Tandem solar cell

Abstract

One embodiment of the present invention discloses a tandem solar cell comprising: a first photoelectric conversion unit; a second photoelectric conversion unit on the first photoelectric conversion unit; and an intermediate layer located between the first photoelectric conversion unit and the second photoelectric conversion unit, 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 doping layer located on a first surface of the first photoelectric conversion layer between the first photoelectric conversion layer and the intermediate layer, and the surface roughness of the second surface is greater than that of the first surface.

Description

[Technical Field]

[0001] This invention relates to a tandem solar cell. [Background technology]

[0002] Crystalline silicon (c-Si) solar cells, as a representative single-junction solar cell, are currently widely used as commercial solar cells.

[0003] However, since crystalline silicon solar cells have now reached their theoretical efficiency limit, development of tandem solar cells, which can achieve higher efficiency, is actively underway.

[0004] Tandem solar cells have the advantage of being able to efficiently utilize incoming sunlight and increase efficiency by linking solar cells with different band gaps together.

[0005] One of the tandem solar cells mentioned above, the perovskite / silicon tandem solar cell, has attracted considerable attention because it can achieve a high photoelectric conversion efficiency of over 30%. In perovskite, the band gap can be easily adjusted, allowing for efficient distribution of incident light when a perovskite solar cell and a silicon solar cell are joined together.

[0006] On the other hand, while perovskite solar cells can be formed on silicon solar cells by solution processes or vapor deposition processes, if the lower layer is not flat during the formation of perovskite solar cells, it is difficult to form each layer of the perovskite solar cell uniformly with a constant thickness, which can result in a decrease in the photoelectric conversion efficiency of the tandem solar cell. [Overview of the project] [Problems that the invention aims to solve]

[0007] Embodiments of the present invention provide a tandem solar cell with improved photoelectric conversion efficiency. [Means for solving the problem]

[0008] A tandem solar cell according to one aspect of the present invention includes a first photoelectric conversion unit, a second photoelectric conversion unit on the first photoelectric conversion unit, and an intermediate layer located between the first photoelectric conversion unit and the second photoelectric conversion unit, electrically connecting the first photoelectric conversion unit and the second photoelectric conversion unit, wherein the first photoelectric conversion unit includes a first photoelectric conversion layer and a first doping layer located on the first surface of the first photoelectric conversion layer between the first photoelectric conversion layer and the intermediate layer, and the surface roughness of the second surface of the first photoelectric conversion layer, which is the opposite surface of the first surface, is greater than the surface roughness of the first surface.

[0009] In this embodiment, the first photoelectric conversion unit is a silicon solar cell, and the crystallinity of the first doping layer may be 30% to 70%.

[0010] In this embodiment, the thickness of the first doping layer may be 40 nm to 100 nm.

[0011] In this embodiment, the optical band gap of the first doping layer may be 1.2 eV to 1.8 eV.

[0012] In this embodiment, the second surface may have an uneven surface structure.

[0013] The tandem solar cell of this embodiment 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.

[0014] The tandem solar cell of this embodiment may further include a protective layer covering the second doping layer.

[0015] In this embodiment, the second photoelectric conversion unit may include a first charge transport layer, a second charge transport layer, and a second photoelectric conversion layer between the first charge transport layer and the second charge transport layer.

[0016] In this embodiment, the second photoelectric conversion layer may include a compound having a perovskite structure.

[0017] In this embodiment, the second photoelectric conversion portion may further include a conductive oxide electrode layer on an outer surface thereof.

[0018] A tandem solar cell according to another aspect of the present invention includes: a silicon solar cell; a perovskite solar cell on the silicon solar cell; and an intermediate interlayer 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 includes a silicon semiconductor layer and a first doping layer positioned between the silicon semiconductor layer and the intermediate interlayer on a first surface of the silicon semiconductor layer, a crystallinity of the silicon semiconductor layer and a crystallinity of the first doping layer are different from each other, and the crystallinity of the first doping layer is 30% to 70%.

[0019] In this embodiment, the silicon solar cell may further include a second doping layer positioned on a second surface of the silicon semiconductor layer that is opposite to the first surface, and a surface roughness of the second surface may be greater than a surface roughness of the first surface.

[0020] In this embodiment, the second surface may have an uneven structure.

[0021] In this embodiment, a thickness of the first doping layer may be 40 nm to 100 nm.

[0022] In this embodiment, an optical band gap of the first doping layer may be 1.2 eV to 1.8 eV.

[0023] In this embodiment, the perovskite solar cell may include a first charge transport layer, a second charge transport layer, and a perovskite layer between the first charge transport layer and the second charge transport layer. Effects of the Invention

[0024] According to an embodiment of the present invention, the generation of defects in the first doping layer is prevented, and each layer constituting the intermediate layer on the first photoelectric conversion unit and the second photoelectric conversion unit is formed uniformly, whereby the generation of leakage current can be prevented, and the photoelectric conversion efficiency and stability of the tandem solar cell can be improved.

[0025] Further, since the crystal grains in the first doping layer have a nano-size, the first doping layer has a wide optical band gap, current matching between the first photoelectric conversion unit and the second photoelectric conversion unit connected in series is optimized, and the efficiency of the tandem solar cell can be improved. Brief Description of the Drawings

[0026] [Figure 1] 1 is a cross-sectional view schematically showing a tandem solar cell according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view schematically showing an example of a first photoelectric conversion unit of the tandem solar cell of Fig. 1. [Figure 3] 3 is a cross-sectional image showing the formation result of an intermediate layer by a first doping layer of the first photoelectric conversion unit of Fig. 2. [Figure 4] 4 is a cross-sectional image showing the formation result of an intermediate layer by a first doping layer of the first photoelectric conversion unit of Fig. 2. [Figure 5] 5 is a cross-sectional view schematically showing an example of a second photoelectric conversion unit of the tandem solar cell of Fig. 1. [Figure 6] 6 is a graph showing I-V characteristics of the tandem solar cell according to the present invention. Mode for Carrying Out the Invention

[0027] Various modifications may be made to the present invention, and various embodiments are possible, with specific embodiments being illustrated in the drawings and described in detail. The effects and features of the present invention, as well as methods for achieving them, will become clear from 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 embodied in various forms.

[0028] In the following embodiments, terms such as "first," "second," etc., are not limited in meaning but are used to distinguish one component from another.

[0029] In the following embodiments, a singular expression includes plural expressions unless they have a clearly different meaning in context.

[0030] In the following embodiments, terms such as “includes” or “having” mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0031] In the following embodiments, the description that a part such as a film, region, or component is on top of another part includes not only cases where the part is directly on top of another part, but also cases where another film, region, component, etc. is interposed between those parts.

[0032] In the drawings, the size of components may be exaggerated or reduced for illustrative purposes. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for illustrative purposes, and the present invention is not necessarily limited to those shown.

[0033] Embodiments of the present invention will be described in detail below with reference to the attached drawings, and in the description with reference to the drawings, the same or corresponding components are denoted by the same reference numerals.

[0034] Figure 1 is a schematic cross-sectional view showing a tandem solar cell according to one embodiment of the present invention.

[0035] Referring to Figure 1, the 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 located between the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200.

[0036] The first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 are each capable of absorbing sunlight and generating electrical energy, and the intermediate layer 300 electrically connects the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200. That is, the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 can be connected in series.

[0037] The current generated in the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 may flow to the outside of the tandem solar cell 10 via the first electrode 400 and the second electrode (the second electrode 500 in Figure 2). For example, the first electrode 400 may be located on the second photoelectric conversion unit 200 on the side where sunlight is incident, and the second electrode (the second electrode 500 in Figure 2) may be located on the lower surface of the first photoelectric conversion unit 100.

[0038] The first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 may contain photoelectric conversion layers made of different materials. Therefore, the absorption light spectra of the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 may differ, and the magnitudes of the currents generated in the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200 may differ. To prevent a decrease in the efficiency of the tandem solar cell 10, it is important to match the magnitudes of the currents generated in the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200, which are connected in series.

[0039] 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.

[0040] As described above, short-wavelength light incident on the tandem solar cell 10 is absorbed by the perovskite solar cell located above, generating an electric charge, while long-wavelength light that passes through the perovskite solar cell is absorbed by the silicon solar cell located below, generating an electric charge.

[0041] Therefore, the thermal loss caused by the difference between conventional photon energy and band gap can be reduced, and the light conversion efficiency of the tandem solar cell 10 can be increased.

[0042] The intermediate layer 300 plays the role of joining the first photoelectric conversion unit 100 and the second photoelectric conversion unit 200. As a result, the second photoelectric conversion unit 200 is electrically connected to the first photoelectric conversion unit 100 via the intermediate layer 300.

[0043] The intermediate layer 300 may 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 is incident on the first photoelectric conversion unit 100 located below it without transmission loss. Alternatively, the intermediate layer 300 may be doped with an n-type or p-type substance.

[0044] In the above configuration, the transparent conductive oxides that can be used include 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. As the carbonaceous conductive material, graphene or carbon nanotubes can be used.

[0045] The intermediate layer 300 may be implemented as a multilayer structure in which silicon layers having different refractive indices are alternately stacked multiple times. In this case, the multilayer structure may have a structure in which low refractive index layers and high refractive index layers are alternately stacked. This allows short-wavelength light to be reflected towards the second photoelectric conversion unit 200 and long-wavelength light to be transmitted towards the first photoelectric conversion unit 100, with respect to the intermediate layer 300. Through this, selective light harvesting of the tandem solar cell 10, which is a perovskite / silicon tandem solar cell, becomes possible.

[0046] Figure 2 is a schematic cross-sectional view showing an example of the first photoelectric conversion section of the tandem solar cell shown in Figure 1, and Figures 3 and 4 are cross-sectional images showing the results of the formation of the intermediate layer by the first doping layer of the first photoelectric conversion section in Figure 2, respectively.

[0047] First, referring to Figure 2, the first photoelectric conversion unit 100 may include a first photoelectric conversion layer 110, a first doping layer 120 located between the first photoelectric conversion layer 110 and the intermediate layer 300 on the first surface S1 of the first photoelectric conversion layer 110, and a second doping layer 130 located on the second surface S2 of the first photoelectric conversion layer 110, which is the opposite surface to the first surface S1. The first photoelectric conversion unit 100 may further include a protective layer 140 covering the second doping layer 130, and a second electrode 500 may be located on the protective layer 140, penetrating the protective layer 140 and electrically connected to the second doping layer 130.

[0048] The first photoelectric conversion layer 110 may contain crystalline silicon. The first photoelectric conversion layer 110 may contain single-crystal silicon or polycrystalline silicon. The first photoelectric conversion layer 110 may have a first conductivity type of p-type or n-type.

[0049] The first doping layer 120 is formed by doping it with a first impurity having a second conductivity type opposite to that of the first photoelectric conversion layer 110. For example, if the first photoelectric conversion layer 110 is p-type, the first doping layer 120 is doped with an n-type impurity, and if 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. Furthermore, the first doping layer 120 may be formed to prevent carrier recombination by hydrogen passivation.

[0050] 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.

[0051] For example, the amorphous silicon layer may be deposited by CVD such as LPCVD or PECVD, with a gas ratio of SiH4 to PH3 set to 5:1 to 5:6. Subsequently, the amorphous silicon layer can undergo a crystallization step to form the first doping layer 120. At this time, by partially crystallizing the first doping layer 120, the crystal particles of the first doping layer 120 can be made to be nano-sized. As an example, the degree of crystallinity of the first doping layer 120 may be 30% to 70%. That is, the degree of crystallinity of the first photoelectric conversion layer 110 and the degree of crystallinity of the first doping layer 120 may be different from each other.

[0052] On the other hand, if the crystallinity of the first doping layer 120 is less than 30%, the conductivity of the first doping layer 120 is insufficient, making it difficult for it to function as an emitter layer or field layer. If the crystallinity of the first doping layer 120 is greater than 70%, defects at the grain boundaries of the polycrystalline silicon may make it difficult to form a uniform perovskite solar cell, as described later.

[0053] Furthermore, by adjusting the crystallinity of the first doping layer 120 to 30% to 70%, the crystalline particles of the first doping layer 120 are formed to a particle size of several nanometers to tens of nanometers, and the first doping layer 120 has an optical band gap of 1.2 eV to 1.8 eV, which improves the absorption rate of light in the long wavelength region, and when it has a tandem structure with the perovskite solar cell, the current matching with the perovskite solar cell can be optimized.

[0054] The first doping layer 120 described above 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 for it to function as an emitter layer or field layer. Furthermore, the flatness of the upper surface of the first doping layer 120 may decrease, making it difficult to uniformly form each layer of the perovskite solar cell formed on the first doping layer 120 so that it has 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.

[0055] On the other hand, in order to ensure that the first doping layer 120 is formed uniformly with a certain thickness, it is preferable that the first surface S1 has 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.

[0056] Furthermore, a tunnel layer may be formed between the first photoelectric conversion layer 110 and the first doping layer 120. As an example, the tunnel layer may be made of silicon nitride (SiN x ), aluminum oxide (AlO x ), silicon oxynitride (SiO x N y ) may include and may be formed by an oxidation process or vapor deposition. The tunnel layer may also be formed to a thickness of 3 Å to 10 Å for the tunneling effect.

[0057] Figures 3 and 4 are cross-sectional images showing the results of the formation of the intermediate layer 300 by the first doping layer 120, respectively. Figure 3 is an image showing the case where the crystallinity of the first doping layer 120 is 70% according to the present invention, and Figure 4 is an image showing the case where the first doping layer 120 is formed of polycrystalline silicon.

[0058] As can be seen from Figures 3 and 4, in the case shown in Figure 3, no defects occurred in the first doping layer 120, and the intermediate layer 300 was formed uniformly with a constant thickness, whereas in the case shown in Figure 4, it can be seen that the intermediate layer 300 was formed unevenly on the upper surface of the first doping layer 120 due to defects D at the grain boundaries of the polycrystalline silicon layer. On the other hand, as shown in Figure 4, if the intermediate layer 300 and the perovskite solar cell on the intermediate layer 300 are formed unevenly, 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, the stability of the tandem solar cell can be improved by preventing the occurrence of such leakage current.

[0059] Referring again to Figure 2, a second doping layer 130 may be further positioned on the second surface S2 of the first photoelectric conversion layer 110.

[0060] 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 enabling the formation of a back surface field (BSF).

[0061] 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 therein. As an alternative 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, and by moving carriers through the tunnel effect, electrons or holes can be selectively collected to improve the open circuit voltage.

[0062] On the other hand, 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. As an example, the second surface S2 may have a surface roughness greater than that of the first surface S1 by having a concavo-convex structure. Said concavo-convex structure induces scattering of long-wavelength light incident into the first photoelectric conversion unit 100 and improves the light absorptivity of the first photoelectric conversion layer 110, thereby increasing the current density of the first photoelectric conversion unit 100.

[0063] The protective layer 140 is formed so as to cover the second doping layer 130. On the other hand, since the second surface S2 has a concavo-convex structure, the second doping layer 130 and the protective layer 140 may also be formed to have a concavo-convex structure.

[0064] The protective layer 140 is made of aluminum oxide (AlO x ), silicon nitride (SiN x ), silicon oxide (SiO x ), silicon oxynitride (SiO x N y ) has a single-layer or multi-layer structure including at least one of the above, and may be formed by various processes such as atomic layer deposition (ALD), chemical vapor deposition (CVD, PECVD, LPCVD, APCVD). Such a protective layer 140 can reduce the recombination density on the second surface S2 of the first photoelectric conversion layer 110 to improve carrier lifetime, and minimize the reflection of light incident on the rear surface of the first photoelectric conversion unit 100.

[0065] The second electrode 500 may be electrically connected to the second doping layer 130 through the protective layer 140. The second electrode 500 may be composed 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 500 may be formed by a variety of methods such as screen printing, plating, thermal evaporation, and sputtering using a metal paste.

[0066] Figure 5 is a schematic cross-sectional view showing an example of the second photoelectric conversion section of the tandem solar cell shown in Figure 1.

[0067] Referring to Figure 5, the second photoelectric conversion unit 200 may include a first charge transport layer 210, a second charge transport layer 230, and a second photoelectric conversion layer 220 between the first charge transport layer 210 and the second charge transport layer 230. The second photoelectric conversion unit 200 may further include a conductive oxide electrode layer 240 on the outer surface to which light is incident.

[0068] The first charge transport layer 210 may be an electron transport layer or a hole transport layer. Specifically, in the first photoelectric conversion layer, when electrons move to the front and holes move to the back to form electrical energy, the first charge transport layer 210 may be a hole transport layer. In the above case, the second charge transport layer 230 may be an electron transport layer.

[0069] On the other hand, if the first photoelectric conversion layer is configured such that holes move to the front and electrons move to the back, the first charge transport layer 210 may be an electron transport layer, and the second charge transport layer 230 may be a hole transport layer.

[0070] The electron transport layer may include a transparent conductive oxide (TCO) with high electrical conductivity and a carbonaceous conductive material. 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, and SrTi oxide, etc. The carbonaceous conductive material may be graphene, carbon nanotubes, or fullerene (C60), etc.

[0071] The hole transport layer may be formed from a conductive polymer. Specifically, the hole transport layer may include selected polymers 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.

[0072] The second photoelectric conversion layer 220 is formed so that hole-electron pairs generated by receiving light energy from the sun are separated into electrons or holes. The second photoelectric conversion layer 220 may include a compound having the perovskite structure of the following chemical formula (1) as a perovskite layer.

[0073] [ka]

[0074] In the above chemical formula (1), A is an alkali metal or a C1-C25 substituted or unsubstituted alkyl group.

[0075] When 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.

[0076] The aforementioned B includes a metal cation selected from the group consisting of Pb, Sn, Ge, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, and combinations thereof.

[0077] The aforementioned X may include a halide anion or a chalcogenide anion.

[0078] More specifically, A may contain formamidinium, methylammonium, cesium, rubidium, potassium, sodium, lithium, guanidine, butylammonium, ethylammonium, or phenethylammonium, and B may contain lead, tin, germanium, cadmium, zinc, magnesium, etc. Substance X may contain iodide, bromide, chloride, fluoride, thiocyanate, cyanate, selenocyanate, formate, acetate, etc.

[0079] 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, or a vapor-assisted solution process.

[0080] The conductive oxide electrode layer 240 may be made of a transparent conductive oxide (TCO) with high electrical conductivity.

[0081] A first electrode 400, formed from a material with excellent electrical conductivity, is located on the conductive oxide electrode layer 240, and can collect electric charge. The first electrode 400 is preferably formed using glass frit that can be fired at low temperatures in order to prevent the second photoelectric conversion layer 220 from being oxidized by heat.

[0082] Furthermore, an anti-reflective coating (not shown) may be provided on the conductive oxide electrode layer 240. The anti-reflective coating may be made of magnesium fluoride (MgF2) or silicon oxide (SiO2). x ) and titanium dioxide (TiO x ) may be formed as a single film or multilayer film structure including at least one of the above.

[0083] Figure 6 is a graph showing the IV results of the tandem solar cell according to the present invention.

[0084] Figure 6(A) shows the IV results for a silicon / perovskite tandem solar cell in which the first doping layer is partially doped to have a crystallinity of 50% and is formed to a thickness of 100 nm, according to the embodiment. Figure 6(B) shows the IV results for a silicon / perovskite tandem solar cell in which the first doping layer, which is 100 nm thick, is formed on polycrystalline silicon. Figures 6(A) and 6(B) are the IV values ​​for the tandem solar cells shown in Figures 3 and 4, respectively.

[0085] As can be seen from Figure 6, in case (A), the fill factor (FF) increased compared to case (B). This is because the crystallinity of the first doping layer was formed to 50%, and the perovskite solar cell formed on the first doping layer was uniformly formed, preventing the generation of leakage current. Additionally, because the crystal particles of the first doping layer have a particle size of several nanometers to tens of nanometers, the first doping layer has a wide optical band gap, improving the absorption rate of light in the long wavelength region, and resulting in a match between the current value generated by the perovskite solar cell and the current value generated by the silicon solar cell.

[0086] As described above, the present invention has been described with reference to one embodiment shown in the drawings, but this is merely illustrative, and a person with ordinary skill in the art will understand that various modifications and changes to the embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical idea of ​​the appended claims.

Claims

1. First photoelectric conversion unit, The second photoelectric conversion unit on the first photoelectric conversion unit, It includes an intermediate layer located between the first photoelectric conversion unit and the second photoelectric conversion unit, which electrically connects the first photoelectric conversion unit and the second photoelectric conversion unit, The first photoelectric conversion unit is, The first photoelectric conversion layer, The first doping layer is located on the first surface of the first photoelectric conversion layer between the first photoelectric conversion layer and the intermediate layer, A tandem solar cell in which the surface roughness of the second surface of the first photoelectric conversion layer, which is the opposite surface of the first surface, is greater than the surface roughness of the first surface.

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

3. The tandem solar cell according to claim 1, wherein the thickness of the first doping layer is 40 nm to 100 nm.

4. The tandem solar cell according to claim 1, wherein the optical band gap of the first doping layer is 1.2 eV to 1.8 eV.

5. The tandem solar cell according to claim 1, wherein the second surface has an uneven structure.

6. The tandem solar cell according to claim 1, further comprising a second doping layer located on the second surface of the first photoelectric conversion layer, which is the opposite surface of the first surface.

7. The tandem solar cell according to claim 6, further comprising a protective layer covering the second doping layer.

8. The tandem solar cell according to claim 1, wherein the second photoelectric conversion unit includes a first charge transport layer, a second charge transport layer, and a second photoelectric conversion layer between the first charge transport layer and the second charge transport layer.

9. The tandem solar cell according to claim 8, wherein the second photoelectric conversion layer comprises a compound having a perovskite structure.

10. The tandem solar cell according to claim 8, wherein the second photoelectric conversion unit further includes a conductive oxide electrode layer on its outer surface.

11. Silicon solar cells and The perovskite solar cell on the aforementioned silicon solar cell, It includes an intermediate layer located between the silicon solar cell and the perovskite solar cell, which electrically connects the silicon solar cell and the perovskite solar cell. The silicon solar cell includes a silicon semiconductor layer and a first doping layer located between the silicon semiconductor layer and the intermediate layer on the first surface of the silicon semiconductor layer. The crystallinity of the silicon semiconductor layer and the crystallinity of the first doping layer are different from each other. A tandem solar cell in which the crystallinity of the first doping layer is 30% to 70%.

12. The silicon solar cell further includes a second doping layer located on the second surface of the silicon semiconductor layer, which is the opposite surface to the first surface. The tandem solar cell according to claim 11, wherein the surface roughness of the second surface is greater than the surface roughness of the first surface.

13. The tandem solar cell according to claim 12, wherein the second surface has an uneven structure.

14. The tandem solar cell according to claim 11, wherein the thickness of the first doping layer is 40 nm to 100 nm.

15. The tandem solar cell according to claim 11, wherein the optical band gap of the first doping layer is 1.2 eV to 1.8 eV.

16. The tandem solar cell according to claim 11, wherein the perovskite solar cell includes a first charge transport layer, a second charge transport layer, and a perovskite layer between the first charge transport layer and the second charge transport layer.

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