TW201725746A - Tandem solar cell and method for manufacturing thereof, and solar panel - Google Patents

Abstract

A tandem solar cell, a method for manufacturing thereof, and a solar panel are provided. The tandem solar cell includes a top solar cell and a bottom solar cell. The top solar cell and the bottom solar cell each have a respective front surface and a rear surface, with the respective front surfaces being adapted for facing a radiation source during use. The top solar cell is arranged with its rear surface overlying the front surface of the bottom solar cell. The top solar cell includes a photovoltaic absorber layer with a bandgap greater than that of crystalline silicon. The bottom solar cell includes a crystalline silicon substrate. On at least a portion of the front surface of the bottom solar cell a passivating layer stack is disposed which includes a thin dielectric film and a secondary layer of either selective carrier extracting material or polysilicon. The thin dielectric film is arranged between the silicon substrate and the secondary layer.

Description

Hybrid tandem solar cell

This invention relates to a tandem solar cell. Furthermore, the present invention relates to a method of fabricating such a tandem solar cell. Furthermore, the invention relates to a solar panel comprising at least one such tandem solar cell.

It is known that a tandem solar cell is composed of a crystalline germanium bottom cell having an amorphous silicon (a-Si) heterojunction and a higher band gap top solar cell. Although the bottom solar cell provides a high _Voc that is beneficial for tandem performance due to the amorphous germanium heterojunction, such a bottom solar cell design has several disadvantages. These disadvantages are, for example, i) the low lateral conductivity of the amorphous germanium heterojunction and the low lateral conductance necessitating the use of transparent conductive oxide (TCO) electrodes (unless using InO, for example doped with hydrogen or tungsten) _An expensive material such as _x , indium oxide or the like) the transparent conductive oxide electrode has a large infrared radiation (IR) absorption rate; ii) the amorphous thermal passivation has low thermal robustness and is at the 2-end string The processing of the top cell in the case of a 2-terminal tandem structure is also thermally limited, the low thermal stability means that the resulting battery cannot be soldered regularly for interconnection; iii) formed with amorphous germanium The interdigitated back contact version of a heterojunction battery inevitably introduces complicated processes and high costs.

It is an object of the present invention to overcome or attenuate the various disadvantages of the prior art.

The object is achieved by a tandem solar cell comprising: a top solar cell and a bottom solar cell; the top solar cell and the bottom solar cell respectively have respective front and back surfaces; respective The front surface is adapted to face the radiation source during use; the top solar cell is configured such that its rear surface is adjacent to the front surface of the bottom solar cell (ie, stacked on the front surface of the bottom solar cell or covering the front surface of the bottom solar cell) The top solar cell includes a photovoltaic absorber layer having a band gap larger than that of the crystalline germanium; the bottom solar cell includes a crystalline germanium substrate; wherein at least a portion of a region of the front surface of the crystalline germanium substrate A passivation layer stack is disposed, and the passivation layer stack includes a thin dielectric such as a thin oxide ("tunnel oxide") film and an auxiliary layer formed of a selective carrier extraction material or polysilicon, thin The dielectric film is disposed between the germanium substrate and the auxiliary layer.

Advantageously, since the material in the passivation layer stack can be selected to be thermally stable compared to prior art amorphous heterojunction layers, the present invention provides improved thermal stability of the bottom solar cell and more string The production cost of the amorphous germanium heterojunction battery as the bottom solar cell in the tandem solar cell is relatively low in production cost. Such high thermal stability can enable the use of relatively high temperature manufacturing processes such as standard fire-through metallization.

In addition, a passivation dielectric having a thin (e.g., tunnel oxide) in combination with the auxiliary passivation layer stack of layers may provide a relatively low charge carrier recombination rate, so that to achieve this higher V _oc and FF values and string The higher performance of the connected solar cell. This is especially true when the auxiliary layer provides selective carrier extraction (also described as selective carrier collection) from the substrate, in which case the passivation layer stack is known as a passivated contact or passivation contact. Passivating contact. The enhancement of tandem solar cells is also particularly seen when the auxiliary layer is intrinsic (unintentionally doped, lightly doped) polycrystalline germanium layer, which does not achieve passivated contacts but provides excellent passivation.

Furthermore, the prior art application of a transparent conductive oxide electrode for compensating for low lateral conductance in an amorphous heterojunction may be omitted, due to the selective carrier extraction material of the auxiliary layer (eg, a thickness of at least The highly doped polysilicon of rice provides lateral conductance.

In the current scientific understanding, it is believed that good carrier selectivity requires good interface passivation (interfacing between the substrate and the carrier collection layer stack), for example by thin yttrium oxide. In this sense, the thin dielectric can be considered as part of the selective carrier collection structure, and the auxiliary layer itself does not necessarily have very strong carrier selectivity without using a thin dielectric. . However, thin yttrium oxide itself does not produce selectivity for electrons or holes. This selectivity must be produced by a material placed on a thin yttria. Thus, when referring to a selective carrier extraction or collection material herein is meant a material or layer that is disposed on a thin yttria or thin dielectric film to initiate selective carrier collection properties. In addition, in the current scientific understanding, a thin dielectric performs at least three functions: i) passivating the interface with the germanium substrate to reduce carrier recombination, and ii) reducing a small number of charge carriers from the germanium substrate to the selective carrier extracting material. Transmission (where "minority" is defined as the polarity or type opposite to the polarity or type of selective carrier extraction material), and iii) transmission of most charge carriers sufficient to not exceed the small resistive loss of the bottom solar cell .

Thin dielectrics that produce good performance are, for example, cerium oxide (e.g., cerium oxide) and cerium oxynitride. Other possible thin dielectrics are, for example, aluminum oxide or cerium oxide. Typical cerium oxide or cerium oxynitride has a thickness of between -0.5 nm and ～5 nm, preferably ～1 nm to ～2 nm. Depending on process conditions such as thermal annealing processes that produce pinholes in thin oxide films, thin oxides thicker than about 1.5 nm can achieve good passivation and sufficient transport for most charge carriers. And the required functions for a sufficiently low transmission of a small number of charge carriers.

A wide bandgap top cell typically consists of an absorbing layer (eg, a metal organic halide perovskite, a sulphur copper tin zinc ore such as copper sulphide sulphide, a chalcogenide such as copper indium gallium selenide, a film ruthenium, Organic absorbing layer (Organic Photo Voltaic (OPV), Dye Sensitized Solar Cell (DSSC)), Group III-V compound semiconductor, CdTe, layer containing quantum dots, etc.), for example, Chalcogen Suitable translucent electrodes for forming pn heterojunctions and possibly auxiliary layers of the window layer in the case of a junction or CdS/CdTe junction and/or frequently used in organic photovoltaic solar cells And a charge selective layer in a metal organic halide perovskite solar cell.

The selective charge transport layer can be composed of a stack of different materials having, for example, different doping levels or chemically different compounds. Ideally, the ancillary layers are highly transparent as needed and have suitable electronic properties for charge injection and charge transport. The electrode and charge transport layer are typically located on either side of the absorber layer, however in the case of a back contacted cell (see U. Bach 2016 for an example) the electrode and charge transport layer may be located in the absorber layer On one side. An example is known in which a single charge selective layer is sufficient to achieve a good working device (Graetzel Science (April 2014)).

According to one aspect, the present invention provides a tandem solar cell as described above, wherein a thin dielectric layer, together with a stack of auxiliary layers, forms a selective carrier collection contact to the bottom cell.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the auxiliary layer comprises polycrystalline germanium. In general, films of polycrystalline germanium having a thickness ranging from ～5 nm to ～500 nm have a relatively high absorptivity in the visible range of the spectrum, but are transparent in the infrared radiation range, which enables the use of polycrystalline germanium as a string. The front layer of the solar cell at the bottom of the solar cell. Therefore, the integrated body in a tandem solar cell structure is a polycrystalline tantalum passivated front contact or a polycrystalline tantalum passivated front layer stacked solar cell that would have very poor performance from the original (ie, used as a separate single junction). Get the most efficient solution for your battery. Furthermore, when a crystalline germanium cell with a polysilicon passivated contact is used independently, the polysilicon passivated contact is applied only to the back side, and an additional processing step is required to provide, for example, a high quality diffused junction on the front side and requires photolithography Contacts with very small contact areas are provided on the front side for high performance. According to an aspect of the invention, polycrystalline germanium can be applied to both the front side and the back side of the germanium wafer, and for example by, for example, printing a boron dopant source on one side and implanting on the other side Phosphorus dopant is implanted, followed by thermal annealing, and the front side polysilicon and the back side polysilicon can be doped to have opposite polarities, thereby making the bottom cell battery processing sequence simple and low cost and still enabling the tandem battery and module Achieve high performance.

Polycrystalline germanium is an intrinsic polycrystalline germanium (meaning a polycrystalline germanium that is lowly doped or unintentionally doped, such as a dopant concentration <10 ¹⁸ cm ^-3 ) or doped with impurities of a first conductivity type or a second conductivity type, The second conductivity type is opposite to the first conductivity type. Being doped to a sufficiently high level (typically less than 10 ¹⁹ cm ^-3 or 10 ¹⁹ cm ^-3) in the case of polysilicon, forming a passivation layer stack is also selectively collected contact carrier (the bottom cell contact passivated ).

The thickness of the polycrystalline germanium may range from ～5 nm to ～500 nm, with ～10 nm to ～200 nm being more preferred. For so-called burn-through contacts, to avoid damage to the thin dielectric due to contact metal penetration through the polysilicon layer, ~100 nm or more is preferred.

Alternatively, the auxiliary layer comprises a metal oxide that achieves selective carrier collection properties. Such a metal oxide is selected from the group consisting of molybdenum oxide, nickel oxide, tungsten oxide, vanadium oxide, aluminum-doped zinc oxide for the hole contact, or titanium oxide containing for the electrical contact. , a group of cerium oxide, indium tin oxide. In this case, the passivation layer stack also forms a selective carrier collection contact to the bottom cell. Alternatively, the auxiliary layer may comprise, for example, polyethylene dioxythiophene: polystyrenesulfonic acid (PEDOT:PSS), [6,6]-phenyl-C61-butyl, which achieves selective carrier collection properties. Methyl ester (PCBM), 2,2',7,7'-tetrakis (N,N-di-p-methoxyphenyl-amino) 9,9'-spirodioxime (Spiro-OMeTAD) An n-type or p-type organic semiconductor material.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein said front surface of said bottom solar cell is textured, and at least some of said sharp features of texture are greater than about 25 nm The increased radius of curvature up to about 1000 nm is rounded or smoothed.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the textured front surface comprises a pyramidal shape having a valley in between, the valley having a thickness selected from ～25 nm to ～1000 奈The curvature of the radius of the meter range is rounded.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the top solar cell comprises a thin film photovoltaic layer structure, the thin film photovoltaic layer structure comprising an upper carrier extraction layer, a lower carrier extraction layer, and a photovoltaic absorber layer disposed between the upper carrier extraction layer and the lower carrier extraction layer, and the top solar cell includes at least a first contact layer configured to be in contact with the upper extraction layer; The bottom solar cell includes a germanium substrate of a substantially conductive type having at least a first contact terminal at a rear surface thereof.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the top solar cell comprises a second contact layer underlying the photovoltaic layer structure in contact with the lower carrier extraction layer; The first contact layer has a first polarity and the second contact layer has a second polarity opposite the first polarity; the bottom solar cell includes a second contact terminal, the polarity of the second contact terminal is The first contact terminals have opposite polarities, and the second contact terminals contact the auxiliary layer, and the second contact layer is electrically connected to the second contact terminals.

Depending on the polarity of the second contact terminal and the auxiliary layer, a two terminal (2T) tandem solar cell or a three terminal (3T) tandem solar cell can be constructed.

If the insulating layer or substantially the insulating space is disposed between the passivation layer stack of the bottom solar cell and the second contact terminal and the rear surface of the top solar cell, a four terminal (4T) tandem solar cell can be constructed.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein one of the lower carrier extraction layer or the second contact layer is in the auxiliary layer or the second contact terminal One of them coincides.

If desired, if the coincident layers are also capable of extracting carriers from the photovoltaic layer of another battery, the lower extraction layer in the top solar cell may coincide with the auxiliary layer in the bottom solar cell.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the tandem solar cell includes a third contact layer between the bottom solar cell and the top solar cell, A third contact layer contacts the lower carrier extraction layer and contacts the auxiliary layer on the crystalline germanium cell, wherein the lower carrier extraction layer has a polarity opposite to that of the auxiliary layer.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein one of the lower carrier extraction layer or the lower contact layer directly contacts the auxiliary layer or the second contact terminal One of them.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein said lower carrier is extracted at said auxiliary layer as a selective carrier extraction layer and said rear surface at a top solar cell a composite layer disposed between the layers, the composite layer electrically contacting the auxiliary layer and the lower carrier extraction layer, and the first contact layer of the top solar cell has a first polarity, and the A contact terminal has a second polarity opposite the first polarity.

As such, a two-terminal (2T) tandem solar cell can be constructed using a composite layer for providing efficient recombination of charge carriers from the lower extraction layer and charge carriers from the auxiliary layer. The composite layer is optional if the interface between the lower extraction layer and the auxiliary layer provides efficient compounding.

According to one aspect, the present invention provides a tandem solar cell as described above, wherein the auxiliary layer as a selective carrier extraction layer electrically contacts the lower extraction layer at the rear surface of the top solar cell And the first contact layer of the top solar cell has a first polarity and the first contact terminal has a second polarity opposite the first polarity.

According to one aspect, the present invention provides a method of fabricating a tandem solar cell, the method comprising: providing a bottom solar cell having a front surface and a back surface; providing a top solar cell having a front surface and a back surface; The top solar cell is configured such that the rear surface is on the front surface of the bottom solar cell such that the front surface of the top solar cell and the front surface of the bottom solar cell are in use Facing the radiation source; wherein the top solar cell comprises a photovoltaic absorber layer, the photovoltaic absorber layer has a band gap larger than that of the crystalline germanium; the bottom solar cell comprises a crystalline germanium substrate; On the front surface, the crystalline germanium substrate comprises a passivation layer stack, the passivation layer stack comprises a thin dielectric film and an auxiliary layer, and the thin dielectric film is disposed on the germanium substrate and the auxiliary Between the layers; the auxiliary layer is made of a selective carrier extraction material or polycrystalline germanium.

Advantageous embodiments are further defined by the scope of the independent patent application.

In accordance with the present invention, the tandem solar cell includes a stack of top solar cells (or top photovoltaic devices) and bottom solar cells (or bottom photovoltaic devices), with the top solar cells being disposed atop the bottom solar cells. The top solar cell and the bottom solar cell are stacked in such a manner that the rear surface of the top solar cell is stacked on the front surface of the bottom solar cell.

The front surface refers to the surface of the corresponding solar cell that substantially faces the radiation source (the sun) during use. The back surface refers to the surface of the respective solar cell that faces away from the source of radiation during use of the solar cell.

The bandgap of the top solar cell photovoltaic material and the bandgap of the bottom solar cell photovoltaic material are configured such that the top solar cell is substantially transparent to the radiation whose wavelength is to be absorbed by the bottom solar cell. The top solar cell can be based, for example, on a metal organic halide perovskite photovoltaic material absorber layer that absorbs radiation in the visible range of the spectrum (wavelength: ~400 nm to ~700 nm) and is relatively transparent to infrared radiation, Cd -Te photovoltaic material absorption layer or copper sulfide tin sulfide (CZTS) photovoltaic material absorption layer, and the bottom solar cell can be a crystalline germanium solar cell, the crystalline germanium solar cell is mainly used in this configuration in the spectrum Radiation in the infrared portion (wavelength: ~700 nm to ~1100 nm).

An additional solar cell with even a wider bandgap may be included on top of this configuration, or an additional solar cell with even smaller bandgap may be included under this configuration to produce as much as is known in the art. A tandem cell with 2 absorber layers or junctions.

1 shows a cross-sectional view of a tandem solar cell in accordance with an embodiment of the present invention.

The tandem solar cell 1 includes a top solar cell 10 and a bottom solar cell 30.

The top solar cell 10 is stacked on top of the bottom solar cell, and the rear surface RT of the top solar cell faces the front surface FB of the bottom solar cell.

The top solar cell 10 is a wide bandgap solar cell that is substantially transparent to light in the infrared region. The band gap of the top solar cell needs to be wider than the band gap of the crystalline germanium. It is capable of allowing about 1.35 electron volts (eV) to 2.9 eV for a 4-terminal configuration and about 1.35 eV to 1.9 eV for a 2-terminal configuration, so that a crystalline 矽 bottom cell can theoretically be used. Achieve 35% performance.

A first contact layer 18 is disposed on top of the top solar cell 10 (ie, on one side of the front surface FT of the top solar cell). A second contact layer 20 is further disposed on the top solar cell (eg, on one side of the rear surface RT of the top solar cell 10). The first contact layer 18 and the second contact layer 20 have different polarities and form a first terminal and a second terminal of the tandem solar cell.

A superstrate 22 is disposed on the front surface FT of the top solar cell 10. Such a panel may be a layer of glass provided with a textured surface and/or an antireflection (ARC) coating (not shown).

The bottom solar cell 30 is based on a crystalline germanium substrate 32 of a substantially conductive type having at least a lower contact terminal 34 at the rear surface RB of the bottom solar cell 30. There may be features between the lower contact terminals and the substrate for producing a germanium solar cell, such as doped at the back surface of the substrate, such as by diffusion or deposition. Layer, anti-reflective coating, etc.

A crystalline germanium substrate 32 having a passivation layer stack 36 is disposed on the front surface FB of the bottom solar cell 30. This passivation layer stack includes a thin dielectric film 38 (eg, a tunnel oxide film) and an auxiliary layer 40. The thin dielectric film 38 is disposed between the crystalline germanium substrate 32 and the auxiliary layer 40.

The bottom solar cell 30 may be a front-and-back contacted solar cell, and the front and back contact solar cells are provided with a polar upper portion on the front surface FB of the bottom solar cell. The contact terminals (as schematically indicated by the dashed outline 42) and the lower contact terminals on the rear surface RB are of opposite polarity. In this case, the passivation layer stack is a passivated contact, which in turn enables selective extraction of a carrier from the substrate. Layer 40 can be, for example, a doped polysilicon layer. Alternatively, the bottom solar cell 30 may be a back contact type solar cell having contact terminals of different polarities disposed on the rear surface RB of the bottom solar cell. The back contact solar cell can be a metal-wrap-through (MWT) solar cell or an interdigitated back-contact (IBC) solar cell. If it is a crossed back contact cell, the auxiliary layer 40 may be an intrinsic polysilicon layer or a near intrinsic (unintentionally doped) polysilicon layer, whereby the passivation layer stack provides excellent passivation, but not from the substrate Extract the carrier.

The contact terminals 34, 42 of the bottom solar cell form a third terminal and a fourth terminal of the tandem solar cell 1.

A spacer layer or layer stack 24 may be disposed on the rear surface RT of the top solar cell 10. The barrier layer 24 forms an intermediate layer between the rear surface RT of the top solar cell 10 and the front surface FB of the bottom solar cell 30.

The barrier layer 24 couples the top solar cell 10 to the bottom solar cell 30. The barrier layer 24 can be based on an encapsulating material. The barrier layer 24 (encapsulation material) mechanically and optionally connects the top solar cell 10 to the bottom solar cell 30.

The auxiliary layer 40 can be, for example, an intrinsic or doped polysilicon layer to create a passivated contact, or can be a transparent conductive metal oxide to produce a passivated contact as explained above.

In accordance with the present invention, the auxiliary layer 40 causes infrared radiation (or any radiation) that is not absorbed by the top solar cell 10 to be transmitted to the bottom solar cell 30, i.e., transparent to radiation in the infrared range. As explained above, the combination of a thin dielectric 38 such as tunneling oxide and the auxiliary layer 40 of the selective carrier extraction material provides a relatively low charge carrier recombination rate, thereby providing a higher V for the bottom solar cell. _Oc value and FF value. Furthermore, the transparency in the infrared range of the spectrum enables absorption of infrared radiation in the solar cells at the bottom of the crystalline crucible.

In an embodiment, the crystalline germanium substrate 32 is n-type and the auxiliary layer 40 is a p-type doped polysilicon.

2 shows a schematic cross-sectional view of a four terminal tandem solar cell in accordance with yet another embodiment of the present invention.

In FIG. 2, entities having the same reference numerals as those shown in FIG. 1 refer to corresponding or similar entities.

The embodiment shown in Fig. 2 shows a tandem solar cell 2 comprising a top solar cell 10 and a bottom solar cell 130 as described above.

The top solar cell 10 is a wide bandgap solar cell, for example, the top solar cell includes a photovoltaic absorber layer 12, and the photovoltaic absorber layer 12 is sandwiched between upper carrier extraction layers for carriers of the first polarity (eg, electrons) 14 is between the lower carrier extraction layer 16 for a carrier (e.g., a hole) for a second polarity opposite to the first polarity.

In an embodiment, the photovoltaic absorber layer 12 is a layer of methylammonium-lead-triiodide perovskite, and the upper carrier extraction layer 14 is a layer for extracting electrons (including TiO ₂ ) and is used to extract holes The lower carrier extraction layer 16 is a spiro-OMeTAD ([2,2',7,7'-tetra(N,N-di-p-methoxyphenyl-amino) 9,9'-spirocyclic ring The second layer]).

Other electron and hole extraction layers are known in the art as variations of the perovskite composition (e.g., replacing some of the iodine with bromine) to alter the band gap or other properties. The top contact layer is a transparent conductive oxide layer (eg, indium tin oxide). Similarly, the lower contact layer is a transparent conductive oxide layer (eg, indium tin oxide). Alternative contact layers of indium tin oxide (e.g., hydrogenated indium oxide) that enable higher transmission are known in the art.

Other thin film solar cells may be present, such as, for example, translucent CdTe solar cells known in the art wherein the top contact layer is CTO/ZTO; the top carrier extraction layer is replaced by a CdS window layer, and the CdS window layer forms a pn with CdTe. The junction; the bottom carrier extraction layer may be omitted and the bottom contact layer is, for example, ZnTe:Cu or selected from other suitable translucent back contact layers for CdTe. As is known in the art, the structure of the top solar cell can be modified locally to complete a monolithic interconnection (ie, a series circuit of strips of solar cells) to increase the output voltage and reduce resistive losses.

The bottom solar cell 130 is similar to the tethered bottom solar cell 30 shown in FIG. 1 and includes both the upper contact terminal 42 on the front surface FB and the lower contact terminal 34 on the rear surface RB.

Further, the front surface FB and the rear surface RB of the crystalline germanium substrate 32 are provided to have textures T1, T2.

In this embodiment, the textured front surface FB includes a passivation layer stack 36 as a selective carrier collection layer stack (passivated contacts), the passivation layer stack 36 being made of a thin dielectric 38 (eg, a tunnel oxide film) And the auxiliary layer 40 is composed. The auxiliary layer 40 is covered by an anti-reflective (ARC) coating, and the anti-reflective (ARC) coating is also applied to a tunneling oxide/germanium deposited by plasma enhanced chemical vapor deposition (PECVD). The interface (eg, ytterbium-rich hydrogen hydride (SiN _x :H)) provides hydrogen. The upper contact terminal 42 is connected to the auxiliary layer 40 by an anti-reflection coating. Such a connection of the upper contact terminal 42 to the auxiliary layer 40 can be a so-called thick film metal paste burn-through connection as is known in the art.

The textured back surface RB of the bottom solar cell 130 includes a second passivation layer stack 136 comprised of a second thin tunnel oxide film 138 and a back surface auxiliary layer 140. The back surface auxiliary layer 140 is covered by a second anti-reflective coating formed of SiN _x :H functionally similar to the front side anti-reflective coating. The lower contact terminal 34 is connected to the rear surface auxiliary layer 140 by a second anti-reflective coating.

The auxiliary layer 40 on the front surface FB may be a doped polysilicon layer of a first conductivity type (eg, n-type). The auxiliary layer 140 on the back surface RB has a second conductivity type opposite to the first conductivity type, such as a p-type doped polysilicon layer. Doping level of at least 1'10 ¹⁹ cm ^-3, or preferably a higher (e.g. about 1'10 ²⁰ cm ^-3 to 3'10 ²⁰ cm ^-3). The thickness of the polycrystalline germanium is preferably between ～10 nm and ～300 nm. If burn through contacts are used, the thickness is preferably at least ~100 nm to avoid damage to the passivated thin oxide from the metal burn-through contacts. Positioning the p-type polysilicon layer at the back side and positioning the n-type polysilicon layer at the front side is advantageous because the n-type polysilicon is more easily doped to a higher concentration and has a higher carrier mobility. Unexpectedly found that for a given polysilicon layer, the optional free carrier absorption (FCA) placed behind the tantalum solar cell is more optional than the free carrier placed in front of the solar cell. The absorption rate is large, so placing the higher doped n-type polysilicon in front reduces the free carrier absorption rate. Also for reasons of lower carrier mobility, it is advantageous to position the p-type polysilicon later, where a tighter metallization grid may be present in the absence of shading loss.

The thickness of the polycrystalline silicon on the front and back sides (if polycrystalline germanium is used on the back side) is not necessarily the same, but if the polycrystalline germanium is uniformly deposited on both sides by, for example, low pressure chemical vapor deposition (LPCVD), The thicknesses can be substantially the same, which can reduce process complexity. For example, the front side polysilicon and the back side polysilicon can be doped by, for example, printing a boron dopant source on one side and implanting a phosphorous dopant on the other side, followed by thermal annealing. The simple and low-cost battery processing sequence of the bottom battery and the high performance of the series-connected batteries and modules.

According to an embodiment, the texture on the front surface FB and/or the back surface RB may have been rounded after texturing. Such rounding or smoothing means that the radius of curvature of at least some of the sharp features of the texture (especially the valley between the textured pyramids in the case of the pyramidal texture) is increased, for example, only a few nanometers. (about 25 nm) increases to about 100 nm to about 200 nm, or even larger (eg, up to 1000 nm).

The rounding can be accomplished by etching methods known in the art.

3 shows a schematic cross-sectional view of a four terminal tandem solar cell in accordance with an embodiment of the present invention.

In the four-terminal tandem solar cell 2a of this embodiment, the front surface of the bottom solar cell 132 is similar to the front surface of the tethered bottom solar cell 130 shown in FIG. 2 and includes the upper contact terminal 42 on the front surface FB.

Further, the front surface FB of the crystalline germanium substrate 132 is provided with a texture T1.

In this embodiment, the textured front surface FB includes a passivation layer stack 36 as a selective carrier collection layer stack (passivated contact) 12, the passivation layer stack 36 being composed of a thin dielectric 38 (eg, tunneling oxide) The film) and the auxiliary layer 40 are composed.

The auxiliary layer 40 is covered by an anti-reflective (ARC) coating, and the anti-reflective (ARC) coating is also applied to a tunneling oxide region (eg, yttrium-rich yttrium nitride) deposited by plasma enhanced chemical vapor deposition (PECVD). (SiN _x :H)) provides hydrogen. The upper contact terminal 42 is connected to the auxiliary layer 40 by an anti-reflection coating.

Such a connection of the upper contact terminal 42 to the auxiliary layer 40 can be a so-called thick film metal paste burn-through connection as is known in the art.

The rear surface RB of the bottom solar cell is disposed as a so-called back surface of the passivated emitter and rear cell (PERC) or a double-sided passivated emitter and a rear surface of the rear cell. This means that the back surface is arranged in such a way that the back surface is smoothed or ground to some extent and comprises a second passivation consisting of a dielectric layer or dielectric layer stack 134 used in a PERC solar cell. A layer stack, such as a stack of aluminum oxide and tantalum nitride (aluminum is located between the substrate and tantalum nitride), or a stack of tantalum oxide and tantalum nitride (the tantalum oxide is between the substrate and tantalum nitride). A metal layer 138 or layer stack is applied over the dielectric stack 134 (the dielectric stack is between the metal layer and the substrate), partially penetrates the dielectric layer stack, and penetrates the dielectric layer in the metal layer 138 or layer stack A local back surface field of the aluminum doped crucible 136 is formed at the layer stack. The metal layer may be disposed over substantially all of the back surface or partially over the back surface to achieve a double-sided bottom cell. In Figure 3, it is shown as being set locally.

For example, this embodiment can be formed in the following manner. After texturing, a thin oxide and polysilicon film can be applied to at least the front side. If desired, polycrystalline germanium can then be doped on at least the front side, for example by diffusion in a gaseous POCl ₃ atmosphere at elevated temperatures. Doping can also be carried out, for example, by implantation and annealing. If any polysilicon is deposited on the back, the polysilicon can then be removed from the back and the back can be smoothed or ground by a single side etch. In further processing, as is known in the description of techniques for PERC solar cell processing, a coating and a metallization layer are provided.

Alternatively, in an alternate embodiment, the rear surface RB of the bottom solar cell 132 is textured, or ground or at a level interposed therebetween. The back surface includes a second passivation layer stack consisting of a thin dielectric layer and a polysilicon layer, which may be similar to the front side (eg, similar in similar thickness or similar composition), but substantially Undoped on top. A metal layer or layer stack is applied on top of the back layer stack (the back layer stack is located between the metal layer and the substrate), partially penetrates the back layer stack, and forms an aluminum doped layer after the metal layer or layer stack penetrates the layer stack. The partial back surface field of the cockroach. The metal layer may be disposed over substantially all of the back surface or partially over the back surface to achieve a double-sided bottom cell.

For example, this embodiment can be formed in the following manner. After texturing and, if necessary, post-grinding, oxides and substantially intrinsic polycrystalline germanes are applied to the front and back surfaces. The polysilicon is then doped only on the front side, for example by implantation and annealing or by printing a dopant paste and annealing on the front side or by other methods known in the art for local doping. If necessary, a diffusion barrier that blocks the front side dopant may be provided later. In further processing, a coating and a metallization layer are provided. Applying a hydrogen-rich cerium nitride or other hydrogen-rich coating layer on the post-polysilicon is beneficial for enhancing the surface passivation of the post-polysilicon. The metallization layer on the rear can be provided, for example, by the following steps for a PERC battery or a double-sided PERC battery: first a hole is provided in the layer stack on the rear, followed by a metal layer, and then, for example, in a so-called firing High temperatures are provided in (firing).

According to an embodiment, the texture on the front surface FB may have been rounded after texturing. Such rounding or smoothing means that the radius of curvature of at least some of the sharp features of the texture (especially the valley between the textured pyramids in the case of pyramidal textures) increases, for example from only a few nanometers (about 25 Nano) increases to about 100 nm to about 200 nm, or even larger (eg, up to 1000 nm).

The rounding can be accomplished by etching methods known in the art.

4 shows a schematic cross-sectional view of a two terminal tandem solar cell in accordance with an embodiment of the present invention.

In FIG. 4, entities having the same reference numerals as those shown in FIG. 1 or FIG. 2 or FIG. 3 refer to corresponding or similar entities.

The embodiment shown in FIG. 4 shows a tandem solar cell 3 that includes a top solar cell 210 stacked on a bottom solar cell 230.

The bottom solar cell 230 is based on a crystalline germanium substrate 232 of a substantially conductive type with a lower contact terminal 234 at the rear surface RB of the bottom solar cell 230.

A germanium substrate 232 having a passivation layer stack 236 is disposed on the front surface FB of the bottom solar cell 230. This passivation layer stack includes a thin dielectric (eg, tunnel oxide) film 238 and an auxiliary layer 240. The thin dielectric film 238 is disposed between the germanium substrate 232 and the auxiliary layer 240.

The top solar cell 210 is a wide bandgap solar cell that substantially transmits light in the infrared region. A top contact layer 218 is disposed on top of the solar cell 210 (ie, on one side of the front surface FT of the top solar cell). On the rear surface RT of the top solar cell 210, a spacer layer 250 is disposed between the rear surface layer of the top solar cell and the auxiliary layer 240 of the bottom solar cell 230.

The spacer layer 250 includes at least one composite layer 252 for connecting one polarity of the top solar cell 210 to the auxiliary layer 240 of the bottom solar cell (which is of opposite polarity).

The top contact layer 218 of the top solar cell 210 and the lower contact terminal 234 of the bottom solar cell form a first terminal and a second terminal of the tandem solar cell 3, respectively.

In an embodiment, the top solar cell 210 includes a photovoltaic absorber layer 212 that is sandwiched between an upper carrier extraction layer 214 for a carrier of a first polarity (eg, electrons) and as a back surface layer. Between the lower carrier extraction layer 216 of a carrier of a second polarity (eg, a hole) opposite the first polarity. For example, the photovoltaic absorber layer 212 is a layer of a metal organic halide perovskite such as methylammonium-lead-triiodide perovskite, and the upper carrier extraction layer 214 is used for extracting electrons (including TiO ₂ ). The lower carrier extraction layer 216 for layer extraction and extraction is 2,2',7,7'-tetra(N,N-di-p-methoxyphenyl-amine) 9,9'- The layer of the spiral ring. The top contact layer 218 is a transparent conductive oxide layer (eg, indium tin oxide) combined with a metal grid.

The germanium substrate 232 can be n-type, and the auxiliary layer 240 at the interface with the top solar cell can be an n-type doped polysilicon to match the opposite polarity of the lower carrier extraction layer of the top solar cell, and the top solar cell The back surface auxiliary layer is in this case a p-type doped polysilicon (opposite to the polarity of the front surface).

Figure 5 shows a schematic cross-sectional view of a two terminal tandem solar cell in accordance with an embodiment of the present invention.

In FIG. 5, entities having the same reference numerals as those shown in the foregoing FIGS. 1 to 4 refer to corresponding or similar entities.

The embodiment shown in FIG. 5 shows a tandem solar cell 4 comprising a top solar cell 210 and a bottom solar cell 330 as described above with reference to FIG.

The bottom solar cell 330 is similar to the tethered bottom solar cell 230 shown in FIG. 4, except that the front surface FB and the rear surface RB of the ruthenium substrate 32 are provided with textures T1, T2.

In this embodiment, as described above with reference to Figures 1-4, the textured front surface FB includes a passivation layer stack 336 comprised of a thin dielectric film 338 and an auxiliary layer 340. The auxiliary layer 340 is covered by an anti-reflective coating. As previously described with respect to Figure 2, the bottom cell can include polysilicon passivated contacts on the front and back sides.

In addition, the tandem solar cell includes an auxiliary layer disposed on the back surface layer of the top solar cell (in the embodiment: the lower carrier extraction layer 216) and the passivation layer stack of the bottom solar cell 330 for providing electrical connection. A spacer layer 350 between the layers 340. The spacer layer 350 includes a composite layer that provides carriers that are extracted by the auxiliary layer 340 and those that are opposite in polarity extracted at the rear surface of the top solar cell (in the embodiment: by the carrier extraction layer 216) The efficient compounding of the child.

The spacer layer 350 or the lower carrier extraction layer 216 may be adapted to form a smooth layer to form a substantially flattened surface of the lower contact layer on which the top solar cell is disposed. This can be done, for example, by liquid deposition (printing, spraying, slot die coating) of materials that preferably fill the layers of valleys between texture features (eg, pyramids). Etc., and/or after the deposition of the materials, an etch back process (eg, plasma etching, mechanical etching) is performed to flatten the materials. The production of a thin film solar cell including a thin film layer stack is simplified by providing a flattened surface. When the front side of the bottom solar cell should preferably be textured, and when the top solar cell process is not able to conformally conform to the texture features of the bottom cell without degrading the performance of the top cell, The flattening process is beneficial not only for tandem solar cells according to the present invention but also for tandem solar cells in the general sense.

It should be noted that as an alternative or in addition, the lower contact layer 216 of the top solar cell may be suitable as a smooth layer.

It should also be noted that as an alternative, the separation layer 350 may be omitted if sufficient recombination occurs at the interface between layer 340 and layer 216.

As described with respect to Figure 2, the texture features on the front and/or back side may be rounded prior to placement of the passivation layer stack.

FIG. 6 shows a schematic cross-sectional view of a two-terminal tandem solar cell 4a according to an embodiment of the present invention.

In FIG. 6, the entities whose reference numerals are the same as those shown in the foregoing FIGS. 1 to 5 refer to corresponding or similar entities.

In the embodiment shown in FIG. 6, bottom solar cell 132 corresponds to solar cell 132 shown and described with respect to FIG. The rear surface RB of the bottom solar cell is set to the rear surface of the PERC battery or the double-sided PERC battery. The back surface is smoothed or ground to some extent and includes a second passivation layer stack consisting of a dielectric layer or dielectric layer stack 134 used in so-called PERC solar cells, such as alumina and nitridation A stack of germanium (aluminum is located between the substrate and tantalum nitride), or a stack of tantalum oxide and tantalum nitride (the tantalum oxide is between the substrate and tantalum nitride). A metal layer 138 or layer stack is applied over the dielectric stack 134 (the dielectric stack is between the metal layer and the substrate), partially penetrates the dielectric layer stack, and penetrates the dielectric layer in the metal layer 138 or layer stack A partial back surface field of the aluminum doped crucible 136 is formed at the stack of layers. The metal layer may be disposed over substantially all of the back surface or partially over the back surface to achieve a double-sided bottom cell.

It should be noted that a similar finish as shown in FIG. 6 can be made to the rear surface RB of the bottom solar cell 230 as shown in FIG.

It should be further noted that the present invention includes embodiments in which a passivation layer stack is disposed on a front surface of a bottom solar cell, the passivation layer stack including a thin dielectric film and an auxiliary layer formed of a selective carrier extraction material or polysilicon. The thin dielectric film is disposed between the germanium substrate and the auxiliary layer, wherein the passivation layer stack is disposed in a specific partial pattern, or is patterned into a specific partial pattern, wherein each pattern has a varying thickness or doping level or A selective carrier extracts the composition of the material.

Such a partial pattern may be a grid pattern that is aligned with, for example, a contact metallization grid (eg, a metallized grid represented by finger portion 42 in Figures 2 and 3). For example, if the passivation layer stack comprises a thin oxide and a film formed of doped polysilicon, the polysilicon can be thinned or completely removed in the region of the front surface FB between the fingers of the grid. Advantageously, such embodiments of the present invention can be used to provide a selective carrier extraction material between a metal grid finger portion and a wafer substrate (eg, a doped polysilicon having a thickness of 100 nanometers or more) The greater thickness of the film, in turn, can reduce the recombination induced by the metal grid fingers and provide a smaller thickness on the wafer surface area on the FB between the fingers of each grid to allow for infrared wavelengths. The so-called free carrier absorption rate of photons is reduced. Therefore, the performance of the bottom solar cell can be improved. Such variations in thickness can be accomplished, for example, by a local chemical etch back process for polycrystalline germanium as is known in the art. Advantageously, the selective carrier extraction material used between the metal grid finger portion and the wafer substrate extends laterally from the metal grid finger portion by a length to provide alignment during the application of the metal grid finger portion. Alignment tolerance. For example, the finger portion of the selective carrier extraction material located below the metal grid finger portion can be 100 microns to 500 microns wider than the metal grid finger portion. Advantageously, in the front surface of the wafer substrate of the bottom cell (for example in a surface located between and below the fingers of each grid), a blend of the same carrier type as the selective carrier extraction material may be provided. The impurity layer, which reduces the series resistance of the bottom cell.

A tandem solar cell according to an embodiment of the present invention may be fabricated from a tantalum substrate-based bottom solar cell and a thin film photovoltaic device based top solar cell.

A method of manufacturing such a tandem solar cell includes: providing a bottom solar cell having a front surface and a rear surface; providing a top solar cell having a front surface and a rear surface; configuring the top solar cell such that the rear surface is at the bottom sun The front surface of the battery such that the front surface of the top solar cell and the front surface of the bottom solar cell face the radiation source during use; wherein the top solar cell comprises photovoltaic absorption, the photovoltaic absorption having a larger band gap than the crystalline germanium a band gap; the bottom solar cell comprises a crystalline germanium substrate; on the front surface of the bottom solar cell, the germanium substrate comprises a passivation layer stack comprising a thin dielectric film and formed by a selective carrier collecting material or polysilicon The auxiliary layer is disposed between the germanium substrate and the auxiliary layer.

The foregoing invention has been described with reference to the specific embodiments of the invention However, it will be apparent that various modifications and changes can be made thereto without departing from the scope of the invention as set forth in the appended claims.

In addition, retouching may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed,

In particular, specific features of various aspects of the invention may be combined. Aspects of the invention may be further advantageously enhanced by the addition of features already described for another aspect of the invention.

It is to be understood that the invention is limited only by the scope of the appended claims and their technical equivalents. In this document and in the scope of its patent application, the verb "to comprise" and its variations are used in their non-limiting sense to mean to include the item that follows the word, and does not exclude Items not specifically mentioned. In addition, an element having the indefinite article "a" or "an" or "an" The indefinite article "a" or "an" is often used to mean "at least one."

1, 2, 3, 4‧‧‧ tandem solar cells
2a‧‧‧ four-terminal tandem solar cell
4a‧‧‧Two-terminal tandem solar cell
10, 210‧‧‧ top solar cells
12. 212‧‧‧Photovoltaic absorption layer
14, 214‧‧‧ upper carrier extraction layer
16‧‧‧Lower carrier extraction layer
18‧‧‧First contact layer
20‧‧‧Second contact layer
22‧‧‧Slate
24‧‧‧ partition wall/layer stacking
30, 130, 230‧‧‧ bottom solar cells / tethered bottom solar cells
32, 232, 332‧‧ ‧ crystallization substrate
34‧‧‧Lower contact terminal/contact terminal
36‧‧‧ Passivation layer stacking
38‧‧‧Thin dielectric film/thin dielectric
40, 340‧‧‧Auxiliary layer/layer
42‧‧‧Upper contact terminal/contact terminal/finger
44‧‧‧Anti-reflective coating
132‧‧‧Bottom solar cell
134‧‧‧Dielectric layer stacking
136‧‧‧Second passivation layer stack/aluminum doped germanium
138‧‧‧Second thin tunnel oxide film/metal layer
140‧‧‧Back surface auxiliary layer/auxiliary layer
144‧‧‧Anti-reflective coating
216‧‧‧Lower carrier extraction layer/lower contact layer/layer
218‧‧‧ top contact layer
234‧‧‧Lower contact terminal
236, 336‧‧‧ Passivation layer stacking
238, 338‧‧‧ Thin dielectric film
240‧‧‧Auxiliary layer
250, 350‧‧‧ separate layers
FB, FT‧‧‧ front surface
RB, RT‧‧‧ rear surface
T1, T2‧‧‧ texture

The invention will be explained in more detail below with reference to the drawings in which an illustrative embodiment of the invention is illustrated. 1 shows a schematic cross-sectional view of a four terminal tandem solar cell in accordance with an embodiment of the present invention. 2 shows a schematic cross-sectional view of a four terminal tandem solar cell in accordance with an embodiment of the present invention. 3 shows a schematic cross-sectional view of a four terminal tandem solar cell in accordance with an embodiment of the present invention. 4 shows a schematic cross-sectional view of a two terminal tandem solar cell in accordance with an embodiment of the present invention. Figure 5 shows a schematic cross-sectional view of a two terminal tandem solar cell in accordance with an embodiment of the present invention. Figure 6 shows a schematic cross-sectional view of a two terminal tandem solar cell in accordance with an embodiment of the present invention.

3‧‧‧ tandem solar cells

22‧‧‧Slate

210‧‧‧Top solar cell

212‧‧‧Photovoltaic absorption layer

214‧‧‧Upper carrier extraction layer

216‧‧‧Lower carrier extraction layer/lower contact layer/layer

218‧‧‧ top contact layer

230‧‧‧Bottom solar cell/矽 bottom solar cell

232‧‧‧crystal substrate

234‧‧‧Lower contact terminal

236‧‧‧ Passivation layer stacking

238‧‧‧Thin dielectric film

240‧‧‧Auxiliary layer

250‧‧‧Separation layer

FB, FT‧‧‧ front surface

RB, RT‧‧‧ rear surface

Claims (29)

A tandem solar cell comprising a top solar cell and a bottom solar cell; the top solar cell and the bottom solar cell respectively have respective front and back surfaces; the respective front surfaces are adapted to face during use a radiation source; the top solar cell being configured to cover the back surface of the top solar cell to the front surface of the bottom solar cell; the top solar cell comprising a photovoltaic absorber layer, the photovoltaic absorption The layer has a band gap larger than that of the crystalline germanium; the bottom solar cell includes a crystalline germanium substrate; a passivation layer stack is disposed on at least a portion of the front surface of the bottom solar cell, the passivation layer stack including A thin dielectric film and an auxiliary layer formed of a selective carrier extraction material or a polysilicon, the thin dielectric film being disposed between the germanium substrate and the auxiliary layer. The tandem solar cell of claim 1, wherein the auxiliary layer comprises an intrinsic polysilicon. The tandem solar cell of claim 1, wherein the auxiliary layer comprises a polysilicon doped with an impurity of a first conductivity type or a second conductivity type. A tandem solar cell according to any one of the preceding claims, wherein the auxiliary layer is substantially transparent to infrared radiation. The tandem solar cell according to any one of claims 1 to 4, wherein the thin dielectric film has a thickness of between 0.5 nm and 5 nm. The tandem solar cell according to any one of claims 1 to 4, wherein the thin dielectric film is yttrium oxide having a thickness between 1 nm and 2.5 nm. Or a layer formed by ruthenium oxynitride. The tandem solar cell of any one of claims 1 to 6, wherein the polycrystalline germanium has a range of from about 5 nm to about 500 nm, preferably about 10 The thickness between nano and about 200 nm. The tandem solar cell according to claim 6 or 7, wherein the doping level of the polycrystalline germanium layer is higher than about 1 ́10 ¹⁹ cm ^-3 . The tandem solar cell of claim 1, wherein the auxiliary layer comprises a metal oxide. The tandem solar cell of claim 9, wherein the metal oxide is selected from the group consisting of molybdenum oxide, nickel oxide, tungsten oxide, vanadium oxide, and aluminum doped oxidation for the hole contact. a group of zinc; or for an electrical contact selected from the group consisting of titanium oxide, cerium oxide, indium tin oxide. A tandem solar cell according to any of the preceding claims, wherein the top solar cell comprises a metal organic halide perovskite layer as a photovoltaic absorber layer. A tandem solar cell according to any one of the preceding claims, wherein the top solar cell comprises a CdTe layer as a photovoltaic absorber layer. A tandem solar cell according to any of the preceding claims, wherein the front surface of the bottom solar cell is textured and at least some of the sharp features of the texture are greater than about 25 nm The increased radius of curvature up to about 1000 nm is rounded (smoothed). The tandem solar cell of claim 13, wherein the textured front surface comprises a pyramid shape having a valley in between, the valley having a shape selected from about 25 nm to about 1000 nm The curvature of the radius of the meter range is rounded. A tandem solar cell according to any one of the preceding claims, wherein the top solar cell comprises a thin film photovoltaic layer structure comprising an upper carrier extraction layer, a lower carrier extraction layer and a configuration The photovoltaic absorber layer between the upper carrier extraction layer and the lower carrier extraction layer, and the top solar cell includes at least a first contact layer configured to be in contact with the upper extraction layer; The bottom solar cell includes a germanium substrate of a substantially conductive type having at least a first contact terminal at a rear surface of the bottom solar cell. The tandem solar cell of claim 15, wherein the top solar cell comprises a second contact layer under the photovoltaic layer structure in contact with the lower carrier extraction layer; The contact layer has a first polarity and the second contact layer has a second polarity opposite the first polarity; the bottom solar cell includes a second contact terminal, a polarity of the second contact terminal and the first The polarity of the contact terminals is opposite, and the second contact terminals contact the auxiliary layer, and the second contact layer is electrically connected to the second contact terminals. The tandem solar cell of claim 16, wherein one of the lower carrier extraction layer or the second contact layer and one of the auxiliary layer or the second contact terminal Coincident. The tandem solar cell of claim 17, wherein the tandem solar cell comprises a third contact layer between the bottom solar cell and the top solar cell, the third contact A layer contacts the lower carrier extraction layer and contacts the auxiliary layer on the crystalline germanium cell, wherein the lower carrier extraction layer has a polarity opposite to that of the auxiliary layer. The tandem solar cell of claim 17, wherein one of the lower carrier extraction layer or the lower contact layer directly contacts one of the auxiliary layer or the second contact terminal By. The tandem solar cell according to claim 17, wherein the auxiliary layer as a selective carrier extraction layer and the lower carrier extraction layer at the rear surface of the top solar cell Interposed with a composite layer electrically contacting the auxiliary layer and the lower carrier extraction layer, and the first contact layer of the top solar cell has a first polarity, and the first contact The terminal has a second polarity opposite the first polarity. The tandem solar cell of claim 15, wherein the auxiliary layer as a selective carrier extraction layer electrically contacts the lower extraction layer at the rear surface of the top solar cell, and The first contact layer of the top solar cell has a first polarity and the first contact terminal has a second polarity opposite the first polarity. The tandem solar cell according to any one of the preceding claims, wherein the thin dielectric layer is a ruthenium dioxide layer or a ruthenium oxynitride layer. A method of manufacturing a tandem solar cell, comprising: providing a bottom solar cell having a front surface and a rear surface; providing a top solar cell having a front surface and a rear surface; configuring the top solar cell to cause the top solar cell The rear surface is located on or adjacent to the front surface of the bottom solar cell such that the front surface of the top solar cell and the bottom solar cell The front surface faces the radiation source during use; wherein the top solar cell comprises a photovoltaic absorber layer having a larger band gap than the crystalline germanium; the bottom solar cell comprises a crystalline germanium substrate; On the front surface of the bottom solar cell, the crystalline germanium substrate includes a passivation layer stack, the passivation layer stack includes a thin dielectric film and an auxiliary layer, and the thin dielectric film is disposed on the Between the substrate and the auxiliary layer; the auxiliary layer is made of a selective carrier extraction material or polycrystalline germanium. A method of manufacturing a tandem solar cell according to claim 23, comprising: said top solar cell comprising a second contact layer in contact with said lower extraction layer of said photovoltaic layer structure at said rear surface The first contact layer has a first polarity and the second contact layer has a second polarity opposite to the first polarity; the bottom solar cell includes a second contact terminal, a polarity of the second contact terminal The polarity of the first contact terminal is opposite. A method of manufacturing a tandem solar cell according to claim 24, wherein the method comprises disposing an insulating layer between the auxiliary layer of the bottom solar cell and the rear surface of the top solar cell. The method of claim 24, wherein the second contact layer electrically contacts the second contact terminal. A method of manufacturing a tandem solar cell according to claim 23, comprising: disposing a third contact layer between the auxiliary layer of the bottom solar cell and the lower carrier extraction layer of the top solar cell; The third contact layer electrically contacts the auxiliary layer and the lower carrier extraction layer, and the auxiliary layer and the lower carrier extraction layer have the same polarity. A method of manufacturing a tandem solar cell according to claim 23, comprising: disposing a composite layer between the auxiliary layer of the bottom solar cell and the lower carrier extraction layer of the top solar cell; . A solar panel comprising at least one of the tandem solar cells of any one of the preceding claims, or any one of items 23 to 28 of the aforementioned patent application. The method described is made.