Stacked III-V multi-junction solar cell

Abstract

The invention relates to a stacked III-V multi-junction solar cell having an upper side and a lower side, comprising: a metal upper side contact region formed on the upper side of the multi-junction solar cell, the upper side contact region comprising a first metal layer; a metallic underside contact region formed in a planar manner on the underside of the multi-junction solar cell; an opening which continuously extends from the upper side to the lower side, the opening having an upper edge region formed on the upper side and a lower edge region formed on the lower side, the upper edge region adjoining the upper side contact region, the side walls and the two edge regions being completely covered by a dielectric layer, the dielectric layer has an upper side and a lower side, a first metal cover layer is formed on a surface of the first metal layer, and a second metal cover layer is formed on the upper side of the dielectric layer and on a portion of the first metal layer adjoining the upper edge region.

Description

Technical Field

[0001] The invention relates to a stacked III-V multi-junction solar cell. Background Art

[0002] US 9,680,035 B1 discloses a solar cell contact assembly with a solar cell stack, comprising: a plurality of III-V subcells on a GaAs substrate with a back-contacted front side. In this case, holes are produced by means of a wet chemical etching process, which extend from the top side of the solar cell through the subcells into the substrate layer that has not yet been thinned. Before the substrate layer is thinned, passivation and metallization of the front side and passivation and metallization of the holes are carried out. Summary of the invention

[0003] Against this background, the object of the present invention is to provide a device which expands the prior art.

[0004] This object is achieved by the stacked III-V multi-junction solar cell according to the invention. Advantageous embodiments of the invention are listed below.

[0005] According to this subject matter, a stacked III-V multi-junction solar cell is provided, wherein the III-V multi-junction solar cell has an upper side and a lower side.

[0006] A substrate layer is formed on the bottom side. A first solar cell having a first band gap is arranged above the substrate layer.

[0007] A second solar cell is arranged above the first solar cell, wherein the second solar cell has a second band gap, wherein the second band gap is greater than the first band gap.

[0008] A tunnel diode is formed between the first solar cell and the second solar cell.

[0009] The multijunction solar cell comprises, on the top side, a metallic top contact region which comprises a first metal layer.

[0010] A planar metallic underside contact region is arranged on the underside of the multijunction solar cell for electrical attachment to the substrate, wherein the multijunction solar cell is electrically attached by means of the top-side contact region and the underside contact region.

[0011] The continuous oval opening extends from the upper side to the lower side.

[0012] The oval opening has a circumferential side wall and an upper edge region formed on the upper side and a lower edge region formed on the lower side, wherein the upper edge region adjoins the upper contact region.

[0013] It should be noted that the diameter of the opening of the ellipse is in the range between 10 μm and 300 μm or in the range between 50 μm and 150 μm.

[0014] In one embodiment, the elliptical opening is also designed to be exactly circular, ie has a constant radius.

[0015] The side walls and the two edge regions are completely covered by the dielectric layer, wherein the dielectric layer has a top side and a bottom side.

[0016] In one embodiment, the dielectric layer comprises silicon oxide, in particular silicon dioxide and / or silicon nitride. Alternatively, the dielectric layer consists of silicon oxide, in particular silicon dioxide and / or consists of silicon nitride. In an extension, the thickness of the dielectric layer is in a range between 5 nm and 500 nm or in a range between 50 nm and 200 nm.

[0017] It is understood that the dielectric layer is applied by means of a deposition method, in particular by means of a CVD method or an ALD method.

[0018] Furthermore, the dielectric layer forms a cohesive connection with the semiconductor material in the region of the side flanks and in the upper edge region and in the lower edge region.

[0019] A first metal covering layer is formed on the surface of the first metal layer, wherein the thickness of the first metal covering layer is in the range between 5 nm and 300 nm or in the range between 10 nm and 200 nm or in the range between 20 nm and 100 nm.

[0020] A second metallic covering layer is formed on the top side of the dielectric layer and on a part of the first metallic layer adjoining the upper edge region, wherein the thickness of the second metallic covering layer is in the range between 10 nm and 100 nm or in the range between 20 nm and 50 nm.

[0021] A second metal layer is arranged on the second metal covering layer in a portion adjoining the upper edge region and in the upper edge region and in a region of the side wall adjoining the upper edge region.

[0022] The second metal layer and the second metal cover layer are respectively connected in a material-locked manner. Here, the metal cover layer includes titanium or a titanium compound and / or includes nickel or a nickel compound. In an extended solution, the metal cover layer is composed of titanium or a titanium compound and / or is composed of nickel or a nickel compound.

[0023] It should furthermore be noted that the respective metal layer is in the form of a conductor track, wherein in one embodiment the metal layer has both a finger-shaped and a planar structure.

[0024] Preferably, III-V solar cells are used in the field of extraterrestrial applications. Especially in the case of extraterrestrial applications, a reliable electrical contact is of particular importance.

[0025] The advantage is that the metal layer on the surface can be passivated well by means of the metal cover layer. In this case, the metal cover layer does not contain gold or silver and does not contain gold compounds and / or silver compounds. Since the metal cover layer contains titanium or nickel or a compound consisting of titanium and / or nickel, different metal layers can be constructed reliably and durably on top of each other. It should be understood that the second metal layer cannot be constructed directly after the first metal layer.

[0026] In one configuration, the thickness of the III-V multi-junction solar cell is in the range between 50 μm and 600 μm or in the range between 100 μm and 250 μm.

[0027] In one embodiment, a layered compound consisting of titanium and oxygen and / or nitrogen is formed between the second metal cover layer and the dielectric layer. Hereinafter, the layered compound is also referred to as an adhesion layer. The advantage is that the adhesion layer improves the reliability of the connection and improves the peeling or breaking of the second cover layer.

[0028] In one configuration, the thickness of the dielectric layer is in each case in the range between 2 nm and 30 nm or in the range between 3 nm and 10 nm or in the range between 4 nm and 7 nm.

[0029] In one configuration, the third metallic covering layer is formed on the surface of the second metallic layer.

[0030] In one embodiment, the fourth metal cover layer is formed on the lower edge region and on the region of the side wall adjacent to the lower edge region and on the part of the second metal layer formed on the side wall. In addition to passivating and protecting the second metal layer, the fourth metal cover layer improves adhesion when the third metal layer is applied to the second metal layer. In other words, when applying the third metal layer, a reliable and low-ohmic connection can be formed between the two metal layers by arranging the fourth cover layer.

[0031] In one embodiment, a third metal layer is formed on the fourth metal cover layer, wherein the third metal layer extends continuously from the lower edge region and the part of the side wall adjacent to the lower edge region to the part of the second metal layer covered by the fourth metal cover layer. In this case, the third metal layer is connected to the corresponding base in a material-locking manner.

[0032] In one embodiment, the lower edge region is spaced apart from the lower contact region.

[0033] In another embodiment, a contact surface to the third metal layer is formed in the lower edge region. In other words, the third metal layer is at least partially formed as a contact layer for electrical attachment of the III-V multijunction cell.

[0034] In one configuration, the bottom contact region has a fourth metal layer. In one embodiment, the third metal layer and the fourth metal layer are formed in a common process step or in different process steps.

[0035] In another embodiment, a further metal covering layer is formed on the surface of the fourth metal layer. This has the advantage that the reliability of the contacting is increased by means of the further metal covering layer.

[0036] In another embodiment, the upper contact region is electrically connected to the contact surface on the lower side by means of the second metal layer and the third metal layer. In other words, the front side of the III-V multi-junction solar cell can be contacted, i.e. electrically attached, from the back side. This simplifies the electrical contacting of the III-V multi-junction solar cell.

[0037] In one embodiment, the side wall is completely covered by the second metal layer and the third metal layer all around. Here, it should be noted that two metal layers are required to achieve complete coverage of the side wall.

[0038] In a further configuration, after application of the metal layer, the opening has a clear width. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In the following, the invention is explained in more detail with reference to the drawings. Identical parts are labeled with the same names. The embodiments shown are highly schematic, i.e. the spacings and the lateral and vertical extensions are not to scale and do not have any geometrical relationships that can be derived from one another unless otherwise stated. It is shown in the drawings:

[0040] Figure 1 A view showing a stacked III-V multi-junction solar cell with through openings,

[0041] Figure 2 Show Figure 1 A view of a further development of the embodiment shown,

[0042] Figure 3 Show Figure 2 A view of a development of the embodiment shown. DETAILED DESCRIPTION

[0043] Figure 1 The illustration shows a view of an embodiment having a stacked III-V multi-junction solar cell MJ with an upper side OS and an underside US.

[0044] The stacked III-V multi-junction solar cell MJ comprises a substrate layer SUB, which is constructed on a lower side US, and has a first solar cell S1 and a second solar cell S2, wherein the first solar cell is arranged above the substrate layer SUB, and the first solar cell has a first band gap, and the second solar cell is arranged above the first solar cell S1, and the second solar cell has a second band gap, wherein the second band gap is constructed to be larger than the first band gap.

[0045] A tunnel diode T1 is formed between the first solar cell S1 and the second solar cell S2 .

[0046] A metallic top contact region OSKB is formed on the top side of the multijunction solar cell MJ, wherein the top contact region OSKB comprises a first metal layer M1 .

[0047] For electrical attachment of the substrate SUB, a planar, metallic underside contact region USKB is arranged on the underside US of the multijunction solar cell MJ.

[0048] By means of the upper side contact region OSKB and the lower side contact region USKB the multijunction solar cell MJ is electrically attached.

[0049] The continuous oval-shaped opening DU extends from the upper side OS to the lower side US.

[0050] The opening DU has a peripheral side wall DS and an upper edge region OR formed on the upper side OS and a lower edge region UR formed on the lower side US.

[0051] In this case, the upper edge region OR adjoins the upper contact region OSKB.

[0052] Furthermore, the side wall DS and the two edge regions OR, UR are completely covered by the dielectric layer DI, wherein the dielectric layer DI has an upper side and an underside.

[0053] Furthermore, the dielectric layer DI forms a cohesive connection with the semiconductor material on the bottom side in the region of the side walls DI.

[0054] A first metal covering layer TN1 is formed on the surface of the first metal layer M1 , wherein the thickness of the first metal covering layer TN1 is in the range between 5 nm and 300 nm.

[0055] exist Figure 2 The diagram shows Figure 1 Only the differences are explained below.

[0056] A second metallic cover layer TN2 is formed on the upper side of the dielectric layer DI and on a part of the first metallic layer M1 adjoining the upper edge region OR.

[0057] Preferably, the thickness of the second metal cap layer TN2 is in the range between 10 nm and 100 nm.

[0058] A second metal layer M2 is arranged on the second metal cover TN2 , on a portion adjacent to the upper edge region OR and on the upper edge region OR, and in a region of the side wall DS adjacent to the upper edge region OR.

[0059] The second metal layer M2 and the second metal covering layer TN2 each form a cohesive connection.

[0060] A compound composed of titanium and oxygen is formed between the second metal cover layer TN2 and the dielectric layer DI. It should be understood that this compound is formed in a layered manner.

[0061] exist Figure 3 Another embodiment is shown in the figure of FIG. Figure 2 The difference in implementation methods.

[0062] A third metal covering layer TN3 is formed on the surface of the second metal layer M2 .

[0063] Furthermore, a fourth metal cover layer TN4 is formed on the lower edge region UR and on regions of the side walls DS adjoining the lower edge region UR and on parts of the second metal layer M2 formed on the side walls DS.

[0064] A third metal layer M3 is formed on the fourth metal cover layer TN4 , which extends continuously from the lower edge region UR and the portion of the side wall DS adjoining the lower edge region UR to the portion of the second metal layer M2 covered by the fourth metal cover layer TN4 .

[0065] Furthermore, the third metal layer M3 and the base each form a material-bonded connection.

[0066] The lower edge region UR is spaced apart from the lower contact region USKB.

[0067] A contact surface to the third metal layer M3 is formed in the lower edge region UR.

[0068] The underside contact region USKB has a fourth metal layer M4 , on the surface of which a further metal covering layer TNR is formed.

[0069] Furthermore, the top contact region OSKB is electrically connected to the contact surface on the underside US by means of the second metal layer M2 and the third metal layer M3 .

[0070] Furthermore, the sidewall DS is completely and circumferentially covered by the second metal layer M2 and the third metal layer M3 .

[0071] Furthermore, after applying the metal layers M1 - M4 , the opening DU has a clear width.

Claims

1. A stacked III-V multi-junction solar cell (MJ), the stacked III-V multi-junction solar cell having an upper side (OS) and a lower side (US), the stacked III-V multi-junction solar cell having a substrate layer (SUB) which is formed on the underside (US), a first solar cell (S1), the first solar cell being arranged above the substrate layer (SUB), the first solar cell having a first band gap, a second solar cell (S2), the second solar cell being arranged above the first solar cell (S1), the second solar cell having a second band gap, wherein: The second band gap is configured to be larger than the first band gap, a tunnel diode (T1), the tunnel diode being constructed between the first solar cell (S1) and the second solar cell (S2), a metallic top contact region (OSKB), which is formed on the top side of the multi-junction solar cell (MJ), wherein the top contact region (OSKB) comprises a first metal layer (M1), a metallic bottom contact region (USKB) which is formed in a planar manner on the bottom side (US) of the multi-junction solar cell (MJ) for electrically attaching the substrate (SUB), wherein the multi-junction solar cell (MJ) is electrically attached by means of the top contact region (OSKB) and the bottom contact region (USKB), an oval opening (DU), which extends continuously from the upper side (OS) to the lower side (US), The opening (DU) has a circumferential side wall (DS) and an upper edge region (OR) formed on the upper side (OS) and a lower edge region (UR) formed on the lower side (US), wherein the upper edge region (OR) adjoins the upper contact region (OSKB), The side wall (DS) and the two edge regions (OR, UR) are completely covered by a dielectric layer (DI), wherein the dielectric layer (DI) has a top side and a bottom side, the dielectric layer (DI) forming a cohesive connection with the semiconductor material on the bottom side (US) in the region of the side wall (DI), A first metal cover layer (TN1) is formed on the surface of the first metal layer (M1), wherein the thickness of the first metal cover layer (TN1) is in the range between 5 nm and 300 nm. A second metal cover layer (TN2) is formed on the upper side of the dielectric layer (DI) and on a part of the first metal layer (M1) adjoining the upper edge region (OR), wherein the thickness of the second metal cover layer (TN2) is in the range between 10 nm and 100 nm, A second metal layer (M2) is arranged on the second metal covering layer (TN2), in a portion adjacent to the upper edge region (OR), in the upper edge region (OR), and in a region of the side wall (DS) adjacent to the upper edge region (OR), and the second metal layer (M2) and the second metal covering layer (TN2) are respectively formed with a material-bonded connection.

2. The stacked III-V multi-junction solar cell (MJ) according to claim 1, characterized in that: A layered compound of titanium and oxygen and / or nitrogen is formed between the second metallic covering layer (TN2) and the dielectric layer (Di).

3. The stacked III-V multi-junction solar cell (MJ) according to claim 1 or claim 2, characterized in that: A third metal covering layer (TN3) is formed on the surface of the second metal layer (M2).

4. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that A fourth metal covering layer (TN4) is formed on the lower edge region (UR), on regions of the side flanks (DS) adjoining the lower edge region (UR), and on portions of the second metal layer (M2) formed on the side flanks (DS).

5. The stacked III-V multi-junction solar cell (MJ) according to claim 4, characterized in that: A third metal layer (M3) is constructed on the fourth metal covering layer (TN4), and the third metal layer (M3) extends continuously from the lower edge region (UR) and the part of the side wall (DS) adjacent to the lower edge region (UR) to the part of the second metal layer (M2) covered by the fourth metal covering layer (TN4), and the third metal layer (M3) is connected to the corresponding base structure material.

6. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that The lower edge region (UR) is spaced apart from the lower contact region (USKB).

7. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that A contact surface to the third metal layer (M3) is formed in the lower edge region (UR).

8. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that The underside contact region (USKB) has a fourth metal layer (M4), and a further metal cover layer (TNR) is formed on the surface of the fourth metal layer (M4).

9. The stacked III-V multi-junction solar cell (MJ) according to any one of claims 5 to 7, characterized in that: The top contact region (OSKB) is electrically connected to the contact surface on the bottom side (US) by means of the second metal layer (M2) and the third metal layer (M3).

10. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that The sidewall (DS) is completely and circumferentially covered by the second metal layer (M2) and the third metal layer (M3).

11. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that After application of the metal layers (M1-M4), the opening (DU) has a clear width.

12. The stacked III-V multi-junction solar cell (MJ) according to any one of the preceding claims, characterized in that The metallic covering layers (TN1-TN4, TNR) are designed as titanium layers or as nickel layers or at least comprise titanium and / or nickel.

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