode (as in Comparative Example 1-2), as shown in Table 1-3, the electrical comparison between the example and the comparative example, The influence of the absorption layer / titanium oxide layer modified by different metal ions on battery electrical properties can be compared.

Table 1 (Titanium oxide thickness of Example 1 = 10 nm)

Table 2 (Titanium oxide thickness of Example 2 = 10nm)

The results in Table 1-2 show that the open circuit voltage (V _oc ) of the battery of Comparative Example 1-2 is slightly higher than that of Example 1-2 (surface modified layer with titanium oxide layer / titanium oxide layer). Compare Table 1 The short-circuit current (J _SC ) of the two-structure battery, the battery of Example 1 is about 2.3 mA / cm ² higher than the battery of Comparative Example 1. It is inferred that the titanium oxide film should be provided with higher light penetration. Comparing the FF of the two structures, Then Example 1 is significantly higher than Comparative Example 1 by about 2%. There is no significant difference between the series resistance (R _s ) and the parallel resistance (Rsh). If the battery efficiency of the two is compared, it can be seen that the battery efficiency of Example 1 is higher than that of Comparative Example 1. The efficiency of the battery is about 1.0% higher. The main reason for the increase in efficiency is the increase in short-circuit current and the increase in FF value. Comparing the short-circuit current (J _SC ) of the two structures of Table 2, the battery of Example 2 is about 2.3 mA / cm ² higher than the battery of Comparative Example 2. If the FF of the two structures is compared, Example 2 is higher than the comparative example. 0.5%, there is no significant difference between the series resistance (R _s ) and the parallel resistance (R _sh ). If the battery efficiency of the two is compared, it can be seen that the battery efficiency of Example 2 is about 0.4% higher than that of Comparative Example 2. The increase is mainly due to the increase in short-circuit current and the increase in FF value.

Example 3-6

The manufacturing method of Example 3-6 is similar to that of Example 1, except that the surface modification process of forming a thin absorption layer on the absorption layer is different. The electrical measurements of Examples 3-6 are shown in Table 4.

Table 3 (Titanium oxide thickness = 10nm)

As shown in Table 4, as the thickness of the surface treatment of the absorbing layer increases (1 minute to 20 minutes), V _oc decreases (from 0.567 V to 0.553 V). The possible cause is the excessive diffusion of Cd ions due to the excessively long Cd surface treatment time. As a result, the V _{oc of the} battery decreases. In addition, as the surface treatment time of Cd increases, the J _SC ratio decreases slightly. If the FF value is compared, it decreases significantly with the increase of Cd surface treatment time. The main reason for the decrease in FF is _{Due to the} decrease in R _sh and the increase in R _s , the overall electrical results are reflected in the battery efficiency. The battery efficiency decreases significantly with the increase of the Cd surface treatment time (13.07% (1 min), 11.81% (20 min)), which is evident in The surface modification process does not take too long.

Examples 7-10

The manufacturing method of Example 7-10 is similar to that of Example 1, except that the titanium oxide layer is plated by the ALD method, and the thickness of the coating film is different. The electrical measurement of each example in which the thickness of the titanium oxide layer was changed is shown in Table 5.

Table 4

As shown in Table 4, as the thickness of titanium oxide increases (4 nm to 15 nm), V _oc decreases (0.571 V to 0.555 V), and the J _SC ratio decreases slightly. If the FF value is compared, it decreases significantly. The reason is that R _{s has} risen. The overall electrical results are reflected in the battery efficiency. The battery efficiency decreases significantly with the increase of the thickness of titanium oxide (13.23% (4 nm), 12.17% (15 nm)). The thickness of titanium oxide is obvious. It doesn't need to be too thick.

FIG. 3 is an EQE comparison of two batteries manufactured in the same manner as Comparative Example 1 and Example 1. It can be seen from the figure that the TiO ₂ / Cd surface modification / CIGS battery is compared with the i-ZnO / CdS / CIGS battery. The higher quantum conversion efficiency is due to the fact that the TiO ₂ / Cd surface modification / CIGS battery allows more incident light to enter the absorption layer than the iZnO / CdS / CIGS battery. The J of the battery calculated by EQE _SC is 34.55 mA / cm ² (TiO ₂ / Cd surface modification / CIGS) and 32.37 mA / cm ² (iZnO / CdS / CIGS), which are consistent with the electrical measurement results. The battery energy gap calculated by EQE is two All of them are consistent, and the value is 1.103 eV, which reflects V _{oc with the} same battery performance.

In summary, although the present invention has been disclosed as above with various embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

10, 20‧‧‧ solar cells

100‧‧‧metal electrode

200‧‧‧ photoelectric conversion layer

210‧‧‧ Absorptive layer

220‧‧‧ Surface modification layer of absorption layer

300‧‧‧ titanium oxide layer

400‧‧‧ transparent conductive layer

500‧‧‧ on metal electrode

600‧‧‧ substrate

FIG. 1 is a schematic diagram of a solar cell according to an embodiment of the disclosure. FIG. 2 is a schematic diagram of a solar cell according to an embodiment of the disclosure. FIG. 3 is a comparison example of an embodiment of the disclosure and an EQE comparison diagram of the embodiment.

Claims (19)

A solar cell includes: a metal electrode; a photoelectric conversion layer disposed on the metal electrode, wherein the photoelectric conversion layer includes an absorption layer and a surface modification layer of the absorption layer, and the surface modification layer of the absorption layer includes A bivalent or / and trivalent metal ion modified absorption layer; a titanium oxide layer disposed on the photoelectric conversion layer; and a transparent conductive oxide layer disposed on the titanium oxide layer. The solar cell according to item 1 of the scope of patent application, wherein the absorption layer is disposed between the metal electrode and a surface modification layer of the absorption layer. The solar cell according to item 1 of the patent application scope, wherein the divalent metal includes Zn, Cd, Mg or Sn. The solar cell according to item 1 of the patent application scope, wherein the trivalent metal includes In, Al, Ga, or Sn. The solar cell according to item 1 of the patent application scope, wherein the absorption layer comprises copper indium gallium selenium, copper indium gallium selenium sulfide, copper gallium selenium, copper gallium selenosulfide, or copper indium selenium. The solar cell according to item 1 of the patent application scope, wherein the titanium oxide layer further includes sulfur or selenium. The solar cell according to item 1 of the scope of patent application, wherein the thickness of the surface modification layer of the absorption layer is greater than 0 nm and less than 100 nm. The solar cell according to item 1 of the patent application scope, wherein the thickness of the titanium oxide layer is greater than 0 nm and less than 100 nm. The solar cell according to item 1 of the scope of the patent application, wherein the material of the metal electrode includes chromium, molybdenum, copper, silver, gold, platinum, or an alloy thereof. The solar cell according to item 1 of the patent application scope, wherein the material of the transparent conductive oxide layer includes indium tin oxide, indium zinc oxide, aluminum zinc oxide, gallium zinc oxide, aluminum gallium zinc oxide, cadmium Tin oxide, zinc oxide, or zirconia. The solar cell according to item 1 of the patent application scope, wherein the titanium oxide layer is an amorphous phase. A method for manufacturing a solar cell includes: providing a substrate; forming a metal electrode on the substrate; forming an absorption layer on the metal electrode; and applying a bivalent or / and trivalent metal ionic liquid to the substrate. The surface of the absorption layer is subjected to ion exchange treatment to form a surface modification layer of the absorption layer on the absorption layer, wherein the operating temperature of the ion exchange treatment is between 25 ° C and 100 ° C; a titanium oxide layer is formed on the absorption layer; A surface modification layer of the absorption layer; and forming a transparent conductive oxide layer on the titanium oxide layer. The method for manufacturing a solar cell according to item 12 of the application, wherein the metal ionic liquid includes an ionic liquid of an acidic or alkaline solution. The method for manufacturing a solar cell according to item 12 of the application, wherein the divalent metal includes Zn, Cd, Mg, or Sn. The method for manufacturing a solar cell according to item 12 of the application, wherein the trivalent metal includes In, Al, Ga, or Sn. The method for manufacturing a solar cell according to item 12 of the application, wherein the titanium oxide layer further includes sulfur or selenium. The method for manufacturing a solar cell according to item 12 of the scope of patent application, wherein the thickness of the surface modification layer of the absorption layer is greater than 0 nm and less than 100 nm. The method for manufacturing a solar cell according to item 12 of the application, wherein the thickness of the titanium oxide layer is greater than 0 nm and less than 100 nm. The method for manufacturing a solar cell according to item 12 of the application, wherein the titanium oxide layer is formed by an atomic layer deposition method.