Solar cell and method for manufacturing the same

Abstract

The present invention provides a method for manufacturing a solar cell. [Solution] The method includes forming a second photoelectric conversion unit including a semiconductor substrate, a first semiconductor layer on one surface of the semiconductor substrate, and a second semiconductor layer having a different conductivity type from the first semiconductor layer on the other surface of the semiconductor substrate, forming a junction layer on the first semiconductor layer, changing the surface characteristics of the front surface of the junction layer, forming a first photoelectric conversion unit including a photoelectric conversion layer made of a perovskite compound on the front surface of the junction layer, and forming a first electrode electrically connected to the first photoelectric conversion unit on one surface of the first photoelectric conversion unit, and a second electrode electrically connected to the second photoelectric conversion unit on the other surface of the second photoelectric conversion unit. Therefore, in a series structure in which a first photoelectric conversion unit including a perovskite compound and a second photoelectric conversion unit including a semiconductor substrate are provided, the adhesion characteristics can be improved by converting the junction layer between the first photoelectric conversion unit and the second photoelectric conversion unit to be hydrophilic.

Description

Technical Field

[0001] The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell having an improved structure and a method for manufacturing the same.

Background Art

[0002] Solar cells including semiconductor substrates are widely used because they have excellent efficiency. However, solar cells including semiconductor substrates have certain limitations in improving efficiency, and various structures of solar cells capable of improving the photoelectric conversion efficiency have been proposed.

[0003] As an example, a solar cell including a perovskite compound that absorbs short-wavelength light and performs photoelectric conversion using the short wavelength as a photoelectric conversion unit has been proposed. In a solar cell including such a perovskite compound as a photoelectric conversion unit, as described in Korean Patent Publication No. 10-2016-0040925, usually, by laminating another photoelectric conversion unit having a structure or material different from that of the photoelectric conversion unit including the perovskite compound, excellent efficiency is realized.

[0004] In a solar cell having such a structure, in order to improve the efficiency, it is very important that a plurality of photoelectric conversion units laminated on each other have excellent connection characteristics.

[0005] Therefore, Korean Patent No. 10-2018-0026454 discloses a multi-junction optoelectronic device. In the above-described prior art, a series solar cell in which a heterojunction structure and a perovskite solar cell are laminated is claimed for protection, and a TCO is applied as a bonding layer between the two, that is, a composite layer.

[0006] However, in the above-described structure, due to the surface energy difference between the TCO, which is a hydrophilic bonding layer, and the material of the hole transport layer (HTL) having hydrophobicity, the bonding between the two surfaces becomes unstable.

[0007] Therefore, in the hole transport layer process, a necessary spin coating process or wet process is involved, or another different connection process is required.

Prior Art Documents

Patent Documents

[0008] Korean Patent Publication No. 10-2016-0040925 (April 15, 2016) Korean Patent Publication No. 10-2018-0026454 (March 16, 2018)

Summary of the Invention

Problems to be Solved by the Invention

[0009] This embodiment aims to provide a solar cell having excellent efficiency and a method for manufacturing the same. In particular, this embodiment aims to provide a solar cell having excellent efficiency and a method for manufacturing the same, which has a tandem structure provided with a photoelectric conversion part containing a perovskite compound and another photoelectric conversion part having a different substance or structure.

[0010]

[0011] More specifically, this embodiment aims to provide a solar cell having excellent efficiency and a method for manufacturing the same, which improves the junction characteristics between two photoelectric conversion parts in a tandem structure provided with a plurality of photoelectric conversion parts, smoothes the carrier movement.

Means for Solving the Problems

[0012] ​The solar cell according to this embodiment includes a photoelectric conversion unit, a bonding layer, a first electrode, and a second electrode. The photoelectric conversion unit includes a first photoelectric conversion unit including a photoelectric conversion layer made of a perovskite compound and a second photoelectric conversion unit including a semiconductor substrate. The bonding layer is formed between the first photoelectric conversion unit and the second photoelectric conversion unit. The first electrode is electrically connected to the photoelectric conversion unit on one surface of the photoelectric conversion unit, and the second electrode is electrically connected to the photoelectric conversion unit on the other surface of the photoelectric conversion unit. The bonding layer includes a back surface in contact with the second photoelectric conversion unit and a front surface in contact with the first photoelectric conversion unit, and the back surface and the front surface have different surface characteristics.

[0013] The second photoelectric conversion unit may include the semiconductor substrate, a first semiconductor layer of a first conductivity type on one surface of the semiconductor substrate, and a second semiconductor layer of a second conductivity type on the other surface of the semiconductor substrate.

[0014] The back surface of the bonding layer may have a hydrophilic surface characteristic, and the front surface of the bonding layer may have a hydrophobic surface characteristic.

[0015] The bonding layer includes a transparent conductive type oxide layer (TCO) formed on the first conductor layer of the first conductivity type and having a hydrophilic surface characteristic.

[0016] The front surface of the transparent conductive type oxide layer of the bonding layer may have a hydrophobic surface characteristic by plasma surface treatment.

[0017] The bonding layer may further include an interface layer in contact with the first photoelectric conversion unit on the transparent conductive type oxide layer.

[0018] The interface layer may include a doped semiconductor layer and may have a hydrophobic surface characteristic.

[0019] A tunneling layer may be further included between the semiconductor substrate and the second semiconductor layer of the second conductivity type, and the interface layer may be formed to have a thickness thinner than that of the tunneling layer.

[0020] The first photoelectric conversion unit may include the photoelectric conversion layer made of the perovskite compound, a first transport layer formed on the upper portion of the photoelectric conversion layer, and a second transport layer formed on the lower portion of the photoelectric conversion layer. The second transport layer may be formed to be joined to the junction layer, and the second transport layer may have hydrophobic surface characteristics.

[0021] The second transport layer may include NPB or Spiro-TTB having hydrophobic surface characteristics.

[0022] The first photoelectric conversion unit may be positioned on one surface of the second photoelectric conversion unit, the first electrode may be positioned on the first photoelectric conversion unit, the second electrode may be positioned on the second semiconductor layer of the second photoelectric conversion unit, the second semiconductor layer may include a polycrystalline portion, and the laminated structures of the first electrode and the second electrode may be different from each other.

[0023] Moreover, a method for manufacturing a solar cell according to an embodiment of the present invention includes steps of forming a second photoelectric conversion unit including a semiconductor substrate, a first semiconductor layer on one surface of the semiconductor substrate, and a second semiconductor layer having a conductivity type different from that of the first semiconductor layer on the other surface of the semiconductor substrate; forming a junction layer on the first semiconductor layer; changing surface characteristics of a front surface of the junction layer; forming a first photoelectric conversion unit including a photoelectric conversion layer made of a perovskite compound on the front surface of the junction layer; and forming a first electrode electrically connected to the first photoelectric conversion unit on one surface of the first photoelectric conversion unit and a second electrode electrically connected to the second photoelectric conversion unit on the other surface of the second photoelectric conversion unit.

[0024] In the step of forming the bonding layer, a transparent conductive type oxide layer (TCO) having hydrophilic surface characteristics may be formed on the first semiconductor layer of the semiconductor substrate.

[0025] In the step of changing the surface characteristics of the bonding layer, the treatment may be performed such that the back surface of the bonding layer has hydrophilic surface characteristics and the front surface of the bonding layer has hydrophobic surface characteristics.

[0026] In the step of changing the surface characteristics of the bonding layer, plasma surface treatment may be performed so as to form a hydrophobic surface characteristic on the front surface of the transparent conductive type oxide layer of the bonding layer.

[0027] The plasma surface treatment may be performed at a temperature of 200 degrees or less and may be performed by CH4 plasma or fluorine plasma treatment.

[0028] The step of changing the surface characteristics of the bonding layer may further include a step of forming an interface layer in contact with the first photoelectric conversion unit on the transparent conductive type oxide layer.

[0029] The step of forming the interface layer may include a step of depositing an amorphous silicon layer on the transparent conductive type oxide layer and a step of implanting a high-concentration dopant on the amorphous silicon layer so as to change the surface characteristics to hydrophobic.

[0030] A tunneling layer may be further included between the semiconductor substrate and the second semiconductor layer, and the interface layer may be formed to have a thickness thinner than that of the tunneling layer.

[0031] The first photoelectric conversion unit is formed to include the photoelectric conversion layer made of the perovskite compound, a first transport layer formed on the upper part of the photoelectric conversion layer, and a second transport layer formed on the lower part of the photoelectric conversion layer. The second transport layer may be formed to be in contact with the junction layer, and the second transport layer may be formed by depositing a substance having hydrophobic surface characteristics.

Advantages of the Invention

[0032] According to this embodiment, in the series structure provided with the first photoelectric conversion unit including the perovskite compound and the second photoelectric conversion unit including the semiconductor substrate, the junction characteristics can be improved by converting the junction layer between the first photoelectric conversion unit and the second photoelectric conversion unit to be hydrophilic.

[0033] In addition, since the TCO can be directly applied as the junction layer, when there is no wet process having process instability, it can be replaced with a dry process, and further a series cell structure can be realized.

[0034] Thereby, in the lamination of the junction layer and the first photoelectric conversion unit, the matching property is improved, which contributes to the enlargement of the area.

[0035] Even if sandwiching or plasma treatment is performed, the above-mentioned junction layer can have the same optical and electrical characteristics of the TCO, and by improving the junction characteristics between the TCO and the hole transport layer, the hole mobility can be improved, and by increasing the fill factor (FF), the driving performance of the series cell can be improved.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7a

Figure 7b

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12a

Figure 12b

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to such embodiments and can be modified into various forms.

[0038] To clearly and concisely describe the present invention, drawings of parts not related to the description are omitted, and throughout the specification, the same or extremely similar parts are denoted by the same reference numerals. For the sake of clearer description, thickness, width, etc. are shown enlarged or reduced in the drawings, and the thickness, width, etc. of the present invention are not limited to those shown in the figures.

[0039] Throughout the specification, when a part is referred to as "including" another part, unless otherwise stated to the contrary, it does not exclude the other part and may further include the other part. When a part such as a layer, film, region, plate, etc. is "on" another part, this includes not only the case where it is directly "on" the other part but also the case where the other part is positioned in the center thereof. When a part such as a layer, film, region, plate, etc. is referred to as being directly "on" another part, it means that the other part is not positioned in the center.

[0040] Hereinafter, the solar cell and its manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings. In this specification, the expressions "first" or "second" are used merely for distinguishing between each other, and the present invention is not limited thereto.

[0041] FIG. 1 is a cross-sectional view schematically showing a solar cell according to an embodiment of the present invention, and FIG. 2 is a front plan view showing the front of the solar cell shown in FIG. 1. For the sake of clear understanding, in FIG. 2, the illustration of the first electrode layer of the first electrode is omitted, and mainly the second electrode layer is shown.

[0042] Referring to FIG. 1, the solar cell 100 according to this embodiment may include a photoelectric conversion unit 10 including a first photoelectric conversion unit 110 and a second photoelectric conversion unit 120. That is, the photoelectric conversion unit 10 may have a series structure including a plurality of photoelectric conversion units 110 and 120 stacked on each other. At this time, the junction layer (tunneling junction layer) 130 is located on one surface (for example, the front surface) of the second photoelectric conversion unit 120 or on the first semiconductor layer 124, and electrically connects the second photoelectric conversion unit 120 and the first photoelectric conversion unit 110 located thereon. In FIG. 1, the junction layer 130 has a plurality of layered structures and is disposed between the first semiconductor layer 124 of the second photoelectric conversion unit 124 and the second transport layer 116 of the first photoelectric conversion unit 110, but the present invention is not limited thereto. Such a junction layer 130 may have a thin thickness so as to smoothly perform carrier tunneling and may be configured as multiple layers.

[0043] More specifically, the photoelectric conversion unit 10 may include a first photoelectric conversion unit 110 including a photoelectric conversion layer 112 made of a perovskite compound, and a second photoelectric conversion unit 120 including a semiconductor substrate (for example, a silicon substrate) 122. At this time, the second photoelectric conversion unit 120 may include a semiconductor substrate 122, a first semiconductor layer 124 formed separately from the semiconductor substrate 122 on one surface (for example, the front surface) of the semiconductor substrate 122, and a second semiconductor layer 126 formed separately from the semiconductor substrate (10) on the other surface (for example, the back surface) of the semiconductor substrate 122. And the solar cell 100 may include a first electrode 42 electrically connected to the photoelectric conversion unit 10 on one surface (for example, the front surface) of the photoelectric conversion unit 10, and a second electrode 44 electrically connected to the photoelectric conversion unit 10 on the other surface (for example, the back surface) of the photoelectric conversion unit 10. A more detailed description is as follows.

[0044] In this embodiment, in the second photoelectric conversion unit 120, the semiconductor substrate 122 may be composed of a crystalline semiconductor (e.g., single crystal or polycrystalline semiconductor, for example, single crystal or polycrystalline silicon) containing a single semiconductor substance (for example, a Group IV element). And because it is based on a semiconductor substrate 122 with high crystallinity and few defects, the second photoelectric conversion unit 120 can have excellent electrical characteristics. In particular, since the semiconductor substrate 122 may be composed of a single crystal semiconductor (for example, single crystal silicon), it has even more excellent electrical characteristics. As described above, the second photoelectric conversion unit 120 may have a crystalline silicon solar cell structure including the crystalline semiconductor substrate 122.

[0045] The front and / or back surface of the semiconductor substrate 122 may be textured to have unevenness or an antireflection structure. As an example, the unevenness or antireflection structure may have a pyramid shape in which the surface constituting the front and / or back surface of the semiconductor substrate 122 is configured as the (111) plane of the semiconductor substrate 122 and has an irregular size. Thereby, when having a relatively large surface roughness, the reflectance of light can be reduced. The drawings illustrate the case where unevenness or an antireflection structure is formed on the front and back surfaces of the semiconductor substrate 122 respectively to maximize the antireflection effect. However, the present invention is not limited to this, and an unevenness or antireflection structure may be formed on at least one of the front and back surfaces, or an unevenness or antireflection structure may be provided on both the front and back surfaces.

[0046] In this embodiment, the semiconductor substrate 122 may be doped with a first or second conductive type dopant at a doping concentration lower than that of the first semiconductor layer 124 or the second semiconductor layer 126 to be configured as a base region having the first or second conductive type. That is, the semiconductor substrate 122 may not be provided with a doping region formed by additionally doping a dopant in the base region, and only the base region may be provided.

[0047] In this embodiment, the first semiconductor layer 124 located on one surface (for example, the front surface) of the semiconductor substrate 122 may be a semiconductor layer containing a first-conductivity-type dopant and having a first conductivity type. And the second semiconductor layer 126 located on the other surface (for example, the back surface) of the semiconductor substrate 122 may be a second semiconductor layer containing a second-conductivity-type dopant and having a second conductivity type.

[0048] As an example, for the first-conductivity-type dopant and the second-conductivity-type dopant, elements of Group 3 such as boron (B), aluminum (Al), gallium (Ga), indium (In), etc. may be used as p-type dopants, and elements of Group 5 such as phosphorus (P), arsenic (As), bismuth (Bi), antimony (Sb), etc. may be used as n-type dopants. The first-conductivity-type dopant of the semiconductor substrate 122 or the second-conductivity-type dopant and the first-conductivity-type dopant or the second-conductivity-type dopant of the first semiconductor layer 124 or the second semiconductor layer 126 may also be the same substance as each other, and may also be different substances from each other.

[0049] Depending on the conductivity types of the semiconductor substrate 122, the first semiconductor layer 124, and the second semiconductor layer 126, the functions of the first semiconductor layer 124 and the second semiconductor layer 126, and the substances and functions of the first transport layer 114 and the second transport layer 116 included in the first photoelectric conversion unit 110 may be different. This will be further described in more detail after the description of the first photoelectric conversion unit 110, the first electrode 42, and the second electrode 44.

[0050] And a first intermediate film 124a may be provided between the front surface of the semiconductor substrate 122 and the first semiconductor layer 124, and a second intermediate film 126a may be provided between the back surface of the semiconductor substrate 122 and the second semiconductor layer 126. Thereby, by simplifying the structure, the carrier movement path can be simplified, but the present invention is not limited thereto, and various modifications are possible.

[0051] The first intermediate film 124a and the second intermediate film 126a may function as a barrier against electrons and holes, thereby allowing only majority carriers having a predetermined amount of energy or more to pass through the first intermediate film 124a and the second intermediate film 126a after accumulating in the portions adjacent to the first intermediate film 124a and the second intermediate film 126a, without allowing minority carriers to pass through. As an example, the first intermediate film 124a and the second intermediate film 126a may be tunneling films. At this time, majority carriers having a predetermined amount of energy or more can easily pass through the first intermediate film 124a and the second intermediate film 126a due to the tunneling effect.

[0052] Such first intermediate film 124a and second intermediate film 126a may contain various substances that enable carrier tunneling, and as an example, may include nitrides, semiconductors, conductive polymers, and the like. For example, the first intermediate film 124a and the second intermediate film 126a may include silicon oxide, silicon nitride, silicon oxynitride, intrinsic amorphous semiconductor (as an example, intrinsic amorphous silicon), intrinsic polycrystalline semiconductor (as an example, intrinsic nano polycrystalline silicon), and the like. At this time, the first intermediate film 124a and the second intermediate film 126a may include an intrinsic amorphous semiconductor. As an example, the first intermediate film 124a and the second intermediate film 126a may be configured as an amorphous silicon (a-Si) layer, an amorphous silicon carbide (a-SiCx) layer, an amorphous silicon oxide (a-SiOx) layer, or the like. And since the first intermediate film 124a and the second intermediate film 126a have characteristics similar to those of the semiconductor substrate 122, the surface characteristics of the semiconductor substrate 122 can be more effectively improved.

[0053] At this time, the first intermediate film 124a and the second intermediate film 126a may be entirely formed on the front and back surfaces of the semiconductor substrate 122, respectively. Thereby, the front and back surfaces of the semiconductor substrate 122 can be entirely passivated, and can be easily formed without performing additional patterning. The thicknesses of the first intermediate film 124a and the second intermediate film 126a may be smaller (for example, 5 nm or less) than the thicknesses of the conductive regions 124 and 126 in order to sufficiently realize the tunneling effect. However, the present invention is not limited thereto, and the first intermediate film 124a and the second intermediate film 126a may have various substances, shapes, thicknesses, etc.

[0054] In this embodiment, the first semiconductor layer 124 and the second semiconductor layer 126 and / or the first intermediate film 124a and the second intermediate film 126a may be entirely formed on the front and back surfaces of the semiconductor substrate 122, respectively. Thereby, the first semiconductor layer 124 and the second semiconductor layer 126 and / or the first intermediate film 124a and the second intermediate film 126a can be formed in a sufficient area without performing additional patterning. However, the present invention is not limited thereto.

[0055] In this embodiment, the first semiconductor layer 124 and the second semiconductor layer 126 may be formed as the same semiconductor layer as the substrate 122 and have the same crystal structure, or may be configured as semiconductor layers formed separately from the semiconductor substrate 122 or the base region. That is, the crystal structures of the first semiconductor layer 124 and the second semiconductor layer 126 and the semiconductor substrate 122 may be different from each other or the same.

[0056] Note that the first semiconductor layer 124 may have the same crystal structure as the semiconductor substrate 122, and conversely, the second semiconductor layer 126 may have a crystal structure different from that of the semiconductor substrate 122.

[0057] The bonding layer (tunneling bonding layer) 130 is located on one surface (in one example, the front surface) of the second photoelectric conversion unit 120 or on the first semiconductor layer 124, and electrically connects the second photoelectric conversion unit 120 and the first photoelectric conversion unit 110 located thereon. FIG. 1 shows a case where the bonding layer 130 is formed as a single layer in contact with the first semiconductor layer 124 of the second photoelectric conversion unit 120 and the second transport layer 116 of the first photoelectric conversion unit 110, but it is not limited thereto.

[0058] Such a bonding layer 130 may have a thin thickness. As one example, the thickness of the layer may be thinner than the thickness of the first electrode layer 420 of the first electrode 42 so as to smoothly perform carrier tunneling.

[0059] The bonding layer 130 may electrically connect the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120, and may contain a substance that can transmit light (in one example, long-wavelength light) used for the first photoelectric conversion unit 110. As one example, the bonding layer 130 may contain a transparent conductive substance (in one example, transparent conductive oxide) (TCO). As one example, it may be formed of a substance containing at least one of tin-doped indium oxide (ITO), tungsten-doped indium oxide (IWO), cesium-doped indium oxide (ICO), and fluorine-doped tin oxide (FTO).

[0060] Note that the bonding layer 130 may contain at least one of various substances such as a conductive carbon substance, a conductive polymer, n-type or p-type amorphous silicon. Or, the bonding layer 130 may reflect light (in one example, short-wavelength light) used for the second photoelectric conversion unit 120 in the second photoelectric conversion unit 120, make light (in one example, long-wavelength light) used for the first photoelectric conversion unit 110 transmissible, and provide it to the first photoelectric conversion unit 110.

[0061] The bonding layer 130 may be formed to have an area smaller than the area of the second photoelectric conversion unit 120, and the area of the first photoelectric conversion unit 110 formed thereon may be the same as or smaller than the area of the bonding layer 130, but is not limited thereto.

[0062] When the above-described bonding layer 130 is formed of a transparent conductive material (TCO), the TCO may have a hydrophilic surface property, but has a surface treatment surface 134 so as to have a hydrophobic property on its surface, that is, on the front surface in contact with the first photoelectric conversion unit 110.

[0063] Therefore, the two surfaces of the bonding layer 130 have different surface properties from each other.

[0064] That is, the back surface 132 of the bonding layer 130 in contact with the second photoelectric conversion unit 120 has hydrophilicity, and the front surface 134 of the bonding layer 130 in contact with the first photoelectric conversion unit 110 has hydrophobicity.

[0065] As described above, when the surface 134 in contact with the first photoelectric conversion unit 110 has hydrophobicity, the first photoelectric conversion unit 110 formed later may be formed by a dry method.

[0066] A first photoelectric conversion unit 110 including a photoelectric conversion layer 112 containing a perovskite compound may be positioned on the bonding layer 130. More specifically, the first photoelectric conversion unit 110 includes a first transport layer (first carrier transport layer) (114) positioned between the photoelectric conversion layer 112 and the first electrode 42 on the other surface of the photoelectric conversion layer 112 opposite to one surface of the photoelectric conversion layer 112 adjacent to the second photoelectric conversion unit 120, and a second transport layer (second carrier transport layer) 116 positioned between the bonding layer 130 and the photoelectric conversion layer 112 on one surface of the photoelectric conversion layer 112 adjacent to the second photoelectric conversion unit 120.

[0067] For example, the photoelectric conversion layer 112 may be made of a perovskite compound having a perovskite structure and may also be a photoactive layer that is excited by light to form carriers (electrons and holes). As an example, the perovskite structure may have a chemical formula of AMX3 (where A is a monovalent organic ammonium cation or a metal cation, M is a divalent metal cation, and X means a halogen anion). Such a photoelectric conversion layer 112 functions as AMX3, which is CH3NH3PbI3, CH3NH3PbI x Cl (3-x) , CH3NH3PbI x Br (3-x) , CH3NH3PbCl x Br (3-x) , HC(NH2)2PbI3, HC(NH2)2PbI x Cl (3-x) , HC(NH2)2PbIxBr (3-x) , HC(NH2)2PbCl x Br (3-x) and the like, or may include a compound in which Cs is partially doped into A of AMX3. However, the present invention is not limited thereto, and various substances may be used as the photoelectric conversion layer 112.

[0068] On the other surface (for example, the back surface) of the photoelectric conversion layer 112, the second transport layer 116 located between the bonding layer 130 and the photoelectric conversion layer 112 is a layer that extracts and transports the second carrier based on the bandgap relationship with the photoelectric conversion layer 112. And, on one surface (for example, the front surface) of the photoelectric conversion layer 112, the first transport layer 114 located between the photoelectric conversion layer 112 and the first electrode 42 is a layer that extracts and transports the first carrier based on the bandgap relationship with the photoelectric conversion layer 112. Here, the first carrier refers to the carrier that moves to the first semiconductor layer 124 based on the first conductivity type of the first semiconductor layer 124, and is the majority carrier with respect to the first conductivity type. When the first semiconductor layer 124 is of n-type, the first carrier is an electron, and when the first semiconductor layer 124 is of p-type, the first carrier is a hole. And, the second carrier refers to the carrier that moves to the second semiconductor layer 126 based on the second conductivity type of the second semiconductor layer 126, and is the majority carrier with respect to the second conductivity type. When the second semiconductor layer 126 is of p-type, the second carrier is a hole, and when the second semiconductor layer 126 is of n-type, the second carrier is an electron.

[0069] Among the first transport layer 114 and the second transport layer 116, the layer that transports electrons may be referred to as an electron transport layer, and the layer that transports holes may be referred to as a hole transport layer. For example, when the second transport layer 116 is a hole transport layer, the hole transport layer may contain a spirobifluorene compound (for example, 2,2´,7,7´-tetrakis(N,N-di-p-methoxyaniline)-9,9´-spirobifluorene (spiro-OMeTAD), 2,2´,7,7´-tetrakis(N,N-dimethoxyaniline)-2,7-diamino-9,9-spirobifluorene (spiro-TAD), 2,2´,7,7´-tetrakis(N,N-di-p-tolyl)amino-9,9-spirobifluorene (spiro-TTB), n-propyl bromide (NPB), etc.), poly-triarylamine (PTAA), or a metal compound (for example, molybdenum oxide, etc.).

[0070] At this time, since the front surface 134 of the bonding layer 130 has hydrophobicity, for substances having hydrophobicity, as an example, 2,2´,7,7´-tetrakis(N,N-di-p-tolyl)amino-9,9-spirobifluorene (spiro-TTB) and n-propyl bromide (NPB) may be applied as the hole transport layer which is the second transport layer 116. Therefore, since the surface characteristics of the bonding layer 130 and the second transport layer 116 are kept the same, the hole mobility can be improved, the bonding characteristics can be improved, and the fill factor (FF) can be increased. The improvement of the above-described characteristics can induce the improvement of the series cell driving performance.

[0071] And, as the electron transport layer, fullerene (C 60 ) or a derivative thereof (for example, phenyl-C61-butyric acid methyl ester (PCBM), etc.) may be included. However, the present invention is not limited thereto, and various substances capable of performing the action of transporting the first carrier or the second carrier through the first transport layer 114 and the second transport layer 116, or the electron transport layer and the hole transport layer may be included.

[0072] FIG. 1 illustrates a case where the second transport layer 116, the photoelectric conversion layer 112, and the first transport layer 114 are in contact with each other to minimize the carrier movement path. However, the present invention is not limited thereto, and various modifications are possible.

[0073] The first electrode 42 may be located on the photoelectric conversion unit 10 (as an example, located on the first transport layer 114 on the front surface of the first photoelectric conversion unit 110), and the second electrode 44 may be located on the photoelectric conversion unit 10 (as an example, located on the second semiconductor layer 126 on the back surface of the second photoelectric conversion unit 120).

[0074] In this embodiment, the first electrode 42 may include a first electrode layer 420 and a second electrode layer 422 sequentially laminated on one surface (as an example, the front surface) of the photoelectric conversion unit 10.

[0075] Here, the first electrode layer 420 may be entirely formed on the photoelectric conversion unit 10 (for example, located on the first transport layer 114 on the front side of the first photoelectric conversion unit 110). As an example, the first electrode layer 420 may be entirely formed thereon while contacting the photoelectric conversion unit 10 (for example, located on the first transport layer 114 on the front side of the first photoelectric conversion unit 110). In this specification, entirely forming means not only covering the entire photoelectric conversion unit 10 when there is no empty space or empty region, but also including the case where necessarily a part is not formed. As described above, when the first electrode layer 420 is entirely formed on the first photoelectric conversion unit 110, the first carriers can easily reach the second electrode layer 422 through the first electrode layer 420, and the resistance in the horizontal direction can be reduced.

[0076] As described above, since the first electrode layer 420 is entirely formed on the first photoelectric conversion unit 110, the first electrode layer 420 may be made of a light-transmittable substance (light-transmissive substance). That is, the first electrode layer 420 is made of a transparent conductive substance so as to be light-transmissive and allow carriers to move easily. Thereby, even if the first electrode layer 420 is entirely formed on the photoelectric conversion unit 10, light transmission is not hindered. As an example, the first electrode layer 420 may include a transparent conductive substance such as (for example, transparent conductive oxide, and as an example, metal-doped indium oxide, carbon nanotube (CNT), etc.). Examples of metal-doped indium oxide include tin-doped indium oxide (ITO), tungsten-doped indium oxide (IWO), cesium-doped indium oxide (ICO), etc. However, the present invention is not limited thereto, and the first electrode layer 420 may include various other substances.

[0077] And the second electrode layer 422 may be formed on the first electrode layer 420. As an example, the second electrode layer 422 may be formed in contact with the first electrode layer 422. The second electrode layer 422 may be made of a material having a conductivity better than that of the first electrode layer 420. Thereby, characteristics such as carrier collection efficiency and resistance reduction by the second electrode layer 422 can be further improved. As an example, the second electrode layer 422 may be made of an opaque metal having excellent conductivity or a metal having a lower transparency than the first electrode layer 420.

[0078] As described above, since the second electrode layer 422 can prevent light incidence due to being opaque or having low transparency, it may be partially formed as a predetermined pattern so as to minimize shading loss. Thereby, light can enter the portion where the second electrode layer 422 is not formed.

[0079] For example, the second electrode layer 422 may include a plurality of finger electrodes 42a spaced apart from each other while having a predetermined pitch. FIG. 2 illustrates a case where the finger electrodes 42a are parallel to each other and parallel to the main edge of the photoelectric conversion unit 10 (as an example, the semiconductor substrate 122), but the present invention is not limited thereto. And the second electrode layer 422 may include a bus bar electrode 42b formed in a direction intersecting the finger electrodes 42a and connecting the finger electrodes 42a. Such a bus electrode 42b may also be provided only one, and as shown in FIG. 2, a plurality of bus bar electrodes 42b may be provided while having a pitch larger than the pitch of the finger electrodes 42a. At this time, the width of the bus bar electrode 42b may be larger than the width of the finger electrode 42a, but the present invention is not limited thereto. Therefore, the width of the bus bar electrode 42b may be the same as the width of the finger electrode 42a, or may have a width narrower than that. However, the present invention is not limited thereto, and the second electrode layer 422 may have various planar shapes.

[0080] In this embodiment, the second electrode 44 may have a stacked structure different from that of the first electrode 42. This may be considered in view of the crystal structures of the material of the first photoelectric conversion unit 110 and the second semiconductor layer 126 included in the second photoelectric conversion unit 120.

[0081] For example, in this embodiment, the second electrode 44 may include a metal electrode layer 442 located on the other surface (as an example, the back surface) of the photoelectric conversion unit 10. As an example, the second electrode 44 may be configured as a single layer of the metal electrode layer 442 in contact with the photoelectric conversion unit 10 (more specifically, the second semiconductor layer 126), and a transparent conductive oxide layer or the like may not be provided.

[0082] The metal electrode layer 442 of the second electrode 44 may be made of a material having a conductivity superior to that of the first electrode layer 420 of the first electrode 42. As an example, the metal electrode layer 442 of the second electrode 42 may be made of an opaque metal having excellent conductivity or a metal having a lower transparency than the first electrode layer 420 of the first electrode 42. As described above, the metal electrode layer 442 may be partially formed on the photoelectric conversion unit 10 so as to have a predetermined pattern. Thereby, in the double-sided light receiving structure, light can enter the portion where the metal electrode layer 442 is not formed.

[0083] For example, the metal electrode layer 442 may include a plurality of finger electrodes that are isolated from each other while having a predetermined pitch, and may further include a bus bar electrode that is formed in a direction intersecting the finger electrodes and connects the finger electrodes. Except for the point that the metal electrode layer 442 is located on the other surface of the photoelectric conversion unit 10, the description of the finger electrodes 42a and the bus bar electrode 42b included in the second electrode layer 422 of the first electrode 42 may be applicable to the finger electrodes and the bus bar electrode of the metal electrode layer 442. At this time, the widths, pitches, etc. of the finger electrodes 42a and the bus bar electrode 42b of the first electrode 42 may have the same or different values from the widths, pitches, etc. of the finger electrodes and the bus bar electrode of the second electrode 44. And the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 may have the same or different materials, compositions, shapes, or thicknesses from each other.

[0084] In this embodiment, the metal electrode layer 442 including an opaque or metal among the first electrode 42 and the second electrode 44 of the solar cell 100 has a bifacial structure including a predetermined pattern so that light can be incident on the front and back surfaces of the photoelectric conversion units 110 and 120. Thereby, by increasing the amount of light used in the solar cell 100, it is possible to contribute to improving the efficiency of the solar cell 100.

[0085] In the above description, it is exemplified that the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 have the same or similar planar shapes while having patterns respectively. However, the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 may have different planar shapes. As an example, when the solar cell 100 has a single-sided light-receiving structure where light does not enter the back surface, the second electrode 44 or the metal electrode layer 442 may also be entirely formed (contacted and formed) on the photoelectric conversion unit 10 (more specifically, the second semiconductor layer 126). As described above, various deformations are possible for the shapes, arrangements, etc. of the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44.

[0086] In this embodiment, the second electrode layer 422 or the metal electrode layer 442 may include a printed layer containing a metal and a resin. Here, the second electrode layer 422 is formed in contact with the first electrode layer 420, and since there is no insulating film provided on the surface of the second semiconductor layer 126 where the metal electrode layer 442 is positioned, it does not require a fire-through through an insulating film or the like. In this regard, in this embodiment, a glass frit made of a predetermined metal compound (as an example, an oxide containing oxygen, a carbide containing carbon, a sulfide containing sulfur) is not provided, and a printed layer may be formed using a low-temperature firing paste containing only a metal and a resin (adhesive, curing agent, additive).

[0087] More specifically, a glass frit may not be provided, and a low-temperature firing paste containing a metal and a resin may be applied and heat-treated to cure it to form a printed layer. Thereby, the printed layer included in the second electrode layer 422 or the metal electrode layer 442 can have conductivity without sintering of a plurality of metal particles and aggregating while contacting each other. As an example, by curing the low-temperature firing paste at a temperature lower than the temperature used in the conventional low-temperature process (as an example, 150 °C or lower), in the printed layer included in the second electrode layer 422 or the metal electrode layer 442, a plurality of metal particles are not completely necked and may have a shape of connecting while contacting each other.

[0088] As described above, when the second electrode layer 422 or the metal electrode layer 442 includes a printed layer formed using a low-temperature firing paste, the second electrode layer 422 or the metal electrode layer 442 can be formed by a simple process, and in the process of forming the second electrode layer 422 or the metal electrode layer 442, it is possible to prevent the occurrence of degradation phenomena such as the degradation of the first photoelectric conversion unit 110 containing the perovskite compound. However, the present invention is not limited thereto. The second electrode layer 422 or the metal electrode layer 442 may also include an additional metal layer other than the printed layer, and the second electrode layer 422 or the metal electrode layer 442 may not include the printed layer, but may also include an electroplated layer, a sputtering layer, and the like. Various other modifications are possible.

[0089] The second electrode layer 422 or the metal electrode layer 442 may include a plurality of metals. For example, the second electrode layer 422 or the metal electrode layer 442 may include a plurality of metals such as silver, copper, gold, and aluminum. In this embodiment, the second electrode layer 422 and the metal electrode layer 442 may also have the same substance, structure, shape, thickness, etc. as each other, and may also have different substances, structures, shapes, thicknesses, etc. from each other. As an example, the width of the second electrode layer 422 may be smaller than the width of the metal electrode layer 442, and / or the thickness of the second electrode layer 422 may be larger than the thickness of the metal electrode layer 442. This is to ensure sufficient resistivity while reducing the light shielding loss caused by the second electrode layer 422 located on the front surface, but the present invention is not limited thereto.

[0090] As described above, the photoelectric conversion unit 10 according to this embodiment may have a series structure in which a second photoelectric conversion unit 120 based on a single semiconductor material (as an example, silicon) and a first photoelectric conversion unit 110 based on a perovskite compound are joined by a joining layer 130. At this time, the first photoelectric conversion unit 110 has a larger bandgap than the second photoelectric conversion unit 120. That is, the first photoelectric conversion unit 110 has a relatively large bandgap and causes photoelectric conversion by absorbing a short wavelength having a relatively short wavelength, and the second photoelectric conversion unit 120 has a lower bandgap than the first photoelectric conversion unit 110 and efficiently absorbs a long wavelength having a wavelength larger than the light used for the first photoelectric conversion unit 110 to cause photoelectric conversion using the same.

[0091] More specifically, when light is incident on the front surface of the solar cell 100, the first photoelectric conversion unit 110 absorbs the short wavelength and generates electrons and holes by photoelectric conversion. At this time, the first carrier moves to and is collected by the first electrode 42, and the second carrier moves to and is collected on the second electrode 44 side through the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120. When the long wavelength that has not been used in the first photoelectric conversion unit 110 and has passed through it reaches the second photoelectric conversion unit 120, the second photoelectric conversion unit 120 absorbs it and generates a first carrier and a second carrier by photoelectric conversion. At this time, the first carrier moves to and is collected on the first electrode 42 side through the first photoelectric conversion unit 110, and the second carrier moves to and is collected on the second electrode 44 side.

[0092] As described above, the first electrode 42 adjacent to the first photoelectric conversion unit 110 and the second electrode 44 adjacent to the second photoelectric conversion unit 120 may have different laminated structures.

[0093] The first semiconductor layer 124 located on the front surface of the semiconductor substrate 122 may include an amorphous portion (as an example, an amorphous layer) doped with a dopant of the first conductivity type. More specifically, in this embodiment, the first semiconductor layer 124 may be formed from amorphous silicon doped with a dopant of the first conductivity type.

[0094] For example, the first semiconductor layer 124 may include an amorphous silicon layer doped with a dopant of the first conductivity type.

[0095] As an example, when the first semiconductor layer 124 includes an amorphous silicon layer, by including the same semiconductor material as the semiconductor substrate 122, the characteristic difference from the semiconductor substrate 122 can be minimized.

[0096] And the second semiconductor layer 126 located on the back surface of the semiconductor substrate 122 may include a polycrystalline portion (as an example, a polycrystalline layer) doped with a dopant of the second conductivity type. More specifically, in this embodiment, the second semiconductor layer 126 may include a polycrystalline portion doped with a dopant of the second conductivity type and hydrogenated (that is, a polycrystalline portion containing hydrogen). Therefore, as an example, in order to improve the passivation characteristics of the second semiconductor layer 126, a hydrogen implantation process for implanting hydrogen into the second semiconductor layer 126 may be performed.

[0097] Here, including a polycrystalline portion may include not only the case of having an overall polycrystalline structure, but also the case where the volume ratio of the portion having a polycrystalline structure is larger than the volume ratio of the portion having an amorphous structure. As an example, in this embodiment, the second semiconductor layer 126 may be composed of a polycrystalline semiconductor layer having an overall polycrystalline structure so as to have excellent photoelectric conversion efficiency and excellent electrical characteristics.

[0098] For example, the second semiconductor layer 126 may include a polycrystalline silicon layer doped with a dopant of a second conductivity type and containing hydrogen. Here, the polycrystalline silicon layer may mean that a polycrystalline portion mainly composed of silicon is provided. As an example, the second semiconductor layer 126 may be composed of a polycrystalline silicon layer doped with a dopant of a second conductivity type, containing hydrogen, and having an overall polycrystalline structure.

[0099] As described above, when the second semiconductor layer 126 is composed of a polycrystalline portion, it can have a high carrier mobility, and thus can have excellent photoelectric conversion efficiency and excellent electrical characteristics.

[0100] Thereby, the semiconductor substrate 122, the second semiconductor layer 126 and / or the second intermediate film 126a may include the same semiconductor material (for example, silicon) as each other, and may have an insulation-junction structure or a tunnel-junction structure joined via the second intermediate film 126a made of an insulating material (that is, an insulating film). At this time, since the thickness of the second intermediate film 126a is thin, it does not hinder the movement of carriers.

[0101] In this embodiment, the second semiconductor layer 126 located on the back surface of the semiconductor substrate 122 may be composed of a polycrystalline portion that absorbs relatively more light, and the first semiconductor layer 124 located on the front surface of the semiconductor substrate 122 may be composed of an amorphous portion that absorbs less light than the second semiconductor layer 126. Thereby, undesirable light absorption on the front surface of the semiconductor substrate 122 can be minimized. And in the second semiconductor layer 126 located on the back surface of the semiconductor substrate 122, carrier movement characteristics, electrical connection characteristics, etc. can be effectively improved.

[0102] And the first semiconductor layer 124 positioned adjacent to the first photoelectric conversion unit 110 may be composed of an amorphous portion, whereby the matching property of the first photoelectric conversion unit 110 containing a perovskite compound can be improved and the carrier movement characteristics can be improved.

[0103] The first semiconductor layer 124 may be in direct contact with the first photoelectric conversion unit 110 via the bonding layer 130. That is, the bonding layer 130 may be positioned to contact the first semiconductor layer 124, and the first photoelectric conversion unit 110 may be positioned to contact the bonding layer 130. As a result, the structure can be simplified, and the movement of carriers can be made smooth.

[0104] The second semiconductor layer 126 positioned on the surface of the semiconductor substrate 122 opposite to the surface where the first photoelectric conversion unit 110 is positioned may include a polycrystalline portion, thereby effectively improving carrier movement characteristics, electrical connection characteristics, and the like.

[0105] At this time, the thickness of the second semiconductor layer 126 may be the same as or greater than the thickness of the first semiconductor layer 124. As an example, the thickness of the second semiconductor layer 126 may be greater than the thickness of the first semiconductor layer 124. This is because since the second semiconductor layer 126 is positioned on the back surface of the semiconductor substrate 122, even if it has a relatively large thickness, it does not significantly obstruct the incident light. Alternatively, the thickness of the first semiconductor layer 124 may be 10 nm or less (as an example, 5 nm to 10 nm), and the thickness of the second semiconductor layer 126 may be 10 nm or more (as an example, more than 10 nm and 500 nm or less). Such thicknesses are considered in view of the characteristics of the first semiconductor layer 124 and the second semiconductor layer 126, the amount of light passing through them, etc., but the present invention is not limited thereto.

[0106] Also, as described above, the bonding layer 130 may be divided into a back surface 132 in contact with the first semiconductor layer 124 and a front surface 134 in contact with the second transport layer 116.

[0107] The above division schematically indicates that the surface characteristics of the front surface 134 and the back surface 132 are different for the single-layer bonding layer 130 formed of the same material.

[0108] That is, the back surface 132 has a hydrophilic surface which is a characteristic of the transparent conductive material (TCO) constituting the single bonding layer 130, and the front surface 134 changes the surface characteristics to have a hydrophobic surface and other surface characteristics by surface-treating the TCO.

[0109] As mentioned above, depending on the conductive types of the semiconductor substrate 122, the first semiconductor layer 124, and the second semiconductor layer 126, the functions, materials, etc. of the first semiconductor layer 124, the second semiconductor layer 126, the first transport layer 114, and the second transport layer 116 may be different. Considering this, the structure of the solar cell 100 according to an example of this embodiment will be described with reference to FIG. 3, and the carrier movement characteristics thereof will be described with reference to FIG. 4.

[0110] FIG. 3 is a diagram schematically showing an example of the conductive types and functions of a plurality of layers included in the photoelectric conversion unit 10 of the solar cell 100 according to an embodiment of the present invention. For clarity of understanding, FIG. 3 does not specifically show irregularities or an antireflection structure, etc., but mainly shows the stacking order, conductive type, and function of the plurality of layers included in the photoelectric conversion unit 10.

[0111] Referring to FIG. 3, in this example, the semiconductor substrate 122 may have an n-type. When the semiconductor substrate 122 has an n-type, the bulk characteristics are excellent, and the lifetime of carriers can be improved.

[0112] In this embodiment, the first semiconductor layer 124 may have an n-type conductivity type that is the same as that of the semiconductor substrate 122, and may have a doping concentration higher than that of the semiconductor substrate 122. Also, the second semiconductor layer 126 may have a p-type conductivity type different from that of the semiconductor substrate 122. Thereby, the second semiconductor layer 126 located on the back surface of the semiconductor substrate 122 may form an emission region that forms a pn junction with the semiconductor substrate 122. And the first semiconductor layer 124 located on the front surface may be configured to form a front surface field in order to prevent a composite front electric field region. Since the emission region directly involved in photoelectric conversion is located on the back surface, the emission region may be formed to have a sufficient thickness (as an example, formed thicker than the front electric field region), thereby improving the photoelectric conversion efficiency. And the first semiconductor layer 124, which is the front electric field region, may be formed thinly, thereby minimizing losses.

[0113] In such a case, in the first photoelectric conversion unit 110 located on the second photoelectric conversion unit 120, the upper first transport layer 114 may be configured as an electron transport layer that transports electrons, and the lower second transport layer 116 may be configured as a hole transport layer that transports holes. In such a case, the first photoelectric conversion unit 110 may have excellent effects.

[0114] In such a solar cell 100, when light is incident on the front surface of the solar cell 100, the first photoelectric conversion unit 110 absorbs short wavelengths and generates electrons and holes by photoelectric conversion. At this time, the electrons move through the first transport layer 114 to the first electrode 42 side and are collected, and the holes move through the second transport layer 116 and the second photoelectric conversion unit 120 to the second electrode 44 side and are collected. When the long wavelengths that are not used in the first photoelectric conversion unit 110 and pass through it reach the second photoelectric conversion unit 120, the second photoelectric conversion unit 120 absorbs it and generates electrons and holes by photoelectric conversion. At this time, the electrons move through the first semiconductor layer 124 and the first photoelectric conversion unit 110 to the first electrode 42 side and are collected, and the holes move through the second semiconductor layer 126 to the second electrode 44 side and are collected.

[0115] FIG. 4 is a diagram schematically showing the energy band of the solar cell shown in FIG. 3 and the energy band of the solar cell according to Comparative Example 1. In FIG. 4, the illustration of the first intermediate film, the second intermediate film, the second electrode layer of the first electrode, and the second electrode is omitted.

[0116] Referring to FIG. 4, in this embodiment, the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120 have an energy band diagram in which the movement of holes and electrons moves smoothly. That is, in each of the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120, the energy of the conduction band tends to gradually decrease in the electron flow direction, and the energy of the valence electron conduction band tends to gradually increase in the electron flow direction. That is, the first semiconductor layer 124 is configured as an amorphous portion with a low energy band gap (1.5 to 1.7 eV) to form an energy band diagram in which carriers can flow smoothly, so the movement characteristics of the carriers are extremely excellent.

[0117] When a transparent conductive material (TCO) is applied as the bonding layer 130, the surface characteristics of the front surface 134 bonded to the second transport layer 116 change from hydrophilic to hydrophobic by plasma surface treatment, and hydrophobic substances such as NPB, Spiro-TTB, and TAD may be applied as the second transport layer 116.

[0118] At this time, NPB has a hydrophobicity measured at a measurement angle of about 68 to 70°, and Spiro-TTB has a hydrophobicity measured at about 83 to 87°.

[0119] Therefore, a substance that satisfies the energy band gap, satisfies the carrier flow, and satisfies the surface characteristics may be applied as the second transport layer 116, which is a hole transport layer.

[0120] FIG. 4 shows, as an example, the structure of the solar cell 100 shown in FIG. 3. When the conductivity types of the semiconductor substrate 122, the first semiconductor layer 124, and the second semiconductor layer 126 are different, the tendency of the energy band diagram may also have a tendency to improve the carrier movement characteristics.

[0121] As described above, according to the present embodiment, by changing the surface characteristics of the bonding layer 130, the matching property of the first photoelectric conversion unit 110 including the perovskite compound formed on the upper part can be improved, and the carrier movement characteristics can be improved. And the second semiconductor layer 126 may be configured as a polycrystalline part having excellent carrier mobility, whereby the carrier movement characteristics can be improved, and the material cost of the second electrode 44 can be reduced to simplify the manufacturing process. Thereby, the efficiency and productivity of the solar cell 100 having a series structure can be improved.

[0122] A method for manufacturing the solar cell 100 having the above structure will be described in detail with reference to FIGS. 5 to 12b. For the content already described in the above description, the detailed description thereof will be omitted, and the parts not described will be described in detail.

[0123] FIG. 5 is a flowchart of a method for manufacturing a solar cell according to an embodiment of the present invention, FIG. 6 is a detailed sequence diagram up to the formation of the doping layer in FIG. 5, FIGS. 7a and 7b are cross-sectional views for explaining the manufacturing method in FIG. 6, FIG. 8 is a detailed sequence diagram up to the formation of the bonding layer in FIG. 5, FIG. 9 is a cross-sectional view showing the manufacturing method in FIG. 8, FIG. 10 shows a contact angle representing the surface property change of the bonding layer in FIG. 8, FIG. 11 is a detailed sequence diagram for forming the first photoelectric conversion unit and electrodes in FIG. 5, and FIGS. 12a to 12b are cross-sectional views showing the manufacturing method in FIG. 11.

[0124] Referring to FIG. 5, the method for manufacturing the solar cell 100 according to this embodiment may include a step of forming double-sided tunneling layers on both sides of the second photoelectric conversion unit (S10), a step of forming the first semiconductor layer and the second semiconductor layer (S20), a hydrogen injection step (S30), a bonding layer forming step (S40), a plasma treatment step (S50), a first photoelectric conversion unit forming step (S60), and an electrode forming step (S70).

[0125] Referring to FIG. 6, the doping layer forming step (S20) may be further divided, and thus, it may include six steps.

[0126] Specifically, first, a semiconductor substrate 122 configured as a base region having a first conductivity type dopant or a second conductivity type dopant is created. At this time, texturing may be performed on at least one of the front and back surfaces of the semiconductor substrate 122 so as to have unevenness and an antireflection structure (S11). As the texturing of the surface of the semiconductor substrate 122, wet or dry texturing may be used. The wet texturing may be performed by immersing the semiconductor substrate 122 in a texturing solution, and the double-sided texturing may be performed by immersing it in a TMAH or KOH solution.

[0127] Also, as shown in FIG. 7a, when performing texturing only on the back surface, a front polishing process (S12) may be additionally performed. The back polishing process may be performed by immersing only one surface in an etching solution, may be performed in an acid solution of HF or HNO3, and either a conveyance method or a floating method may be applied. Note that the semiconductor substrate 122 may be textured by reactive ion etching (RIE) or the like. As described above, in the present invention, the semiconductor substrate 122 may be textured by a plurality of methods.

[0128] Next, as shown in FIG. 7a, a second intermediate film 126a and a first intermediate film 124a are formed on both surfaces of the semiconductor substrate 122 (S13).

[0129] As an example, the above-described second intermediate film 126a and first intermediate film 124a may be formed by a thermal oxidation method, a deposition method (for example, chemical vapor deposition (CVD), atomic layer deposition (ALD)), or the like. Specifically, after polishing, both surfaces may be cleaned, and DIO3 and H2O2 may be applied to both surfaces of the cleaned semiconductor substrate by a wet method to oxidize, and thermal oxidation may be performed in a furnace by a dry method or UVO may be executed. As described above, the generated silicon oxide film may be used as the second intermediate film 126a on the back surface of the semiconductor substrate 122 and may also be used as the first intermediate film 124a on the front surface.

[0130] The silicon oxide films formed on the front and back surfaces are formed to be thinner than 2 nm in thickness so that tunneling can be performed.

[0131] Subsequently, as shown in FIG. 7b, intrinsic polycrystalline silicon layers 124b and 126b (S21) are formed on both surfaces.

[0132] As described above, after the formed intrinsic polycrystalline silicon layers 124b and 126b are formed on the front and back surfaces of the semiconductor substrate 122 and selectively and entirely formed on the side surfaces, by removing the intrinsic polycrystalline silicon layers 124b and 126b formed on the side surfaces of the semiconductor substrate 122, the intrinsic polycrystalline silicon layers 124b and 126b can be formed only on the front and back surfaces of the semiconductor substrate 122.

[0133] For example, the intrinsic polycrystalline silicon layers 124b and 126b may be formed by a thermal oxidation method, a deposition method (e.g., chemical vapor deposition (CVD), atomic layer deposition (ALD)), etc. For example, the intrinsic polycrystalline silicon layers 124b and 126b may be formed by a deposition method (e.g., by chemical vapor deposition (CVD), as an example, low-pressure chemical vapor deposition (LPCVD)), etc. In this embodiment, the intrinsic polycrystalline silicon layers 124b and 126b may be formed as polycrystalline portions made of a semiconductor material that does not contain a dopant. The intrinsic polycrystalline silicon layers 124b and 126b may be formed to a thickness of 100 nm or less at 600 °C or less in an SiH4 atmosphere by low-pressure chemical vapor deposition.

[0134] Subsequently, a doping layer (not shown) is formed on the intrinsic polycrystalline silicon layer 126b on the back surface (S22).

[0135] The doping layer may be formed by atmospheric pressure chemical vapor deposition or plasma chemical vapor deposition (APCVD or PECVD), and when the second semiconductor layer 126 is formed on the back surface of the semiconductor substrate 122, when the second semiconductor layer 126 is of p-type, boron silicate glass (BSG) or undoped silicate glass (USG) may be deposited and used as a doping source. At this time, during deposition in an atmosphere of SiH4, O2, B2H2, and H2, the thickness of the doping layer is formed to satisfy 80 to 150 nm.

[0136] Also, a front doping layer is formed on the front surface of the semiconductor substrate 122 (not shown). At this time, when the first conductivity type is n-type, the front doping layer may be formed as phosphosilicate glass (PSG).

[0137] Therefore, PSG is formed as a doping layer on the front surface of the semiconductor substrate 122, and BSG / USG is formed as a doping layer that retains the second type dopant on the back surface.

[0138] Subsequently, heat treatment is performed to execute doping on each of the lower intrinsic polycrystalline silicon layers 124b and 126b (S22).

[0139] Specifically, as shown in FIG. 7b, the first semiconductor layer 124 and the second semiconductor layer 126 are formed by activation.

[0140] Specifically, when heat treatment is performed at a temperature of 900° C. or higher in a POCl3 atmosphere in a furnace apparatus, the intrinsic polycrystalline silicon layers 124b and 126b formed on the front and back surfaces of the substrate 122 are doped and recrystallized by dopant diffusion from the corresponding doping layers laminated on the upper part.

[0141] Therefore, a semiconductor layer having a polycrystalline structure with the second semiconductor layer 126 is formed by diffusing the second dopant on the back surface, and the first semiconductor layer 124 is formed by diffusing the first dopant diffusion on the front surface.

[0142] At this time, when the first semiconductor layer 124 is formed in the same layer as the semiconductor substrate 122 by doping, it may be formed while having an amorphous crystal structure similar to that of the semiconductor substrate 122.

[0143] Subsequently, by completely removing the doping layers remaining on the upper and lower portions of the semiconductor substrate 122, the first semiconductor layer 124 can be exposed on the front surface of the substrate 122, and the second semiconductor layer 126 can be exposed on the back surface of the substrate 122.

[0144] The above-described cleaning and doping layer removal may be performed by etching with DHF, but is not limited thereto.

[0145] Subsequently, hydrogen implantation is performed on both surfaces of the semiconductor substrate 122 (S30).

[0146] In the hydrogen implantation step, hydrogen is implanted into the first semiconductor layer 124 and the second semiconductor layer 126. As described above, since the first semiconductor layer 124 and the second semiconductor layer 126 are formed at a high temperature of 900°C or higher or 600 - 800°C, even if the first semiconductor layer 124 and the second semiconductor layer 126 contain hydrogen, dehydrogenation can be achieved by the high temperature. By performing the hydrogen implantation step after forming the first semiconductor layer 124 and the second semiconductor layer 126, the hydrogen content is increased and hydrogen passivation is sufficiently performed.

[0147] As an example, a hydrogen implantation layer containing hydrogen may be formed on the first semiconductor layer 124 and the second semiconductor layer 126 of the semiconductor substrate 122 (not shown), and heat treatment may be performed at a temperature higher than room temperature (for example, 400 - 600°C) to implant hydrogen.

[0148] Here, an insulating layer that may contain hydrogen with a high content, for example, a silicon nitride layer containing hydrogen, an aluminum oxide layer containing hydrogen, etc. may be used as the hydrogen implantation layer. After the hydrogen implantation step, the hydrogen implantation layer is removed.

[0149] However, the present invention is not limited thereto, and the hydrogen implantation layer may be left and used as a back surface passivation film, a reflective film, an antireflection film, etc. A plurality of other methods are possible.

[0150] And the hydrogen injection method in the hydrogen injection step is not limited to the above method. For example, heat treatment may be performed at a temperature higher than room temperature (as an example, 400 to 600 °C) in a mixed gas atmosphere in which hydrogen and a carrier gas (for example, argon (Ar), nitrogen (N2), etc.) are mixed to inject hydrogen. In addition, hydrogen can also be injected using hydrogen plasma or the like.

[0151] As described above, when the hydrogen injection into the first semiconductor layer 124 and the second semiconductor layer 126 is completed respectively, as shown in FIG. 8, a bonding layer 130 (S41, S40) is formed on the first semiconductor layer 124.

[0152] More specifically, the bonding layer 130 may be formed on at least a part of the first semiconductor layer 124 of the second photoelectric conversion unit 120. As an example, the bonding layer 130 may be formed by a sputtering process. The sputtering process may be performed at a low temperature, and the bonding layer 130 may be formed only on the second semiconductor layer 124 by a single-sided process. However, the present invention is not limited thereto, and a plurality of methods such as a coating method are applicable.

[0153] The area of the bonding layer 130 may be formed in the same manner as the second photoelectric conversion unit 120, but differently, it may be formed smaller than the second photoelectric conversion unit 120.

[0154] This may be achieved by arranging a mask (not shown) so as to form only in the central region while exposing the edge region of the second photoelectric conversion unit 120, and then performing a sputtering process, but it is not limited thereto, and it may be formed by a plurality of methods.

[0155] The bonding layer 130 formed at this time may have a thin thickness so as to smoothly perform carrier tunneling, and the thickness of the layer may be thinner than the thickness of the first electrode layer 420 of the first electrode 42.

[0156] The bonding layer 130 may electrically connect the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120, and may include a substance that can transmit light (for example, long-wavelength light) used in the first photoelectric conversion unit 110. The bonding layer 130 may be formed of a transparent conductive substance (for example, transparent conductive oxide) (TCO). As an example, it may be formed of a substance containing at least one of tin doped indium oxide (ITO), tungsten-doped indium oxide (IWO), cesium-doped indium oxide (ICO), and fluorine-doped tin oxide (FTO).

[0157] Note that the bonding layer 130 may reflect light (for example, short-wavelength light) used in the second photoelectric conversion unit 120 in the second photoelectric conversion unit 120, and may transmit light (for example, long-wavelength light) used in the first photoelectric conversion unit 110 and provide it to the first photoelectric conversion unit 110.

[0158] When the above-described bonding layer 130 is formed of a transparent conductive substance (TCO), the transparent conductive substance has a hydrophilic surface property. Therefore, it has the property of a very small contact angle.

[0159] Subsequently, surface treatment may be performed on the front surface 134 (that is, the surface in contact with the first photoelectric conversion unit 110) of the formed bonding layer 130 so as to change the hydrophilic surface property to a hydrophobic surface property (S51, S50).

[0160] Specifically, as shown in FIG. 9, by performing plasma treatment, the front surface 134 having a modified hydrophobic state is formed on the surface.

[0161] The above-described plasma treatment arranges the substrate 122 in a plasma device such as PVD, PECVD, or PEALD, and performs plasma surface treatment in an atmosphere of CH4, CH4 / H2, or CH4 / N2.

[0162] As an example, as shown in Table 1 below, plasma surface treatment may be performed so as to satisfy the process conditions.

[0163] [Table 1] JPEG0007699671000001.jpg29154

[0164] That is, plasma treatment may be performed under a plurality of process conditions in the plasma equipment, and as shown in the four experimental examples in Table 1, it has a process time of 1 second or more in the equipment where the power density (POWER DENSITY) is within 60 - 70, and has a process time of within 30 seconds in the equipment where the power density satisfies 300 - 350. However, in a plurality of equipment, the process temperature also satisfies within 200°C, specifically, 150°C or less, and within 40°C - 120°C, thereby preventing the deterioration of the amorphous silicon applied as the substrate. As described above, as shown in Table 1, the processed plasma treatment contains CH4, and may be performed in an atmosphere with other H2 and N2 added. As shown in FIG. 10, according to the effect, it changes to have similar hydrophobic surface characteristics.

[0165] Referring to FIG. 10, cesium-doped indium oxide (ICO) is applied as the bonding layer 130 before plasma treatment, and the contact angle result of its surface is about 68.3°.

[0166] At this time, as shown in Experimental Examples 1 - 4, by subjecting the surface of the surface-treated cesium-doped indium oxide (ICO) to CH4 plasma treatment, it is possible to maintain hydrophobicity with a contact angle of 90° or more.

[0167] At this time, each contact angle is measured according to the ASTM D5936 standard.

[0168] As described above, the hydrophilic surface of the cesium-doped indium oxide (ICO) treated with CH4 plasma can be changed to hydrophobic, and there are both sides with different properties shown in FIG. 9.

[0169] That is, the back surface 132 of the bonding layer 130 in contact with the second photoelectric conversion unit 120 has hydrophilicity, and the front surface 134 of the bonding layer 130 in contact with the first photoelectric conversion unit 110 has hydrophobicity.

[0170] Also, although CH4 plasma treatment has been described in the present invention, alternatively, fluorine plasma treatment may be performed.

[0171] When performing fluorine plasma treatment, plasma treatment is carried out in a fluorine atmosphere such as CF4, SF6, NF3, etc. in the same plasma equipment.

[0172] By the above-described fluorine plasma treatment, surface modification changes from a hydrophilic surface to a hydrophobic surface may be performed. In the fluorine plasma treatment, the process temperature may also be set to 150°C or lower.

[0173] Subsequently, after the above-described surface treatment, a first photoelectric conversion unit 110 including a photoelectric conversion layer 112 containing a perovskite compound is formed on the hydrophobic front surface 134 having the bonding layer 130.

[0174] That is, as shown in FIGS. 11 and 12, by forming the first photoelectric conversion unit 110 and the electrodes, a series-type solar cell 100 (S60, S70 in FIG. 5) is formed.

[0175] In the step (S60) of forming the first photoelectric conversion unit 110, as shown in FIG. 12a, the first photoelectric conversion unit 110 is formed on the bonding layer 130. More specifically, a second transport layer 116, a photoelectric conversion layer 112, and a first transport layer 114 (S61, S62, S63) may be sequentially formed on the bonding layer 130.

[0176] The second transport layer 116, the photoelectric conversion layer 112, and the first transport layer 114 may be formed by a plurality of methods. In particular, the second transport layer 116 may be formed by a dry process without a wet process.

[0177] As an example, for the second transport layer 116, a hydrophobic Spiro-TTB or NPB is deposited on the front surface of the hydrophobic bonding layer by deposition (for example, dry methods such as physical vapor deposition, chemical vapor deposition, plasma deposition, etc.).

[0178] As described above, since the second transport layer 116 formed by deposition has hydrophobicity, the energy difference between the front surface 134 and the surface of the hydrophobic bonding layer 130 is very small, and a uniform and thin substrate can be formed without further detachment.

[0179] As described above, when depositing in a state where the surface energy difference is very small, the leakage current is reduced between the second transport layer and the bonding layer, and the hole transport is performed smoothly. As a result, the open voltage and the fill factor (FF) are improved, and the overall efficiency of the tandem solar cell 100 is improved.

[0180] The photoelectric conversion layer 112 and the first transport layer 114 may be formed on the second transport layer 116 by a plurality of methods.

[0181] That is, it may be formed by deposition like the second transport layer 116. Depending on the characteristics of the photoelectric conversion layer 112, the photoelectric conversion layer 112 and the first transport layer 114 may be formed by a printing method or the like. Here, the printing method may include inkjet printing, gravure printing, spray coating, doctor blade, bar coating, gravure coating, brush coating, slit coating, and the like.

[0182] Next, as shown in FIG. 12b, in the electrode formation step (S70), the first electrode 42 and the second electrode 44 may be formed.

[0183] That is, the first electrode layer 420 (S71) of the first electrode 42 may be formed on the first photoelectric conversion unit 110 (more specifically, the first transport layer 114), and the second electrode layer 422 (S72) may be formed on the first electrode layer 420. Then, the metal electrode layer 442 of the second electrode 44 may be formed on the second photoelectric conversion unit 120 (more specifically, the second semiconductor layer 126 configured as a polycrystalline portion).

[0184] As an example, the first electrode layer 420 of the first electrode 42 may be formed by a vacuum deposition process or a sputtering process. The vacuum deposition process or the sputtering process may be performed at a low temperature, and the first electrode layer 420 of the first electrode 42 may be formed only on one-sided front. However, the present invention is not limited thereto, and a plurality of methods such as a coating method may be applied. And in this embodiment, the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 may be formed. As an example, a low-temperature firing paste containing a metal and a resin may be applied, and a curing heat treatment for curing it may be performed to form the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44.

[0185] As an example, after forming the first electrode layer 420 of the first electrode 42, a low-temperature firing paste for the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 is applied, and a curing heat treatment for simultaneous curing of the low-temperature firing paste used for the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 is performed. The curing heat treatment may be performed at a low temperature of 150 ° C or lower, thereby preventing characteristic changes, deterioration, etc. of the first photoelectric conversion unit 110 containing a perovskite compound.

[0186] The order of the formation process of the first electrode layer 420 of the first electrode 42, the coating process and the heat treatment process of the second electrode layer 422 of the first electrode 42, and the coating process and the heat treatment process of the metal electrode layer 442 of the second electrode 44 can be variously deformed.

[0187] The above description illustrates simplifying the process by forming the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44 by a printing method. However, the present invention is not limited to this, and various modifications are possible for the formation method, process conditions, etc. of the second electrode layer 422 of the first electrode 42 and the metal electrode layer 442 of the second electrode 44.

[0188] According to this embodiment, productivity can be improved by forming a series-structured solar cell having excellent efficiency through a simple manufacturing process. At this time, by keeping the process temperature, such as the electrode formation step (S70) executed after the first photoelectric conversion unit formation step (ST60) for forming the first photoelectric conversion unit 110 containing a perovskite compound, at a low temperature (for example, 150 ° C or lower), deterioration of the characteristics of the first semiconductor layer 124 configured as an amorphous portion or the first photoelectric conversion unit 110 containing a perovskite compound can be effectively prevented.

[0189] In this embodiment, unevenness or an antireflection structure by texturing is provided on the front surface of the semiconductor substrate 122 so as to perform an antireflection function. Accordingly, an antireflection film is not provided on the front surface of the solar cell 100. At this time, unevenness or an antireflection structure corresponding to the unevenness or antireflection structure formed on the front surface of the semiconductor substrate 122 may also be provided on both side surfaces of the first semiconductor layer 124, the bonding layer 130, the second transport layer 116, the photoelectric conversion layer 112, the first transport layer 114, and the first electrode layer 420 located on the front surface of the semiconductor substrate 122. As described above, since no additional antireflection structure is provided, the structure can be simplified. However, the present invention is not limited to this, and as shown in FIG. 12b, an antireflection film 460 may also be provided on at least a part of the first electrode layer 420 of the first electrode 42. Various other modifications are possible (S73).

[0190] In this embodiment, an additional passivation film is not provided on the second semiconductor layer 126, so a case having a simple structure is illustrated. This is because the second semiconductor layer 126 contains a sufficient amount of hydrogen by a hydrogen implantation step and has excellent passivation characteristics, so the effect due to the remaining passivation film is not significant. However, the present invention is not limited to this.

[0191] Hereinafter, another embodiment of the present invention will be described with reference to FIG. 13. FIG. 13 schematically shows a cross-sectional view of a solar cell according to another embodiment of the present invention.

[0192] Referring to FIG. 13, a quantum dot type solar cell according to another application example of the present invention may have a series structure further including a photoelectric conversion layer 112 containing a perovskite compound in a first photoelectric conversion unit 110 and a second photoelectric conversion unit 120 having a substance or structure different from that of the first photoelectric conversion unit 110.

[0193] In the solar cell 100 according to this application example, the second photoelectric conversion unit 120 may have a pn junction structure including a semiconductor substrate 122. As an example, the second photoelectric conversion unit 120 may include a semiconductor substrate 122 and conductive regions 124 and 126 formed in or on the semiconductor substrate 122. The conductive regions 124 and 126 may include a first conductive region 124 having a first conductivity type and a second conductive region 126 having a second conductivity type.

[0194] The semiconductor substrate 122 may be made of a crystalline semiconductor (for example, a single crystal or polycrystalline semiconductor, as an example, a single crystal or polycrystalline silicon) containing a single semiconductor substance (as an example, a Group IV element). And because it is based on a semiconductor substrate 122 with high crystallinity and few defects, the second photoelectric conversion unit 120 can have excellent electrical characteristics. As an example, the second photoelectric conversion unit 120 may have a crystalline silicon solar cell structure.

[0195] Since the arrangement of the semiconductor substrate 122 is the same as that of the semiconductor substrate 122 in FIG. 1, a detailed description thereof will be omitted.

[0196] On the front surface of the semiconductor substrate 122, a first conductive region 124 having a first conductivity type may be formed. In addition, a second conductive region 126 having a second conductivity type opposite to the first conductivity type of the semiconductor substrate 122 may be positioned (contacted in one example).

[0197] The first conductive region 124 may be a region that includes a first conductivity type dopant and has a first conductivity type. And the second conductive region 126 may be a region that includes a second conductivity type dopant and has a second conductivity type.

[0198] The first conductive region 124 and the second conductive region 126 may each include the same semiconductor material as the semiconductor substrate 122 (more specifically, a single semiconductor material, silicon in one example). As one example, the first conductive region 124 and the second conductive region 126 may be configured as an amorphous silicon (a-Si) layer, an amorphous silicon carbide (a-SiCx) layer, an amorphous silicon oxide (a-SiOx) layer, or the like. And the characteristic differences that may occur when the first conductive region 124 and the second conductive region 126 have the same characteristics as the semiconductor substrate 122 and include different semiconductor materials from each other can be minimized.

[0199] For example, each of the first conductive region 124 and the second conductive region 126 may be formed by doping an amorphous semiconductor or the like that can be easily manufactured by a plurality of methods such as deposition with a first conductivity type dopant or a second conductivity type dopant. And the first conductive region 124 and the second conductive region 126 can be easily formed by a simple process. Also, each of the first conductive region 124 and the second conductive region 126 may be manufactured as a nanocrystalline silicon or polycrystalline silicon layer by a plurality of methods such as deposition, and may be formed by doping with a first conductivity type dopant or a second conductivity type dopant. And the first conductive region 124 and the second conductive region 126 may be easily formed by a simple process.

[0200] When the first conductive region 124 and the second conductive region 126 have crystal characteristics different from those of the semiconductor substrate 122, tunneling layers 124a and 126a may be additionally included between the substrate 122, and the description thereof is omitted because it is the same as that in FIG. 1.

[0201] In this embodiment, when the semiconductor substrate 122 (or the base region) has a first conductivity type, the second conductive region 126 may be configured as an emission region that forms a pn junction with the semiconductor substrate 122. The first conductive region 124 may be configured to form a front surface field in order to prevent a composite front electric field region. And since the emission region directly involved in photoelectric conversion is located on the back surface, the emission region may be formed to have a sufficient thickness (as an example, formed thicker than the front electric field region), whereby the photoelectric conversion efficiency can be further improved. However, the present invention is not limited thereto. Therefore, the semiconductor substrate 122 may also have a second conductivity type, whereby the first conductive region 124 constitutes an emission region, and the second conductive region 126 constitutes a back surface electric field region.

[0202] In this embodiment, the first conductive region 124 and the semiconductor substrate 122 may have an n-type, and the second conductive region 126 may have a p-type. In the first photoelectric conversion unit 110 located on the second photoelectric conversion unit 120, the first transport layer 114 located at the upper part may transport electrons, and the second transport layer 116 located at the lower part may transport holes. In such a case, the first photoelectric conversion unit 110 can have excellent effects compared to the reverse case. Note that the semiconductor substrate 122 may have an n-type, thereby improving the life time of carriers. However, the present invention is not limited thereto, and various modifications are possible regarding whether the semiconductor substrate 122 has a first conductivity type or a second conductivity type, and whether it is an n-type or a p-type.

[0203] The bonding layer (tunneling bonding layer) 110a is located on the front (front surface) of the second photoelectric conversion unit 120 and connects the second photoelectric conversion unit 120 and the first photoelectric conversion unit 110 located thereon. Although the drawings show that the bonding layer 130 is in direct contact with the first conductive region 124 and the first photoelectric conversion unit 110 respectively, the present invention is not limited thereto. Such a bonding layer 130 may have a thin thickness. As an example, it may have a thickness thinner than that of the electrode layers 420 and 440 so as to smoothly perform carrier tunneling.

[0204] At this time, different from the solar cell 100 in FIG. 1, the bonding layer 130 in FIG. 13 has a plurality of layered structures.

[0205] That is, the bonding layer 130 further includes an interface layer 136 on the base bonding layer 132.

[0206] The base bonding layer 132 may electrically connect the first photoelectric conversion unit 110 and the second photoelectric conversion unit 120, and may contain a substance that can transmit light (as an example, long-wavelength light) used for the first photoelectric conversion unit 110. The base bonding layer 132 may be formed of a transparent conductive substance (as an example, transparent conductive oxide) (TCO). As an example, it may be formed of a substance containing at least one of tin-doped indium oxide (ITO), tungsten-doped indium oxide (IWO), cesium-doped indium oxide (ICO), and fluorine-doped tin oxide (FTO).

[0207] Such a bonding layer 130 may reflect light (as an example, short-wavelength light) used for the second photoelectric conversion unit 120 in the second photoelectric conversion unit 120, and may transmit and provide light (as an example, long-wavelength light) used for the first photoelectric conversion unit 110 to the first photoelectric conversion unit 110.

[0208] When the base bonding layer 132 is formed of a transparent conductive material (TCO), the transparent conductive material (TCO) has hydrophilic surface properties. Therefore, it has the characteristic of a very small contact angle.

[0209] An interface layer 136 is further formed on the base bonding layer 132.

[0210] The interface layer 136 is formed on the base bonding layer 132 and is formed of a material having surface properties such that the bonding surface with the first photoelectric conversion unit 110 has hydrophobicity while inducing a similar tunneling effect.

[0211] The above-described interface layer 136 may be formed to have a thickness thinner than that of the tunneling layers 124a and 126a, and may be formed so as not to affect the overall electrical characteristics of the bonding layer 130.

[0212] The above-described interface layer 136 may be formed by performing high-concentration doping on the same amorphous silicon as the semiconductor substrate 122.

[0213] Due to the high-concentration doping of the above-described dopant, the surface properties may have hydrophobicity.

[0214] As an example, after forming an amorphous silicon layer on the transparent conductive material (TCO) which is the base bonding layer 132 by chemical vapor deposition or the like, doping may be performed in an atmosphere of B2H6 or PH3.

[0215] The above-described deposition and doping heat treatments may both be performed at a temperature within 100°C.

[0216] Note that, differently, a resin layer having hydrophobicity may be thinly formed and may be used as the interface layer 136. Polytetrafluoroethylene (PTFE) may be applied as the resin layer having the above-described hydrophobicity.

[0217] The above-described interface layer 136 may be formed to have a thin thickness within 1.5 to 2 nm.

[0218] Therefore, while forming the interface layer 136 to maintain the tunneling effect, the front surface of the junction layer 130 (i.e., the surface in contact with the first photoelectric conversion unit 110) may be formed to have hydrophobic surface characteristics.

[0219] On the hydrophobic junction layer 130, a first photoelectric conversion unit 110 containing a perovskite compound is formed.

[0220] The first photoelectric conversion unit 110 may include a photoelectric conversion layer 112, a second transport layer (second carrier transport layer) 116 located between the junction layer 130 and the photoelectric conversion layer 112 on one side of the photoelectric conversion layer 112, and a first transport layer (first carrier transport layer) 114 located between the photoelectric conversion layer 112 and the first electrode 42 on the other side of the photoelectric conversion layer 112.

[0221] At this time, the formed second transport layer 116 may be applied as spiro-TTB, NPB, etc. having hydrophobic surface characteristics by a dry process, whereby a large-area tandem solar cell 100 can be formed.

[0222] Since the structure and materials of each layer of the first photoelectric conversion unit 110 are the same as those in FIG. 1, a detailed description thereof will be omitted.

[0223] Note that the first electrode 42 may be located on the first photoelectric conversion unit 110 (as an example, located on the first transport layer 114 on its front surface), and the second electrode 44 may be located on the second photoelectric conversion unit 120 (as an example, located on the second conductive region 126 on its back surface). That is, the solar cell 10 according to this embodiment may have a tandem structure in which a second photoelectric conversion unit 120 based on a single semiconductor material (as an example, silicon) and a first photoelectric conversion unit 110 based on a perovskite compound are joined by a junction layer 130.

[0224] As described above, the solar cell of the present invention formed has the characteristics shown in FIGS. 14 to 15.

[0225] FIG. 14 is a diagram showing the change in the surface properties of the junction layer, and FIG. 15 is a graph showing the optical properties that change according to the surface properties of the junction layer.

[0226] Referring to FIG. 14, it shows the surface of a substrate to which ICO is applied as a transparent conductive material (TCO) applied as the junction layer 130 or the base junction layer 132, and it can be confirmed by the water droplet experiment that it has hydrophilicity to the eye.

[0227] At this time, when inspecting the comparison image, when CH4 plasma treatment is performed on the ICO surface, or when an amorphous silicon layer doped with an N-type dopant is included as the interface layer 136, or when doped with a PH3 dopant, it can be confirmed that the surface has changed to hydrophobicity.

[0228] Also, referring to FIG. 15, it shows the change in optical properties due to a plurality of substrate treatments.

[0229] Typically, as optical properties, the refractive index n and the extinction coefficient k are limited, and the optical properties of a general glass substrate are shown in FIG. 15a.

[0230] That is, in the wavelength band of 200 nm to 1000 nm, which is the wavelength band passing through the junction layer 130 of the present invention, the refractive index n shows the characteristic of decreasing according to the wavelength, and in the wavelength band, the extinction coefficient k converges to almost 0.

[0231] At this time, FIG. 15b analyzes the optical properties after performing CH4 plasma treatment, and FIGS. 15c and 15d analyze the optical properties after performing PH3 doping treatment.

[0232] As shown in FIG. 15b, after the plasma treatment, no difference was observed between the optical properties and the optical properties of a general glass substrate.

[0233] Referring to FIGS. 15c and 15d, FIG. 15c in the PH3 low-doping state exhibits optical properties at the same level as a general glass substrate. However, when doping at a low concentration, the surface properties tend to reduce the tendency to exhibit hydrophobicity.

[0234] At this time, as shown in FIG. 15d, when doping the dopant excessively, when comparing the optical properties with a general glass substrate, some differences occur, or the surface properties exhibit strong hydrophobicity.

[0235] At this time, when observing FIG. 15d in more detail, within the wavelength band of light required for the bonding layer 130 of the present invention, which is 400 to 800 nm, it can be observed that it has an extinction coefficient k of 1 or less and there is actually no significant difference in optical properties.

[0236] Therefore, in the series-type solar cell 100, by including an amorphous silicon layer doped excessively in the interface layer 136 as the bonding layer 130, it is not affected by the optical properties and at the same time, the surface properties can be kept hydrophobic.

[0237] Therefore, while applying TCO as a general conductive layer to the bonding layer 130 and changing the hydrophilic surface to hydrophobic by surface treatment or an interface layer, the covering range of the first photoelectric conversion unit 110 formed on the upper part can be improved while maintaining the optical properties, and the process matching property and the surface shape influence property can be improved.

[0238] The above features, structures, effects, etc. are included in at least one embodiment of the present invention and are not necessarily limited to only one embodiment. Note that the features, structures, effects, etc. exemplified in each embodiment can also be implemented by those skilled in the art by combining or modifying other embodiments. Therefore, the content regarding such combinations and modifications should be construed as being included within the scope of the present invention.

Explanation of Reference Numerals

[0239] 100: Solar cell 10: Photoelectric conversion unit 110: First photoelectric conversion unit 112: Photoelectric conversion layer 114: First transport layer 116: Second transport layer 120: Second photoelectric conversion unit 122: Semiconductor substrate 124: First semiconductor layer 126: Second semiconductor layer 42: First electrode 44: Second electrode 130: Junction layer 132: Back surface / base junction layer 136: Interface layer

Claims

1. A solar cell including a photoelectric conversion unit, a junction layer, a first electrode, and a second electrode, wherein the photoelectric conversion unit has a first photoelectric conversion unit including a photoelectric conversion layer made of a perovskite compound and a second photoelectric conversion unit including a semiconductor substrate, the junction layer is formed between the first photoelectric conversion unit and the second photoelectric conversion unit, and a front surface of the junction layer has hydrophobic surface characteristics, the first electrode is electrically connected to the photoelectric conversion unit on one surface of the photoelectric conversion unit, the second electrode is electrically connected to the photoelectric conversion unit on the other surface of the photoelectric conversion unit, the junction layer includes a back surface in contact with the second photoelectric conversion unit and a front surface in contact with the first photoelectric conversion unit, and the back surface and the front surface have different surface characteristics, the first photoelectric conversion unit includes the photoelectric conversion layer made of the perovskite compound, a first transport layer formed on an upper portion of the photoelectric conversion layer, and a second transport layer formed on a lower portion of the photoelectric conversion layer, the second transport layer is formed to be joined to the junction layer, the second transport layer has hydrophobic surface characteristics, the second transport layer includes NPB or Spiro-TTB having hydrophobic surface characteristics solar cell.

2. The second photoelectric conversion unit includes the semiconductor substrate, a first semiconductor layer of a first conductivity type on one surface of the semiconductor substrate, and a second semiconductor layer of a second conductivity type on the other surface of the semiconductor substrate The solar cell according to claim 1.

3. The back surface of the junction layer has hydrophilic surface characteristics, The solar cell according to claim 2.

4. The junction layer includes a transparent conductive type oxide layer (TCO) formed on the first conductor layer of the first conductivity type and having hydrophilic surface characteristics The solar cell according to claim 3.

5. The front surface of the transparent conductive type oxide layer of the junction layer is formed to have hydrophobic surface characteristics by plasma surface treatment The solar cell according to claim 4.

6. The junction layer further includes an interface layer in contact with the first photoelectric conversion unit on the transparent conductive type oxide layer The solar cell according to claim 4.

7. The interface layer includes a doped semiconductor layer and has hydrophobic surface characteristics The solar cell according to claim 6.

8. Further includes a tunneling layer between the semiconductor substrate and the second semiconductor layer of the second conductivity type, and the interface layer is formed with a thickness thinner than that of the tunneling layer The solar cell according to claim 6.

9. The first photoelectric conversion part is positioned on one surface of the second photoelectric conversion part, The first electrode is positioned on the first photoelectric conversion part, The second electrode is positioned on the second semiconductor layer of the second photoelectric conversion part, The second semiconductor layer includes a polycrystalline part, The first electrode and the second electrode have different laminated structures from each other The solar cell according to claim 3.

10. A method for manufacturing a solar cell, Forming a second photoelectric conversion part including a semiconductor substrate, a first semiconductor layer on one surface of the semiconductor substrate, and a second semiconductor layer having a conductivity type different from that of the first semiconductor layer on the other surface of the semiconductor substrate; Forming a bonding layer on the first semiconductor layer; Changing the surface characteristics of the front surface of the bonding layer; Forming a first photoelectric conversion part including a photoelectric conversion layer made of a perovskite compound on the front surface of the bonding layer; Forming a first electrode electrically connected to the first photoelectric conversion part on one surface of the first photoelectric conversion part and a second electrode electrically connected to the second photoelectric conversion part on the other surface of the second photoelectric conversion part; The first photoelectric conversion part is formed to include the photoelectric conversion layer made of the perovskite compound, a first transport layer formed on the upper part of the photoelectric conversion layer, and a second transport layer formed on the lower part of the photoelectric conversion layer; The second transport layer is formed to be in contact with the bonding layer; The second transport layer is formed by depositing a substance containing NPB or Spiro-TTB having a hydrophobic surface characteristic; In the step of changing the surface characteristics of the bonding layer, perform treatment so that the front surface of the bonding layer has a hydrophobic surface characteristic A method for manufacturing a solar cell.

11. In the step of forming the bonding layer, form a transparent conductive type oxide layer (TCO) having a hydrophilic surface characteristic on the first semiconductor layer of the semiconductor substrate The method for manufacturing a solar cell according to claim 10.

12. In the step of changing the surface characteristics of the bonding layer, perform treatment so that the back surface of the bonding layer has a hydrophilic surface characteristic The method for manufacturing a solar cell according to claim 11.

13. In the step of changing the surface characteristics of the bonding layer, plasma surface treatment is performed on the front surface of the transparent conductive type oxide layer of the bonding layer so as to form a surface characteristic having hydrophobicity. The method for manufacturing a solar cell according to claim 12.

14. The plasma surface treatment is performed at a temperature of 200 degrees or less and is executed by CH4 plasma or fluorine plasma treatment. The method for manufacturing a solar cell according to claim 13.

15. The step of changing the surface characteristics of the bonding layer further includes a step of forming an interface layer in contact with the first photoelectric conversion unit on the transparent conductive type oxide layer. The method for manufacturing a solar cell according to claim 12.

16. The step of forming the interface layer includes a step of depositing an amorphous silicon layer on the transparent conductive type oxide layer and a step of implanting a high-concentration dopant on the amorphous silicon layer so as to change the surface characteristics to hydrophobicity. The method for manufacturing a solar cell according to claim 15.

17. further includes a tunneling layer between the semiconductor substrate and the second semiconductor layer, and the interface layer is formed to have a thickness thinner than that of the tunneling layer. The method for manufacturing a solar cell according to claim 16. ​

Images