Tandem solar cell

Abstract

An embodiment of the present invention discloses a tandem solar cell comprising: a first photoelectric conversion unit; a second photoelectric conversion unit above the first photoelectric conversion unit; and an intermediate layer positioned between the first photoelectric conversion unit and the second photoelectric conversion unit and electrically connecting the first photoelectric conversion unit to the second photoelectric conversion unit, wherein the first photoelectric conversion unit includes: a first photoelectric conversion layer; a first doping layer positioned between the first photoelectric conversion layer and the intermediate layer on a first surface of the first photoelectric conversion layer, and the surface roughness of the second surface is greater than the surface roughness of the first surface.

Description

tandem solar cells

[0001] The present invention relates to a tandem solar cell.

[0002] Crystalline silicon (c-Si) solar cells are a representative single-junction solar cell and are widely used commercially. However, as crystalline silicon solar cells are approaching their theoretical efficiency limit, active development is underway on tandem solar cells that can achieve high efficiency. Tandem solar cells have the advantage of efficiently utilizing incident sunlight by connecting solar cells with different bandgaps, thereby increasing efficiency.

[0003] Among these, perovskite / silicon tandem solar cells are attracting significant attention due to their ability to achieve high photoelectric conversion efficiencies of over 30%. Because perovskite has a readily adjustable bandgap, efficient incident light distribution is possible when joining perovskite and silicon solar cells.

[0004] Meanwhile, perovskite solar cells can be formed on silicon solar cells by a solution process or a deposition process. However, when forming a perovskite solar cell, if the lower layer is not flat, it is difficult for each layer of the perovskite solar cell to be formed uniformly with a certain thickness, and as a result, the photoelectric conversion efficiency of the tandem solar cell may decrease.

[0005] Embodiments of the present invention provide a tandem solar cell with improved photoelectric conversion efficiency.

[0006] A tandem solar cell according to one aspect of the present invention comprises: a first photoelectric conversion unit; a second photoelectric conversion unit on the first photoelectric conversion unit; and an intermediate layer positioned between the first photoelectric conversion unit and the second photoelectric conversion unit and electrically connecting the first photoelectric conversion unit and the second photoelectric conversion unit; wherein the first photoelectric conversion unit comprises: a first photoelectric conversion layer; and a first doped layer positioned between the first photoelectric conversion layer and the intermediate layer on a first surface of the first photoelectric conversion layer; wherein a surface roughness of the second surface may be greater than a surface roughness of the first surface.

[0007] According to embodiments of the present invention, the occurrence of defects in the first doping layer is prevented, and the intermediate layer on the first photoelectric conversion unit and each layer forming the second photoelectric conversion unit are uniformly formed, thereby preventing the occurrence of leakage current and improving the photoelectric conversion efficiency and stability of the tandem solar cell.

[0008] In addition, since the crystal grains in the first doping layer have a nano size, the first doping layer has a wide optical band gap, and the current matching between the first photoelectric conversion unit and the second photoelectric conversion unit connected in series is optimized, so that the efficiency of the tandem solar cell can be improved.

[0009] FIG. 1 is a cross-sectional view schematically illustrating a tandem solar cell according to one embodiment of the present invention.

[0010] FIG. 2 is a cross-sectional view schematically illustrating an example of a first photoelectric conversion unit of the tandem solar cell of FIG. 1.

[0011] Figures 3 and 4 are cross-sectional views each showing the results of forming an intermediate layer according to the first doping layer of the first photoelectric conversion unit of Figure 2.

[0012] Fig. 5 is a cross-sectional view schematically illustrating an example of a second photoelectric conversion unit of the tandem solar cell of Fig. 1.

[0013] Figure 6 is a graph showing the IV results of a tandem solar cell according to the present invention.

[0014] A tandem solar cell according to one aspect of the present invention comprises: a first photoelectric conversion unit; a second photoelectric conversion unit on the first photoelectric conversion unit; and an intermediate layer positioned between the first photoelectric conversion unit and the second photoelectric conversion unit and electrically connecting the first photoelectric conversion unit and the second photoelectric conversion unit; wherein the first photoelectric conversion unit comprises: a first photoelectric conversion layer; and a first doped layer positioned between the first photoelectric conversion layer and the intermediate layer on a first surface of the first photoelectric conversion layer; wherein a surface roughness of the second surface may be greater than a surface roughness of the first surface.

[0015] In the present embodiment, the first photoelectric conversion unit is a silicon solar cell, and the crystallinity of the first doping layer may be 30% to 70%.

[0016] In this embodiment, the thickness of the first doping layer may be 40 nm to 100 nm.

[0017] In this embodiment, the optical band gap of the first doping layer may be 1.2 eV to 1.8 eV.

[0018] In this embodiment, the second surface may have a rough structure.

[0019] It may further include a second doping layer located on the second surface of the first photoelectric conversion layer, which is the opposite surface of the first surface.

[0020] In this embodiment, a protective layer covering the second doping layer may be further included.

[0021] In the present embodiment, the second photoelectric conversion unit may include a first charge transfer layer, a second charge transfer layer, and a second photoelectric conversion layer between the first charge transfer layer and the second charge transfer layer.

[0022] In the present embodiment, the second photoelectric conversion layer may include a compound having a perovskite structure.

[0023] In the present embodiment, the second photoelectric conversion unit may further include a conductive oxide electrode layer on the outer surface.

[0024] According to another aspect of the present invention, a tandem solar cell comprises: a silicon solar cell; a perovskite solar cell on the silicon solar cell; and an intermediate layer positioned between the silicon solar cell and the perovskite solar cell and electrically connecting the silicon solar cell and the perovskite solar cell; wherein the silicon solar cell comprises a silicon semiconductor layer and a first doping layer positioned between the silicon semiconductor layer and the intermediate layer on a first surface of the silicon semiconductor layer, wherein the silicon semiconductor layer and the first doping layer have different crystallinities, and the crystallinity of the first doping layer may be 30% to 70%.

[0025] In the present embodiment, the silicon solar cell further includes a second doping layer located on a second surface of the silicon semiconductor layer, which is opposite to the first surface, and the surface roughness of the second surface may be greater than the surface roughness of the first surface.

[0026] In this embodiment, the second surface may have a rough structure.

[0027] In this embodiment, the thickness of the first doping layer may be 40 nm to 100 nm.

[0028] In this embodiment, the optical band gap of the first doping layer may be 1.2 eV to 1.8 eV.

[0029] In the present embodiment, the perovskite solar cell may include a first charge transfer layer, a second charge transfer layer, and a perovskite layer between the first charge transfer layer and the second charge transfer layer.

[0030] The present invention is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, as well as the methods for achieving them, will become clearer with reference to the embodiments described in detail below, along with the drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various forms.

[0031] In the examples below, the terms first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0032] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0033] In the examples below, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0034] In the following examples, when a part such as a film, region, component, etc. is said to be on or above another part, it includes not only a case where it is directly on top of the other part, but also a case where another film, region, component, etc. is interposed in between.

[0035] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to what is shown.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings, and when describing with reference to the drawings, identical or corresponding components will be given the same drawing reference numerals.

[0037] FIG. 1 is a cross-sectional view schematically illustrating a tandem solar cell according to one embodiment of the present invention.

[0038] Referring to FIG. 1, a tandem solar cell (10) according to one embodiment of the present invention may include a first photoelectric conversion unit (100), a second photoelectric conversion unit (200) on the first photoelectric conversion unit (100), and an intermediate layer (300) positioned between the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200).

[0039] The first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) can each absorb sunlight to generate electrical energy, and the intermediate layer (300) electrically connects the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200). Therefore, that is, the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) can be connected in series.

[0040] The current generated from the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) can flow to the outside of the tandem solar cell (10) through the first electrode (400) and the second electrode (500 in FIG. 2). For example, the first electrode (400) can be positioned on the second photoelectric conversion unit (200) on the side where sunlight is incident, and the second electrode (500 in FIG. 2) can be positioned on the lower surface of the first photoelectric conversion unit (100).

[0041] The first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) may include photoelectric conversion layers made of different materials. Therefore, since the absorption light spectra of the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) are different, and the magnitudes of the currents generated from the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) may be different, it is important to match the magnitudes of the currents generated from the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200) that are connected in series in order to prevent a decrease in the efficiency of the tandem solar cell (10).

[0042] For example, the first photoelectric conversion unit (100) may be a silicon solar cell, and the second photoelectric conversion unit (200) may be a perovskite solar cell.

[0043] Accordingly, light in the short wavelength region among the light incident on the tandem solar cell (10) is absorbed by the perovskite solar cell placed on top to generate charges, and light in the long wavelength region that passes through the perovskite solar cell is absorbed by the silicon solar cell placed on the bottom to generate charges.

[0044] Accordingly, the thermal loss caused by the difference between the photon energy and the band gap can be reduced, thereby increasing the photoconversion efficiency of the tandem solar cell (10).

[0045] The intermediate layer (300) serves to bond the first photoelectric conversion unit (100) and the second photoelectric conversion unit (200). Accordingly, the second photoelectric conversion unit (200) is electrically connected to the first photoelectric conversion unit (100) via the intermediate layer (300).

[0046] The intermediate layer (300) can be implemented using a transparent conductive oxide (TCO) or a carbonaceous conductive material so that long-wavelength light passing through the second photoelectric conversion unit (200) can be incident on the first photoelectric conversion unit (100) positioned underneath without transmission loss. In addition, the intermediate layer (150) can be doped with an n-type or p-type material and used.

[0047] At this time, as transparent conductive oxides, ITO (Indium Tin Oxide), ZITO (Zinc Indium Tin Oxide), ZIO (Zinc Indium Oxide), ZTO (Zinc Tin Oxide), GITO (Gallium Indium Tin Oxide), GIO (Gallium Indium Oxide), GZO (Gallium Zinc Oxide), AZO (Aluminum doped Zinc Oxide), FTO (Fluorine Tin Oxide), or ZnO can be used. As carbonaceous conductive materials, graphene or carbon nanotubes can be used.

[0048] The intermediate layer (300) may be implemented as a multi-layer structure in which silicon layers having different refractive indices are alternately laminated multiple times. In this case, the multi-layer structure may have a structure in which low-refractive index layers and high-refractive index layers are alternately laminated. Accordingly, short-wavelength light can be reflected toward the second photoelectric conversion unit (200) based on the intermediate layer (300), and long-wavelength light can be transmitted toward the first photoelectric conversion unit (100). Through this, selective light capture of the perovskite / silicon tandem solar cell (10) can be enabled.

[0049] FIG. 2 is a cross-sectional view schematically illustrating an example of a first photoelectric conversion unit of the tandem solar cell of FIG. 1, and FIGS. 3 and 4 are cross-sectional views each illustrating the result of forming an intermediate layer according to the first doping layer of the first photoelectric conversion unit of FIG. 2.

[0050] First, referring to FIG. 2, the first photoelectric conversion unit (100) may include a first photoelectric conversion layer (110), a first doped layer (120) positioned between the first photoelectric conversion layer (110) and an intermediate layer (300) on a first surface (S1) of the first photoelectric conversion layer (110), and a second doped layer (130) positioned on a second surface (S2) of the first photoelectric conversion layer (110) opposite the first surface (S1). In addition, the first photoelectric conversion unit (100) may further include a protective layer (140) covering the second doped layer (130), and a second electrode (500) may be positioned on the protective layer (140) and electrically connected to the second doped layer (130) by penetrating the protective layer (140).

[0051] The first photoelectric conversion layer (110) may include crystalline silicon. The first photoelectric conversion layer (110) may include single-crystal silicon or polycrystalline silicon. The first photoelectric conversion layer (110) may have a first conductivity type of p-type or n-type.

[0052] The first doping layer (120) is formed by doping with a first impurity having a second conductivity type opposite to that of the first photoelectric conversion layer (110). For example, when the first photoelectric conversion layer (110) is p-type, the first doping layer (120) is doped with an n-type impurity, and when the first photoelectric conversion layer (110) is n-type, the first doping layer (120) is doped with a p-type impurity. In this way, when the first photoelectric conversion layer (110) and the first doping layer (120) have opposite conductivity types, a PN junction is formed at the interface between the first photoelectric conversion layer (110) and the first doping layer (120). In addition, the first doping layer (120) may be formed to be hydrogen passivated to prevent recombination of carriers.

[0053] The first doping layer (120) can be formed by forming an amorphous silicon layer doped with a first impurity on the first surface (S1) of the first photoelectric conversion layer (110) and then partially crystallizing the amorphous silicon layer.

[0054] For example, an amorphous silicon layer can be deposited by CVD, such as LPCVD or PECVD, with the gas ratio of SiH4 and PH3 set to 5:1 to 5:6. Thereafter, the amorphous silicon layer can go through a crystallization step to form a first doped layer (120). At this time, the first doped layer (120) can be partially crystallized so that the crystal grains of the first doped layer (120) have a nano size. For example, the crystallinity of the first doped layer (120) can be 30% to 70%. That is, the crystallinity of the first photoelectric conversion layer (110) and the first doped layer (120) are different from each other.

[0055] Meanwhile, if the crystallinity of the first doping layer (120) is less than 30%, the conductivity of the first doping layer (120) may not be sufficient, making it difficult to perform its role as an emitter layer or an electric field layer. If the crystallinity of the first doping layer (120) is greater than 70%, it may be difficult to uniformly form a perovskite solar cell, which will be described later, due to defects in the grain boundaries of the polycrystalline silicon.

[0056] In addition, since the crystallinity of the first doping layer (120) is controlled to 30% to 70%, the crystal grains of the first doping layer (120) are formed with a particle size of several nm to several tens of nm, and since the first doping layer (120) has an optical band gap of 1.2 eV to 1.8 eV, the absorption rate of light in the long wavelength region is improved, so that when it has a tandem structure with a perovskite solar cell, current matching with the perovskite solar cell can be optimized.

[0057] This first doping layer (120) may have a thickness of 40 nm to 100 nm. When the thickness of the first doping layer (120) is less than 40 nm, the conductivity of the first doping layer (120) may not be sufficient, making it difficult to function as an emitter layer or an electric field layer. In addition, the flatness of the upper surface of the first doping layer (120) may be reduced, making it difficult for each layer of the perovskite solar cell formed on the first doping layer (120) to be uniformly formed with a constant thickness. On the other hand, when the thickness of the first doping layer (120) is greater than 100 nm, the current density of the first photoelectric conversion unit (100) may decrease due to increased light absorption in the first doping layer (120).

[0058] Meanwhile, in order to ensure that the first doping layer (120) is formed uniformly with a constant thickness, it is preferable that the first surface (S1) have a smaller surface roughness than the second surface (S2). For example, the uneven structure formed on the first surface (S1) may have a smaller size than the uneven structure on the second surface (S2).

[0059] In addition, a tunnel layer may be further formed between the first photoelectric conversion layer (110) and the first doping layer (120). For example, the tunnel layer may include silicon nitride (SiNx), aluminum oxide (AlOx), or silicon oxynitride (SiOxNy), and may be formed by an oxidation process or deposition. In addition, the tunnel layer (113) may be formed to have a thickness of 3 Å to 10 Å for a tunneling effect.

[0060] FIG. 3 and FIG. 4 are cross-sectional views each showing the result of forming an intermediate layer (300) according to the first doping layer (120). FIG. 3 shows a case in which the crystallinity of the first doping layer (120) is 70% according to the present invention, and FIG. 4 shows a case in which the first doping layer (120) is formed of polycrystalline silicon.

[0061] As can be seen in FIGS. 3 and 4, in the case of FIG. 3, since no defects occur in the first doping layer (120), the intermediate layer (300) is uniformly formed with a constant thickness, whereas in the case of FIG. 4, the intermediate layer (300) is unevenly formed on the upper surface of the first doping layer (120) due to defects (S) at the grain boundaries of the polycrystalline silicon layer. Meanwhile, as shown in FIG. 4, if the intermediate layer (300) and the perovskite solar cell on the intermediate layer (300) are unevenly formed, a short circuit may occur between the perovskite solar cell and the first doping layer (120), resulting in leakage current. Therefore, according to the present invention, by preventing the occurrence of such leakage current, the stability of the tandem solar cell can be improved.

[0062] Referring again to FIG. 2, a second doping layer (130) may be further positioned on the second surface (S2) of the first photoelectric conversion layer (110).

[0063] The second doping layer (130) has the same conductivity type as the first photoelectric conversion layer (110) and has a higher impurity concentration than the first photoelectric conversion layer (110), thereby forming a back surface field (BSF).

[0064] The second doping layer (130) can be formed by doping the first photoelectric conversion layer (110) with a second impurity having the same conductivity type as the first photoelectric conversion layer (110) through the second surface (S2). As another example, the second doping layer (130) can be formed by forming crystalline silicon on the second surface (S2) of the first photoelectric conversion layer (110) and doping the second impurity. In an optional embodiment, a tunnel layer is further formed between the second surface (S2) of the first photoelectric conversion layer (110) and the second doping layer (130), so that carriers can be moved through a tunnel effect, thereby selectively collecting electrons or holes to improve the open circuit voltage.

[0065] Meanwhile, the second surface (S2) of the first photoelectric conversion layer (110) may have a surface roughness greater than or equal to that of the first surface (S1). For example, the second surface (S2) may be textured to have a rough structure, thereby having a surface roughness greater than that of the first surface (S1). The roughness may cause scattering of long wavelength light incident into the first photoelectric conversion unit (100), thereby improving the light absorption rate of the first photoelectric conversion layer (110), thereby increasing the current density of the first photoelectric conversion unit (100).

[0066] The protective layer (140) is formed to cover the second doping layer (130). Meanwhile, as the second surface (S2) has a rough structure, the second doping layer (130) and the protective layer (140) can also be formed to have a rough structure.

[0067] The protective layer (140) has a single-layer or multi-layer structure including at least one of aluminum oxide (AlOx), silicon nitride (SiNx), silicon oxide (SiOx), and silicon oxynitride (SiOxNy), and can be formed by various processes such as atomic layer deposition (ALD) and chemical vapor deposition (CVD, PECVD, LPCDV, APCVD). Such a protective layer (140) can reduce the recombination density of the second surface (S2) of the first photoelectric conversion layer, thereby improving the lifespan of carriers, and can minimize reflection of light incident on the rear surface of the first photoelectric conversion unit (100).

[0068] The second electrode (150) can penetrate the protective layer (140) and be electrically connected to the second doped layer (130). The second electrode (150) can be formed of at least one conductive material selected from the group consisting of nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin (Sn), zinc (Zn), indium (In), titanium (Ti), gold (Au), and combinations thereof. The second electrode (150) can be formed by various methods, such as screen printing using a metal paste, plating, thermal evaporation, and sputtering.

[0069] Fig. 5 is a cross-sectional view schematically illustrating an example of a second photoelectric conversion unit of the tandem solar cell of Fig. 1.

[0070] Referring to FIG. 5, the second photoelectric conversion unit (200) may include a first charge transfer layer (210), a second charge transfer layer (230), and a second photoelectric conversion layer (220) between the first charge transfer layer (120) and the second charge transfer layer (230). In addition, the second photoelectric conversion unit (200) may further include a conductive oxide electrode layer (240) on the outer surface onto which light is incident.

[0071] The first charge transfer layer (210) may be an electron transfer layer or a hole transfer layer. Specifically, if electrons move to the front side and holes move to the back side in the first photoelectric conversion layer to generate electric energy, the first charge transfer layer (210) may be a hole transfer layer. In addition, the second charge transfer layer (230) may be an electron transfer layer.

[0072] On the other hand, when the first photoelectric conversion layer is configured so that holes move to the front and electrons move to the back, the first charge transfer layer (210) may be an electron transfer layer and the second charge transfer layer (230) may be a hole transfer layer.

[0073] The electron transport layer may include a transparent conductive oxide (TCO) having high electrical conductivity, a carbonaceous conductive material, etc. The transparent conductive oxide may be Ti oxide, Zn oxide, In oxide, Sn oxide, W oxide, Nb oxide, Mo oxide, Mg oxide, Zr oxide, Sr oxide, Yr oxide, La oxide, V oxide, Al oxide, Y oxide, Sc oxide, Sm oxide, Ga oxide, In oxide, SrTi oxide, etc. The carbonaceous conductive material may be graphene, carbon nanotube, or fullerene (Fullerene, C60).

[0074] The hole transport layer may be formed of a conductive polymer. Specifically, the hole transport layer may include a material selected from the group consisting of Spiro-OMeTAD, PEDOT:PSS, G-PEDOT, PANI:PSS, PANI:CSA, PDBT, P3HT, PCPDTBT, PCDTBT, PTAA, 2PACz, Me-4PACz, MoO3, V2O5, NiO, WO3, CuI, CuSCN, and combinations thereof.

[0075] The second photoelectric conversion layer (220) is formed so that hole-electron pairs generated by receiving light energy from the sun can be separated into electrons or holes. The second photoelectric conversion layer (220) is a perovskite layer and may include a compound having a perovskite structure represented by the following chemical formula 1.

[0076] [Chemical Formula 1]

[0077] ABX3

[0078] In the above chemical formula 1,

[0079] The above A is an alkali metal or a substituted or unsubstituted alkyl group of C1-25,

[0080] When the above A is substituted, the substituent is an amino group, a hydroxyl group, a cyano group, a halogen group, a nitro group or a methoxy group;

[0081] wherein B comprises a metal cation selected from the group consisting of Pb, Sn, Ge, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, and combinations thereof; and

[0082] The above X may include a halide anion or a chalcogenide anion.

[0083] More specifically, the A may include Formamidinium, Methylammonium, Cesium, Rubidium, Potassium, Sodium, Lithium Guanidine, Butylammonium, Ethylammonium, or Phenethylammonium, and the B may include Lead, Tin, Germanium, Cadmium, Znic, Magnesium, etc. The X substance may include Iodide, Bromide, Chloride, Fluoride, Thiocyanate, Cyanate, Selenocyanate, Formate, Acetate, etc.

[0084] The second photoelectric conversion layer (220) can be formed by a single-step spin-coating method, a multi-step spin-coating method, a dual-source vapor deposition method, and a vapor-assisted solution process.

[0085] The conductive oxide electrode layer (240) can be implemented with a transparent conductive oxide (TCO) having high electrical conductivity.

[0086] A first electrode (400) formed of a material with excellent electrical conductivity is positioned on the conductive oxide electrode layer (240) to collect charges. The first electrode (400) is preferably formed using a glass frit capable of low-temperature firing to prevent the second photoelectric conversion layer (220) from being oxidized by heat.

[0087] Additionally, an anti-reflection film (not shown) may be further provided on the conductive oxide electrode layer (240). The anti-reflection film may be formed in a single-film or multi-layer structure including at least one of magnesium fluoride (MgF2), silicon oxide (SiOx), and titanium oxide (TiOx).

[0088] Figure 6 is a graph showing the IV results of a tandem solar cell according to the present invention.

[0089] Fig. 6(A) shows the IV results of a silicon / perovskite tandem solar cell formed with a thickness of 100 nm and a crystallinity of 50% by partially doping the first doping layer according to an embodiment, and Fig. 6(B) shows the IV results of a silicon / perovskite tandem solar cell when the first doping layer having a thickness of 100 nm is formed of polycrystalline silicon. Fig. 6(A) and (B) show the IV values ​​of the tandem solar cells illustrated in Figs. 3 and 4, respectively.

[0090] As can be seen in Fig. 6, in case of (A), the FF (fill factor) is increased compared to (B), which is because the crystallinity of the first doping layer is formed to be 50%, and thus the perovskite solar cell formed on the first doping layer is uniformly formed, thereby preventing leakage current generation, and at the same time, since the crystal grains of the first doping layer have a particle size of several nm to several tens of nm, the first doping layer has a wide optical band gap, thereby improving the absorption rate of light in the long wavelength range, resulting in matching of the current value generated in the perovskite solar cell and the current value generated in the silicon solar cell.

[0091] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and variations of the embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. First photoelectric conversion unit; A second photoelectric conversion unit on the first photoelectric conversion unit; and An intermediate layer positioned between the first photoelectric conversion unit and the second photoelectric conversion unit and electrically connecting the first photoelectric conversion unit and the second photoelectric conversion unit; The above first photoelectric conversion unit is, a first photoelectric conversion layer; and A first doping layer positioned between the first photoelectric conversion layer and the intermediate layer on the first surface of the first photoelectric conversion layer; A tandem solar cell wherein the surface roughness of the second surface is greater than the surface roughness of the first surface.

2. In paragraph 1, The above first photoelectric conversion unit is a silicon solar cell, A tandem solar cell wherein the crystallinity of the first doping layer is 30% to 70%.

3. In paragraph 1, A tandem solar cell wherein the thickness of the first doping layer is 40 nm to 100 nm.

4. In paragraph 1, A tandem solar cell wherein the optical band gap of the first doping layer is 1.2 eV to 1.8 eV.

5. In paragraph 1, The second surface is a tandem solar cell having a rough structure.

6. In paragraph 1, A tandem solar cell further comprising a second doping layer located on a second surface of the first photovoltaic layer, which is opposite to the first surface.

7. In paragraph 6, A tandem solar cell further comprising a protective layer covering the second doped layer.

8. In paragraph 1, A tandem solar cell, wherein the second photoelectric conversion unit comprises a first charge transfer layer, a second charge transfer layer, and a second photoelectric conversion layer between the first charge transfer layer and the second charge transfer layer.

9. In paragraph 8, A tandem solar cell wherein the second photoelectric conversion layer includes a compound having a perovskite structure.

10. In paragraph 8, A tandem solar cell wherein the second photoelectric conversion unit further includes a conductive oxide electrode layer on the outer surface.

11. Silicon solar cells; A perovskite solar cell on the above silicon solar cell; and An intermediate layer positioned between the silicon solar cell and the perovskite solar cell and electrically connecting the silicon solar cell and the perovskite solar cell; The silicon solar cell includes a silicon semiconductor layer and a first doping layer positioned between the silicon semiconductor layer and the intermediate layer on a first surface of the silicon semiconductor layer, The above silicon semiconductor layer and the first doping layer have different crystallinity, A tandem solar cell wherein the crystallinity of the first doping layer is 30% to 70%.

12. In paragraph 11, The above silicon solar cell further includes a second doping layer located on the second surface of the silicon semiconductor layer, which is the opposite surface of the first surface, A tandem solar cell having a surface roughness of the second surface greater than that of the first surface.

13. In paragraph 12, The second surface is a tandem solar cell having a rough structure.

14. In paragraph 11, A tandem solar cell wherein the thickness of the first doping layer is 40 nm to 100 nm.

15. In paragraph 11, A tandem solar cell wherein the optical band gap of the first doping layer is 1.2 eV to 1.8 eV.

16. In paragraph 11, The above perovskite solar cell is a tandem solar cell including a first charge transfer layer, a second charge transfer layer, and a perovskite layer between the first charge transfer layer and the second charge transfer layer.

Images