Antireflection layer, composite layer, solar battery, method for manufacturing antireflection layer, and coating material

Abstract

To provide an antireflection layer that can be formed by a simple method.SOLUTION: An antireflection layer 10 contains a compound represented by the following formula (1), and has a fine uneven structure on its surface. In the formula (1), A denotes a monovalent group including a nitrogen-containing aromatic ring, B denotes a monovalent group including a hydrocarbon aromatic ring having a hydroxy group, L denotes a divalent group which is -N=CH- or -N=N-, and a carbon of the nitrogen-containing aromatic ring of A and a carbon next to a carbon bonded to the hydroxy group in the hydrocarbon aromatic ring of B are connected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an antireflective layer, a composite layer, a solar cell provided with an antireflective layer or a composite layer, a method for producing an antireflective layer, and a coating material for forming an antireflective layer. [Background technology]

[0002] Conventionally, a technique for suppressing (reducing) surface reflection of light by providing a microstructure (fine uneven structure) on the surface has been known. For example, by providing such a microstructure (anti-reflection structure) on the surface of a solar cell, it is possible to reduce the reflection of sunlight and allow more sunlight to enter the solar cell (Non-Patent Documents 1 and 2).

[0003] Non-Patent Document 1 discloses the formation of a fine uneven structure by chemical etching. By treating a silicon (Si) substrate with a mixed solution of silver nitrate and hydrofluoric acid, one-dimensional nanowire structures and nanohole structures can be formed on the surface of the Si substrate. Non-Patent Document 2 discloses the formation of a fine structure by reactive ion etching. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Jpn J. Appl. Phys. 55 (6), 065001 (2016). DOI: 10.7567 / JJAP.55.065001 [Non-Patent Document 2] Nanotechnology 30 (34), 344001 (2019). DOI: 10.1088 / 1361-6528 / ab0451 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while the chemical etching disclosed in Non-Patent Document 1 is a relatively simple process, the types of substrates that can be used are limited. In addition, the formation of the anti-reflection structure (chemical etching) must be carried out as a process prior to the assembly of the solar cell. This causes the inconvenience of restricting the order of manufacturing steps. In addition, the reactive ion etching disclosed in Non-Patent Document 2 requires expensive equipment, which increases manufacturing costs. In addition, like chemical etching, reactive ion etching must also be carried out prior to the assembly of the solar cell, which restricts the order of manufacturing steps.

[0006] The present invention is intended to solve these problems. That is, the present invention provides an antireflection layer that can be formed by a simple method. [Means for solving the problem]

[0007] As a result of intensive research into achieving the above object, the inventors have found that the above object can be achieved by the following configuration.

[0008] [1] An antireflection layer comprising a compound represented by formula (1) described below and having a fine uneven structure on its surface. [2] The antireflection layer according to [1], wherein in formula (1), A is a group represented by any one selected from the group consisting of formulas (A1) to (A4) described below. [3] The antireflection layer according to [1], wherein in formula (1), A is a group containing a triazole ring. [4] The antireflection layer according to any one of [1] to [3], wherein in formula (1), B is a group represented by any one selected from the group consisting of formulas (B1) to (B4) described below. [5] The antireflection layer according to any one of [1] to [3], wherein in formula (1), B is a group containing a phenol ring. [6] The antireflection layer according to [1], wherein the compound represented by formula (1) is a compound represented by the following formula (1-1) described below. [7] The antireflection layer according to any one of [1] to [6], wherein the compound represented by formula (1) has fluorescent properties. [8] The antireflection layer according to any one of [1] to [7], further comprising quantum dots. [9] A composite layer comprising the antireflection layer according to any one of [1] to [8] and a protective layer formed on the antireflection layer.

[10] The composite layer according to [9], wherein the protective layer is a metal oxide layer.

[11] A solar cell comprising the antireflection layer according to any one of [1] to [8].

[12] A solar cell comprising a composite layer according to [9] or

[10] .

[13] A method for producing an antireflection layer according to any one of [1] to [8], preparing a coating material containing a compound represented by formula (1) and a solvent capable of dissolving the compound; Applying the coating material to a substrate to form a coating film; and drying the coating film to obtain the antireflection layer.

[14] A coating material for forming the antireflection layer according to any one of [1] to [8], comprising a compound represented by formula (1) described below and a solvent. Effect of the Invention

[0009] The antireflection layer of the present invention can be formed by a simple method (typically, by applying a coating material and drying it), which can reduce production costs and shorten production time. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram (cross-sectional view) of an antireflection layer of the present embodiment. [Diagram 2] 2 is a flowchart illustrating a method for manufacturing an antireflection layer according to the present embodiment. [Diagram 3] FIG. 4 is a schematic diagram (cross-sectional view) of a composite layer according to a modified example of the present embodiment. [Figure 4] 3A to 3C are diagrams illustrating a presumed mechanism for forming the uneven structure of the antireflection layer of the present embodiment. [Diagram 5]1 is a synthetic reaction formula for the compound represented by formula (1-1). [Figure 6] FIG. 6(a) shows the results of FT-IR analysis of the compound represented by formula (1-1) synthesized in the Examples, and FIG. 6(b) shows the results of 1H-NMR analysis. [Figure 7] 2 shows optical microscope images of the surface of an antireflection layer 1 produced in an example at different magnifications. [Figure 8] 2 shows SEM images of different observation areas of the surface of an antireflection layer 1 produced in an example. [Figure 9] 1 shows an SEM image and AFM analysis results of the surface of an antireflection layer 1 produced in an example. [Figure 10] FIG. 2 is a graph showing the results of measuring the reflectance of the antireflection layer 1 produced in an example. [Figure 11] FIG. 2 is a diagram showing the absorption and emission characteristics of the compound represented by formula (1-1) synthesized in the examples. [Figure 12] FIG. 1 is a diagram showing the results of evaluation of JV characteristics of solar cells (with / without antireflection layer 1) produced in an example. [Figure 13] FIG. 2 is a graph showing the external quantum efficiency (EQE) of the solar cells (with and without the antireflection layer 1) produced in the examples. [Figure 14] FIG. 2 is a graph showing the relationship between the content (concentration of paint) of the compound represented by formula (1-1) in the paint used in the production of solar cells produced in the Examples, and the power conversion efficiency (PCE) and current density. [Figure 15] FIG. 1 is a diagram showing the results of evaluating the weather resistance of a solar cell (with an antireflection layer 1 and an ITO protective layer) produced in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "~" means a range including the numerical values ​​before and after "~" as the lower and upper limits.

[0012] In the description of groups (atomic groups) in this specification, the description that does not indicate whether substituted or unsubstituted includes both unsubstituted and substituted groups, as long as it does not impair the effects of the present invention. For example, "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups), but also alkyl groups that have a substituent (substituted alkyl groups). This also applies to each compound.

[0013] <Anti-reflection layer> The antireflection layer 10 of this embodiment (see FIG. 1) contains a compound represented by the following formula (1) (hereinafter, appropriately referred to as a "specific compound"), and has a fine uneven structure on the surface.

[0014] [ka] In formula (1), A is a monovalent group containing a nitrogen-containing aromatic ring, B is a monovalent group containing a hydrocarbon aromatic ring having a hydroxy group, L is a divalent group which is -N=CH- or -N=N-, and links a carbon of the nitrogen-containing aromatic ring of A to a carbon adjacent to the carbon to which the hydroxy group is bonded in the hydrocarbon aromatic ring of B.

[0015] An example of the specific compound is shown in Fig. 4, and a presumed mechanism for the formation of the uneven structure of the antireflection layer 10 will be described. The mechanism described below is merely presumed and does not affect the scope of the present invention. The specific compound shown in Fig. 4 is a compound represented by formula (1-1) described later, in which A in formula (1) is a triazole ring, B is a phenol ring, and L is -N=CH-.

[0016] The antireflection layer 10 of this embodiment can be manufactured by a very simple method, for example, by applying a solution (paint) of the specific compound to the substrate 40 and drying it. As shown in FIG. 4, the specific compound in the paint has an intramolecular hydrogen bond between the nitrogen atom of L in formula (1) and the hydrogen atom of the hydroxyl group of B (phenol ring), and no intermolecular aggregation is observed. B (phenol ring) in formula 1 of the specific compound is bonded to L by a single bond and is rotatable. In the process of applying the paint to the substrate 40 and drying it, the intramolecular hydrogen bond is broken by the rotation of B (phenol ring) in formula 1, and instead, aggregation occurs due to intermolecular hydrogen bonds between the nitrogen atom of A (triazole ring) and the hydroxyl group of B (phenol ring). This self-aggregation of the specific compound forms a fine (nano-order) uneven structure on the surface of the antireflection layer 10 (see FIGS. 7 to 9). This fine uneven structure causes the refractive index to change continuously at the interface between air and the substrate 40, and as a result, surface reflection can be suppressed (reduced). For example, when the antireflection layer 10 is provided on the surface 41 of a solar cell, it is possible to suppress (reduce) the reflection of at least a portion of the incident light (sunlight) (e.g., light with a wavelength of 200 nm to 1000 nm), thereby allowing a larger amount of light to be captured, and as a result, the photoelectric conversion efficiency of the solar cell can be improved. The antireflection layer 10 of this embodiment can be manufactured by a very simple method, and therefore the manufacturing cost is low. For solar cells, being able to form the antireflection layer 10 at low cost is a very significant advantage.

[0017] A in formula (1) representing the specific compound is not particularly limited as long as it is a monovalent group containing a nitrogen-containing aromatic ring. The nitrogen-containing aromatic ring may be a single ring or a condensed ring, and from the viewpoint of stability, a 5-membered ring, a 6-membered ring, or a combination thereof (condensed ring) is preferable. The number of nitrogen elements contained in the nitrogen-containing aromatic ring may be, for example, 1 to 6, or 2 to 3. The nitrogen-containing aromatic ring may be unsubstituted or may have a substituent within the range in which the effects of this embodiment are exhibited. Examples of the substituent include a short-chain aliphatic group (which may be linear or branched, and preferably has 20 or less atoms), a halogen atom, and the like.

[0018] Examples of A in formula (1) include groups represented by the following formulae (A1) to (A4): In formulae (A1) to (A4), * indicates the linking position to L.

[0019] [ka]

[0020] In terms of obtaining a more excellent effect of the present invention, A in formula (1) is preferably a group containing a triazole ring. The group containing a triazole ring is, for example, a group represented by formula (A1) or a group in which a substituent is added to the ring of formula (A1). Examples of the substituent include those mentioned above.

[0021] B in formula (1) representing the specific compound is not particularly limited as long as it is a monovalent group containing a hydrocarbon aromatic ring having a hydroxy group. The hydrocarbon aromatic ring does not contain a heteroatom as an element constituting the ring. The hydrocarbon aromatic ring may be a single ring or a condensed ring, and from the viewpoint of stability, a 5-membered ring, a 6-membered ring, or a combination thereof (condensed ring) is preferable. The number of hydroxy groups may be, for example, 1 to 6, 2 to 3, or 1. The hydrocarbon aromatic ring contained in B may not have a substituent other than a hydroxy group, or may have a substituent within the range in which the effect of this embodiment is exhibited. Examples of the substituent include a short-chain aliphatic group (which may be linear or branched, and preferably has 20 or less atoms), a halogen atom, and the like.

[0022] Examples of B in formula (1) include groups represented by the following formulae (B1) to (B4). In formulae (B1) to (B4), * indicates the linking position with L, and in formula (B2), n is an integer of 1 to 4.

[0023] [ka]

[0024] In terms of obtaining a more excellent effect of the present invention, B in formula (1) is preferably a group containing a phenol ring. The group containing a phenol ring is, for example, a group represented by formulae (B1) to (B3), or a group in which a substituent has been added to these rings. Examples of the substituent include those mentioned above.

[0025] In formula (1), L is a divalent group of -N=CH- or -N=N-. L connects a carbon of the nitrogen-containing aromatic ring of A to a carbon adjacent to a carbon to which a hydroxyl group is bonded in a hydrocarbon aromatic ring of B. When L is -N=CH-, the specific compound is a Schiff base, and when L is -N=N-, the specific compound is an azo compound. Since L and the above-mentioned B are bonded by a single bond, B can easily rotate and can aggregate with other molecules by hydrogen bonding (see FIG. 4).

[0026] In terms of obtaining a more excellent effect of the present invention, the specific compound is preferably a compound represented by the following formula (1-1).

[0027] [ka]

[0028] The compound represented by formula (1-1) is 2-((1H-1,2,4-triazol-3-ylimino)methyl)phenol, in which A in formula (1) is a triazole ring, B is a phenol ring, and L is -N=CH-.

[0029] The molecular weight of the specific compound represented by formula (1) may be 150 to 350, 188 to 300, or 188 to 250. The specific compound is not a polymer, but has a relatively low molecular weight. Therefore, the coating material can easily move and aggregate during the process of applying the coating material to the substrate 40 and drying, and a fine uneven structure can be efficiently formed.

[0030] The specific compound may have a fluorescent property, and may have, for example, aggregation-induced emission (AIE) property, which shows fluorescence by aggregation. AIE-characteristic materials are weakly fluorescent or non-fluorescent when each molecule is dissolved in a dilute solution, but emit strong fluorescence when aggregated to form an aggregate. That is, the aggregated specific compound of the antireflection layer 10 of the present embodiment is capable of wavelength shifting, which shifts the wavelength of incident light to a longer wavelength side. The specific compound may, for example, absorb (be excited by) light with a wavelength of 200 to 400 nm and emit light with a wavelength of 500 to 700 nm. This allows short-wavelength ultraviolet light, which has a low photoelectric conversion efficiency of solar cells, to be efficiently converted into electrical energy, and the photoelectric conversion efficiency of solar cells can be further improved.

[0031] The specific compounds explained above may be used alone or in combination of two or more.

[0032] The synthesis method of the specific compound is not particularly limited, and may be synthesized by a conventionally known method. For example, when the specific compound is a Schiff base (when L is -N=CH-), the specific compound may be synthesized from an amine (A-NH2) and a carbonyl compound (H(O=)CB) by dehydration condensation through the formation of a hemiaminal by a nucleophilic addition reaction. When the specific compound is an azo compound (when L is -N=N-), the specific compound may be synthesized by an azo coupling reaction or the like. The specific compound may be a commercially available product.

[0033] The antireflection layer 10 of this embodiment may further contain quantum dots. Quantum dots are nano-sized (e.g., 1 nm to 20 nm) particles that have a wavelength shift function of absorbing (being excited by) light of a short wavelength (e.g., wavelength of 200 to 400 nm) and emitting light of a longer wavelength (e.g., wavelength of 500 to 700 nm). By containing quantum dots, short-wavelength ultraviolet light, which has a low photoelectric conversion efficiency, can be efficiently converted into electrical energy, and the photoelectric conversion efficiency of the solar cell can be further improved.

[0034] The quantum dots are not particularly limited, and conventionally known ones can be used. For example, quantum dots made of Si, Ge, CdS, CdSe, PbS, ZnO, AglnSe2, CulnS2, Sb2S3, ZnS, Ag2Se, PbSeS, InP, etc. can be mentioned. The quantum dots may be commercially available products or may be self-synthesized by a known method. The quantum dots may be used alone or in combination of two or more types.

[0035] The antireflection layer 10 of the present embodiment may be composed of only the specific compound, or may be composed of only the specific compound and quantum dots, or may contain other conventionally known additives. The specific compound is the main component of the antireflection layer 10, and the content (SC / ARL) of the specific compound (SC) in the antireflection layer 10 (ARL) may be 90% by mass or more, 95% by mass or more, 99% by mass or more, or 100% by mass. When quantum dots are contained, the mass ratio (QD / SC) of the quantum dots (QD) to the specific compound (SC) may be, for example, 0.05% by mass to 0.5% by mass. The additive is not particularly limited as long as it is within a range that exhibits the effects of the present invention. It is preferable not to contain a polymer that functions as a binder, since it may hinder the formation of a concave-convex structure due to self-aggregation of the specific compound.

[0036] A nano-order fine uneven structure (nano uneven structure) is formed on the surface of the antireflection layer 10 of this embodiment by aggregation of a specific compound. This fine uneven structure can suppress (reduce) reflection of light with a wavelength of 200 nm to 1000 nm, for example. For example, a repeating pattern of a minute flower shape may be formed on the surface of the antireflection layer 10 by this fine unevenness (see the examples described later, and Figs. 7 and 8). The fine uneven structure is composed of, for example, linear aggregates (microfibers) of a specific compound, and this linear aggregate is presumed to be a one-dimensional supramolecular zigzag chain formed by intermolecular hydrogen bonds of the specific compound (see Fig. 4). The surface shape pattern of the fine uneven structure is very complicated and has poor regularity because it is formed by self-aggregation of the specific compound, and precise control of the pattern shape is difficult. However, from the viewpoint of achieving the effects of the present invention, precise control of the pattern shape is not necessary. A fine uneven structure (nano uneven structure) formed by self-aggregation of a specific compound can be expected to have a sufficient light reflection suppression effect regardless of the shape of the surface pattern of the antireflection layer 10. For example, by providing the antireflection layer 10, the reflection of light with a wavelength of 200 nm to 1000 nm can be reduced by 15% to 50% compared to the case where the antireflection layer 10 is not provided.

[0037] The size of the fine uneven structure is not particularly limited as long as it is within the range in which the effects of the present invention are achieved, but for example, the average height Sa of the uneven structure may be 50 nm to 500 nm, the interval (the interval between adjacent beaks (protrusions)) may be 10 nm to 100 nm, and the average surface roughness Ra of the fine uneven structure may be 10 nm to 50 nm.

[0038] The thickness of the antireflection layer 10 is not particularly limited. The thickness of the antireflection layer 10 is preferably larger (thicker) than the height of the fine uneven structure so that a continuous layer can be formed. If the thickness is too thick, the amount of transmitted light decreases, which is problematic when used in, for example, a solar cell. From the above viewpoints, the thickness of the antireflection layer 10 may be 60 nm to 2000 nm, or 100 to 200 nm.

[0039] The antireflection layer 10 of the present embodiment exerts an antireflection effect by itself as a single layer, and therefore has an advantage in that the manufacturing costs can be reduced compared to, for example, a conventional antireflection layer having a multilayer structure in which materials having different refractive indices are alternately laminated.

[0040] <Method of manufacturing anti-reflection layer> The method for producing the antireflection layer 10 of this embodiment is not particularly limited, but for example, as shown in the flowchart of Fig. 2, the antireflection layer 10 may be produced by a production method including a step S1 of preparing a coating material containing a specific compound and a solvent for dissolving the specific compound, a step S2 of applying the coating material onto a substrate 40 to form a coating film, and a step S3 of drying the coating film to obtain the antireflection layer 10. Each step will be described below.

[0041] Step S1: Prepare the paint The solvent contained in the coating material is not particularly limited as long as it can dissolve the specific compound (powder at normal temperature and pressure) and does not react with the specific compound, but a volatile solvent is preferable from the viewpoint of being easy to dry and efficiently forming the anti-reflection layer 10. From the viewpoint of having an appropriate drying speed and being easy to form a uniform film, for example, the boiling point of the solvent may be 30°C to 90°C, 50°C to 80°C, or 60°C to 80°C. In addition, the solvent may be selected based on the type of substrate so as not to erode or dissolve the substrate 40 to which the coating material is applied. Specific examples of the solvent include ethanol, methanol, 2-propanol (IPA), acetone, etc., and among them, ethanol, methanol, and acetone are preferable, and ethanol and methanol are more preferable. These solvents may be used alone or in combination of two or more.

[0042] The content of the specific compound in the paint (paint concentration) is not particularly limited as long as it is a soluble amount. From the viewpoint of efficiently forming unevenness, the content (concentration) of the specific compound in the solution may be, for example, 0.5 mg / mL to 3.0 mg / mL, or 1.0 mg / mL to 2.0 mg / mL.

[0043] The coating material may be composed of only a solvent and a specific compound, or may contain other components as necessary. Examples of other components include the above-mentioned quantum dots and conventionally known additives. The concentration of other components in the solution may be appropriately adjusted based on the composition of the anti-reflection layer 10 to be manufactured.

[0044] The paint may be a commercially available product or may be prepared at home. The paint of the present embodiment can be prepared by dissolving and / or dispersing a specific compound and, if necessary, other components (e.g., quantum dots, etc.) in a solvent by a conventionally known method.

[0045] Process S2: Coating The prepared (prepared) paint is applied to the substrate 40 to form a coating film. The material of the substrate 40 to which the paint is applied is not particularly limited, and the degree of freedom in material selection is very high. Examples include silicon (Si), various compound semiconductors (III-V group, CdTe-based, CIGS-based), glass, various ceramics, various plastics, etc. When the substrate 40 is silicon (Si), it may be single crystal, polycrystalline, or amorphous, and the type of crystal plane of the coating surface 41 to which the paint is applied is not particularly limited. The coating surface 41 of the substrate 40 (see FIG. 1) is preferably smooth to such an extent that it does not affect the uneven shape of the antireflection layer 10 formed thereon.

[0046] The method of applying the coating material to the substrate 40 is not particularly limited, and any conventionally known method can be used, such as a casting method. The thickness of the coating film to be formed may be appropriately adjusted based on the thickness of the antireflection layer 10 to be finally obtained, the coating material concentration, etc.

[0047] Process S3: Drying In the process of drying the formed coating film, the specific compound aggregates as described above, and unevenness naturally forms on the coating film surface, thereby obtaining the anti-reflection layer 10 of this embodiment. Drying may be natural drying (room temperature), or may be dried by heating (warming) as necessary. When a volatile solvent is used in the coating material, the solvent in the coating film can be sufficiently removed by natural drying. The drying temperature may be, for example, 20°C to 80°C. The drying time is not particularly limited, and may be, for example, 10 seconds to 120 seconds.

[0048] <Applications of anti-reflection layer> The antireflection layer 10 of this embodiment can be used in, for example, a solar cell. A solar cell including the antireflection layer 10 of this embodiment can capture a larger amount of light by suppressing the reflection of incident light (for example, light with a wavelength of 200 nm to 1000 nm), and as a result, the photoelectric conversion efficiency can be improved. Furthermore, when the specific compound has a fluorescent property (for example, aggregation induced emission property (AIE)), it can convert short-wavelength ultraviolet light (for example, wavelength of 200 to 400 nm) with low photoelectric conversion efficiency into long-wavelength light (for example, wavelength of 500 to 700 nm) that can be efficiently converted into electrical energy, and as a result, the photoelectric conversion efficiency of the solar cell can be further improved.

[0049] The type of solar cell is not particularly limited, and examples thereof include silicon solar cells (crystalline silicon, thin-film silicon, hybrid, etc.), chemical semiconductor solar cells (III-V, CdTe, CIGS, etc.), organic semiconductor solar cells, and dye-sensitized solar cells (perovskite type, etc.).

[0050] In a solar cell (solar cell module), the antireflection layer 10 of this embodiment may be formed, for example, on a solar cell (for example, a silicon (Si) wafer or the like on which electrodes and the like are formed). For example, in FIG. 1, the substrate 40 is a solar cell. In the case of a silicon-based solar cell, the surface 41 on which the antireflection layer 10 is formed is made of silicon (Si).

[0051] The antireflection layer 10 of this embodiment can be formed by a very simple method (typically, coating and drying a paint), and therefore the manufacturing cost can be significantly reduced. For solar cells, the ability to form the antireflection layer 10 at low cost is a very significant advantage. In addition, the antireflection layer 10 can be easily formed after the solar cell is fabricated, and therefore does not affect the manufacturing process of the solar cell at all.

[0052] The antireflection layer 10 of the present embodiment can be applied to devices and components other than solar cells, for example, photodetectors.

[0053] <Modification> From the viewpoint of improving weather resistance, a protective layer 20 may be further provided on the antireflection layer 10. Fig. 3 shows a composite layer 30 consisting of the antireflection layer 10 and the protective layer 20 formed on the antireflection layer 10. The antireflection layer 10 has been described above, so a description thereof will be omitted.

[0054] The protective layer 20 is preferably a metal oxide layer having high durability and light transmittance (transparency). Examples of such metal oxide layers include indium iron oxide (ITO), silicon oxide (SiO2), and zinc oxide (ZnO). The thickness of the protective layer 20 is not particularly limited, but if it is too thick, the light transmittance may decrease, and if it is too thin, the uneven structure of the anti-reflection layer 10 may not be sufficiently covered. From these viewpoints, the thickness of the protective layer 20 may be, for example, 5 nm to 100 nm. The method for forming the protective layer 20 is not particularly limited, and the protective layer 20 may be formed by a conventionally known method such as sputtering or vacuum deposition.

[0055] The composite layer 30 of this modification includes the antireflection layer 10, and exerts the same effects as those exerted by the above-mentioned antireflection layer 10. Furthermore, by providing the protective layer 20 on the upper side (light incident side) of the antireflection layer 10, high weather resistance can be achieved.

[0056] The composite layer 30 can be applied to various devices and components in which the single layer antireflection layer 10 described in the above embodiment can be used, similarly to the single layer antireflection layer 10. For example, the composite layer 30 can be used in a solar cell, and can increase the photoelectric conversion efficiency of the solar cell and improve its weather resistance. In a solar cell (solar cell module), the composite layer 30 of this modification may be formed, for example, on silicon of a solar cell (a silicon (Si) wafer on which electrodes and the like are formed). In this case, in FIG. 3, the substrate 40 is a solar cell, and the surface 41 on which the composite layer 30 (antireflection layer 10) is formed is made of silicon (Si). EXAMPLES

[0057] The present invention will be described in more detail below based on examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0058] [Paint 1] Paint 1 containing a specific compound and a solvent was prepared by the method described below.

[0059] <Synthesis and structural analysis of specific compounds> As a specific compound, 2-((1H-1,2,4-triazol-3-ylimino)methyl)phenol, a compound represented by formula (1-1), was synthesized. The synthesis reaction formula is shown in Figure 5. First, 10 mM salicylaldehyde and 10 mM 3-amino-1,2,4-triazole were added to 100 mL of ethanol, heated to 80°C, and held for 3 hours. After the condensation reaction was completed, the pale yellow product was separated and dried.

[0060] FT-IR analysis of the product, and 1 H-NMR analysis (solvent: DMSO-d6) was performed. The results are shown in Figures 6(a) and 6(b). As shown in Figure 6(a), the FT-IR analysis showed a peak at 760 cm due to ortho-substituted benzene. -1 and a strong peak at 1615 cm-1 The characteristic -C=N- stretching was observed at 3000cm. -1 ~3400cm -1 As shown in Figure 6(b), the characteristic secondary amine (-NH-) and tertiary amine peaks were observed. 1 In the H-NMR analysis, the signal of the benzene ring was observed at 6.9 ppm to 7.9 ppm, and the two singlet signals of the CHN and triazole protons bonded to the aryl group were observed at 8.55 ppm and 9.4 ppm, respectively. From the above analysis results, it was confirmed that the product was the compound represented by formula (1-1).

[0061] <Preparation of paint 1> The synthesized specific compound (powder) was dissolved in ethanol to prepare paint 1 (specific compound concentration: 1.5 mg / mL).

[0062] [Paint 2] Paint 2 was prepared in the same manner as Paint 1, except that methanol was used instead of ethanol as the solvent.

[0063] [Paint 3] Paint 3 was prepared in the same manner as paint 1, except that acetone was used instead of ethanol as the solvent.

[0064] [Paint 4] Paint 4 was prepared in the same manner as Paint 1, except that isopropyl alcohol (IPA) was used instead of ethanol as the solvent.

[0065] [Paint 1-1] Paint 1-1 was prepared in the same manner as Paint 1, except that the concentration of the specific compound in the paint was 0.5 mg / mL.

[0066] [Paint 1-2] Paint 1-2 was prepared in the same manner as Paint 1, except that the concentration of the specific compound in the paint was 1.5 mg / mL.

[0067] [Paint 1-3] Paint 1-3 was prepared in the same manner as Paint 1, except that the concentration of the specific compound in the paint was 2.0 mg / mL.

[0068] [evaluation] <Surface evaluation of anti-reflection layer> A polished p-type silicon (Si) substrate (resistance: 1-10 Ω / cm, thickness: 280 μm-300 μm) was prepared. Paint 1 (approximately 15 μL) was applied to the substrate (Si substrate) surface (approximately 0.5 cm 2 ) and was held there until the solvent was completely evaporated to form an antireflective layer. The antireflective layer formed using paint 1 is referred to as "antireflective layer 1." The surface of antireflective layer 1 was observed with an optical microscope, SEM (scanning electron microscope, SEM), and AFM (atomic force microscope, AFM) analysis. The results are shown in Figures 7 to 9.

[0069] As shown in FIG. 7 (optical microscope image) and FIG. 8 (SEM image), a nano-order fine uneven structure formed by self-aggregation of a specific compound was observed on the surface of the anti-reflection layer 1. More specifically, a repeating pattern of minute flower shapes (microflowers) was formed, and these patterns were composed of linear aggregates (microfibers). The linear aggregates are presumed to be one-dimensional supramolecular zigzag chains formed by intermolecular hydrogen bonds of a specific compound (see FIG. 4). Each of the repeating flower-shaped patterns had a central valley point (concave), from which multiple convex and concave portions extended radially and intermittently, forming a very complicated structure.

[0070] The AFM analysis was used to measure the variation in height of the uneven structure of the antireflection layer 1. The average height Sa of the uneven structure of the coating material 1 was about 130 nm, and the average surface roughness Ra was 23.9 nm.

[0071] Antireflective layers were prepared using paints 2 to 4 in the same manner as paint 1, and their surfaces were evaluated. The antireflective layers formed using paints 2 to 4 are referred to as "antireflective layers 2 to 4", respectively. A fine (nano-order) uneven structure due to the self-aggregation of a specific compound was also confirmed on the surfaces of antireflective layers 2 to 4, and a repeating pattern of minute flower shapes (microflowers) was formed as in antireflective layer 1. The uneven structure of antireflective layer 2 (solvent: methanol) was the same size as the uneven structure of antireflective layer 1. On the other hand, the uneven structure of antireflective layer 3 (solvent: acetone) was finer than the uneven structure of antireflective layer 1. In addition, in antireflective layer 4 (solvent: IPA), the paint spread on the substrate (Si) was slightly poorer than the other antireflective layers 1 to 3, and therefore the obtained antireflective layer was slightly non-uniform.

[0072] <Measurement of reflectance of anti-reflection layer> The reflectance of the antireflection layer 1 for light with wavelengths of 200 nm to 1600 nm was measured. The results are shown in Figure 10. For comparison, the reflectance of the surface of a Si substrate on which no antireflection layer was formed was also measured in the same manner. The results are also shown in Figure 10.

[0073] 10, in the wavelength range of 200 nm to 1000 nm, the reflectance of the antireflection layer 1 was significantly reduced to about 15 / 100 to 50 / 100 of the reflectance of the Si substrate. For example, in the wavelength range of 500 nm to 1000 nm, the reflectance of the Si substrate, which is about 35%, was reduced to about 20% or less by providing the antireflection layer 1. It is presumed that such an antireflection effect is due to the fine (nano-order) uneven structure formed on the surface of the antireflection layer 1. It is presumed that the antireflection layers 2 to 4 also show a similar antireflection effect because they have a fine uneven structure formed on their surfaces.

[0074] <Absorption and emission characteristics of specific compounds> The absorption spectrum and emission spectrum of the synthesized specific compound (compound represented by formula (1-1)) were measured. The results are shown in FIG.

[0075] The absorption spectrum was measured by dissolving a specific compound in ethanol. As shown in Figure 11, * Transitions and π-π * The transitions gave rise to two maximum absorption peaks at 288 nm and 345 nm, but the specific compound in ethanol solution did not show any fluorescence. On the other hand, when water was added to the ethanol solution, the specific compound aggregated and began to exhibit fluorescence (aggregation-induced emission (AIE)). The fluorescence spectrum of the specific compound in a mixed solvent of ethanol / water = 30 / 70 (volume ratio) is shown in Figure 11 (excitation light: 365 nm). The aggregated specific compound exhibited strong green fluorescence with a photoexcited luminescence quantum yield (PLQY) of 43% with a maximum at 525 nm.

[0076] The specific compound represented by formula (1-1) has a very small distance between -OH and -C=N-, so it is easy to form a six-membered ring through an intramolecular hydrogen bond (see Figure 4). This is thought to cause excited-state intramolecular proton transfer (ESIPT), which leads to the disappearance of fluorescence. On the other hand, when the specific compound aggregates, this intramolecular hydrogen bond is destroyed, inhibiting the progress of ESIPT, which is thought to increase the fluorescence.

[0077] From the above results, the aggregation induced emission property (AIE) of the specific compound was confirmed. It is presumed that the specific compound is also aggregated in the antireflection layers 1 to 4, and therefore shows similar fluorescence.

[0078] <Evaluation of solar cell characteristics> (a) Fabrication of solar cell with anti-reflection layer A silicon (Si)-based Al-BSF (Back Surface Field) solar cell was fabricated by the method described below. First, the same silicon substrate as that used in the above-mentioned "Surface evaluation of anti-reflection layer" was prepared (polished p-type silicon substrate, resistance value: 1-10 Ω / cm, thickness: 280 μm-300 μm). The silicon substrate was cut into 1.5 cm square cubes and ultrasonically cleaned with a mixed solution of acetone and water for 10 minutes. The silicon substrate was then immersed in a piranha solution at 80°C for 15 minutes. After washing with water, the substrate surface from which the native oxide film was removed with an HF solution (5%) was spin-coated at 2000 rpm with a SOD (spin-on dopant) solution as a phosphorus (P) dopant, and dried at 200°C for 15 minutes. A commercially available phosphosilicic acid solution P509 (manufactured by Filmtronics Inc.) was used as the SOD solution. A high-temperature short-time anneal (RTA) was performed to diffuse phosphorus into the n+ emitter. The annealing was performed under a mixed gas of N2 (flow rate: about 500 sccm) and O2 (flow rate: about 150 sccm). Next, the substrate was immersed in a HF solution (5%) for 5 minutes to remove the phosphosilicate glass (PSG) layer. A commercially available Al paste was screen-printed on the rear surface of the Si substrate and baked at 630°C for 1 second to form a rear Al contact electrode. A Ti / Ag front contact electrode (thickness 50 nm / 250 nm) was also formed on the surface of the Si substrate by magnetron sputtering.

[0079] The silicon surface of the fabricated solar cell (approximately 0.5 cm 2 ) and was held until the solvent was completely evaporated to form an antireflection layer 1. The solar cell on which the antireflection layer 1 was formed is referred to as "solar cell 1."

[0080] (b) JV characterization and external quantum efficiency (EQE) measurements The JV characteristics and external quantum efficiency (EQE) of solar cell 1 were measured at room temperature. The respective results are shown in Figures 12 and 13. For comparison, the same measurements were also performed on a solar cell that did not have an anti-reflection layer formed. The results are also shown in Figures 12 and 13.

[0081] As shown in FIG. 12, the current density (J SC: Short circuit current) is 26.84mA / cm 2 to 31.94mA / cm 2 (an improvement of about 20%). Finally, a power conversion efficiency (PCE) of about 11.8% was achieved. OC ) improved slightly from 0.55 V to 0.56 V, and the fill factor (FF) did not change. In addition, as shown in Figure 13, by forming the antireflection layer 1, the external quantum efficiency (EQE) improved in a wide range from the ultraviolet region to 1000 nm.

[0082] The improvement in the solar cell characteristics explained above (see Figs. 12 and 13) is attributed to the anti-reflection effect of the anti-reflection layer 1, and is also presumably due to the fluorescent properties of the anti-reflection layer 1. In particular, the wavelength range in which the external quantum efficiency (EQE) is increased shown in Fig. 13 coincides well with the wavelength range in which the reflectance is suppressed shown in Fig. 10.

[0083] (c) Effect of the content of specific compounds in the paint (paint concentration) Solar cells with antireflection layers were produced in the same manner as in "(a) Production of solar cell with antireflection layer" above, except that paint 1 was replaced with paints 1-1 to 1-3. The solar cells produced using paints 1-1 to 1-3 are referred to as "solar cells 1-1 to 1-3", respectively. The power conversion efficiency (PCE) and current density (JSC: short-circuit current) of solar cells 1-1 to 1-3 were measured in the same manner as in "(b) JV characteristic evaluation and external quantum efficiency (EQE) measurement" above. The evaluation results of solar cells 1-1 to 1-3 are shown in FIG. 14 together with the evaluation results of solar cell 1 described above and the evaluation results of a solar cell without an antireflection layer.

[0084] As shown in Figure 14, compared to the solar cell without an anti-reflection layer (paint concentration: 0.0 mg / mL), the power conversion efficiency (PCE) and current density were improved in all solar cells with an anti-reflection layer, regardless of the paint concentration. In particular, the power conversion efficiency (PCE) and current density were higher when the paint concentration was 1.0 mg / mL to 2.0 mg / mL.

[0085] (d) Weather resistance evaluation An ITO protective layer of about 80 nm thickness was formed by vapor deposition on the anti-reflection layer 1 of the solar cell 1. This resulted in the formation of a composite layer consisting of the anti-reflection layer 1 and the ITO protective layer. The solar cell with the composite layer formed was left in the air for one month, and the power conversion efficiency (PCE) was measured periodically and the change in PCE over time was recorded. The results are shown in Figure 15.

[0086] At the start of exposure to air, the PCE of the solar cell with the composite layer formed was about 1.2 times (initial value) that of the solar cell without the anti-reflection layer due to the effect of the anti-reflection layer 1 (see FIG. 12). As shown in FIG. 15, the solar cell with the composite layer did not show any decrease in PCE during exposure to air for one month, and maintained the initial value (1.0 in FIG. 15).

[0087] The cells were then left in air for four months, after which the PCE was measured again and the surface of the composite layer was observed using an optical microscope. Even after four months in air, the solar cell with the composite layer maintained the initial PCE value (approximately 1.2 times that of the solar cell without the anti-reflection layer). Surface observation of the composite layer also confirmed that the fine uneven structure of the anti-reflection layer 1 was maintained even after four months in air.

[0088] The uneven structure of the anti-reflection layer 1 is formed due to self-aggregation caused by intermolecular hydrogen bonds of a specific compound. For this reason, there are concerns about the effect of moisture in the air on the uneven structure. However, from the above results, it was confirmed that high weather resistance can be obtained for a long period of time by providing a protective layer on the microstructure. [Industrial Applicability]

[0089] The anti-reflection layer of the present embodiment described above can be formed by a very simple method, and can reduce the manufacturing cost and time. For example, the anti-reflection layer can be used in various devices such as solar cells. [Explanation of symbols]

[0090] 10 Anti-reflection layer 20 protective layer 30 composite layers 40 Base material 41 Substrate surface

Claims

1. An anti-reflective layer, The compound is represented by the following formula (1): An anti-reflective layer having a fine, uneven surface structure. 【Chemistry 1】 In equation (1), A is a monovalent group containing a nitrogen-containing aromatic ring, B is a monovalent group containing a hydrocarbon aromatic ring with a hydroxyl group, L is a divalent group with -N=CH- or -N=N-, and it connects the carbon of the nitrogen-containing aromatic ring of A to the carbon adjacent to the carbon to which the hydroxyl group is bonded in the hydrocarbon aromatic ring of B.

2. The anti-reflective layer according to claim 1, wherein in formula (1), A is a group selected from the group consisting of the following formulas (A1) to (A4). 【Chemistry 2】 In equations (A1) to (A4), * indicates the connection position.

3. The anti-reflective layer according to claim 1, wherein in formula (1), A is a group containing a triazole ring.

4. The anti-reflective layer according to claim 1, wherein in formula (1), B is a group selected from the group consisting of the following formulas (B1) to (B4). 【Transformation 3】 In equations (B1) to (B4), * indicates the linking position, and in equation (B2), n is an integer from 1 to 4.

5. The anti-reflective layer according to claim 1, wherein in formula (1), B is a group containing a phenol ring.

6. The anti-reflective layer according to claim 1, wherein the compound represented by formula (1) is the compound represented by the following formula (1-1). 【Chemistry 4】

7. The anti-reflective layer according to claim 1, wherein the compound represented by formula (1) has fluorescent properties.

8. Furthermore, the anti-reflective layer according to claim 1, further containing quantum dots.

9. An anti-reflective layer according to any one of claims 1 to 8, A composite layer comprising a protective layer formed on the anti-reflective layer.

10. The composite layer according to claim 9, wherein the protective layer is a metal oxide layer.

11. A solar cell comprising the anti-reflective layer described in any one of claims 1 to 8.

12. A solar cell comprising the composite layer described in claim 9.

13. A method for manufacturing an anti-reflective layer according to any one of claims 1 to 8, A paint containing a compound represented by formula (1) and a solvent for dissolving the compound, The process involves applying the aforementioned paint to a substrate to form a coating film, A method for manufacturing an anti-reflective layer, comprising drying the coating film to obtain the anti-reflective layer.

14. A paint for forming an anti-reflective layer according to any one of claims 1 to 8, The compound represented by formula (1), A paint containing a solvent.

Images